US20060267171A1 - Semiconductor device modules, semiconductor devices, and microelectronic devices - Google Patents

Abstract

Supports (40) of microelectronic devices (10) are provided with underfill apertures (60) which facilitate filling underfill gaps (70) with underfill material (74). The underfill aperture may have a longer first dimension (62) and a shorter second dimension (64). In some embodiments, a method of filling the underfill gap (70) employs a removable stencil (80). If so desired, a stencil (80) can be used to fill multiple underfill gaps through multiple underfill apertures in a single pass.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a divisional application of U.S. patent application Ser. No. 09/944,465, entitled “METHOD OF MANUFACTURING MICROELECTRONIC DEVICES, INCLUDING METHODS OF UNDERFILLING MICROELECTRONIC COMPONENTS THROUGH AN UNDERFILL APERTURE,” filed Aug. 30, 2001, now U.S. Pat. No. 6,756,251, issued Jun. 29, 2004, which claims foreign priority benefits of Singapore Application No. 200105099-6, filed Aug. 21, 2001, both of which are herein incorporated by reference in their entireties.
TECHNICAL FIELD
• This invention relates to microelectronic devices having microelectronic components mounted on substrates and methods of manufacturing such devices. The invention has particular utility in connection with flip-chip packaging.
BACKGROUND
• Microelectronic devices, such as memory devices and microprocessors, typically include one or more microelectronic components attached to a substrate. The microelectronic components commonly include at least one die including functional features such as memory cells, processor circuits, and interconnecting circuitry. The dies of the microelectronic components may be encased in a plastic, ceramic or metal protective covering. Each die commonly includes an array of very small bond pads electrically coupled to the functional features. These terminals can be used to operatively connect the microelectronic component to the substrate.
• One type of microelectronic component which is gaining increased acceptance is the “flip-chip” semiconductor device. These components are referred to as “flip-chips” because they are typically manufactured in wafer form having bond pads which are initially facing upwardly. After manufacture is completed and the semiconductor die is singulated from the wafer, it is inverted or “flipped” such that the surface bearing the bond pads faces downwardly for attachment to a substrate. The bond pads are usually coupled to terminals, such as conductive “bumps,” which are used as electrical and mechanical connectors connecting the die to the substrate. A variety of materials may be used to form the bumps on the flip-chip, such as various types of solder and conductive polymers. In applications using solder bumps, the solder bumps are reflowed to form a solder joint between the flip-chip component and the substrate. This leaves a small gap between the flip-chip and the substrate. To enhance the joint integrity between the microelectronic component and the substrate, an underfill material is introduced into the gap between the components. This underfill material helps equalize stress placed on the components and protects the components from contaminants, such as moisture and chemicals.
• The underfill material typically is dispensed into the underfill gap by injecting the underfill material along one or two sides of the flip-chip. As shown schematically inFIG. 1, a bead of an underfill material U may be dispensed along one side of the die D. The underfill material will then be drawn into the gap between the die D and the substrate S by capillary action. The direction of this movement is indicated by the arrows inFIG. 1. While such a “single stroke” process yields good results, the processing time necessary to permit the underfill material U to flow across the entire width of the die can reduce throughput of the manufacturing process.
• FIG. 2 illustrates an alternative approach wherein the underfill material U is applied in an L-shaped bead which extends along two adjacent sides of the die D. By reducing the average distance which the underfill material has to flow to fill the underfill gap, processing times can be reduced. However, this L-stroke approach can lead to more voids in the underfill material, adversely affecting the integrity of the bond between the die D and the substrate S.
• Typically, the underfill material U dispensed along the edge(s) of the die D in this process has a relatively high viscosity at dispensing temperatures. This permits a well-defined bead of material to be applied adjacent a single die D, facilitating a more dense arrangement of dies on the surface of the substrate. To get the underfill material U to flow into the underflow gap, the substrate is typically heated sufficiently to reduce the viscosity of the underfill material. This significantly increases manufacturing time and complexity.
• Others have proposed pumping an underfill material into the underfill gap through an opening in the substrate. For example, U.S. Pat. No. 6,057,178 (Galuschki et al, the teachings of which are incorporated herein by reference) adds the underfill material via an orifice in the substrate. A viscous underfill material is added to the orifice (e.g., by dispensing it under pressure). The assembly must then be heated to allow the underfill material to flow into the underfill gap.
• U.S. Pat. No. 5,697,148 (Lance Jr. et al., the teachings of which are incorporated herein by reference) also suggests dispensing an underfill material into the underfill gap through the substrate. The underfill material is injected under hydraulic pressure through an injection port using a needle. Injecting underfill material using a dispenser such as suggested in this patent and in the Galuschki et al. patent requires precise placement of the dispensing tip in the relatively small opening in the substrate. Fairly complex vision systems must be employed to ensure that the dispensing tip is properly aligned with the opening. Using a small dispenser also makes it more difficult to fill multiple underfill gaps between different die-substrate pairs at one time.
SUMMARY OF THE INVENTION
• The present invention provides certain improvements in microelectronic devices and various aspects of their manufacture. In accordance with one embodiment, the invention provides a microelectronic device assembly which includes a microelectronic component and a first support. The microelectronic component has a facing surface, an exterior surface, and a first terminal array carried on the facing surface. The first support has a component surface, a mounting surface, a second terminal array, and an aperture which extends through the support from the component surface to the mounting surface. The second terminal array is carried on the component surface and is electrically coupled to the first terminal array of the microelectronic component. The aperture has a first dimension and a second dimension less than the first dimension. The component surface of the support is juxtaposed with the facing surface of the microelectronic component to define a first underfill gap between the component surface and the facing surface. A first underfill material at least substantially fills the first underfill gap.
• In an alternative embodiment, the microelectronic device assembly further includes a second support such as a circuit board. In this embodiment, the first support includes a third terminal array on its mounting surface. A second support has a fourth terminal array carried on a terminal surface. The third terminal array of the first support is electrically coupled to the fourth terminal array of the second support. The mounting surface of the first support is juxtaposed with the terminal surface of the second support a define a second underfill gap therebetween. A second underfill material, which may be the same as the first underfill material, substantially fills the second underfill gap.
• Another embodiment of the invention provides a method for underfilling a microelectronic component which is electrically coupled to a support to define an underfill gap, with an underfill aperture extending through the support and in fluid communication with the underfill gap. In accordance with this method, a stencil is placed adjacent the underfill aperture, the stencil having a stencil opening in registry with the underfill aperture. The stencil opening defines, at least in part, a fill volume at least as great as the volume of the underfill gap. The stencil opening is filled with a flowable underfill material which is permitted to flow through the support via the underfill aperture and substantially fill the first underfill gap. The stencil may be removed, leaving a completed, underfilled microelectronic device assembly.
• Another embodiment of the invention provides a method of manufacturing a microelectronic device assembly including a support and a plurality of microelectronic components. Each of the microelectronic components may have a facing surface carrying a terminal array and the support may have a mounting surface, a component surface carrying a plurality of terminal arrays, and a plurality of underfill apertures. For each microelectronic component, a connecting material is deposited on the terminal array of the microelectronic component and/or an associated one of the terminal arrays of the support. The facing surface of each microelectronic component is juxtaposed with the component surface of the support such that the connecting material electrically couples the terminal array of the microelectronic component with the associated terminal array of the support. The facing surface of each microelectronic component is spaced from the component surface of the support to define a separate underfill gap between each microelectronic component and the support. At least one of the underfill apertures in the support is in fluid communication with each of the underfill gaps. A stencil is placed adjacent to the mounting surface of the support, with the stencil having a separate stencil aperture in registry with each of the underfill apertures in the support. Each stencil aperture defines, at least in part, a fill volume at least as great as the volume of the underfill gap in fluid communication with the underfill aperture with which the stencil aperture is registered. All of the stencil apertures are filled with a flowable underfill material, preferably in a single pass. The underfill material is permitted to flow through the support via the apertures and laterally outwardly therefrom to substantially fill each of the underfill gaps. The stencil may be removed, leaving the final microelectronic device assembly.
• In accordance with still another embodiment, the invention provides a method of underfilling a microelectronic component which is electrically coupled to a support such that the microelectronic component and the support define an underfill gap therebetween. According to this method, an underfill aperture in the support is filled with an underfill material. The underfill aperture has a first dimension and second dimension less than the first dimension. The underfill material is allowed to flow outwardly from the underfill aperture to substantially fill the underfill gap. In one particular adaptation of this embodiment, the microelectronic component has a pair of spaced-apart lateral edges and a pair of spaced-apart transverse edges. The underfill aperture is spaced farther from each of the lateral edges than from either of the transverse edges. The underfill material flows outwardly from the underfill aperture a greater distance, and covers a greater surface area, in a lateral direction than in a transverse direction.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic illustration of a prior art underfill process.
• FIG. 2 is a schematic illustration of another prior art underfill process.
• FIG. 3 is a top elevation view of a microelectronic component in accordance with an embodiment of the invention.
• FIG. 4 is a top elevation view of a support which may be connected to the die ofFIG. 3 in accordance with an embodiment of the invention.
• FIG. 5 is top elevation view of a support in accordance with another embodiment of the invention.
• FIG. 6 is a top elevation view of a support in accordance with yet another embodiment of the invention.
• FIG. 7 is a top elevation view of a support in accordance with still another embodiment of the invention.
• FIG. 8 is a top elevation view of a support in accordance with still another embodiment of the invention.
• FIG. 9 is a top elevation view of a support in accordance with still another embodiment of the invention.
• FIGS. 10-12 are side elevation views schematically illustrating a method of assembling a microelectronic device in accordance with an embodiment of the invention.
• FIG. 13 is a top elevation view schematically illustrating placement of stencil to fill a plurality of underfill gaps in a single step in accordance with another alternative embodiment of the invention.
• FIG. 14 is a top elevation view of a circuit board which may be coupled to the support ofFIG. 4 in accordance with another embodiment of the invention.
• FIGS. 15-17 are side elevation views schematically illustrating a method for assembling a microelectronic device in accordance with an alternative embodiment of the invention.
DETAILED DESCRIPTION
• Various embodiments of the present invention provide microelectronic devices or methods of manufacturing microelectronic devices. The following description provides specific details of certain embodiments of the invention illustrated in the drawings to provide a thorough understanding of those embodiments. It should be recognized, however, that the present invention can be reflected in additional embodiments and the invention may be practiced without some of the details in the following description.
• FIGS. 3, 4, and10-12 schematically depict the manufacture of amicroelectronic device10 in accordance with one embodiment of the invention. Themicroelectronic device10 generally includes amicroelectronic component20 and asupport40. Themicroelectronic component20 may be SIMM, DRAM, flash-memory, processors or any of a variety of other types of microelectronic devices. Typically, themicroelectronic component20 will be a semiconductor device of the type commonly used in flip-chip manufacture. While themicroelectronic component20 is illustrated in the drawings as being a single element, it should be understood that themicroelectronic component20 can comprise any number of subcomponents. For example, themicroelectronic component20 may comprise one or more dies attached to a common substrate, such as in a stacked-die assembly.
• FIG. 3 is a top view of themicroelectronic component20. The microelectronic component includes a pair of spaced-apart lateral edges22aand22band a pair of spaced-aparttransverse edges24aand24b. Themicroelectronic component20 also includes an exterior surface28 (FIGS. 10-12) and a facingsurface26. The facingsurface26 includes aterminal array30 comprising a plurality ofterminals32 arranged on the facingsurface26 in a predefined pattern. Theterminals32 are electrically connected to functional components of themicroelectronic component20.
• FIG. 4 shows an embodiment of asupport40 which is adapted for use with themicroelectronic component20 shown inFIG. 3. Thesupport40 may be flexible or rigid and have any desired configuration. Thesupport40 may be formed of material commonly used to manufacture microelectronic substrates, such as ceramic, silicone, glass, or combinations thereof. Thesupport40 can alternatively be formed of an organic material or other materials suitable for PCBs. In one embodiment of the invention, thesupport40 comprises a printed circuit board such as an FR-4 PCB. In another embodiment, thesupport40 may comprise a flexible interposer such as a conventional polyimide tape (e.g., UPILEX, commercially available from Ube Industries, Inc. of Tokyo, Japan; KAPTON or MICROLUX, both commercially available from E.I. du Pont de Nemours and Co. of Delaware, USA; or ESPANEX, commercially available from Nippon Steel Chemical Co., Ltd. of Tokyo, Japan) and thismicroelectronic device10 may be attached to a circuit board, as mentioned below in connection withFIGS. 15-17.
• Thesupport40 shown inFIG. 4 includes a pair of spaced-apart lateral edges42aand42band a pair of spaced-aparttransverse edges44aand44bwhich together define the circumference of the substrate. In the illustrated embodiment, thesupport40 is a parallelogram, with the lateral edges42aand42bbeing parallel to one another and perpendicular to both of thetransverse edges44aand44b.
• Thesupport40 has acomponent surface46 and a mounting surface48 (FIGS. 10-12). Thecomponent surface46 includes a plurality ofterminals52 defining aterminal array50. Theterminals52 on thecomponent surface46 are arranged in a predefined pattern which may generally correspond to the pattern of theterminals32 of theterminal array30 on themicroelectronic component20. Theterminals52 of theterminal array50 may be thought of as defining a footprint of thesupport40. If so desired, theterminals52 may be electrically connected to functional components contained within or attached to thesupport40. In the illustrated embodiment, each of theterminals52 is connected to a single mountingterminal56 carried on the mountingsurface48. These mountingterminals56 may be arranged in a predefined pattern to define a mountingterminal array54 on the mounting surface. This can be particularly useful where thesupport40 is intended to be connected to a second support, as discussed below.
• Thesubstrate40 also includes anunderfill aperture60 which passes through the substrate from thecomponent surface46 to the mountingsurface48. Theunderfill aperture60 has afirst dimension62 andsecond dimension64. Thesecond dimension64 is smaller than thefirst dimension62, yielding an asymmetrical shape to theunderfill aperture60. InFIG. 4, theunderfill aperture60 is typified as an elongate slot. Thefirst dimension62 of theaperture60 may coincide with a major axis of the slot. This major axis may extend along a midline which is parallel to one or both of the lateral edges42aand42b.
• The largerfirst dimension62 of theunderfill aperture64 can be adjusted for differently sizedmicroelectronic components20 and supports40. It is anticipated that in most applications the first dimension will range from 3 mm to 25 mm. The smallersecond dimension64 of theunderfill aperture60 may vary depending on the size and shape of thesupport40 andterminal array50 on the component surface and the nature of the underfill material. In one embodiment of the invention, thesecond dimension64 ranges from 0.03 mm to 0.5 mm. To enhance flow ofunderfill material74 through theunderfill aperture60, the second dimension is desirably at least 50% greater than the largest particle size of any filler present in the underfill material. The aspect ratio of the underfill aperture60 (i.e., the first dimension divided by the shorter second dimension) is greater than one. In one embodiment of the invention, the aspect ratio is greater than five.
• In the embodiment ofFIG. 4, theunderfill aperture60 is spaced farther from each of the lateral edges42aand42bthan from either of thetransverse edges44aand44b. Theaperture60 is shown as being generally centered on thesupport40. In particular, the transverse distance from the periphery of theaperture60 to a firstlateral edge42ais the same as the transverse distance from the other side of theaperture60 to the otherlateral edge42b. Similarly, the lateral distance from the periphery of the aperture to a firsttransverse edge44ais the same as the lateral distance from the periphery of theaperture60 to the othertransverse edge44b. It should be understood, though, that theaperture60 need not be centered, i.e., theaperture60 may be positioned closer to one of the lateral edges42aand42bthan the other and/or closer to one of thetransverse edges44aand44bthan the other.
• FIG. 4 also shows (in phantom) a projection of the location of themicroelectronic component20 with respect to thesupport40 in one adaptation of the invention. When the support is so positioned, theunderfill aperture60 is spaced farther from at least one of the component's lateral edges22aand22bthan it is from one or both of the component'stransverse edges24aand24b. In the illustrated embodiment, thetransverse distance66afrom the periphery of theaperture60 to the firstlateral edge22aof thecomponent20 is the same as thetransverse distance66bfrom the other side of theaperture60 to the otherlateral edge22b. The lateral distances65aand65bfrom the periphery of theaperture60 to the component'stransverse edges24aand24b, respectively, are also equal to one another. However, thetransverse distances66aand66bare each greater than the lateral distances65aand65b.
• FIGS. 5-9 illustrate alternative underfill apertures in accordance with an embodiment of the invention. The support40aofFIG. 5 has a generally I-shapedslot60a. Thesupport40bofFIG. 6 includes a generally T-shapedslot60b.FIG. 7 illustrates asupport40cwhich has a generally star-shapedunderfill aperture60c. This star-shaped aperture may be thought of as a plurality of elongate slots which intersect one another generally at the center of thesupport40cto define the star-shapedaperture60c. Thesupport40dofFIG. 8 has a generallyU-shaped slot60dand thesupport40eofFIG. 9 has a generally L-shapedslot60e. Both theU-shaped slot60dand the L-shapedslot60eare illustrated as being positioned generally within the boundaries of theterminal array50 of thesupport40. If so desired, one or more of the legs of theseslots60dand60emay be positioned outside the area bound by theterminal array50, e.g., between theterminal array50 and one of the lateral edges42. It should be understood that the embodiments ofFIGS. 4-9 are merely illustrative and a wide variety of other underfill aperture shapes could also be employed.
• As noted above, the present invention includes methods for manufacturing microelectronic devices. In the following discussion, reference will be made to themicroelectronic component20 and thesupport40 shown inFIGS. 3 and 4. It should be understood, though, that many of the features shown in these drawings are not required for manufacturing a microelectronic device according to the methods outlined below.
• Initially, theterminal array30 of themicroelectronic component20 is electrically coupled to theterminal array50 on thecomponent surface46 of thesupport40. This electrical coupling may be carried out in any known fashion. For example, these components may be electrically coupled using standard flip chip manufacturing techniques such as those taught in connection with FIG. 3 of U.S. Pat. No. 5,697,148, (Lance, Jr. et al., the entire teachings of which are incorporated herein by reference).
• Techniques for electrically coupling microelectronic components to supports are well known in the art and need not be discussed in great detail here. Briefly, though, a connecting material is deposited on at least one of the twoterminal arrays30 and50 which are to be connected to one another. For example, solder “bumps” may be deposited on one ormore terminals32 of the microelectronic component'sterminal array30. The connecting material need not be solder, though. Instead, it may be any of a variety of other materials known in the art, such as gold, indium, tin, lead, silver, or alloys thereof that reflow to make electrical interconnects. The connecting material may also be formed of conductive polymeric or epoxy materials, which may be plated with metals.
• The facingsurface26 of themicroelectronic component20 may be juxtaposed with thecomponent surface46 of thesupport40, with theterminal arrays30 and50 generally aligned with one another. The connecting material electrically couples one or more terminals of theterminal array30 to a corresponding terminal or terminals of theterminal array50 on thecomponent surface46, as illustrated inFIG. 10. The connecting material may then be reflowed, if necessary, to electrically couple theterminals32 and52. The resultantelectrical connector72 may also serve to mechanically connect themicroelectronic component20 to thesupport40.
• FIG. 10 illustrates such a partially assembledmicroelectronic device10. As can be seen in this drawing, theelectrical connectors72 serve to space the facingsurface26 of themicroelectronic component20 from the support'scomponent surface46. This defines a peripherallyopen underfill gap70 therebetween. Theelectrical connectors72 are encompassed within theunderfill gap70. Theunderfill gap70 is in fluid communication with theunderfill aperture60 in thesupport40. Positioning theunderfill aperture60 within the footprint of the component surface'sterminal array50 assures registry of theaperture60 with theunderfill gap70.
• In conventional manufacture, the flip chip die is positioned above the substrate during the underfill process. In accordance with one embodiment of the present invention, though, the partially assembled microelectronic device is oriented to position thesupport40 above themicroelectronic component20.
• Theunderfill gap70 is filled by delivering an underfill material74 (shown schematically inFIG. 10) through theunderfill aperture60 in thesupport40. Theunderfill material74 may be selected to enhance the mechanical bond between themicroelectronic component20 and thesupport40, to help distribute stress on themicroelectronic component20 and theelectrical connectors72, and to increase structural integrity of themicroelectronic device10. The underfill material may also help protect themicroelectronic component20 and/or theelectrical connectors72 from degradation by contaminants, such as moisture.
• Theunderfill material74 is typically a polymeric material, such as an epoxy or acrylic resin, and may contain various types of inert fillers. These fillers may comprise, for example, silica particles. The underfill material is typically selected to have a coefficient of thermal expansion which approximates that of themicroelectronic device20 and/or thesupport40 to help minimize the stress placed on themicroelectronic device10. As discussed in more detail below, the viscosity of theunderfill material74 is selected to ensure that the underfill material will flow to fill theunderfill gap70 under the selected processing conditions. In particular, the underfill material should flow easily to fill the volume of theunderfill gap70 while minimizing voids, bubbles, and non-uniform distribution of the underfill material within theunderfill gap70.
• Theunderfill material74 is desirably delivered to theunderfill gap70 utilizing at least a majority of theunderfill aperture60. Looking at thesupport40 ofFIG. 4, for example, it is desirable that the underfill material be delivered along substantially the entirefirst dimension62 of theelongated slot60. This may be accomplished in any of a variety of ways. If a dispensing nozzle is utilized, for example, the nozzle may be moved along the length of theaperture60. Alternatively, the nozzle may have an elongated dispensing tip which extends along at least a portion of thefirst dimension62 while having a width which is smaller than thesecond dimension64.
• FIG. 11 shows one embodiment in which theunderfill material74 is delivered to theunderfill gap70 utilizing astencil80. Thestencil80 includes acontact surface82, anexterior surface84, and a stencil aperture oropening86. Thestencil aperture86 passes through the entire thickness of thestencil80, extending from thecontact surface82 to theexterior surface84. As suggested inFIG. 13 (discussed in more detail below), the shape of thestencil aperture86 may, but need not, generally correspond to the shape of theunderfill aperture60 in thesubstrate40. For example, if theunderfill aperture60 is an elongated slot, thestencil aperture86 may also be an elongated slot. If theunderfill aperture60ais generally I-shaped, thestencil aperture86amay be I-shaped, too. If theunderfill aperture60bis generally T-shaped, thestencil aperture86bmay also be T-shaped. If theunderfill aperture60cis generally star-shaped, the stencil opening may also be generally star-shaped. As suggested inFIG. 13, though, thestencil aperture86cmay take a different shape, such as an ellipse. If theunderfill aperture60dis generally U-shaped, the stencil aperture may be U-shaped, and if theunderfill aperture60eis generally L-shaped, the stencil aperture may be L-shaped.
• In one embodiment, thestencil aperture86 is at least as large as theunderfill aperture60 and may be larger than theunderfill aperture60. In particular, thestencil aperture86 may have a periphery which extends outwardly beyond the periphery of theunderfill aperture60 when these two apertures are in registry with one another. For example, thewidth88 of thestencil aperture86 may be greater than the width orsecond dimension64 of theunderfill aperture60. The length of thestencil aperture86 may also be longer than the length orfirst dimension62 of theunderfill aperture60.
• In an alternative embodiment (not specifically illustrated), thestencil aperture86 is no larger than, and may be smaller than, theunderfill aperture60. For example, thewidth88 of thestencil aperture86 may be smaller than the width orsecond dimension64 of theunderfill aperture60 and thestencil aperture86 may also be shorter than thefirst dimension62 of theunderfill aperture60. In such an embodiment, the entire mountingsurface40 of the support adjacent theunderfill aperture60 may be covered by the stencil, reducing the volume of residue which may be left on the surface of thesupport40 when the underfill process is complete.
• Thestencil80 may be made of any desired material. As explained below, thestencil opening86 can be used to control the volume of underfill material being provided to theunderfill aperture60. As a consequence, astencil80 in accordance with one embodiment of the invention may be flexible, but is not readily compressed or stressed under the conditions of use outlined below. Suitable stencil materials may include metals, photoimageable polyamides, dry film photo masks, liquid photoimageable photomasks, silicon, and ceramics. If so desired, thestencil80 may be formed of a material which is not wettable by theunderfill material74.
• In use, thestencil80 is positioned above thesupport40. In the illustrated embodiment, thecontact surface82 of thestencil80 is in direct physical contact with the mountingsurface48 of thesupport40. This can be achieved by providing aseparate stencil80 and positioning it directly on top of thesupport40. The stencil should be positioned to ensure that thestencil aperture86 is in registry with theunderfill aperture60. If so desired, the mountingsurface48 of thesupport40 and thecontact surface82 of thestencil80 may be provided with holes or Vernier patterns (not shown) to serve as alignment guides for aligning thestencil aperture86 with theunderfill aperture60.
• While the drawings illustrate a physicallyseparate stencil80, which may be reusable, it is also contemplated that thestencil80 may be formed directly on the mountingsurface48 of thesupport40, such as by using a coating of a liquid photoimageable photomask. Thestencil80 may be held in place with respect to thesupport40 by tensioning thestencil80 using a frame (not shown) that holds the edges of the stencil against thesupport40.
• Once thestencil80 is properly positioned with respect to thesupport40, theunderfill materials74 may be delivered to theunderfill aperture60 via thestencil aperture86. This may be accomplished, for example, by “squeegeeing.” In accordance with this embodiment, a quantity of theunderfill material74 is applied to theexterior surface84 of thestencil80. Asqueegee blade90 may then be dragged across theexterior surface84, passing over thestencil aperture86. This will deliver a predictable volume of theunderfill material74 to thestencil aperture86.
• The volume ofunderfill material74 delivered through the stencil aperture will depend, in part, on the thickness of thestencil80 and the surface area of thestencil aperture86. Thestencil aperture86, however, is in registry with theunderfill aperture60. As a consequence, at least a portion of theunderfill material74 may pass into theunderfill aperture60 during the process of squeegeeing. The amount ofunderfill materials74 which passes into theunderfill aperture60 as theblade90 passes over thestencil aperture86 will depend, in part, on the viscosity of theunderfill material74. For this reason, thestencil aperture86 may only partly define the fill volume of underfill material being delivered in the squeegeeing process. The fill volume so defined should be at least as great as the volume of theunderfill gap70 to ensure that theunderfill gap70 is substantially filled withunderfill material74.
• Theunderfill material74 is permitted to flow through thestencil aperture86 and theunderfill aperture60 into theunderfill gap70. The fill characteristics of theunderfill material74 may be selected to permit the fill material to substantially fill theunderfill gap70, readily flowing around theelectrical connectors72 to encapsulate and protect theconnectors72, as shown inFIG. 12. If so desired, the viscosity of the underfill material may be selected so it may fill the underfill gap without aid of hydraulic pressure, relying instead on gravity and/or capillary action, for example. In one embodiment, the viscosity of the underfill material at the temperature under which the squeegeeing takes place limits the flow of underfill material into theunderfill gap70. This facilitates delivery of a more precise volume ofunderfill material74 into thecentral aperture86 as thesqueegee blade90 passes over that opening. The viscosity of the underfill material may then be reduced, e.g., by heating, permitting the underfill material to flow through theunderfill aperture60 and substantially fill the underfill gap without requiring hydraulic pressure.
• In another embodiment of the invention, the viscosity of the underfill material is relatively low even at room temperature. In particular, the underfill material can flow through theunderfill aperture60 and substantially fill theunderfill gap70 at room temperature without the aid of hydraulic pressure. While the control of the volume ofunderfill material74 delivered to theaperture86 may be a little less precise, a predictable volume can be delivered by consistently controlling the speed and contact pressure of thesqueegee blade90 during the squeegeeing process.
• As noted above in connection withFIG. 4, in one embodiment of the invention, theunderfill aperture60 is spaced farther from at least one of the microelectronic component's lateral edges22aand22bthan from at least one of the microelectronic component'stransverse edges24aand24b. In the embodiment ofFIG. 4, thetransverse distances66aand66bfrom theunderfill aperture60 tolateral edges22aand22b, respectively, are both greater than either of the lateral distances65aand65bbetween theunderfill aperture60 and thetransverse edges24aand24b, respectively. As a consequence, as the underfill material flows outwardly away from theunderfill aperture60 to fill theunderfill gap70, it will travel a greater distance laterally than it will travel transversely to reach the outer edge of themicroelectronic component20. The surface area of themicroelectronic component20 being covered by the underfill material will also be proportional to the distance traveled, dictating that the underfill material will cover a greater surface area laterally than it does transversely as it flows outwardly away from theunderfill aperture60. The position of theunderfill aperture60 with respect to thesupport40 can appreciably reduce processing time and cost in manufacturingmicroelectronic devices10 in accordance with the invention. Applying the bead of underfill material U along a single edge of the die D, as illustrated inFIG. 1 and discussed above, requires that the underfill material U flow across the entire width of the die D. Applying the underfill material U along to adjacent edges of the die D, as shown inFIG. 2, can reduce the average distance which the underfill material U must travel to completely fill the underfill gap. However, as the two fronts of the underfill material converge, they may trap air, creating voids in the underfill material. Additionally, at least some of the underfill material must travel the entire width of the die D to reach the farthest corner of the die.
• Delivering the underfill material through theunderfill aperture60 reduces the distance which the underfill material has to travel to fill theunderfill gap70. For a given underfill material, this will decrease the processing time necessary to fill theunderfill gap70. Notably, surface tension will also tend to keep theunderfill material74 from flowing beyond the outer edge of thesupport40. As a consequence, delivering theunderfill material74 to theunderfill gap70 via theunderfill aperture60 allows multiplemicroelectronic components20 to be added to a single support without risk that capillary action will draw underfill material U intended for one die D under an adjacent component on the associated substrate S, which is a risk in the process shown inFIGS. 1 and 2.
• Others have proposed delivering underfill material to a small, centrally located orifice through a substrate. For example, U.S. Pat. No. 5,697,148 proposes pumping an underfill material through a small hole drilled through a substrate. As can be seen inFIG. 5 of this patent, this still requires that the underfill material flow a substantial distance to completely fill the underfill gap. Using anelongate underfill aperture60 in accordance with an embodiment of the present invention, however, can materially reduce the distance which the underflow material must travel to fill theunderfill gap70. In addition, the relatively restrictive opening through the substrate suggested in this and other patents limits the rate at which the underfill material can be delivered to the underfill gap. Hence, either it will take significantly longer to deliver the underfill material to the underfill gap or the underfill material must be delivered at an appreciably higher pressure, which can create its own difficulties. Such a restricted opening in the substrate can also make it difficult to deliver enough underfill material to fill the underfill gap using a stencil process such as that outlined above.
• In comparison, theunderfill aperture60 in accordance with one embodiment of the present invention provides a materially greater surface area through which the underfill material can be delivered without unduly sacrificing useful substrate real estate which can be used to position functional elements or interconnects in the substrate beneath themicroelectronic component20. Theunderfill aperture60 provides a wider passage way through which underfill material can pass, reducing the pressure needed to get the underfill material into the underfill gap in a reasonable period of time. This also facilitates delivery of the underfill material using thestencil80 as discussed above.
• Once theunderfill material74 has been delivered to theunderfill aperture60, thestencil80 may be removed. In one embodiment, the stencil remains in place until the underfill material has flowed to fill the underfill gap. Thereafter, thestencil80 may be removed, such as by lifting it off the mountingsurface48 of thesupport40. Alternatively, the stencil may be removed by chemical etching or use of a solvent which would remove thestencil80 from thesupport40. Particularly, if a higherviscosity underfill material74 is used and subsequently heated to fill theunderfill gap70, the stencil can be removed before the underfill material fills theunderfill gap70.
• FIGS. 4-12 illustrate embodiments of the invention which utilize a single underfill aperture to fill a single underfill gap beneath a single microelectronic device. Using a stencil in accordance with an embodiment to the present invention, however, can allow the underfilling of multiple underfill gaps in a single step.
• In one such embodiment of the invention, asingle substrate40 is provided with multiplemicroelectronic components20, as shown inFIG. 13. The process of attaching eachmicroelectronic component20 the substrate may be generally as outlined above. In particular, thesupport40 may be provided with multiple terminal arrays, with each terminal array being associated with one of themicroelectronic components20 to be added to thesupport40. Then, for eachmicroelectronic component20, a connecting material can be deposited on one or both of the microelectronic component's terminal array and the associated terminal array of the support. The facing surface of each microelectronic component may then be juxtaposed with the component surface of the support such that the connecting material electrically couples the terminal array of the components with the associated terminal arrays of the support.
• As schematically shown inFIG. 13, the stencil may be applied to the mountingsurface48 of the support with aseparate stencil aperture86,86a,86bor86cin registry with one of theunderfill apertures60,60a,60bor60cin thesupport40. A single, relatively large quantity ofunderfill material74 may be applied to theexterior surface84 of thestencil80. A squeegee blade (not shown inFIG. 13) may then be moved across theexterior surface84 of thestencil80, thereby filling all of the stencil apertures with underfill material in a single pass.
• This can materially reduce processing time to manufacture such multi-component microelectronic devices as compared to prior art methods. For example, in the process suggested in U.S. Pat. No. 5,697,148, the needle would have to be moved from one aperture to the next, requiring relatively complex visualization equipment to ensure proper alignment of the needle. A fixed period of time is necessary to hydraulically deliver an appropriate quantity of underfill material to each underfill gap. If one were to attempt to adapt this technique to a mass manufacturing process, one may utilize multiple needles. However, this would require a dedicated needle array for each microelectronic device configuration. As the configuration of the microelectronic component change from one microelectronic device to another, the entire array of needles would have to be replaced or adjusted.
• FIG. 13 illustrates a singlemicroelectronic device10 having a wide variety of differently sizedmicroelectronic components20 and a wide variety of shapes and sizes ofunderfill apertures60,60a,60b, and60c. This is done primarily to illustrate how various stencil aperture configurations can be positioned in relation to different underfill apertures. It should be understood that in many circumstances all of the underfill apertures and stencil apertures will be of substantially the same size and orientation.
• This method allows asingle substrate40 with multiplemicroelectronic components20 and multiple underfill gaps to be filled in a single pass. In a further embodiment of this method, thesupport40 is subsequently divided into a plurality of separate supports, each of which carries at least one of the microelectronic components. The support may be divided either before or after removing thestencil80. This facilitates the mass manufacture of smaller microelectronic devices by filling in the underfill gaps of multiple microelectronic devices in one simple step.
• In another alternative embodiment of the invention, a plurality of partially assembled microelectronic devices are positioned adjacent to one another. The partially assembled microelectronic devices may comprise one or moremicroelectronic components20 attached to asingle substrate40, such as illustrated inFIG. 10. These microelectronic device assemblies need not be positioned immediately adjacent to or abutting one another; they need only be positioned close enough to enable them to be covered using a single stencil. To facilitate proper alignment of the stencil with the plurality ofsupports40, thesupports40 are desirably aligned such that their mountingsurfaces40 are generally co-planar.
• Thestencil80 may have a plurality ofstencil apertures86 and the stencil would be positioned such that at least one of thestencil apertures86 is in registry with at least oneunderfill aperture60 of each of thesupports40. All of thestencil apertures86 may be filled with flowable underfill material in a single pass, as discussed above in connection withFIG. 13. The underfill material may be permitted to flow through each of the supports via their respective underfill apertures to fill each of the underfill gaps. Removing thestencil80 will yield a plurality of co-formedmicroelectronic device assemblies10.
• FIG. 14 schematically illustrates astylized circuit board110 which may be used in connection with a further embodiment of the invention. Thiscircuit board110 has a pair of spaced-apartlateral edges112aand112band a pair of spaced-aparttransverse edges114aand114b. Thecircuit board110 includes aterminal surface116 and an outer surface118 (FIG. 15). Theterminal surface116 bears a plurality ofterminals122 which define aterminal array120. Thisterminal array120 is configured to be electrically coupled to theterminal array54 on the mountingsurface48 of the support40 (shown inFIG. 4). Thecircuit board110 is shown as including a plurality ofadditional components125 and aninterface126 which can be used to connect the circuit board to another device. If so desired, thecircuit board110 may be a rigid PCB, though any of the materials noted above in connection with thesupport40 could be used instead.
• Thecircuit board110 also includes asecond underfill aperture130 which extends through the thickness of thecircuit board110 from itsterminal surface116 to itsouter surface118. The second underfill aperture has afirst dimension132 and asecond dimension134 which is less than thefirst dimension132. As with theunderfill aperture60 ofFIG. 4, thesecond underfill aperture130 inFIG. 14 is typified as an elongated slot. It should be understood, though, that thissecond underfill aperture130 may take on a variety of different shapes, e.g., shapes analogous to the underfill apertures shown inFIGS. 5-9.
• FIGS. 15-17 schematically illustrate a method of one embodiment to the invention for assembling amicroelectronic device10 such as that discussed above with acircuit board110 or other second support. This yields a largermicroelectronic device100 in which themicroelectronic device10 discussed above may be considered a subassembly. The process illustrated inFIGS. 15-17 is directly analogous to the process outlined above in connection withFIGS. 10-12. In particular, theterminal array120 of thecircuit board110 will be electrically coupled to theterminal array54 on the support's mountingsurface48 viaelectrical connectors142. This will define asecond underfill gap140 between thecircuit board110 and thesupport140. InFIGS. 15-17, thesecond underfill aperture130 is shown as being about the same size and positioned vertically directly above thefirst underfill aperture60. It should be understood, however, that this is not necessary and the twounderfill apertures60,130 can be different sizes and positioned in different locations or orientations with respect to one another.
• Thesecond underfill gap140 may be filled with asecond underfill material144 in any desired fashion. For example, it may be filled using astencil80 andsqueegee blade90 generally outlined above in connection withFIGS. 10-12. Desirably, the second underfill material not only fills the gap between the second support'sterminal surface116 and the other support's mounting surface148, but also fills any remaining void in theunderfill aperture60 in thesupport40. This can be facilitated by positioning thesecond underfill aperture130 directly above thefirst underfill aperture60.
• Thesecond underfill material144 may be different from theunderfill material74. This may be advantageous if different design objectives are required of thesecond underfill material144. In one embodiment of the invention, however, both of theunderfill materials74 and144 have the same composition.
• The process outlined inFIGS. 15-17 start with amicroelectronic device10 wherein theunderfill gap70 is already filled withunderfill material74 before themicroelectronic device10 is attached to thesecond support110. Thereafter, thesecond underfill gap140 is filled with thesecond underfill material144 is a separate step. In an alternative embodiment, thefirst underfill gap70 and thesecond underfill gap140 are filled with a common underfill material in a single step. In accordance with this embodiment, theunderfill aperture60 in thefirst support40 is in fluid communication with thesecond underfill gap140. As shown inFIGS. 15-17, thesecond underfill aperture130 may be positioned directly above thefirst underfill aperture60. The first andsecond underfill gaps70 and140 may then be filled with acommon underfill material74 in a single step, e.g., using astencil80 andsqueegee blade90 analogous to that discussed above in the context ofFIGS. 10-12.
• From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

Claims (23)

1-13. (canceled)

14. A semiconductor device module, comprising:

a support having a mounting surface, a component surface, a plurality of component terminal arrays at the component surface in which individual component terminal arrays are configured to be associated with an individual semiconductor die, and a plurality of elongated slots through the support from the mounting surface to the component surface, wherein individual slots are associated with individual component terminal arrays;

a plurality of semiconductor dies, wherein the individual dies have a front side spaced apart from the component surface by an underfill gap, a backside, and a die terminal array at the front side, and wherein the individual die terminal arrays are electrically connected to corresponding individual component terminal arrays; and

an underfill material at least substantially filling the underfill gaps between the dies and the component surface of the support.

15. The module ofclaim 14 wherein the semiconductor dies are the same type of dies.

16. The module ofclaim 14 wherein the semiconductor dies include first and second dies, and wherein the first dies are different than the second dies.

17. The module ofclaim 14 wherein the underfill material at least partially fills the elongated slots.

18. The module ofclaim 14 wherein the terminals of the die terminal arrays are juxtaposed to corresponding terminals of corresponding component terminal arrays, and wherein the module further comprises solder balls electrically connecting the die terminal arrays to corresponding component terminal arrays.

19. The module ofclaim 18 wherein the underfill material encases the solder balls.

20. The module ofclaim 14 wherein the die terminal arrays and the individual corresponding component terminal arrays have common configurations, and wherein the module further comprises electrical connectors in the underfill gaps extending between the die terminal arrays and corresponding component terminal arrays.

21. The module ofclaim 20 wherein the underfill material encases the electrical connectors.

22. The module ofclaim 14, further comprising electrical connectors between the die terminals and corresponding component terminals, and wherein the underfill material encapsulates the electrical connectors while at least substantially filling the underfill gaps.

23. A semiconductor device, comprising:

a semiconductor die having a front side, a backside, an integrated circuit, and a first terminal array at the front side;

a first support having a component surface, a mounting surface, a second terminal array at the component surface electrically coupled to the first terminal array of the die, a third terminal array at the mounting surface, and a first aperture through the first support from the component surface to the mounting surface, the first aperture having a first dimension and a second dimension different than the first dimension, and the front side of the die being spaced part from the component surface by a first underfill gap;

a second support having a terminal surface, a fourth terminal array at the terminal surface electrically coupled to the third terminal array of the first support, and a second aperture, wherein the mounting surface of the first support is spaced apart from the terminal surface of the second support by a second underfill gap; and

an underfill material at least substantially filling the first underfill gap, the first aperture and the second underfill gap.

24. The semiconductor device ofclaim 23, further comprising first electrical connectors electrically connecting the first terminal array to the second terminal array and second electrical connectors electrically connecting the third terminal array to the fourth terminal array.

25. The semiconductor device ofclaim 24 wherein the underfill material encapsulates the first and second electrical connectors.

26. The semiconductor device ofclaim 24 wherein the underfill material includes a first underfill material at least substantially filling the first underfill gap and a second underfill material at least substantially filling the second underfill gap.

27. The semiconductor device ofclaim 24 wherein the first and second electrical connectors comprise solder balls.

28. The semiconductor device ofclaim 23 wherein the second support comprises a printed circuit board, and wherein the semiconductor device further comprises a plurality of semiconductor dies carried by the printed circuit board.

29. A microelectronic device, comprising:

a microelectronic die having a front side, a backside, and a first terminal array at the front side;

a first support having a component surface, a mounting surface, a second terminal array at the component surface electrically connected to the first terminal array, and an elongated aperture through the first support from the component surface to the mounting surface, wherein the front side of the die faces the component surface of the first support across an underfill gap; and

an underfill material at least substantially filling the underfill gap.

30. The microelectronic device ofclaim 29 wherein the aperture is configured to have one of an I-shape, a T-shape, a star shape, a U-shape or an L-shape.

31. The microelectronic device ofclaim 29 wherein the underfill gap is peripherally open.

32. The microelectronic device ofclaim 29, further comprising:

a second support having a first side, a second side, and an opening through the second support from the first side to the second side, wherein the first support is spaced apart from the second support by a second gap; and

a plurality of electrical connectors electrically coupling the first terminal array to the second terminal array.

33. The microelectronic device ofclaim 32 wherein the underfill material at least substantially fills the underfill gap between the die and the first support and the second gap between the first support and the second support, and wherein the underfill material at least substantially encases the electrical connectors.

34. The microelectronic device ofclaim 33 wherein the underfill material includes a first underfill material between the die and the first support and a second underfill material between the first support and the second support.

35. The microelectronic device ofclaim 33 wherein the underfill material includes a first underfill material between the die and the first support and a second underfill material between the first support and the second support, and wherein the first underfill material has the same composition as the second underfill material.

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