技术领域technical field
本发明一般性涉及镀敷金属的领域。具体而言，本发明涉及浸渍镀银的领域。The present invention relates generally to the field of plated metals. In particular, the present invention relates to the field of immersion silver plating.
背景技术Background technique
浸渍或置换镀敷是无电镀敷加工，但在镀敷领域中将其分为不同的种类。在浸渍镀敷中，沉积作用通过镀敷溶液中的金属离子置换基材的元素金属。在无电镀敷中，一开始通过溶液中的金属离子的自动催化还原反应而发生沉积作用。这种无电镀敷需要在还原试剂存在的条件下进行。Dip or displacement plating is an electroless plating process, but it is classified into different types in the field of plating. In immersion plating, deposition displaces the elemental metal of the substrate by metal ions in the plating solution. In electroless plating, deposition occurs initially by the autocatalytic reduction of metal ions in solution. This electroless plating needs to be carried out in the presence of a reducing agent.
浸渍镀敷并不需要使用外加电流，但其仍为电化学置换反应，该电化学置换反应是由相对于该溶液中欲沉积的金属的电动次序的基材金属位置所驱动。当溶解于镀敷浴槽中的金属离子，被与该镀敷浴槽接触且活性更大(惰性较小)的金属所置换时，即发生镀敷。Immersion plating does not require the use of an applied current, but is still an electrochemical displacement reaction driven by the position of the substrate metal relative to the electrokinetic order of the metal to be deposited in the solution. Plating occurs when metal ions dissolved in a plating bath are replaced by more reactive (less inert) metals in contact with the plating bath.
制造印刷线路板时，典型地在具有焊垫及/或贯穿孔的印刷线路板的基材上形成可焊接的镀层(solderable finishes)，该焊垫及/或贯穿孔系透过罩幕(如，焊锡掩模)而曝露出来。由于无电镀敷亦可在罩幕的表面上沉积金属(此并非所期望的情况)，故这种可焊接的镀层通常通过浸渍镀敷而形成。由于浸渍镀敷反应系由电化学的电位差所驱动，故镀敷仅在被曝露的金属区域发生。然而，就制造印刷线路板时所使用的铅而言，对于更能为环境所接受的替代物的需求仍持续增加。因此，在电子零件中使用铅以及铅合金正面临着不确定的未来。In the manufacture of printed wiring boards, solderable finishes are typically formed on the substrate of the printed wiring board with solder pads and/or through holes passing through a mask (e.g. , solder mask) and exposed. Since electroless plating can also deposit metal on the surface of the mask (which is not the desired case), such solderable coatings are usually formed by immersion plating. Since the immersion plating reaction is driven by an electrochemical potential difference, plating occurs only on exposed metal areas. However, there continues to be an increasing demand for more environmentally acceptable alternatives to lead used in the manufacture of printed wiring boards. Therefore, the use of lead and lead alloys in electronic components is facing an uncertain future.
相对于铅而言，银是另一种更能为环境所接受的选择，并已有建议使用银作为可焊接的镀层。如上所述，沉积这种可焊接的镀层的较佳方法通过浸渍镀敷。例如，美国专利第5,955,141号(Souter et al.)揭示某种适合用于在印刷线路板上沉积银层的浸渍银镀敷浴。Silver is a more environmentally acceptable alternative to lead and has been suggested as a solderable plating. As noted above, the preferred method of depositing such solderable coatings is by dip plating. For example, U.S. Patent No. 5,955,141 (Souter et al.) discloses certain immersion silver plating baths suitable for depositing silver layers on printed wiring boards.
制造印刷线路板时，使用浸渍镀敷仍存有许多限制。这些限制包含相对较慢的镀敷速度以及沉积厚度受到限制，这些限制归因于浸渍镀敷本身，亦即，随着金属沉积的扩大，会有遮蔽底层金属的倾向，因而需要防止更进一步的置换。欲克服此一问题点，习惯上是在浸渍镀敷浴中使用各种添加剂，例如增速剂。然而，这些添加剂可能会对于沉积物的其它重要特性，例如黏着力以及沉积均匀性，产生不利的影响。There are still many limitations to the use of dip plating when manufacturing printed wiring boards. These limitations include relatively slow plating speeds and limitations in deposit thickness due to immersion plating itself, i.e., as the metal deposit expands, it tends to mask the underlying metal, thereby preventing further immersion plating. replacement. To overcome this problem, it is customary to use various additives such as accelerators in the immersion plating bath. However, these additives may adversely affect other important properties of the deposit, such as adhesion and deposition uniformity.
使用常用的银镀敷浴所产生的另一项问题是所形成的银沉积物不平坦或厚度不均匀。这种不平坦的沉积在沉积物的各处具有明显的厚度变化，也就是说，该沉积在某些区域相当厚，而其它区域则相当薄。因此，这种常用的浸渍银镀敷浴很难获得厚度均匀得银层。Another problem that arises with the use of conventional silver plating baths is that the silver deposits formed are not flat or of uniform thickness. This uneven deposit has a pronounced thickness variation throughout the deposit, that is, the deposit is relatively thick in some areas and relatively thin in other areas. Therefore, it is difficult to obtain a silver layer with a uniform thickness in this commonly used immersion silver plating bath.
所以，仍需要一种可以改善浸渍镀敷银沉积的均匀性的方法。更需要一种不会对浸渍镀敷浴所获得的银沉积的重要特性产生不利影响的方法。Therefore, there remains a need for a method that can improve the uniformity of immersion plating silver deposition. There is a further need for a method that does not adversely affect the important characteristics of silver deposits obtained by immersion plating baths.
吡啶甲酸已被用于银与铜的除锈剂组合物，参见印度专利第163677号。Zhuang等人Huaxue Xuebao，1985，vol.43，no.2，pp120-125，亦揭示自含有硝酸银、氨、及吡啶羧酸的镀敷浴电沉积银。但是，这些文献并未揭示在浸渍或无电的银镀敷浴中使用吡啶甲酸。Picolinic acid has been used in silver and copper rust remover compositions, see Indian Patent No. 163677. Zhuang et al. Huaxue Xuebao, 1985, vol. 43, no. 2, pp 120-125, also disclose electrodeposition of silver from plating baths containing silver nitrate, ammonia, and pyridine carboxylic acid. However, these documents do not disclose the use of picolinic acid in immersion or electroless silver plating baths.
发明内容Contents of the invention
已发现含有一或多种羧酸取代的含氮杂环化合物的浸渍银镀敷浴可以形成厚度受控制的银层，该银层相较于不含这种化合物的习用浸渍沉积法所获得的银沉积物具有经改善的厚度均匀性与光泽。It has been found that immersion silver plating baths containing one or more carboxylic acid-substituted nitrogen-containing heterocyclic compounds can form silver layers of controlled thickness compared to those obtained by conventional immersion deposition methods without such compounds. Silver deposits have improved thickness uniformity and gloss.
本发明提供一种浸渍银镀敷浴的组合物，该组合物包含一或多种银离子来源、水、一或多种络合试、以及一或多种羧酸取代的含氮杂环化合物，其中该镀敷浴系不含氨以及铵离子。The present invention provides an immersion silver plating bath composition comprising one or more sources of silver ions, water, one or more complexing reagents, and one or more carboxylic acid substituted nitrogen-containing heterocyclic compounds , wherein the plating bath system does not contain ammonia and ammonium ions.
本发明亦提供一种在基材上沉积银层的方法，该方法包含使基材与浸渍银镀敷浴接触的步骤，该基材具有一金属层且该金属相较于银具有较小的正电性，该浸渍银镀敷浴包含一或多种银离子来源、水、一或多种络合试、以及一或多种羧酸取代的含氮杂环化合物，其中该镀敷浴系不含氨以及铵离子。The present invention also provides a method of depositing a silver layer on a substrate, the method comprising the step of contacting the substrate with an immersion silver plating bath, the substrate having a metal layer and the metal having a smaller Electropositive, the immersion silver plating bath comprises one or more sources of silver ions, water, one or more complexing reagents, and one or more carboxylic acid-substituted nitrogen-containing heterocyclic compounds, wherein the plating bath is Free of ammonia and ammonium ions.
本发明还提供一种改善浸渍银镀敷浴所沉积的银层的厚度均匀性的方法，该方法包含下列步骤：a)提供一浸渍银镀敷浴，该镀敷浴包含一或多种羧酸取代的含氮杂环化合物、一或多种银离子来源、水、及一或多种络合试；以及b)使基材与浸渍银镀敷浴接触足以沉积所需厚度的银层的时间，该基材具有一金属层且该金属相较于银具有较小的正电性。The present invention also provides a method of improving the thickness uniformity of a silver layer deposited from an immersion silver plating bath, the method comprising the steps of: a) providing an immersion silver plating bath comprising one or more carboxyl an acid-substituted nitrogen-containing heterocyclic compound, one or more sources of silver ions, water, and one or more complexing reagents; and b) contacting the substrate with an immersion silver plating bath sufficient to deposit a silver layer of desired thickness Time, the substrate has a metal layer and the metal is less electropositive than silver.
具体实施方式Detailed ways
本说明书中，除非另有明确地指出，下列缩写即表示下列意义：℃＝摄氏温度；ca.＝大约＝接近；g＝克；L＝升；g/L＝克/升；mL＝毫升；wt％＝重量百分比；DI＝去离子的；cm＝公分；μin.＝微英吋；以及μm＝微米(1μin.＝0.0254μm)。In this specification, unless otherwise clearly indicated, the following abbreviations have the following meanings: °C=Celsius; ca.=about=close; g=gram; L=liter; g/L=gram/liter; mL=milliliter; wt% = percent by weight; DI = deionized; cm = centimeter; μin. = microinch; and μm = micrometer (1 μin. = 0.0254 μm).
本说明书全文中“印刷电路板”与“印刷线路板”可以交替使用。在本说明书中术语“络合试”包含配位与螯合试剂。除非另有说明，所有的量均为重量百分比以及所有比例皆以重量计。所有的数字范围皆为包含的且可以任何顺序组合，除非这些数字范围系明显地限制在100％以下。Throughout this specification, "printed circuit board" and "printed circuit board" may be used interchangeably. In this specification the term "complexing reagent" includes complexing and chelating reagents. Unless otherwise indicated, all amounts are percent by weight and all ratios are by weight. All numerical ranges are inclusive and combinable in any order unless such numerical ranges are expressly limited to less than 100%.
本发明提供一种改善浸渍银镀敷浴所沉积的银层的厚度均匀性的方法。术语“改善厚度均匀性”是指沉积银层的方法相较于习用方法，其各处沉积的厚度更均匀。此系使用含有一或多种银离子来源、水、一或多种络合试、以及一或多种羧酸取代的含氮杂环化合物的浸渍镀敷浴且该镀敷浴不含氨及铵离子而达成。本发明提供一种自浸渍银镀敷浴沉积的银层，该银层相较于使用习用浸渍银镀敷浴浸渍沉积的银层具有经改善的厚度均匀性。根据本发明所获得改善厚度均匀性的银沉积亦提供印刷线路板与表面黏着组件之间的较佳表面黏着连接。The present invention provides a method of improving the thickness uniformity of silver layers deposited from immersion silver plating baths. The term "improved thickness uniformity" refers to a method of depositing a silver layer that deposits a more uniform thickness throughout than conventional methods. This system uses an immersion plating bath containing one or more sources of silver ions, water, one or more complexing reagents, and one or more carboxylic acid-substituted nitrogen-containing heterocyclic compounds and the plating bath is free of ammonia and achieved by ammonium ions. The present invention provides a silver layer deposited from an immersion silver plating bath having improved thickness uniformity compared to a silver layer deposited by immersion using conventional immersion silver plating baths. The silver deposition with improved thickness uniformity obtained according to the invention also provides better surface mount connections between printed wiring boards and surface mount components.
任何水可溶的银盐均可用作为本发明镀敷浴的银离子来源。适合的银盐包含，但不限于硝酸银、乙酸银、硫酸银、乳酸银、以及甲酸银。典型地，该银离子来源为硝酸银。亦可使用银盐混合物。该一或多种银离子来源通常系以足以在溶液中提供0.06至32克/升的银离子浓度的量存在，更典型为0.1至25克/升，又更典型为0.5至15克/升。Any water-soluble silver salt can be used as the source of silver ions for the plating baths of the present invention. Suitable silver salts include, but are not limited to, silver nitrate, silver acetate, silver sulfate, silver lactate, and silver formate. Typically, the source of silver ions is silver nitrate. Mixtures of silver salts may also be used. The one or more sources of silver ions are generally present in an amount sufficient to provide a silver ion concentration in the solution of 0.06 to 32 g/L, more typically 0.1 to 25 g/L, still more typically 0.5 to 15 g/L .
亦可使用多种不同的络合或螯合试剂。这种螯合试剂可为单齿配体，例如氰化物及吡啶、或多齿配位体。适合的多齿配位体包含，但非限于：具有2至10个碳原子的氨基酸类；聚羧酸类，例如乙二酸、己二酸、丁二酸、丙二酸、及马来酸；胺基乙酸类，例如氮川三乙酸；烷撑多元胺聚乙酸类，例如乙二胺四乙酸(“EDTA”)、二乙三胺五乙酸(“DTPA”)、N-(2-羟乙基)乙二胺三乙酸、1，3-二胺基-2-丙醇-N，N，N’，N’-四乙酸、双-(羟苯基)-乙二胺二乙酸、二胺基环己烷四乙酸、或乙二醇-双-((β-胺基乙基醚)-N，N’-四乙酸)；多元胺类，例如N，N，N’，N’-四-(2-羟丙基)乙二胺、乙二胺、2，2’，2”-三胺基三乙基胺、三乙四胺、二乙三胺、及四(胺基乙基)乙二胺；柠檬酸盐类；酒石酸盐类；N，N-二-(2-羟乙基)甘氨酸；葡糖酸盐类；环状醚类；穴状配体；多羟基化合物，例如2，2’，2”-氮川三乙醇；杂芳香族化合物，例如2，2’-联二吡啶、1，10-啡咯啉、及8-羟基喹啉；含硫配位体，例如巯基乙酸、及二乙基二硫代胺基甲酸；以及胺基醇类，例如乙醇胺、二乙醇胺、及三乙醇胺。熟习该项领域的技术者应了解螯合试剂的组合亦可用于本发明。A variety of different complexing or chelating agents can also be used. Such chelating agents may be monodentate ligands, such as cyanide and pyridine, or multidentate ligands. Suitable multidentate ligands include, but are not limited to: amino acids having 2 to 10 carbon atoms; polycarboxylic acids such as oxalic acid, adipic acid, succinic acid, malonic acid, and maleic acid ; aminoacetic acids, such as nitrilotriacetic acid; alkylene polyamine polyacetic acids, such as ethylenediaminetetraacetic acid ("EDTA"), diethylenetriaminepentaacetic acid ("DTPA"), N-(2-hydroxy Ethyl)ethylenediaminetriacetic acid, 1,3-diamino-2-propanol-N,N,N',N'-tetraacetic acid, bis-(hydroxyphenyl)-ethylenediaminediacetic acid, di Aminocyclohexanetetraacetic acid, or ethylene glycol-bis-((β-aminoethyl ether)-N,N'-tetraacetic acid); polyamines, such as N,N,N',N'- Tetrakis-(2-hydroxypropyl)ethylenediamine, ethylenediamine, 2,2',2"-triaminotriethylamine, triethylenetetramine, diethylenetriamine, and tetrakis(aminoethyl) ) ethylenediamine; citrates; tartrates; N,N-bis-(2-hydroxyethyl) glycine; gluconates; cyclic ethers; cryptands; polyols such as 2,2',2"-nitrotriethanol; heteroaromatic compounds such as 2,2'-bipyridine, 1,10-phenanthroline, and 8-hydroxyquinoline; sulfur-containing ligands such as Thioglycolic acid, and diethyldithiocarbamic acid; and amino alcohols, such as ethanolamine, diethanolamine, and triethanolamine. Those skilled in the art will appreciate that combinations of chelating agents may also be used in the present invention.
可以使用不同浓度的络合试，典型地以化学计量等量(以银离子量计)或过量存在于浸渍银镀敷浴中，使所有银离子均得以络合。文中所使用的术语“化学计量”系指等摩尔。通常，该一或多种络合试系以高于银离子摩尔浓度的量存在。典型地，该络合试对银离子的摩尔比系≥1∶1，典型系≥1.2∶1，更典型系≥2.0∶1，以及又更典型系≥3.0∶1。通常，该一或多种络合试的总量为从0.1至250克/升。该一或多种络合试的其它适合量为从2至220克/升、自10至200克/升、以及自50至150克/升。Various concentrations of complexing agent can be used, typically present in the immersion silver plating bath in stoichiometric equivalents (based on the amount of silver ions) or in excess to allow complexation of all silver ions. The term "stoichiometric" as used herein means equimolar. Typically, the one or more complexing reagents are present in an amount above the molar concentration of silver ions. Typically, the molar ratio of the complexing agent to silver ion is > 1:1, typically > 1.2:1, more typically > 2.0:1, and still more typically > 3.0:1. Typically, the total amount of the one or more complexing reagents is from 0.1 to 250 g/l. Other suitable amounts of the one or more complexing agents are from 2 to 220 g/L, from 10 to 200 g/L, and from 50 to 150 g/L.
在不欲受限于理论下，相信该羧酸取代的含氮杂环化合物系用作为镀敷速率抑制剂、厚度均匀性增进剂、以及光亮剂。“羧酸取代的含氮杂环化合物”系指任何含氮杂环化合物所具有的一或多个氢被一或多个羧酸基团(-CO2H)取代。亦可使用多种不同的含氮杂环部分，例如，但非限于：吡啶、哌啶、哌嗪、吗啡、吡咯、吡咯啶、三唑、以及咪唑。这种杂环化合物亦可稠合至另一环，例如苯并三唑、苯并咪唑、喹啉或异喹啉；或亦可进一步被取代；或稠合至另一环并被取代。适合的取代基包含，但不限于：羟基、(C1-C10)烷基、(C1-C10)烷氧基、及卤素。羧酸取代的含氮杂环化合物的实例包含，但不限于：吡啶羧酸、吡啶二羧酸、吡啶三羧酸、吡啶羧酸、哌嗪羧酸、及吡咯羧酸。特别有用的是吡啶羧酸，例如吡啶甲酸、喹啉酸(quonolinic acid)、烟酸、及镰孢菌酸。这些化合物通常系市售可得者，例如购自Sigma-Aldrich(Milwaukee，Wisconsin)，或根据文献中已知的方法加以制备。可以使用多种不同浓度的羧酸取代的含氮杂环化合物，典型地这种化合物的总量为从0.01至100克/升、更典型为从0.1至50克/升、又更典型从0.5至25克/升、更典型从1至20克/升。熟习该项领域的技术者应了解，亦可使用一种以上的羧酸取代的含氮杂环化合物。Without wishing to be bound by theory, it is believed that the carboxylic acid substituted nitrogen-containing heterocyclic compounds act as plating rate inhibitors, thickness uniformity enhancers, and brighteners. "Carboxylic acid substituted nitrogen-containing heterocyclic compound" refers to any nitrogen-containing heterocyclic compound in which one or more hydrogens are replaced by one or more carboxylic acid groups (-CO2 H). A variety of different nitrogen-containing heterocyclic moieties can also be used, such as, but not limited to, pyridine, piperidine, piperazine, morphine, pyrrole, pyrrolidine, triazole, and imidazole. Such heterocyclic compounds may also be fused to another ring, such as benzotriazole, benzimidazole, quinoline or isoquinoline; or may be further substituted; or fused to another ring and substituted. Suitable substituents include, but are not limited to, hydroxy, (C1 -C10 )alkyl, (C1 -C10 )alkoxy, and halogen. Examples of carboxylic acid substituted nitrogen-containing heterocyclic compounds include, but are not limited to, pyridinecarboxylic acid, dipicolinic acid, pyridinetricarboxylic acid, pyridinecarboxylic acid, piperazinecarboxylic acid, and pyrrolecarboxylic acid. Particularly useful are pyridinecarboxylic acids such as picolinic acid, quonolinic acid, nicotinic acid, and fusaric acid. These compounds are generally available commercially, eg, from Sigma-Aldrich (Milwaukee, Wisconsin), or prepared according to methods known in the literature. A variety of concentrations of carboxylic acid substituted nitrogen-containing heterocyclic compounds can be used, typically in total amounts of such compounds from 0.01 to 100 g/L, more typically from 0.1 to 50 g/L, still more typically from 0.5 to 25 g/l, more typically from 1 to 20 g/l. Those skilled in the art will appreciate that more than one carboxylic acid substituted nitrogen-containing heterocyclic compound may also be used.
本发明的镀敷浴典型具有1至14的pH值。较佳者，该镀敷浴的pH≥7，以及更佳pH≥8。特别适合的镀敷浴的pH≥8.5，以及特佳为pH≥9。亦可添加缓冲试剂使镀敷浴的pH值维持在所需值。任何可兼容的酸或碱均可用作为缓冲试剂，其可为有机的或无机的。“可兼容的”酸或碱是指使用足量的这些酸或碱使溶液的pH值具有缓冲特性时，该酸或碱不会与溶液中的银离子及/或络合试发生沉淀。缓冲试剂的示例包含，但不限于：碱金属的氢氧化物，例如氢氧化钠、氢氧化钾，碳酸盐类，柠檬酸，酒石酸，硝酸，乙酸、及磷酸。Plating baths of the present invention typically have a pH of 1 to 14. Preferably, the pH of the plating bath is ≥ 7, and more preferably pH ≥ 8. Particularly suitable plating baths have a pH≧8.5, and particularly preferably a pH≧9. Buffering reagents may also be added to maintain the pH of the plating bath at the desired value. Any compatible acid or base can be used as buffering agent, which may be organic or inorganic. "Compatible" acids or bases are those acids or bases that do not precipitate with silver ions and/or complexing reagents in solution when sufficient amounts of these acids or bases are used to impart buffering properties to the pH of the solution. Examples of buffering agents include, but are not limited to: alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, carbonates, citric acid, tartaric acid, nitric acid, acetic acid, and phosphoric acid.
该浸渍银镀敷浴亦可视需要含有一或多种添加成分。适合的添加成分包含，但不限于表面活性剂或湿润剂、银的抗锈剂、抗氧化剂、平整剂、微晶剂、增厚剂、消泡剂、及染料。表面活性剂用于本发明的浸渍镀敷浴时，其用量典型为从0.02至100克/升、更典型为从0.1至25克/升、又更典型为从1至15克/升。这种表面活性剂可为阴离子表面活性剂、阳离子表面活性剂、非离子性表面活性剂、或两性的表面活性剂。表面活性剂的选用系依据所使用的特定浸渍银镀敷浴而定。使用表面活性剂时，以非离子性表面活性剂较佳。The immersion silver plating bath may also optionally contain one or more additional ingredients. Suitable additional ingredients include, but are not limited to, surfactants or wetting agents, silver rust inhibitors, antioxidants, levelers, microcrystalline agents, thickeners, defoamers, and dyes. Surfactants are typically used in the immersion plating baths of the present invention in amounts of from 0.02 to 100 grams/liter, more typically from 0.1 to 25 grams/liter, still more typically from 1 to 15 grams/liter. Such surfactants may be anionic surfactants, cationic surfactants, nonionic surfactants, or amphoteric surfactants. The choice of surfactant will depend on the particular immersion silver plating bath being used. When using a surfactant, a nonionic surfactant is preferred.
亦可使用多种不同的银的抗锈剂，例如三唑、四唑、以及咪唑。这种抗锈剂已为该项领域的技术者所公知。这种抗锈剂的用量为从0.001至50克/升，典型地为从0.005至25克/升，更典型地为从0.01至10克/升。A number of different silver rust inhibitors can also be used, such as triazoles, tetrazoles, and imidazoles. Such antirust agents are known to those skilled in the art. Such rust inhibitors are used in amounts of from 0.001 to 50 g/l, typically from 0.005 to 25 g/l, more typically from 0.01 to 10 g/l.
亦可添加微晶剂改善银沉积的外观。适合的微晶剂包含(C1-C6)醇类以及聚烷醇类，如聚乙二醇。这种微晶剂的用量典型为从0.02至200克/升，较佳为从0.05至100克/升。Microcrystalline agents can also be added to improve the appearance of the silver deposit. Suitable microcrystalline agents include (C1 -C6 )alcohols and polyalkanols, such as polyethylene glycol. Such microcrystalline agents are typically used in amounts of from 0.02 to 200 g/l, preferably from 0.05 to 100 g/l.
较佳者，该浸渍银镀敷浴系不含能够还原银离子的还原剂。更佳者为该浸渍银镀敷浴系不含氰化物离子、氨(NH3)、以及铵离子(即，NH4+)。Preferably, the immersion silver plating bath is free of reducing agents capable of reducing silver ions. More preferably, the immersion silver plating bath is free of cyanide ions, ammonia (NH3 ), and ammonium ions (ie, NH4+ ).
典型地，该浸渍银镀敷浴可依任何顺序，通过结合上述成分而制备。较佳者，该镀敷浴系先将络合试添加至水中形成溶液，再将银离子来源添加至该溶液制备而成。视需要的成分可以以任何顺序与该溶液相组合。Typically, the immersion silver plating bath can be prepared by combining the above ingredients in any order. Preferably, the plating bath is prepared by first adding complexing agent to water to form a solution, and then adding a source of silver ions to the solution. Optional ingredients can be combined with the solution in any order.
该浸渍银镀敷浴亦可经搅拌。可使用任何形式的搅拌。适当的搅拌包含，但不限于搅动、摇动、旋转、曝气、以及音波震动。搅动亦可通过其它适合的方式达成，例如通过悬吊式搅拌器、桨式搅拌器、或搅拌子系统。摇动亦可以不同的方式达成，例如在镀敷浴中以前后方向或以侧向摇动欲镀敷银的基材。曝气可通过起泡或充气的方式将气体注入镀敷浴中，或使用喷雾器，例如利用漩涡喷嘴而达成。透过经烧结的装置(例如，具有玻璃、聚(四氟乙烯)、或其它惰性材料所构成的烧结物的管)利用起泡的方式将气体注入镀敷浴中亦可达成充气。任何气体均可使用，例如空气、氧或惰性气体，较佳者为空气。在特定的具体实例中，使用曝气的方式搅拌镀敷浴。旋转通过实质环形地移动镀敷浴或欲镀敷的基材而达成。该项领域的技术者应了解，亦可结合搅拌方法加以使用，例如结合曝气与搅动。The immersion silver plating bath can also be stirred. Any form of agitation can be used. Suitable agitation includes, but is not limited to, agitation, shaking, rotation, aeration, and sonic vibration. Agitation can also be achieved by other suitable means, such as overhead stirrer, paddle stirrer, or stirring subsystem. Shaking can also be achieved in different ways, for example shaking the substrate to be plated with silver in a back-and-forth direction or sideways in the plating bath. Aeration can be achieved by injecting gas into the coating bath by bubbling or aerating, or using sprayers, for example using swirl nozzles. Aeration can also be achieved by bubbling gas into the plating bath through a sintered device (eg, a tube with a sinter of glass, poly(tetrafluoroethylene), or other inert material). Any gas can be used, such as air, oxygen or an inert gas, preferably air. In certain embodiments, aeration is used to agitate the plating bath. Rotation is achieved by moving the plating bath or substrate to be plated substantially circularly. Those skilled in the art will appreciate that a combination of agitation methods, such as a combination of aeration and agitation, can also be used.
通过使金属层与本发明的镀敷浴的接触，可使银沉积在具有正电性小于银的金属层的任何基材。这种接触可以通过多种不同的方式，例如，但不限于浸没、喷洒、及溢流涂覆(flood coating)。特别适合用以与本发明的组合物接触的方法系溢流模式的喷洒。Silver can be deposited on any substrate having a metal layer that is less electropositive than silver by contacting the metal layer with the plating bath of the present invention. This contacting can be by various means such as, but not limited to, immersion, spraying, and flood coating. A particularly suitable method for contacting the compositions of the invention is spraying in flood mode.
相较于银具有较小正电性的适合金属包含，但不限于锌、铁、锡、镍、铅、铜、或含有一或多种这些金属的合金。特别适合的金属为锡、铜、或锡或铜的合金。特别适合的合金为锡-铜合金。在另一具体实例中，根据本发明沉积浸渍银层前，这种金属本身可经浸渍沉积于适合的金属底层上。例如，该金属可为锡，这种锡是先通过例如浸渍、无电或电解沈淀，沉积在铜上。Suitable metals that are less electropositive than silver include, but are not limited to, zinc, iron, tin, nickel, lead, copper, or alloys containing one or more of these metals. Particularly suitable metals are tin, copper, or alloys of tin or copper. A particularly suitable alloy is a tin-copper alloy. In another embodiment, the metal itself may be immersion deposited on a suitable metal underlayer prior to depositing the immersion silver layer according to the invention. For example, the metal may be tin which is first deposited on copper, for example by immersion, electroless or electrolytic precipitation.
镀敷银之前，较佳系先清洗欲镀敷的金属。清洗为从金属表面移除氧化物与有机污染物以及阻剂残渣，该阻剂残渣系由铜表面未完全显影的光阻剂以及拒焊层残留物所留存下来。这种清洗可利用任何适当的清洗步骤及/或产品。例如，该金属层系铜或铜合金时，使用酸性清洗组合物清洗该金属层较佳。这种清洗程序系熟习该项领域的技术者所能完成。清洗完成后，该基材被洗涤，例如以水洗涤，并视需要加以干燥。该金属层可在清洗步骤前或在清洗步骤后进行微蚀刻，较佳者系在清洗步骤后进行。这种微蚀刻通过使基材上的金属层与微蚀刻组合物接触而达成，该微蚀刻组合物系例如硫酸/过氧化氢或碱金属过硫酸盐，例如过硫酸钠或过硫酸钾。进行这种微蚀刻步骤时，该金属层可接着以水或酸(例如，硫酸)洗涤，以移除清洗及/或蚀刻步骤的残余物。Prior to silver plating, it is preferable to clean the metal to be plated. Cleaning removes oxide and organic contaminants from metal surfaces as well as resist residue left behind by underdeveloped photoresist and solder repellant residue on copper surfaces. Such cleaning may utilize any suitable cleaning steps and/or products. For example, when the metal layer is copper or copper alloy, it is better to use an acidic cleaning composition to clean the metal layer. Such cleaning procedures are within the capabilities of those skilled in the art. After rinsing is complete, the substrate is washed, for example with water, and optionally dried. The metal layer can be microetched before or after the cleaning step, preferably after the cleaning step. This microetching is achieved by contacting the metal layer on the substrate with a microetching composition such as sulfuric acid/hydrogen peroxide or an alkali metal persulfate such as sodium or potassium persulfate. When such a microetching step is performed, the metal layer may then be washed with water or an acid (eg, sulfuric acid) to remove residues of the cleaning and/or etching steps.
视需要，欲镀敷银的金属在清洗后以及与银镀敷浴接触之前，可以与预处理组合物接触。任何适当的预处理组合物均可使用。较佳的预处理组合物包含一或多种唑化合物、水、以及螯合试剂。Optionally, the metal to be plated with silver may be contacted with a pretreatment composition after rinsing and prior to contact with the silver plating bath. Any suitable pretreatment composition can be used. Preferred pretreatment compositions comprise one or more azole compounds, water, and a chelating agent.
多种适当的唑化合物均可用于本发明。适当的唑化合物包含，但非限于三唑、苯并三唑、四唑、咪唑、苯并咪唑、吲唑、及其混合物。这种唑化合物可视需要被取代。A wide variety of suitable azole compounds find use in the present invention. Suitable azole compounds include, but are not limited to, triazoles, benzotriazoles, tetrazoles, imidazoles, benzimidazoles, indazoles, and mixtures thereof. Such azole compounds may be optionally substituted.
特别适合的唑化合物是苯并三唑、被取代的苯并三唑、咪唑或被取代的咪唑，特别典型者为苯并三唑、咪唑、(C1-C16)烷基咪唑、及芳基咪唑。苯基咪唑系较佳的芳基咪唑。(C1-C16)烷基咪唑的示例包含甲基咪唑、乙基咪唑、丙基咪唑、己基咪唑、癸基咪唑、及十一烷基咪唑。这种唑化合物通常系市售可得者，例如购自Sigma-Aldrich(Milwaukee，Wisconsin)，且不需进一步纯化即可使用。该唑化合物可以以不同范围的用量用于本发明。典型地，该唑化合物的用量为从0.005至50克/升。其它适合的量为从0.005至20克/升，以及自0.01至15克/升。唑化合物的用量系依据所选用的特定唑化合物及该化合物在预处理组合物中的溶解度而定。Particularly suitable azole compounds are benzotriazoles, substituted benzotriazoles, imidazoles or substituted imidazoles, particularly typical benzotriazoles, imidazoles, (C1 -C16 )alkylimidazoles, and aromatic Kimidazole. Phenylimidazoles are preferred arylimidazoles. Examples of (C1 -C16 )alkylimidazoles include methylimidazole, ethylimidazole, propylimidazole, hexylimidazole, decylimidazole, and undecylimidazole. Such azole compounds are generally commercially available, eg, from Sigma-Aldrich (Milwaukee, Wisconsin), and used without further purification. The azole compounds can be used in the present invention in varying amounts. Typically, the azole compound is used in an amount of from 0.005 to 50 g/l. Other suitable amounts are from 0.005 to 20 g/l, and from 0.01 to 15 g/l. The amount of azole compound used will depend on the particular azole compound selected and the solubility of that compound in the pretreatment composition.
这种预处理组合物可为碱性或酸性，且具有1至14的pH值。可以改变该预处理组合物的pH值，以增加唑化合物的溶解度。例如，通过增加预处理组合物的pH值，增加苯并三唑的溶解度。This pretreatment composition may be alkaline or acidic and have a pH of 1 to 14. The pH of the pretreatment composition can be varied to increase the solubility of the azole compound. For example, by increasing the pH of the pretreatment composition, the solubility of the benzotriazole is increased.
可以使用多种不同的有机与无机酸，或有机与无机碱调整该预处理组合物的pH值。适合的无机酸包含，但非限于氢氯酸、氢氟酸、氟溴酸、高碘酸、磷酸、硫酸、及硝酸。适合的有机酸包含，但非限于烷基磺酸、及芳基磺酸。适合的无机碱包含，但非限于碱金属氢氧化物碳酸盐，及氢氧化铵。适合的有机碱包含，但非限于四烷基铵氢氧化物、及胺类。该酸及/或碱在该预处理组合物中典型地系以足以提供所需pH值的足量存在。The pH of the pretreatment composition can be adjusted using a variety of different organic and inorganic acids, or organic and inorganic bases. Suitable inorganic acids include, but are not limited to, hydrochloric, hydrofluoric, hydrobromic, periodic, phosphoric, sulfuric, and nitric acids. Suitable organic acids include, but are not limited to, alkylsulfonic acids, and arylsulfonic acids. Suitable inorganic bases include, but are not limited to, alkali metal hydroxide carbonates, and ammonium hydroxide. Suitable organic bases include, but are not limited to, tetraalkylammonium hydroxides, and amines. The acid and/or base are typically present in the pretreatment composition in sufficient amounts to provide the desired pH.
较佳者，该预处理组合物更进一步包含一或多种螯合试剂。这种螯合试剂可为单齿配体，例如氨、氰化物、及吡啶，或多齿配位体。较佳者，该螯合试剂系与后续浸渍银镀敷浴所使用者相同。其它的添加成分亦可视需要地用于该预处理组合物中。这种添加成分包含，但非限于表面活性剂、及金属离子。该表面活性剂可为阴离子表面活性剂、阳离子表面活性剂、非离子性表面活性剂、或两性的表面活性剂。在该预处理组合物中使用表面活性剂时，典型地以至少0.001重量％的量存在，更典型至少0.005重量％，又更典型至少0.01重量％。亦可适当地使用表面活性剂的混合物。Preferably, the pretreatment composition further comprises one or more chelating agents. Such chelating agents may be monodentate ligands, such as ammonia, cyanide, and pyridine, or multidentate ligands. Preferably, the chelating reagent is the same as that used in the subsequent immersion silver plating bath. Other additional ingredients may also be used in the pretreatment composition as desired. Such additional ingredients include, but are not limited to, surfactants, and metal ions. The surfactant may be an anionic surfactant, a cationic surfactant, a nonionic surfactant, or an amphoteric surfactant. Surfactants, when used in the pretreatment composition, are typically present in an amount of at least 0.001 wt%, more typically at least 0.005 wt%, still more typically at least 0.01 wt%. Mixtures of surfactants may also be suitably used.
金属离子存在于该预处例组合物中时，较佳者系该金属即为银要沉积于其上的金属。例如，银要浸渍沉积在铜上时，较佳者系存在于预处理组合物中的金属离子即为铜离子。When metal ions are present in the pre-preparation composition, it is preferred that the metal is the metal on which the silver is to be deposited. For example, where silver is to be dip-deposited on copper, it is preferred that the metal ions present in the pretreatment composition be copper ions.
添加至预处理组成中的金属离子的量依据正电性小于银的特定金属、所使用的特定唑化合物、以及预处理组合物的pH值而定。例如，铜离子存在于预处理组合物中时，其典型地系以至1克/升的量存在，更典型系以至0.05克/升的量存在。The amount of metal ions added to the pretreatment composition depends on the particular metal that is less electropositive than silver, the particular azole compound used, and the pH of the pretreatment composition. For example, when copper ions are present in the pretreatment composition, they are typically present in an amount of up to 1 gram per liter, more typically up to 0.05 gram per liter.
通常，该金属系与该预处理组合物接触一段充分的时间，以增加后续浸渍镀敷所沉积的银层的黏着性。该充分的时间依据所选用的特定金属以及预处理组合物而定。典型地，接触时间系以1秒至15分钟为充分，更典型系5秒至10分钟，又更典型系10秒至5分钟。Typically, the metal system is contacted with the pretreatment composition for a sufficient period of time to increase the adhesion of the silver layer deposited by subsequent immersion plating. The sufficient time will depend upon the particular metal and pretreatment composition selected. Typically, a contact time of from 1 second to 15 minutes is sufficient, more typically from 5 seconds to 10 minutes, and still more typically from 10 seconds to 5 minutes.
该金属与该预处理组合物接触完毕后，可视需要使用例如水进行洗涤，接着视需要进行干燥。进行这种洗涤步骤系较佳者。After the metal has been contacted with the pretreatment composition, it may optionally be washed with, for example, water, followed by optional drying. It is preferred to carry out this washing step.
根据本发明所沉积的银通过使正电性小于银的金属与本发明浸渍银镀敷浴接触。可通过任何适当的方式达成这种接触，例如浸没、喷洒、及溢流涂覆。使用直立式镀敷设备时，该基材典型地浸没于本发明的银镀敷浴中。使用水平式镀敷设备时，该基材典型地以喷洒或溢流的方式与本发明的银镀敷浴接触。Silver is deposited according to the present invention by contacting a metal that is less electropositive than silver with the immersion silver plating bath of the present invention. Such contacting can be achieved by any suitable means, such as immersion, spraying, and flood coating. When using vertical plating equipment, the substrate is typically immersed in the silver plating bath of the present invention. When using horizontal plating equipment, the substrate is typically contacted with the silver plating bath of the present invention by spraying or flooding.
该金属与浸渍银镀敷浴接触的时间应足以沉积所需的银厚度。典型地，该接触时间为从约10秒至15分钟，更典型为从20秒至15分钟，又更典型为从30秒至12分种。The time the metal is in contact with the immersion silver plating bath should be sufficient to deposit the desired thickness of silver. Typically, the contact time is from about 10 seconds to 15 minutes, more typically from 20 seconds to 15 minutes, still more typically from 30 seconds to 12 minutes.
本发明浸渍银镀敷浴可在不同温度下使用。适合的温度包含自10至70℃的范围。其它适合的温度范围为从15至60℃的范围，以及自20至55℃。The immersion silver plating baths of the present invention can be used at different temperatures. Suitable temperatures comprise the range from 10 to 70°C. Other suitable temperature ranges are the range from 15 to 60°C, and from 20 to 55°C.
该银沉积典型地系具有35μin.(0.9μm)或以下的厚度，更典型30μin.(0.76μm)或以下，又更典型25μin.(0.64μm)或以下的厚度。沉积后，该银层系用例如水进行洗涤。在进行后续加工步骤前，该银层可视需要进行干燥。The silver deposit typically has a thickness of 35 μin. (0.9 μm) or less, more typically 30 μin. (0.76 μm) or less, still more typically 25 μin. (0.64 μm) or less. After deposition, the silver layer is washed with, for example, water. The silver layer may optionally be dried prior to subsequent processing steps.
通常，相较于银具有较小正电性的金属是基材上的金属层。根据本发明可以使用多种具有正电性小于银的金属层的基材进行镀敷。适合的基材包含，但不限于珠宝、装饰品、艺术品、半导体封装件、导线框、焊块、金属粉末、金属箔(例如，铜箔)、以及印刷线路板基材。本发明特别适合用于在印刷线路板上沉积可焊接的银镀层。再者，本发明提供一种制造印刷线路板的方法，该方法包含使正电性小于银的金属与浸渍银镀敷浴接触形成银层的步骤，该浸渍银镀敷浴含有一或多种银离子来源、水、一或多种络合试、以及一或多种羧酸取代的含氮杂环化合物，其中该浸渍银镀敷浴系不含氨以及铵离子。该银层系于印刷线路板上作为可焊接的镀层。这种可焊接的镀层典型地形成于具有焊垫、贯孔、以及罩幕(例如，拒焊层)的印刷线路板基材。在这种印刷线路板基材中，经曝露的焊垫与贯孔通常系含有铜层。Typically, the metal that is less electropositive than silver is the metal layer on the substrate. A wide variety of substrates having a metal layer that is less electropositive than silver can be used for plating according to the invention. Suitable substrates include, but are not limited to, jewelry, ornaments, artwork, semiconductor packages, lead frames, solder bumps, metal powders, metal foils (eg, copper foil), and printed wiring board substrates. The invention is particularly suitable for depositing solderable silver coatings on printed wiring boards. Furthermore, the present invention provides a method of manufacturing a printed wiring board comprising the step of forming a silver layer by contacting a metal less electropositive than silver with an immersion silver plating bath containing one or more A source of silver ions, water, one or more complexing reagents, and one or more carboxylic acid substituted nitrogen-containing heterocyclic compounds, wherein the immersion silver plating bath is free of ammonia and ammonium ions. The silver layer is applied to the printed circuit board as a solderable plating. Such solderable plating is typically formed on a printed wiring board substrate having solder pads, vias, and a mask (eg, a solder resist layer). In such printed circuit board substrates, the exposed pads and vias usually contain a copper layer.
在另一具体实例中，本发明亦适合用于具有经曝露的焊垫及/或贯孔且含有锡-银合金作为可焊镀层的印刷线路板基材。因此，本发明亦提供一种制造印刷线路板的方法，该方法系包含下列步骤：a)提供一印刷线路板基材，该基材具有焊垫、贯孔、拒焊层、及金属层；b)在该金属层上沉积锡层；c)使该经锡镀敷的印刷线路板基材与浸渍银镀敷浴接触而在该锡沉积上形成浸渍银沉积，该镀敷浴包含一或多种银离子来源、水、一或多种络合试、以及一或多种羧酸取代的含氮杂环化合物；以及d)加热该银-锡沉积形成锡-银合金。于一具体实例中，该金属层系相较于锡具有较小正电性的金属层，该锡系由含有一或多种锡离子来源、水、及一或多种络合试的浸渍锡镀敷浴所沉积形成者。于另一具体实例中，该金属层是任何导电性金属层，该锡通过无电或电解镀敷沉积形成的。In another embodiment, the present invention is also applicable to printed wiring board substrates having exposed solder pads and/or vias and containing tin-silver alloy as a solderable plating layer. Therefore, the present invention also provides a method for manufacturing a printed circuit board, which method includes the following steps: a) providing a printed circuit board substrate, the substrate has a solder pad, a through hole, a solder repellent layer, and a metal layer; b) depositing a tin layer on the metal layer; c) forming an immersion silver deposit on the tin deposit by contacting the tin-plated printed wiring board substrate with an immersion silver plating bath comprising one or sources of silver ions, water, one or more complexing reagents, and one or more carboxylic acid substituted nitrogen-containing heterocyclic compounds; and d) heating the silver-tin deposit to form a tin-silver alloy. In one embodiment, the metal layer is a less electropositive metal layer than tin obtained by impregnating tin with one or more sources of tin ions, water, and one or more complexing reagents. Formers deposited by plating baths. In another embodiment, the metal layer is any conductive metal layer, the tin being deposited by electroless or electrolytic plating.
在又一具体实例中，通过本发明的方法可获得具光泽的银沉积，该方法包含使基材与浸渍银镀敷浴接触的步骤，该基材具有一金属层且该金属相较于银具有较小的正电性，该镀敷浴包括一或多种银离子来源、水、一或多种络合试、以及一或多种羧酸取代的含氮杂环化合物，且该浸渍银镀敷浴系不含氨以及铵离子。In yet another embodiment, a lustrous silver deposit can be obtained by the method of the present invention, the method comprising the step of contacting a substrate having a layer of metal and the metal being compared to silver With less positive charge, the plating bath includes one or more sources of silver ions, water, one or more complexing reagents, and one or more carboxylic acid-substituted nitrogen-containing heterocyclic compounds, and the impregnated silver The plating bath system does not contain ammonia and ammonium ions.
本发明的浸渍银镀敷浴的pH≥8，特别是pH为9时，可以获得改善厚度均匀性的银沉积。然而，相较于具有较低pH值的类似镀敷浴所沉积的银层的黏着性，这种镀敷浴所沉积的沉积银层的黏着性则变得较差。因此，较佳的是在该浸渍银镀敷浴的pH≥8时，将黏着促进剂添加至该浸渍银镀敷浴中。黏着促进剂的示例包含，但非限于氨基酸，例如谷胺酸、甘氨酸、赖氨酸、β-丙氨酸及天冬胺酸；经羟基取代的芳香族化合物，例如羟基苯并三唑、及5-甲氧基间苯二酚；以及含硫羧酸，例巯基二乙酸。在未含有至少一种羧酸取代的含氮杂环化合物的浸渍银镀敷浴中使用这种黏着促进剂，会形成暗黑色(即，无光泽)且厚度不均匀的银沉积。意外地发现，浸渍银镀敷浴同时含有至少一种黏着促进剂以及至少一种羧酸取代的含氮杂环化合物两者时，相较于常用的浸渍银镀敷浴所获得的银沉积，镀敷浴的pH值≥8亦能形成具有光泽且改善厚度均匀性的高黏着性银沉积。The pH of the immersion silver plating bath of the present invention is ≥ 8, especially at a pH of 9, silver deposition with improved thickness uniformity can be obtained. However, the deposited silver layer deposited by such a plating bath becomes less adherent than the adherence of a silver layer deposited from a similar plating bath having a lower pH. Therefore, it is preferred to add an adhesion promoter to the immersion silver plating bath when the pH of the immersion silver plating bath is > 8. Examples of adhesion promoters include, but are not limited to, amino acids such as glutamic acid, glycine, lysine, beta-alanine, and aspartic acid; hydroxy-substituted aromatic compounds such as hydroxybenzotriazoles, and 5-methoxyresorcinol; and sulfur-containing carboxylic acids such as mercaptodiacetic acid. Use of such adhesion promoters in immersion silver plating baths that do not contain at least one carboxylic acid-substituted nitrogen-containing heterocyclic compound results in the formation of dark (ie, matte) silver deposits of non-uniform thickness. Surprisingly, it has been found that immersion silver plating baths containing both at least one adhesion promoter and at least one carboxylic acid substituted nitrogen-containing heterocyclic compound have a silver deposition compared to that obtained with commonly used immersion silver plating baths. Plating bath pH ≥ 8 can also form highly adherent silver deposits with gloss and improved thickness uniformity.
可以使用多种不同的后处理方法处理根据本发明方法所沉积的银层。例如，已知银(如，银薄膜)长时间曝露于空气中会失去光泽。因此，在某些应用上需要使新沉积的银层与锈蚀抑制剂或抗锈蚀剂接触。这种银的锈蚀抑制剂系该项领域的技术者所公知，包含上述所揭示的。可以利用任何适当的方法使银沉积与该锈蚀抑制剂接触，例如浸没、喷洒、及溢流涂覆。镀敷后并非必然需要使用锈蚀抑制剂，该抑制剂可视需加以使用。亦可有益地使用其它常用的后处理方法。The silver layer deposited according to the method of the present invention can be treated using a number of different post-treatment methods. For example, silver (eg, silver thin films) is known to tarnish upon prolonged exposure to air. Therefore, in some applications it is desirable to contact the freshly deposited silver layer with a rust inhibitor or anti-corrosion agent. Such silver rust inhibitors are known to those skilled in the art, including those disclosed above. The silver deposit can be contacted with the rust inhibitor by any suitable method, such as immersion, spraying, and flood coating. It is not necessary to use a rust inhibitor after plating, the inhibitor can be used if desired. Other commonly used post-processing methods may also be beneficially used.
相较于常用的浸渍银镀敷浴，利用本发明的浸渍银镀敷浴可以使所形成的银层具有改善的厚度均匀性，亦即，厚度的变化较小。因此，本发明提供一种改善浸渍银镀敷浴所沉积的银层厚度均匀性的方法，包括下列步骤：a)提供一浸渍银镀敷浴，该镀敷浴包含一或多种银离子来源、水、一或多种络合试、及一或多种羧酸取代的含氮杂环化合物；以及b)使基材与浸渍银镀敷浴接触足以沉积所需的银层的时间，该基材具有一金属层且该金属相较于银具有较小的正电性。Compared with conventional immersion silver plating baths, the use of the immersion silver plating baths of the present invention allows the formation of silver layers with improved thickness uniformity, ie less variation in thickness. Accordingly, the present invention provides a method of improving the thickness uniformity of a silver layer deposited from an immersion silver plating bath comprising the steps of: a) providing an immersion silver plating bath comprising one or more sources of silver ions , water, one or more complexing reagents, and one or more carboxylic acid substituted nitrogen-containing heterocyclic compounds; and b) contacting the substrate with an immersion silver plating bath for a time sufficient to deposit the desired silver layer, the The substrate has a metal layer and the metal is less electropositive than silver.
除了印刷线路板之外，本发明亦适合用于制造多种不同的电子装置，例如导线框、半导体封装件、以及晶圆上不含铅的焊块，例如锡-银、及锡-铜-银焊料。In addition to printed circuit boards, the present invention is also suitable for the manufacture of various electronic devices, such as lead frames, semiconductor packages, and lead-free solder bumps on wafers, such as tin-silver, and tin-copper- silver solder.
下列的实施例是为了进一步阐述说明本发明的不同方面，但并非以任何观点限制本发明的范围。The following examples are intended to further illustrate different aspects of the present invention, but are not intended to limit the scope of the present invention in any way.
实施例Example
实施例1(比较例)Embodiment 1 (comparative example)
在去离子水中结合100克/升的氮川三乙酸(“NTA”)以及1克/升的硝酸银(最终体积为1升)制备浸渍银镀敷浴。将该镀敷浴的pH值调整至9。该镀敷浴的温度约50℃。An immersion silver plating bath was prepared by combining 100 g/L nitrilotriacetic acid ("NTA") and 1 g/L silver nitrate in deionized water (final volume 1 L). The pH of the plating bath was adjusted to 9. The temperature of the plating bath is about 50°C.
实施例2Example 2
重复实施例1的步骤，除了将1克/升的吡啶甲酸添加至该组合物中作为本实施例。将pH值再次调整至9，该镀敷浴的温度约50℃。The procedure of Example 1 was repeated except that 1 g/L of picolinic acid was added to the composition for this example. The pH was adjusted again to 9 and the temperature of the plating bath was about 50°C.
实施例3Example 3
将铜板(2×6英时或5×15公分)浸入市售的酸清洗剂，以自铜表面移除氧化物与有机残渣，然后以水洗涤。接着使该铜板与市售可得的硫酸/过氧化氢基微蚀刻组合物接触，形成最佳的均匀铜表面及结构，然后以水洗涤。与微蚀刻组合物接触的后，将该铜板浸入实施例1或实施例2的银镀敷浴，历时10分钟。Copper panels (2 x 6 inches or 5 x 15 cm) were immersed in a commercially available acid cleaner to remove oxides and organic residues from the copper surface, and then rinsed with water. The copper plate was then contacted with a commercially available sulfuric acid/hydrogen peroxide based microetching composition to form an optimally uniform copper surface and structure, and then washed with water. After contacting with the microetching composition, the copper panels were immersed in the silver plating bath of Example 1 or Example 2 for 10 minutes.
利用X-线萤光(“XRF”)光谱在铜板表面的数点测量各个银配方在铜板所形成的银层的厚度，并将所测得的厚度范围纪录在表1中。The thickness of the silver layer formed by each silver formulation on the copper plate was measured at several points on the surface of the copper plate by X-ray fluorescence (“XRF”) spectroscopy, and the measured thickness ranges were recorded in Table 1.
表1
由以上数据明显可知，将吡啶甲酸添加至浸渍银镀敷浴中对于所形成的银沉积的厚度与均匀性具有明显的影响。相较于不含吡啶甲酸的浸渍银镀敷浴所获得的沉积，本实施例所获得的银沉积较均匀。From the above data it is evident that the addition of picolinic acid to an immersion silver plating bath has a significant effect on the thickness and uniformity of the silver deposit formed. The silver deposition obtained in this example was more uniform compared to the deposition obtained from an immersion silver plating bath without picolinic acid.
实施例4Example 4
重复实施例1的步骤，除了将3、5、6、8、及10克/升的吡啶甲酸分别添加至组合物中作为实施例4A、4B、4C、4D、及4E。将pH值再次调整至9，该镀敷浴的温度约50℃。The procedure of Example 1 was repeated except that 3, 5, 6, 8, and 10 g/L of picolinic acid were added to the composition as Examples 4A, 4B, 4C, 4D, and 4E, respectively. The pH was adjusted again to 9 and the temperature of the plating bath was about 50°C.
根据实施例3的步骤，使铜板(2×6英时或5×15公分)进行清洗与微蚀刻，然后浸入实施例的银镀敷浴，历时10分钟。根据实施例3的步骤，利用XRF光谱测量各个银配方在铜板所形成的银层的厚度，并将所测得的厚度范围纪录在表2中。Copper panels (2 x 6 inches or 5 x 15 cm) were cleaned and microetched according to the procedure of Example 3, and then immersed in the silver plating bath of the example for 10 minutes. According to the steps of Example 3, the thickness of the silver layer formed by each silver formula on the copper plate was measured by XRF spectrum, and the measured thickness range was recorded in Table 2.
表2
由以上数据明显可知，通过将特定量的吡啶甲酸引入银浸渍镀敷浴中可以控制所沉积的银层的厚度与均匀性。相较于不含吡啶甲酸的浸渍镀敷浴所获得的沉积，本实施例所获得的沉积明显较均匀。It is evident from the above data that the thickness and uniformity of the deposited silver layer can be controlled by introducing specific amounts of picolinic acid into the silver immersion plating bath. The deposition obtained in this example was significantly more uniform than the deposition obtained from an immersion plating bath without picolinic acid.
实施例5(比较例)Embodiment 5 (comparative example)
如实施例1所揭示制备浸渍银镀敷浴。在溶液中分别添加0.05及0.12克/升的1-羟基苯并三唑作为实施例5A及5B。以去离子水稀释溶液至最终体积。将该镀敷浴的pH值调整至9，以及镀敷浴的温度约50℃。An immersion silver plating bath was prepared as disclosed in Example 1. 0.05 and 0.12 g/L of 1-hydroxybenzotriazole were added to the solution as Examples 5A and 5B, respectively. The solution was diluted to final volume with deionized water. The pH of the plating bath was adjusted to 9, and the temperature of the plating bath was about 50°C.
实施例6Example 6
重复实施例5的步骤，除了将吡啶甲酸分别添加至实施例5A、5B以及实施例6A、6B。该吡啶甲酸的添加量系如表3所示。将pH值调整至9，该镀敷浴的温度约50℃。The procedure of Example 5 was repeated except that picolinic acid was added to Examples 5A, 5B and Examples 6A, 6B, respectively. The addition amount of this picolinic acid is as shown in Table 3. The pH was adjusted to 9 and the temperature of the plating bath was about 50°C.
根据实施例3的步骤，使铜板(2×6英时或5×15公分)进行清洗与微蚀刻，然后浸入实施例5A、5B、6A、及6B的银镀敷浴，历时10分钟。根据实施例3利用XRF光谱测量各个银配方在铜板所形成的银层的厚度，并将所测得的厚度范围纪录在表3中。Copper panels (2 x 6 inches or 5 x 15 cm) were cleaned and microetched according to the procedure of Example 3, then immersed in the silver plating baths of Examples 5A, 5B, 6A, and 6B for 10 minutes. According to Example 3, the thickness of the silver layer formed by each silver formulation on the copper plate was measured by XRF spectrum, and the measured thickness range was recorded in Table 3.
表3
未添加吡啶甲酸者，所沉积的银系暗黑且镀敷不均匀的。添加吡啶甲酸可以明显地改善沉积银的光泽与均匀性。If picolinic acid is not added, the deposited silver is dark and unevenly plated. Adding picolinic acid can significantly improve the luster and uniformity of deposited silver.
实施例7(比较例)Embodiment 7 (comparative example)
重复实施例1的步骤，除了将巯基二乙酸添加至各镀敷浴作为实施例7A与7B。添加浓度系如表4所载。以去离子水稀释溶液至最终体积。将该镀敷浴的pH值调整至9，以及镀敷浴的温度约50℃。The procedure of Example 1 was repeated except that mercaptodiacetic acid was added to each plating bath as Examples 7A and 7B. The added concentration system is listed in Table 4. The solution was diluted to final volume with deionized water. The pH of the plating bath was adjusted to 9, and the temperature of the plating bath was about 50°C.
实施例8Example 8
重复实施例7的步骤，除了将6克/升的吡啶甲酸分别添加至实施例7A与7B作为实施例8A与8B。将pH值再次调整至9，该镀敷浴的温度约50℃。The procedure of Example 7 was repeated except that 6 g/L of picolinic acid was added to Examples 7A and 7B as Examples 8A and 8B, respectively. The pH was adjusted again to 9 and the temperature of the plating bath was about 50°C.
根据实施例3的步骤，使铜板(2×6英时或5×15公分)进行清洗与微蚀刻，然后浸入实施例7或8的银镀敷浴，历时10分钟。根据实施例3利用XRF测量各个银配方在铜板所形成的银层的厚度，并将所测得的厚度范围纪录在表4中。Copper panels (2 x 6 inches or 5 x 15 cm) were cleaned and microetched according to the procedure of Example 3, then immersed in the silver plating bath of Examples 7 or 8 for 10 minutes. According to Example 3, XRF was used to measure the thickness of the silver layer formed by each silver formulation on the copper plate, and the measured thickness range was recorded in Table 4.
表4
未添加吡啶甲酸者，所沉积的银系暗黑且镀敷不均匀。添加吡啶甲酸可以明显地改善沉积银的光泽与均匀性。Without adding picolinic acid, the deposited silver system is dark and uneven. Adding picolinic acid can significantly improve the luster and uniformity of deposited silver.
实施例9(比较例)Embodiment 9 (comparative example)
结合100克/升的NTA以及1克/升的硝酸银，以去离子水稀释至最终体积(1升)，制备浸渍银镀敷浴。实施例9A、9B、及9C的银配方系分别含有1.0、3.0、及5.0克/升L-谷胺酸。将该镀敷浴的pH值调整至9，该镀敷浴的温度约50℃。An immersion silver plating bath was prepared by combining 100 g/L NTA and 1 g/L silver nitrate diluted to final volume (1 L) with deionized water. The silver formulations of Examples 9A, 9B, and 9C contained 1.0, 3.0, and 5.0 g/L L-glutamic acid, respectively. The pH of the plating bath was adjusted to 9 and the temperature of the plating bath was about 50°C.
实施例10Example 10
重复实施例9的步骤，除了将6克/升的吡啶甲酸分别添加至各个组合物中作为实施例10A、10B、及10C。将pH值再次调整至9，该镀敷浴的温度约50℃。The procedure of Example 9 was repeated except that 6 g/L of picolinic acid was added to each composition separately as Examples 10A, 10B, and 10C. The pH was adjusted again to 9 and the temperature of the plating bath was about 50°C.
根据实施例2的步骤，使铜板(2×6英时或5×15公分)进行清洗与微蚀刻，然后浸入实施例9或10的银镀敷浴，历时10分钟。根据实施例3利用XRF测量各个银配方在铜板所形成的银层的厚度，并将所测得的厚度范围纪录在表5中。Copper panels (2 x 6 inches or 5 x 15 cm) were cleaned and microetched according to the procedure of Example 2, then immersed in the silver plating bath of Examples 9 or 10 for 10 minutes. According to Example 3, XRF was used to measure the thickness of the silver layer formed by each silver formulation on the copper plate, and the measured thickness range was recorded in Table 5.
表5
未添加吡啶甲酸者，所沉积的银系暗黑且镀敷不均匀。添加吡啶甲酸可以明显地改善沉积银的光泽与均匀性。Without adding picolinic acid, the deposited silver system is dark and uneven. Adding picolinic acid can significantly improve the luster and uniformity of deposited silver.
实施例11Example 11
根据实施例2的步骤制备数个镀敷浴，除了以表6所示的化合物的量取代吡啶甲酸。Several plating baths were prepared according to the procedure of Example 2, except that the picolinic acid was replaced by the amount of the compound shown in Table 6.
表6
实施例12Example 12
根据实施例3的步骤，使铜板进行清洗与微蚀刻，然后与实施例11的镀敷浴接触，沉积银层。The copper plate was cleaned and microetched according to the procedure of Example 3, and then contacted with the plating bath of Example 11 to deposit a silver layer.
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US62095102A | 2002-08-30 | 2002-08-30 | |
| US60/407,044 | 2002-08-30 | ||
| US10/620,951 | 2003-07-16 | ||
| US10/620,951US20040043159A1 (en) | 2002-08-30 | 2003-07-16 | Plating method |
| Publication Number | Publication Date |
|---|---|
| CN1495287Atrue CN1495287A (en) | 2004-05-12 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA031560601APendingCN1495287A (en) | 2002-08-30 | 2003-08-29 | Plating method |
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