CN110318047B - Chemical palladium solution applied to chemical gold-palladium-gold plating layer on PCB - Google Patents
Chemical palladium solution applied to chemical gold-palladium-gold plating layer on PCB Download PDFInfo
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- CN110318047B CN110318047B CN201910685004.0A CN201910685004A CN110318047B CN 110318047 B CN110318047 B CN 110318047B CN 201910685004 A CN201910685004 A CN 201910685004A CN 110318047 B CN110318047 B CN 110318047B
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
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- C23C18/42—Coating with noble metals
- C23C18/44—Coating with noble metals using reducing agents
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- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/18—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using precipitation techniques to apply the conductive material
- H05K3/181—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using precipitation techniques to apply the conductive material by electroless plating
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Abstract
The invention discloses a chemical palladium solution applied to a chemical gold-palladium-gold plating layer on a PCB (printed Circuit Board), which comprises main salt, a coordination agent, a reducing agent, a stabilizing agent, a pH buffering agent and a surfactant, wherein the chemical palladium solution comprises the following components in percentage by mass: palladium concentration in main salt: 0.4-0.6 g/L; a complexing agent: 0.1-30 g/L; reducing agent: 0.1-25 g/L; a stabilizer: 1-150 mg/L; pH buffer: 1-25 g/L; surfactant (b): 0.1-10 mg/L; the rest components are pure water. The palladium layer prepared by the palladium solution can meet good welding and bonding requirements, and is also suitable for surface treatment of lines with line width/line distance of less than 0.5mil/0.5mil or even smaller.
Description
Technical Field
The invention relates to the technical field of PCBs, in particular to a chemical palladium solution applied to a chemical gold-palladium-gold plating layer on a PCB.
Background
COF is an IC packaging technology, in which a Flexible Printed Circuit (FPC) is used as a carrier for packaging a chip, and Gold bumps (Gold bumps) on the chip and Inner leads (Inner leads) on the flexible printed circuit are bonded (Bonding) by thermocompression. After COF production is completed, after an LCD Panel module factory obtains an IC, the IC on a tape is cut into individual pieces by a Punch (Punch) device, and usually, a flexible substrate circuit of the COF has design Input (Input) and Output (Output) external pins (out Lead) at two ends, where the Input external pins are connected to a glass substrate of the LCD and the Input internal pins are connected to a Printed Circuit Board (PCB) of a control signal.
In the era of intelligent portability, small electronic products such as mobile phones, computers, and displays have been rapidly developed. The COF FPC carrier plate adopts a SAP semi-additive production mode completely different from a standard subtractive etching method, and the minimum line-width line distance of the FPC produced by the standard subtractive etching method is generally more than 2mil/2mil, so that the COF carrier plate is basically incapable of being applied to a COF production process with finer lines. And the line width and line distance of the COF FPC are finer than those of the common FPC, and the COF FPC is difficult to produce by adopting a standard subtractive etching method. In particular, the line width/line pitch and the via diameter of a double-sided FPC product for LCD and a flex-rigid board for high-end use are miniaturized by the densification of lines and vias. At present, the line width/line distance of single-sided and double-sided FPCs for LCDs is 1.5mil/1.5mil, and the diameter of a via hole is 0.05mm, which is commonly realized in COFs.
The existing surface treatment processes (nickel-gold, nickel-palladium-gold, silver-plating, tin-plating, OSP and tin spraying) can not simultaneously meet the performances of gold wire bonding, fine circuit (1.5mil/1.5mil and below line width/line distance), bending resistance (bending for 3 times at 180 degrees), and the like. The gold-palladium-gold process can simultaneously meet the performances; wherein the plating layer deposited by the gold-palladium-gold process is divided into three layers of gold-palladium-gold, wherein the first layer is a gold layer and has the thickness of 0.5-1.0 mu inch; the second layer is a palladium layer with a thickness of 3-5 mu inch, and the third layer is a gold layer with a thickness of 2-3 mu inch.
After the surface treatment, the circuit board is mainly treated by two processes of soldering tin (including solder ball welding of IC) and wire bonding (for effective electrical connection with other components). The surface treatment processes such as tin spraying, tin melting, silver melting, OSP and the like in the existing surface treatment mode mainly deal with a soldering tin connection process, and the main defect is that the surface treatment processes can only be applied to the most basic circuit design and electronic products, and the fine and complicated electronic circuit design products are difficult to deal with due to the limitation of soldering tin.
The other connection process is wire bonding, the wire bonding materials in the market at present mainly comprise gold wires, silver wires, palladium-plated copper wires, gold-silver alloy wires and copper wires, the wire diameters of the wires are different, the thickness of the wires is 2mil (50um), and the thinnest can be 0.5mil (12um) or even thinner. Wherein, the thinner the wire diameter is, the stronger the wire bonding capability for fine circuit is. The nickel-gold plating layer is only suitable for surface treatment with the width/line spacing of more than 2mil/2 mil; the nickel palladium gold plating layer is suitable for surface treatment with the line width/line distance of 1.5mil/1.5mil and above; the palladium-gold plating layer is suitable for surface treatment with the line width/line distance of 1.0mil/1.0mil and above; the gold-palladium-gold plating layer can meet good welding requirements, and is also suitable for surface treatment of lines with line width/line distance of less than 0.5mil/0.5mil or even smaller.
Disclosure of Invention
Aiming at the defects in the technology, the invention discloses a chemical palladium solution applied to a chemical gold-palladium-gold plating layer on a PCB, which can meet the requirement of good welding and is also suitable for surface treatment of a circuit with the line width/line distance of less than 0.5mil/0.5mil or even smaller.
In order to achieve the above object, the present invention provides a chemical palladium solution for a chemical gold palladium gold plating layer applied on a PCB, comprising a main salt, a complexing agent, a reducing agent, a stabilizer, a pH buffer and a surfactant, wherein the ratio of the components is, in terms of mass concentration:
palladium concentration in main salt: 0.4-0.6g/L
A complexing agent: 0.1-30g/L
Reducing agent: 0.1-25g/L
A stabilizer: 1-150mg/L
pH buffer: 1-25g/L
Surfactant (b): 0.1-10mg/L
The rest components are pure water;
carrying a stirring pump according to the volume of the palladium tank;
adding 50% pure water into a palladium tank, sequentially adding a coordination agent, a reducing agent, a stabilizing agent and a surfactant in the process of continuously stirring, adjusting the pH value of the tank liquor to be within the range of 7.0-7.8, then adding a pH buffering agent, finally adding main salt and fixing the volume to form a palladium solution.
The palladium layer obtained by the palladium solution has flat and bright appearance, no diffusion plating on fine lines, no leakage plating in the pores of micropores and blind holes, and no whitening and falling-off phenomena of the lines; plating for 8-18 minutes, wherein the thickness of the plating layer is 3.0-5.0 mu inch, the stability of the palladium solution reaches more than 5MTO, and the plating layer by the 3M adhesive tape method has good bonding force; and the palladium solution is suitable for surface treatment of wires with line width/line spacing below 0.5mil/0.5mil and even smaller.
Wherein the main salt is one or more of palladium chloride, palladium tetraammine dichloride, palladium sulfate or palladium ammonia sulfate.
Wherein the complexing agent is: one or more of ethylenediamine, benzylamine, N-benzyl methylamine, 4-fluorobenzylamine, N-methyl-1-naphthalene methylamine and furfuryl amine.
Wherein the stabilizer is one or more of 7- (diethylamino) coumarin, thiodiglycolic acid, 2, 2-bipyridine and 2, 3-dihydroxyquinoxaline.
Wherein the reducing agent is one or more of hydroxylamine hydrochloride, hydroxylamine sulfate, N-diethylhydroxylamine, N-dibenzylhydroxylamine, N-methylhydroxylamine hydrochloride, methoxylamine hydrochloride, O-benzylhydroxylamine hydrochloride and D-mannitol.
Wherein the pH buffering agent is one or more of glycine, ammonium sulfate, ammonium chloride and ammonium acetate.
Wherein the surfactant is one or more of tetrabutylammonium hydrogen sulfate and hexadecyl trimethyl ammonium hydrogen sulfate.
The invention has the beneficial effects that: compared with the prior art, the chemical palladium solution applied to the chemical gold-palladium-gold plating layer on the PCB provided by the invention has the following advantages:
1) the palladium sulfate or palladium ammonia sulfate is used as main salt, a coordination system formed by the palladium sulfate or the palladium ammonia sulfate and the coordination agent in the system is more stable, and the service life of the bath solution is longer;
2) the proper content of the complexing agent can well control the deposition rate of palladium and the compactness of the palladium layer, and meanwhile, the palladium layer with excellent ductility can be obtained;
3) the used reducing agent can not generate byproducts of phosphorus and boron, and a compact pure palladium layer can be obtained, and the pure palladium layer has higher ductility and better bending resistance than the phosphorus-palladium layer; meanwhile, the deposition rate of palladium can be controlled according to the requirement by adjusting the amount of the reducing agent, and the compact palladium layer can also prevent the substrate copper from migrating to the gold layer after multiple times of backflow;
4) the stabilizer can well control the occurrence of autocatalytic reaction in the palladium tank, prevent the precipitation of the palladium tank caused by homogeneous catalysis in use and better ensure the continuous and stable operation of the autocatalytic reaction of the heterogeneous surface in the tank liquor;
5) the existence of the pH buffering agent can ensure that the pH value of the bath solution is maintained in a dynamic equilibrium range in the service cycle of the palladium bath, thereby ensuring the stability of the deposition rate, the quality of a plating layer and the service life of the bath solution;
6) the surfactant can be used for wetting micropores, blind holes and step grooves in the PCB, so that the plating leakage in the bonding pad, the holes and the grooves is prevented;
7) due to the difference of plating layers, the difficulty of depositing palladium on a gold layer is higher than that on a nickel layer, the deposition of a thick palladium layer on the gold layer needs to be realized, and the palladium plating solution needs to have reducibility. Meanwhile, the palladium deposited on the gold layer has different requirements on compactness, binding force and deposition rate than the palladium deposited on the nickel layer;
8) the palladium solution used in the gold-palladium-gold process is suitable for IC carrier plates, wafer packages, printed circuit boards, flexible circuit boards or rigid-flex printed boards;
10) the invention not only meets the good welding requirement, but also is suitable for the surface treatment of the line with the line width/line distance below 0.5mil/0.5mil or even smaller, and the invention can completely meet the improvement of the technical capability of the surface treatment of the precise line and the HDI board; in the gold-palladium-gold process, in order to meet the requirement of good bonding force of alloy layers, the middle palladium layer is deposited in a reduction reaction mode; the deposited palladium layer is a pure palladium layer, does not contain byproducts such as phosphorus, boron and the like, and has better extension and bending properties, and the bending resistance of the gold-palladium-gold is better than that of a common soft-plate nickel-gold plating layer and a nickel-palladium-gold plating layer; meanwhile, the palladium plating solution adopts sulfuric acid type main salt, so that a stable coordination palladium ion system can be obtained, and the attack of the palladium plating solution on solder resist ink can be reduced.
Drawings
FIG. 1 is a graph showing the plating rate and the plating stability of the palladium plating solution in example 1;
FIG. 2 is a graph showing the plating rate and the plating stability of the palladium plating solution in example 2;
FIG. 3 is a graph showing the plating rate and the plating stability of the palladium plating solution in example 3;
FIG. 4 is a graph showing the plating rate and the plating stability of the palladium plating solution in example 4;
FIG. 5 is a graph showing the plating rate and the plating stability of the palladium plating solution in example 5;
FIG. 6 is a graph showing the expression of the plating rate and the plating stability of the palladium liquid in comparative example 1;
FIG. 7 is a graph showing the expression of the plating rate and the plating stability of the palladium liquid in comparative example 2.
Detailed Description
In order to express the present invention more clearly, the present invention is further described below with reference to examples.
The invention provides a chemical palladium solution applied to a chemical gold-palladium-gold plating layer on a PCB (printed Circuit Board), which comprises main salt, a coordination agent, a reducing agent, a stabilizing agent, a pH buffering agent and a surfactant, wherein a 1L preparation tank is prepared as an example, and the ratio of the components is as follows by taking the mass concentration as a unit:
palladium concentration in main salt: 0.4-0.6g/L
A complexing agent: 0.1-30g/L
Reducing agent: 0.1-25g/L
A stabilizer: 1-150mg/L
pH buffer: 1-25g/L
Surfactant (b): 0.1-10mg/L
The rest components are pure water;
carrying a stirring pump according to the volume of the palladium tank; the volume of the palladium tank is mainly used to determine the solvent of the palladium solution to be prepared.
Adding 50% of water into a palladium tank, adding a coordination agent, a reducing agent, a stabilizing agent and a surfactant once in the process of continuously stirring, adjusting the pH value to be within the range of 7.0-7.8, then adding a pH buffering agent, and finally adding main salt to a constant volume of 1L to form a palladium solution.
Compared with the prior art, the chemical palladium solution applied to the chemical gold palladium gold plating layer on the PCB provided by the invention has the following advantages:
1) the palladium sulfate or palladium ammonia sulfate is used as main salt, a coordination system formed by the palladium sulfate or the palladium ammonia sulfate and the coordination agent in the system is more stable, and the service life of the bath solution is longer;
2) the proper content of the complexing agent can well control the deposition rate of palladium and the compactness of the palladium layer, and meanwhile, the palladium layer with excellent ductility can be obtained;
3) the used reducing agent does not produce byproduct phosphorus, and a compact pure palladium layer can be obtained, and the pure palladium layer has higher ductility and better bending resistance than the phosphorus-palladium layer; meanwhile, the deposition rate of palladium can be controlled according to the requirement by adjusting the amount of the reducing agent, and the compact palladium layer can also prevent the substrate copper from migrating to the gold layer after multiple times of backflow;
4) the stabilizer can well control the occurrence of autocatalytic reaction in the palladium tank, prevent the precipitation of the palladium tank caused by homogeneous catalysis in use and better ensure the continuous and stable operation of the autocatalytic reaction of the heterogeneous surface in the tank liquor;
5) the existence of the pH buffering agent can ensure that the pH value of the bath solution is maintained in a dynamic equilibrium range in the service cycle of the palladium bath, thereby ensuring the stability of the deposition rate, the quality of a plating layer and the service life of the bath solution;
6) the surfactant can be used for wetting micropores, blind holes and step grooves in the PCB, so that the plating leakage in the bonding pad, the holes and the grooves is prevented;
7) due to the difference of plating layers, the difficulty of depositing palladium on a gold layer is higher than that on a nickel layer, the deposition of a thick palladium layer on the gold layer needs to be realized, and the palladium plating solution needs to have reducibility. Meanwhile, the palladium deposited on the gold layer has different requirements on compactness, binding force and deposition rate than the palladium deposited on the nickel layer;
8) the palladium solution used in the gold-palladium-gold process is suitable for IC carrier plates, wafer packages, printed circuit boards, flexible circuit boards or rigid-flex printed boards;
10) the invention not only meets the good welding requirement, but also is suitable for the surface treatment of the line with the line width/line distance below 0.5mil/0.5mil or even smaller, and the invention can completely meet the improvement of the technical capability of the surface treatment of the precise line and the HDI board; in the gold-palladium-gold process, in order to meet the requirement of good bonding force of alloy layers, the middle palladium layer is deposited in a reduction reaction mode; the deposited palladium layer is a pure palladium layer, does not contain byproducts such as phosphorus, boron and the like, and has better extension and bending properties, and the bending resistance of the gold-palladium-gold is better than that of a common soft-plate nickel-gold plating layer and a nickel-palladium-gold plating layer; meanwhile, the palladium plating solution adopts sulfuric acid type main salt, so that a stable coordination palladium ion system can be obtained, and the attack of the palladium plating solution on solder resist ink can be reduced;
11) the technology solves the problem that in the palladium-gold surface treatment process on the copper substrate, after repeated reflow soldering, copper ions easily pass through the palladium layer and migrate to the gold layer, so that poor soldering at the later stage is caused; the problem of diffusion plating of fine lines (line width and line distance of 1.5mil/1.5mil and below) during surface treatment after single-sided and double-sided FPC develop towards HDI is solved, and the method can be used for bonding of finer bonding pads; the problem that cracks are easy to generate after the common FPC is subjected to surface treatment and is bent for multiple times is solved.
In the embodiment, the palladium layer obtained by the palladium solution has flat and bright appearance, no diffusion plating on fine lines, no leakage plating in the holes of micropores and blind holes, no whitening and falling off phenomena of the lines, plating for 8-18 minutes, the plating thickness of the plating layer of 3.0-5.0 mu inch, the stability of the palladium solution reaches 5MTO, and the plating layer by a 3M adhesive tape method has good bonding force; and the palladium solution is suitable for fine lines; and the fine line has a line width and a line spacing of 1.5mil or less than 1.5mil, which indicates that the palladium solution is suitable for the fine line; the palladium solution is used at a temperature of 40-60 ℃ and the pH is controlled at 7.0-7.8.
In this embodiment, the main salt is one or more of palladium chloride, palladium tetraammine chloride, palladium sulfate or palladium ammonia sulfate, and the concentration of palladium (in terms of Pd)2+Calculated) is 0.4-0.6 g/L.
In this embodiment, the complexing agent is: one or more of ethylenediamine, benzylamine, N-benzyl methylamine, 4-fluorobenzylamine, N-methyl-1-naphthalene methylamine and furfuryl amine. Wherein when used singly, the weight ratio of ethylene diamine: 1-15g/L, benzylamine: 1-10 g/L; 4-fluorobenzylamine: 0.1-2g/L, furfuryl amine: 0.1-5 g/L. It is stated that, if only one of these is selected, the concentrations are as set forth above, and if a plurality of them are used in combination, they have the same effect.
In this example, the stabilizer is one or more of 7- (diethylamino) coumarin, thiodiglycolic acid, 2, 2-bipyridine, 2, 3-dihydroxyquinoxaline. Wherein, when used alone, the 7- (diethylamino) coumarin: 1-50mg/L, thiodiglycolic acid: 1-100mg/L, and if the composition is used in combination, the composition has the same effect.
In this embodiment, the reducing agent is one or more of hydroxylamine hydrochloride, hydroxylamine sulfate, N-diethylhydroxylamine, N-dibenzylhydroxylamine, N-methylhydroxylamine hydrochloride, methoxylamine hydrochloride, O-benzylhydroxylamine hydrochloride, and D-mannitol. Wherein, when used singly, the ratio of hydroxylamine sulfate: 0.1-10g/L, N, N-diethylhydroxylamine: 0.1-10g/L, D-mannitol: 0.1-5g/L, and if the two are used in combination, the effect is the same.
In this embodiment, the pH buffer is one or more of glycine, ammonium sulfate, ammonium chloride, and ammonium acetate. Wherein when used singly, glycine: 1-10g/L and 1-15g/L of ammonium sulfate, and if the ammonium sulfate and the ammonium sulfate are used in combination, the same effect is achieved.
In the embodiment, the surfactant is one or more of tetrabutylammonium hydrogen sulfate and hexadecyl trimethyl ammonium hydrogen sulfate, wherein when the surfactant is used singly, the tetrabutylammonium hydrogen sulfate is 0.1-2 mg/L; cetyl trimethyl ammonium hydrogen sulfate: 0.1-5mg/L, and if the composition is used in combination, the composition has the same effect.
The Au-Pd-Au plating layer is obtained on the copper substrate by the following method.
Oil removal cleaning (55-60 ℃, 5 minutes) → hot water washing (55-60 ℃, 1-2 minutes) → pure water washing I (room temperature, 1 minute) → microetching (potassium persulfate 80g/L, sulfuric acid 30mL/L, 2-3 minutes) → pure water washing II (room temperature, 1 minute) → presoaking (sulfuric acid 20mL/L, room, 1 minute) → chemical immersion gold (palladium tank water matched with gold palladium gold process, pH 6.2-6.8, 84-90 ℃, 1-3 minutes) → post immersion (post immersion water matched with gold palladium gold process, pH 3.0-4.0, room temperature, 1 minute) → pure water washing III (room temperature, 1 minute) → pure water washing IV (room temperature, 1 minute) → chemical plating palladium (adopting the formula of the palladium plating solution of the embodiment of the invention, pH 7.0-7.8, 40-60 ℃, 8-18 minutes) → pure water washing IV (room temperature, 1 minute) → pure water washing V) (room temperature, 1 minute) → pure water washing I (room temperature, 1 minute), 1 minute) → pure water washing VI (room temperature, 1 minute) → pure water washing VII (room temperature, 1 minute) → chemical gold leaching (the palladium bath solution matched with the my gold-palladium-gold process, the pH value is 6.2-6.8, 84-90 ℃, 10-15 minutes) → hot water washing (70-80 ℃, 1 minute) → pure water washing VIII (room temperature, 1 minute) → drying.
The invention is illustrated by the following specific examples:
example 1:
palladium sulfate (in Pd)2+Meter): 0.3g/L, ethylenediamine: 5g/L, 4-fluorobenzylamine: 2g/L, hydroxylamine sulfate: 3g/L, 7- (diethylamino) coumarin: 15mg/L, glycine: 5g/L, ammonium sulfate: 8g/L, tetrabutyl hydrogen sulfateAmmonium: 2mg/L temperature: 60 ℃ and pH 7.5.
The palladium layer obtained under the parameters has the advantages of flat and bright appearance, no diffusion plating on a fine circuit, no leakage plating in micro and blind holes, no phenomena of whitening and falling off of the circuit and the like, the plating thickness is 4.3 mu inch (plating for 15 minutes), the bath solution stability reaches 6MTO (performing a circulation experiment on palladium plating on a copper substrate, and in the case of plating solution with the build-up bath palladium concentration of 0.3g/L, 0.3g/L of palladium is precipitated on the substrate and is called 1MTO), and the plating layer of the 3M adhesive tape method has good bonding force. Meanwhile, after the bending resistance of the plating layer is tested, no obvious crack is observed after the plating layer is amplified by 100 times; soldering test shows that the pad is well wetted and fully coated with tin; the bonding performance is excellent, and the tensile force of the gold wire reaches more than 10 g.
Example 2:
palladium ammonia sulfate (as Pd)2+Meter): 0.6g/L, ethylenediamine: 10g/L, benzylamine: 1g/L, N, N-diethylhydroxylamine: 10g/L, 7- (diethylamino) coumarin: 50mg/L, glycine: 1g/L, ammonium sulfate: 4g/L, tetrabutylammonium hydrogen sulfate: 0.1mg/L temperature: pH 7.0 at 40 ℃
The palladium layer obtained under the parameters has the advantages of flat and bright appearance, no diffusion plating on a fine circuit, no leakage plating in micro and blind holes, no phenomena of whitening, falling off and the like of the circuit, the plating thickness of 3.2 mu inch (plating for 10 minutes), the bath solution stability of 6MTO and good plating bonding force of a 3M adhesive tape method plating layer. Meanwhile, after the bending resistance of the plating layer is tested, no obvious crack is observed after the plating layer is amplified by 100 times; soldering test shows that the pad is well wetted and fully coated with tin; the bonding performance is excellent, and the tensile force of the gold wire reaches more than 10 g.
Example 3:
palladium ammonia sulfate (as Pd)2+Meter): 0.4g/L, furfuryl amine: 5g/L, benzylamine: 10g/L, D-mannitol: 2g/L, thiodiglycolic acid: 100mg/L, glycine: 3g/L, ammonium sulfate: 15g/L, hexadecyl trimethyl ammonium hydrogen sulfate: temperature of 5 mg/L: 50 ℃ and pH 7.2
The palladium layer obtained under the parameters has the advantages of flat and bright appearance, no diffusion plating on a fine circuit, no leakage plating in micro and blind holes, no phenomena of whitening, falling off and the like of the circuit, the plating thickness of 4.6 mu inch (plating for 15 minutes), the bath solution stability of 5.5MTO and good plating bonding force of a 3M adhesive tape method plating layer. Meanwhile, no obvious crack is observed after the bending resistance of the plating layer is amplified by 100 times; soldering test shows that the pad is well wetted and fully coated with tin; the bonding performance is excellent, and the tensile force of the gold wire reaches more than 10 g.
Example 4:
palladium sulfate (in Pd)2+Meter): 0.5g/L, ethylenediamine: 5g/L, 4-fluorobenzylamine: 2g/L, N, N-diethylhydroxylamine: 3g/L, 7- (diethylamino) coumarin: 15mg/L, glycine: 5g/L, ammonium sulfate:
8g/L, tetrabutylammonium hydrogen sulfate: 2mg/L temperature: pH 7.5 at 40 ℃
The palladium layer obtained under the parameters has the advantages of flat and bright appearance, no diffusion plating on a fine circuit, no leakage plating in micro and blind holes, no phenomena of whitening, falling off and the like of the circuit, the plating thickness of 3.0 mu inch (plating for 8 minutes), the bath solution stability of 5MTO and good plating bonding force of a 3M adhesive tape method plating layer. Meanwhile, no obvious crack is observed after the bending resistance of the plating layer is amplified by 100 times; soldering test shows that the pad is well wetted and fully coated with tin; the bonding performance is excellent, and the tensile force of the gold wire reaches more than 10 g.
Example 5:
palladium ammonia sulfate (as Pd)2+Meter): 0.3g/L, ethylenediamine: 2g/L, 4-fluorobenzylamine: 2g/L, furfuryl amine: 3g/L, hydroxylamine sulfate: 10g/L, 7- (diethylamino) coumarin: 15mg/L, glycine: 5g/L, ammonium sulfate: 8g/L, tetrabutylammonium hydrogen sulfate: 2mg/L temperature: 60 ℃ and pH 7.8
The palladium layer obtained under the parameters has the advantages of flat and bright appearance, no diffusion plating on a fine circuit, no leakage plating in micro and blind holes, no phenomena of whitening, falling off and the like of the circuit, the plating thickness of 5.0 mu inch (plating for 18 minutes), the bath solution stability of 6MTO and good plating bonding force of a 3M adhesive tape method plating layer. Meanwhile, no obvious crack is observed after the bending resistance of the plating layer is amplified by 100 times; soldering test shows that the pad is well wetted and fully coated with tin; the bonding performance is excellent, and the tensile force of the gold wire reaches more than 10 g.
Comparative example 1:
palladium tetraamine sulfate (as Pd)2+Meter): 2.5g/L
Main complexing agent: 30mL/L of ammonia water and 20g/L of malic acid;
auxiliary complexing agent: 1g/L succinic acid and 12g/L potassium sodium tartrate;
reducing agent: 10g/L of formic acid;
a stabilizer: bismuth nitrate 0.1 g/L;
pH buffer: 15g/L of borax;
surfactant (b): none;
plating conditions are as follows: temperature: 60 ℃; pH: 6.5;
the palladium plating solution in the nickel-palladium-gold process is used for preparing a palladium layer in the gold-palladium-gold process by using the parameters, although the test board has no phenomena of missing plating in micro holes and blind holes, lines do not fall off and the like, the appearance of a pad of the test board is dim, obvious color difference exists in the pad, slight diffusion plating is also carried out on fine lines, the plating time is 15 minutes, the plating thickness is 1.4 mu inch, the plating time is prolonged, the increase of the palladium thickness is slowed, and the palladium thickness deposited in 5.0 mu inch needs at least 45 minutes. Meanwhile, the stability of the bath solution in the aging experiment can only achieve 3MTO, and the palladium throwing phenomenon occurs in the binding force of a 3M adhesive tape method coating.
Comparative example 2:
palladium sulfate (in Pd)2+Meter): 1.2 g/L;
complexing agent: 10g/L of ethylenediamine and 10g/L of glycine; triethanolamine 3g/L
Reducing agent: 5g/L of sodium hypophosphite;
a stabilizer: 0.2g/L of thiourea;
pH buffer: 20g/L of monopotassium phosphate;
surfactant (b): none;
plating conditions are as follows: temperature: 60 ℃; pH: 7.0.
the palladium plating solution in the nickel-palladium-gold process is used for preparing the palladium layer in the gold-palladium-gold process by using the parameters, the palladium layer of the test board is flat and bright in appearance and has no leakage plating in a micro blind hole, but the phenomenon that a fine circuit is seriously seeped and plated, the circuit is whitish, the color difference of a bonding pad is serious and the like occurs, the plating is carried out for 10 minutes, the plating thickness is 1.3 mu inch, the plating time is prolonged, the increase of the palladium thickness is slowed down, and the palladium thickness deposited in 5.0 mu inch needs at least 35 minutes. Meanwhile, in an aging experiment, the service life of the bath solution can only reach 4MTO, the bonding force of a 3M adhesive tape method coating is seriously flawed, and the coating has obvious cracks in a bending resistance test.
Combining the results and figures of examples 1-5 above and comparative examples 1, 2, it can be seen that: the palladium plating solutions of comparative examples 1 and 2 are obviously poorer than the palladium plating solution provided by the invention in the aspects of plating speed and plating stability, particularly the comparative examples 1 and 2 cannot meet the requirements of a gold-palladium-gold process on fine lines, and the palladium plating solutions of the comparative examples 1 and 2 have obvious diffusion plating in the fine lines with the line width of 0.5mil and the line spacing of 0.8 mil. The palladium plating formula of the invention has moderate palladium deposition rate and good stability, can generally reach more than 5MTO, can obtain a palladium plating layer with smooth surface, brightness and compactness, particularly has good welding, bonding and fine pattern transfer performances, and can meet the requirements of a new generation of gold-palladium-gold products.
The above disclosure is only for a few specific embodiments of the present invention, but the present invention is not limited thereto, and any variations that can be made by those skilled in the art are intended to fall within the scope of the present invention.
Claims (7)
1. A preparation method of a chemical gold-palladium-gold plating layer applied to a PCB is characterized in that a chemical palladium solution comprises main salt, a coordination agent, a reducing agent, a stabilizing agent, a pH buffering agent and a surfactant, and the chemical palladium solution comprises the following components in percentage by mass:
palladium concentration in main salt: 0.4-0.6g/L
A complexing agent: 0.1-30g/L
Reducing agent: 0.1-25g/L
A stabilizer: 1-150mg/L
pH buffer: 1-25g/L
Surfactant (b): 0.1-10mg/L
The rest components are pure water;
carrying a stirring pump according to the volume of the palladium tank;
firstly adding 50% of pure water into a palladium tank, sequentially adding a coordination agent, a reducing agent, a stabilizing agent and a surfactant in the process of continuously stirring, adjusting the pH value of the tank liquor to be within the range of 7.0-7.8, then adding a pH buffering agent, and finally adding main salt and fixing the volume to form a palladium solution; the palladium layer obtained by the palladium solution has flat and bright appearance, no diffusion plating on fine lines, no leakage plating in the pores of micropores and blind holes, no whitening and falling-off phenomena of the lines, plating for 8-18 minutes, plating thickness of 3.0-5.0 mu inch, stability of the palladium solution reaching 5MTO, and good plating bonding force of a 3M adhesive tape method; and the palladium solution is suitable for the surface treatment of the circuit with the line width/line distance of less than 0.5mil/0.5mil or even smaller;
the plating layer deposited by the gold-palladium-gold process is divided into three layers of gold-palladium-gold, wherein the first layer is a gold layer; the second layer is a palladium layer and the third layer is a gold layer.
2. The method for preparing chemical gold palladium gold plating layer used on PCB of claim 1, wherein the main salt is one or more of palladium chloride, palladium tetraammine chloride, palladium sulfate or palladium ammonia sulfate.
3. The method for preparing chemical gold palladium gold plating layer applied on PCB as claimed in claim 1, wherein the complexing agent is: one or more of ethylenediamine, benzylamine, N-benzyl methylamine, 4-fluorobenzylamine, N-methyl-1-naphthalene methylamine and furfuryl amine.
4. The method for preparing chemical Au-Pd-Au plating layer applied on PCB as recited in claim 1, wherein the stabilizer is one or more of 7- (diethylamino) coumarin, thiodiglycolic acid, 2, 2-bipyridine, 2, 3-dihydroxyquinoxaline.
5. The method of claim 1, wherein the reducing agent is one or more of hydroxylamine hydrochloride, hydroxylamine sulfate, N-diethylhydroxylamine, N-dibenzylhydroxylamine, N-methylhydroxylamine hydrochloride, methoxyamine hydrochloride, O-benzylhydroxylamine hydrochloride, and D-mannitol.
6. The method for preparing chemical gold palladium gold plating layer used on PCB of claim 1, wherein the pH buffer is one or more of glycine, ammonium sulfate, ammonium chloride, ammonium acetate.
7. The method for preparing chemical gold palladium gold plating layer used on PCB of claim 1, wherein the surfactant is one or more of tetrabutylammonium hydrogen sulfate and hexadecyl trimethyl ammonium hydrogen sulfate.
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