Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a pretreatment process for the interfacial bonding force of a nickel-phosphorus alloy plating layer on the surface of high NdFeB, which comprises the following steps:
(1) Performing shot blasting treatment on the surface of the neodymium iron boron substrate to remove the corrosion layer on the surface of the neodymium iron boron substrate, so as to obtain a shot blasting treatment substrate;
(2) Placing the shot-blasting treatment substrate into HEDP alkaline solution for soaking to obtain HEDP alkaline solution-soaked substrate;
(3) Copper powder is added into the HEDP alkaline solution, and the base material is soaked in the HEDP alkaline solution for electroplating, so that a copper-plated base material is obtained;
(4) Soaking the copper-plated substrate in a sodium citrate alkaline solution to obtain a sodium citrate alkaline solution-soaked substrate;
(5) And soaking the base material in the sodium citrate alkaline solution, and performing barrel plating in the nickel-phosphorus alloy plating solution.
Preferably, in the step (1), the shot blasting treatment is performed by adopting glass or ceramic micro powder, and the grain diameter of the shot is 0.4-0.6 mm;
and/or the speed of shot blasting is less than or equal to 70m/s, and the shot blasting time is 4-6 min;
and/or the surface roughness of the shot-blasted substrate is not higher than 3 μm.
Preferably, in step (2), the HEDP alkaline solution comprises the following raw materials in concentration: HEDP is 70-80 g/L, KOH is 40-45 g/L, K2 CO3 20-25 g/L, C6 H11 KO7 5-8 g/L, CH3 COOH is 1-2 g/L;
and/or the soaking time is 30-60 s.
Preferably, in the step (3), the average particle size of the copper powder is 0.2-0.3 μm;
and/or the addition amount of the copper powder is 6-8 g/L.
It should be emphasized that in the step (3), the soaked neodymium iron boron substrate cannot clean the surface before barrel plating, and the workpiece is electrified to be put into a groove during barrel plating, and the impact current is twice as much as the current required by the normal process is used for the first 30 s.
Preferably, in the step (4), the sodium citrate alkaline solution comprises the following raw materials with the following concentrations: c (C)6 H5 Na3 O7 85-95 g/L NaOH 35-40 g/L CH4 N2 S is 2-4 g/L;
and/or the soaking time is 30-60 s.
It should be emphasized that in step (5), the substrate immersed in the alkaline solution of high concentration sodium citrate cannot be cleaned on the surface before barrel plating the nickel-phosphorus alloy, and the workpiece is charged and placed in the tank during barrel plating, and an impact current 50% greater than that required by the normal process is used for the first 30 s.
The beneficial effects of the invention are as follows:
according to the pretreatment process, the plating piece is soaked in the solution containing the high-concentration complexing substance before barrel plating for two times, so that a complex protective layer exists when the surface of the plating piece is not completely protected by the plating layer in the initial stage of barrel plating, corrosion of the plating solution to a substrate is reduced, and the interface binding force of the plating layer is improved. Meanwhile, copper powder is added into the preplating solution to prepare a composite preplating layer containing copper powder, so that the preplating layer can obtain higher density under a thinner thickness, thereby protecting a matrix in the subsequent nickel-phosphorus alloy electroplating process and improving the interfacial binding force of the plating layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, based on the examples herein, which are within the scope of the invention as defined by the claims, will be within the scope of the invention as defined by the claims.
Example 1
The embodiment provides a pretreatment process for improving interfacial bonding force of a nickel-phosphorus alloy plating layer rolled on the surface of neodymium iron boron, which comprises the following steps:
(1) The original roughness of the surface of the selected NdFeB substrate is about 1.2 mu m, shot blasting treatment is carried out to remove the corrosion layer on the surface of the NdFeB substrate, and the shot blasting treatment substrate is obtained after the completion; wherein:
the process conditions of the shot blasting treatment are as follows: the pellet material is ceramic micro powder with the grain diameter of 0.5mm, the shot blasting speed is 70m/s, the time is 6min, and the surface roughness is measured to be about 2.8 mu m after the shot blasting is finished;
(2) Soaking the shot-blasting treated base material in HEDP alkaline solution for 40s, wherein the solutionThe components are as follows: HEDP of 80g/L, KOH of 45g/L, K2 CO3 25g/L, C6 H11 KO (potassium gluconate) 5g/L, CH3 COOH 1.5g/L, then directly carrying out copper rolling in a lower charged tank, adding pure copper powder with the concentration of 6g/L and the particle size of 0.2 mu m into HEDP copper plating solution, and controlling the current density of the initial 30s of the copper rolling to 2A/dm2 Then reduced to 1A/dm2 Taking out after 30min to obtain a copper-plated substrate;
(3) Immersing the copper-plated substrate in a high-concentration sodium citrate alkaline solution for 40s, wherein the solution comprises the following components: c (C)6 H5 Na3 O7 (sodium citrate) 95g/L, naOH 40g/L, CH4 N2 S (thiourea) is 3g/L, then directly electrifying the lower tank to roll nickel-phosphorus alloy, and controlling initial 30S current density at 6A/dm2 Then reduced to 4A/dm2 Taking out after 30 min.
Example 2
The embodiment provides a pretreatment process for improving interfacial bonding force of a nickel-phosphorus alloy plating layer rolled on the surface of neodymium iron boron, which comprises the following steps:
(1) The original roughness of the surface of the selected NdFeB substrate is about 1.2 mu m, shot blasting treatment is carried out to remove the corrosion layer on the surface of the NdFeB substrate, and the shot blasting treatment substrate is obtained after the completion; wherein:
the process conditions of the shot blasting treatment are as follows: the pill material is glass with the grain diameter of 0.5mm, the pill throwing speed is 60m/s, and the time is 4min;
(2) The shot blasting treatment substrate is placed in HEDP alkaline solution to be soaked for 30s, and the solution comprises the following components: HEDP of 70g/L, KOH of 40g/L, K2 CO3 20g/L, C6 H11 KO (potassium gluconate) of 8g/L, CH3 COOH is 2g/L, then directly carrying out copper rolling in a lower electrified tank, adding pure copper powder with the concentration of 8g/L and the particle size of 0.3 mu m into HEDP copper plating solution, and controlling the current density of initial 30s of the copper rolling to be 2A/dm2 Then reduced to 1A/dm2 Taking out after 30min to obtain a copper-plated substrate;
(3) Immersing copper-plated substrate in high-concentration sodium citrate alkaline solution for 40s, and dissolvingThe components of (1) are as follows: c (C)6 H5 Na3 O7 (sodium citrate) 85g/L, naOH 35g/L, CH4 N2 S (thiourea) is 4g/L, then directly electrifying the lower tank to roll nickel-phosphorus alloy, and controlling initial 30S current density at 6A/dm2 Then reduced to 4A/dm2 Taking out after 30 min.
Comparative example 1
The comparative example provides a pretreatment procedure for improving the interfacial bonding force of a nickel-phosphorus alloy plating layer rolled on the surface of neodymium iron boron, which is different from example 1 only in that the shot blasting treatment in the step (1) is carried out, and the process conditions of the shot blasting treatment of comparative example 1 are as follows: the pellet material is ceramic micro powder with the grain diameter of 1mm, the shot blasting speed is 80m/s, the time is 8min, and the surface roughness is measured to be about 6.2 mu m after the shot blasting is finished.
The interface binding force of the coating is tested by using a coating adhesive force scratch instrument, the interface binding force under the condition of the shot blasting process of the embodiment 1 is about 58MPa, and the interface binding force under the condition of the shot blasting process of the comparative embodiment 1 is about 26MPa. Through observation of the section of the plating layer, the pre-plated copper layer is continuous and compact under the shot blasting process condition of the embodiment 1, and has good protection effect on the substrate. Under the condition of the shot blasting process in comparative example 1, the surface roughness of the substrate is large, the surface fluctuation greatly exceeds the average thickness of the copper plating layer, so that the copper plating layer in partial areas is extremely thin and even discontinuous, the substrate is severely corroded, and the interface bonding between the substrate and the nickel-phosphorus alloy plating layer is not tight in many positions.
The shot blasting process parameters are limited, so that the surface roughness is reduced as much as possible while the surface oxide is removed, and the quality problem of a plating layer is prevented when a thin copper layer is electroplated subsequently.
Comparative example 2
This comparative example provides a pretreatment process for improving interfacial bonding force of nickel-phosphorus alloy plating layer roll-plated on neodymium iron boron surface, which is different from example 1 in that the comparative example directly carries out copper rolling without soaking treatment in step (2), and the rest of the operations are the same as example 1.
The interfacial adhesion of the coating was tested using a coating adhesion scratch tester, the coating adhesion of example 1 was about 57MPa, and the coating adhesion of comparative example 2 was about 18MPa. Through observation of the section of the plating layer, the preplating layer under both processing conditions is relatively continuous, but when not immersed, the substrate under the copper layer has a distinct continuous corrosion layer. This indicates that even in alkaline copper plating solutions, neodymium iron boron substrates suffer from relatively severe corrosion and must be protected by presoaking.
The pre-soaking of the plating piece before barrel plating copper is to protect the surface of the plating piece to a certain extent through the adsorbed high-concentration complex, so that the corrosion of the plating solution to the substrate is reduced when the initial plating layer of barrel plating is not completely covered, and the interface binding force is improved.
Comparative example 3
This comparative example provides a pretreatment process for improving the interfacial bonding force of a nickel-phosphorus alloy plating layer on a neodymium iron boron surface, which is different from example 1 in that the present comparative example directly performs barrel plating without soaking treatment in step (3), and the rest of the operations are the same as example 1.
The interfacial adhesion of the coating was tested using a coating adhesion scratch tester, the coating adhesion of example 1 was about 58MPa, and the coating adhesion of comparative example 1 was about 39MPa. By observing the section of the plating, it was found that the pre-copper plating was relatively continuous under both processing conditions and that the substrate under the copper layer was free of continuous corrosion layers. However, without pre-impregnation, the individual locations of the substrate under the copper layer have localized areas of small corrosion where the interface bonding of the plating is not very tight. This suggests that the preplated thin copper layer may still have some porosity and insufficient protection of the substrate. A prepreg must be performed before barrel plating the nickel-phosphorous alloy to further protect the substrate from corrosion.
That is, the pre-dip of the plating piece before barrel plating of the nickel-phosphorus alloy is because the nickel-phosphorus alloy plating solution is very acidic, and the pre-plated copper layer is thinner, which cannot sufficiently protect the substrate. Therefore, the adsorbed high-concentration complex plays a certain role in protecting the surface of the substrate, so that the corrosion of the plating solution to the substrate is reduced when the nickel-phosphorus plating layer of the initial plating layer of barrel plating is not completely covered, and the interface binding force is improved.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.