CN112531431A - Preparation of high-stability low-impedance spring needle electric connector and probe electroplating process - Google Patents

Abstract

The invention relates to the field of Pogo pins of an electric connector, and discloses a preparation and probe electroplating process for providing a high-stability low-impedance spring Pin electric connector, which comprises the following steps: the discrete components are assembled after independent quality treatment, and the needle head is prepared by adopting a high-stability electroplating process; the SUS stainless steel fitting is electroplated with hard gold in a rolling way, the needle tube is prepared by adopting a method of chemical polishing activation and electroless deposition special coating, and a chemical surface plating process is adopted, so that the surface coating hardness HV can exceed HV 165. The electric connector Pogo Pin formed by the structure has the excellent characteristics of high stability and low impedance. The preparation of the special probe is more stable, has targeting property and is environment-friendly.

Description

Preparation of high-stability low-impedance spring needle electric connector and probe electroplating process

Technical Field

The invention relates to the technical field of Pogo pins of an electric connector, in particular to a preparation and probe electroplating process of a high-stability low-impedance spring Pin electric connector.

Background

Connectors are important carriers between electrical and signal transmission. The new and vigorous development of Pogo Pin connectors is a major part of the development of the connector industry. More and more 3C electronic products adopt magnetic attraction charging; more and more special steady-state probes are required to be hardnucleated (e.g., finished "optical, acoustical, electrical, sensing" pole probes). Durability and long life are excellent characteristics of Pogo Pin connectors, as distinguished from other types of connectors. Meanwhile, the Pogo Pin and the probe belong to the same pulse; the probe is a part of the development direction of the probe (such as a precision electric sensor probe). Simple metaphors: the Pogo Pin needle element is a simple probe.

The Pogo Pin connector is a Pogo Pin connector. As a component for electrical connection, it is required to have low impedance and high stability. And in a non-working state, the Pogo Pin is in a free and flat state. And when the transmission (working) state is conducted, the Pogo Pin is compressed (sliding) in a touch mode.

The Pogo Pin is composed of a needle, a needle tube and a spring (without a ball). In order to achieve low impedance of 3 parts, the method of barrel plating hard gold on the independent parts is generally adopted. The needle and the needle tube are then riveted to each other to form an integral unit. The needle head and the needle tube are made of copper alloy materials, and the spring (and the marble) is made of stainless steel or beryllium copper materials. The marble is used as a catalyst for the spring and the needle head and is used as a structural material for bearing a large current design. When in working state, the needle head and the inner barrel wall of the needle tube generate shearing type positive force. The contact resistance requirement of the Pogo Pin connector is low: within 30-50 milliohms. When the forward force is small, the soft metal has the smallest contact resistance, and then gold palladium, hard gold, palladium and palladium nickel are used. When the forward force is large, the resistivity of the inner layer is the dominant factor of the contact resistance; the chemical nickel plating often has poor contact resistance due to inclusion and coarse crystalline phase, which is far greater than the resistance of electrolytic nickel plating. When the forward force is small, the surface conduction is a bottleneck. When the positive force is large, the conduction of the inner layer is a bottleneck. Control of wear between materials is also important because of the use of sliding, pressing, and springing. The barrel plating treatment does not generate dead angles (defects) for parts without inner holes, and all parts have plating layers; however, the barrel plating is generally subject to scaling and is not sufficient when the requirements of ensuring the quality (strength, hardness and thickness) of a plating layer in an inner hole (wall) are required. Such as Pogo Pin inner wall plating requirements: the gold plating on the inner wall of the needle tube with 2.5mm inside is 0.75 micron. Hard gold with a practical periphery of more than 1 micron is far from the requirement. The requirement of the German Bosch group is that the hard gold plating layer is not less than HV140 (gold cobalt, gold iron indium) or not less than HV120 (gold nickel). The wear resistance can be improved by improving the hardness of gold; but increasing the gold hardness also increases the contact resistance. The hardness of the gold is improved, the brittleness of the gold is increased, an abrasive wear mechanism is induced, and the wear performance is reduced. Further: hard gold is not suitable for being applied to occasions with the working temperature of more than 125 degrees. In addition: in an atmosphere of H2S; high temperature and high humidity; it is sufficient to use a palladium alloy. The hardness of the plated PNP palladium nickel is more than 450 HV. The hardness of the PCP palladium-cobalt is more than 400-450 HV. Electroplating pure palladium PDP at 250-350 HV. Palladium is commonly used for preventing silver coating from discoloring and for forming an intermediate barrier coating (preventing silver-gold from being alloyed) of gold after silver coating. The palladium is a noble metal and can be directly plated on the surface of copper or silver. The palladium metal has certain catalytic activity without electroless plating. The palladium plating layer can be soldered, and the contact resistance is also very small. In the electronic industry, a palladium plating process is widely applied to improve the wear resistance of radio elements and waveguide devices during operation and improve the contact reliability of sliding contact elements. In the next 10 years, the research and application of cyanide-free environment-friendly chemical immersion gold obtain great results; the electroless chemical deposition technology is used for depositing the chemical deposition gold layer with extremely fine crystalline phase and controllable growth, and if the chemical deposition gold layer is used as an inner cavity plating layer and matched with palladium gold, the application of parts is more stable and reliable. The palladium electroplating efficiency is 70-90%; hydrogen evolution is accompanied in the palladium plating process. When the thin palladium is electroplated, attention needs to be paid to hydrogen permeation, and the mechanical property of the plated part is prevented from being influenced by hydrogen embrittlement.

The hardness of the copper alloy for Pogo Pin needs to be greater than 400 HV.. Parts of the assembly (after plating): the hardness of the face and body cores is higher than HV 160.

Contact resistance is mainly affected by contact material, positive pressure, surface state, applied voltage and current, etc.: "contact resistance-millivolt method" provides that, in order to prevent the membrane layer on the contact from being broken down, the peak open circuit voltage of the test loop ac or dc should not be more than 20mV, and the contact resistance of the Pogo Pin itself should be low with a current of not more than 100mA. in the ac or dc test: within 30-50 milliohms. Gold is a noble metal: it has high anticorrosion and decorative properties and low impedance (natural low impedance comparison: silver > gold > rhodium > ruthenium > palladium > platinum).

The current situation is as follows: copper alloy needles and tubes are commonly barrel plated with hard gold. Firstly, a nickel-free release process: and barrel-plating white copper tin or cuprous cyanide as a bottom layer, and then barrel-plating hard gold. Of course, rhodium, ruthenium, rhodium ruthenium, white tin cobalt, palladium, silver, tin cerium, copper zinc, matte tin, zinc nickel, copper cerium, copper tin, indium, platinum, etc. may be arranged in the layer (depending on the use and function of the product). Secondly, the nickel process comprises the following steps: modified nickel plating of sulfamic acid type or ordinary nickel matte sulfate, followed by barrel plating of hard gold. The disadvantages are that: firstly, the highly toxic cyanide is electroplated, which is not environment-friendly and not friendly; it is often prohibited due to strict policy. Secondly, the quality of the coating on the inner wall of the needle tube is extremely weak. The saturation depth and the crystal phase hardness fully coated in the inner wall are undesirable and weak; this also results in a weak contact resistance for "positive force" sliding. The condition of plating thick noble metal gold is difficult to be ideal; and the cost amplification does not achieve the problem solution. From the requirements of assembly allowance and compactness of precision parts, over-design thickness gold plating is also insufficient.

When the electroplating quality of the inner cavity needs to be guaranteed, an electroless plating method is often adopted to realize plating. In the field of Pogo pins, the needle head and the needle tube which are the components of the spring needle are freshly plated chemically. In the plating boundary: the PCB area is provided with the methods of chemical nickel plating and chemical gold plating (a static electroplating layer is used). Returning to Pogo Pin, due to chemical nickel phosphorus inclusions and grain coarseness, even if its HV > 500 and as static resistance is not large (not in milliohm scale), even if the "" forward force "" is a large invisible static consideration, the task of transferring the state is very small and sensitive to the impedance requirements; no electrolytic nickel deposition will fail NG.

Disclosure of Invention

The invention aims to provide a preparation and probe electroplating process of a high-stability low-impedance spring pin electric connector, which has the excellent characteristics of high stability and low impedance, is more stable, has targeting property and is environment-friendly for the preparation of special probes, and solves the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme: the preparation method of the high-stability low-impedance spring pin electric connector comprises the following steps: the discrete components are assembled after independent quality treatment, and the needle head is prepared by adopting a high-stability electroplating process; the SUS stainless steel fitting is electroplated with hard gold in a rolling way, the needle tube is prepared by adopting a method of chemical polishing activation and electroless deposition special coating, and a chemical surface plating process is adopted, so that the surface coating hardness HV can exceed HV 165.

Further, depending on the grade of the needle cannula component, the outermost coating may be any one or combination of electroless palladium-P, electroless hard gold, and electroless ruthenium.

A probe electroplating process of a high-stability low-impedance spring pin electric connector is characterized in that electroless copper deposition is used as an intermediate structure barrier layer on a base material copper alloy, and the hard gold index HV140 is referred; the better chemical copper plating needs to ensure HV 150-165.

Further, hard gold is electroplated on a spring roller, and after an SUS material is treated by hydrochloric acid, urotropine and a surfactant, pre-plating nickel sulfamate for correcting a PH system is adopted for bottom plating; the method ensures good plating quality, the barrel plating hard gold can adopt an environment-friendly formula or a formula of a aurous cyanide citric acid system, the environment-friendly formula can adopt a gold potassium citrate system of a Rohm and Haas CM supplementary additive system, and the specific formula is as follows: 2-4 g/L of gold potassium citrate, 140-150 g/L of potassium citrate, 20-30 g/L of citric acid, 4.2-4.5 of PH and 0.3-0.5 g/L of cobalt; the gold plating intermediate additive is suitable; the temperature is 35-40 ℃.

Further, the needle tube is plated with the chemical palladium-P alloy on the chemical copper deposition, and the chemical copper deposition needs activation treatment: 0.05-0.1 g/L of palladium chloride; 0.5-1 ml/L of 37% hydrochloric acid, 1-2S, normal temperature, or: 15-30 mg/L of palladium sulfate; 5-10 ml/L sulfuric acid, normal temperature: 20-40S.

Further, the needle tube is chemically plated with palladium-P alloy, and the formula of the needle tube is as follows: 2g/L of palladium chloride; 4ml/L of 37% hydrochloric acid; 160-164 ml/L of 28% ammonia water; 25ml/L of ethylenediamine; 50mg/L of bismuth nitrate; 10-15 g/L (12 is better) of NaH2PO2. H2O; the temperature is 48-55 degrees; PH is not less than 9.8 plus or minus 0.2, plating speed: about 1um/H, the obtained plating layer is compact and uniform, has no obvious defects and pinholes, and contains P within 3.2-5%.

Further, a plating layer before chemical palladium-P plating is of chemical copper plating HV160 type, weak corrosion is needed after chemical copper plating, the process is that 4% sulfuric acid water is treated at normal temperature for 3-5 seconds, and then the pre-palladium activation is removed after flowing water is washed.

Further, when the needle head and the needle tube are treated corresponding to the copper alloy base material, the surface pretreatment process comprises the following steps: ultrasonic dewaxing, ultrasonic oil removal, chemical polishing, water washing, sulfuric acid activation and water washing.

Further, the chemical polishing process corresponding to the copper alloy substrate comprises the following steps: environmental protection: 40g/L of oxalic acid, 18 g/L of sodium hydroxide, 120-150 ml/L of 30% hydrogen peroxide, 0.1-0.15 g/L of BTA benzotriazole, 4-8 ml/L of ethanol and 3-4 of PH (adjusted by caustic soda grains/glacial acetic acid); normal temperature, 20-40S, non-environmental protection: 40ml of nitric acid; 60ml of glacial acetic acid; 5g of potassium dichromate; 3g of copper chloride; mixing 1 liter; and (5) at normal temperature for 10-15S.

Furthermore, as the bottom plating layer of the needle tube, the chemical copper plating layer is used as an intermediate structure layer, the conjunction between the needle tube base material and the surface layer palladium-P is effectively adjusted, the thickness of the chemical copper plating layer is about 1.5-3 microns, and the specific process comprises the following steps: 12g/L of blue vitriol; KNaC4H4O 613 tetrahydrate/L; 20g/L of disodium EDTA dihydrate; 11ml/L of 37% formaldehyde; 4-12 mg/L of potassium ferrocyanide; 100-150 mg/L of C6H14O2N4.HCl (arginine hydrochloride); 80-140 mg/L of vanadium pentoxide; adjusting pH to 12 with potassium hydroxide; the temperature is 35-40 degrees, and HV is 165 after the coating hardness measurement of 60 um.

Compared with the prior art, the invention has the beneficial effects that:

the electric connector Pogo Pin has the excellent characteristics of high stability and low impedance, and is more stable, targeted and environment-friendly to the preparation of special probes.

Detailed Description

The following examples will explain the present invention in detail, however, the present invention is not limited thereto. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The preparation method of the high-stability low-impedance spring pin electric connector can be widely applied to various special probes (surface treatment manufacturing). The specific Pogo Pin is prepared as follows: the discrete component independent mass processed assembly fabric. The needle head is prepared by adopting a high-stability electroplating process; the preparation method is roll electroplating. SUS stainless steel fittings (springs) were roll plated with hard gold. The needle tube is prepared by adopting a method of chemical polishing activation and electroless deposition of a special coating. In particular, the outermost plating layer can be one or a combination of electroless palladium-P plating, electroless hard gold plating and electroless ruthenium plating according to the grade of the (needle tube) part requirement. By adopting the novel chemical surface plating process, the hardness HV of the surface layer (independent) plating layer can exceed HV165 (the hardness is measured by a palladium-P plating layer containing P2%).

The probe electroplating process for the high-stability low-impedance pogo pin electric connector is characterized in that electroless copper deposition is used as an intermediate structure barrier layer on a base material copper alloy. Reference hard gold index HV 140; the better chemical copper plating needs to ensure HV 150-165, and tests show that the HV can reach HV165 by adopting the novel chemical copper plating process.

And electroplating hard gold on the spring roller. After SUS materials are treated by hydrochloric acid, urotropine and surfactant, pre-plating nickel sulfamate for correcting a PH system is adopted for bottom plating; ensuring good coating quality. The barrel plating hard gold can adopt an environment-friendly formula or a formula of aurous cyanide citric acid system (containing cobalt). The environment-friendly formula can adopt a gold potassium citrate system of a Rohm and Haas CM type supplementary additive system. The specific formula comprises 2-4 g/L of gold potassium citrate, 140-150 g/L of potassium citrate, 20-30 g/L of citric acid, 4.2-4.5 of PH and 0.3-0.5 g/L of cobalt; gold plating type intermediate (organic and inorganic) additives are suitable; the temperature is 35-40 degrees; dk (barrel plating 0.1-0.4A/dm 2).

The tube is plated with chemical palladium-P alloy on chemical deposited copper. Activation treatment is needed after electroless copper plating: 0.05-0.1 g/L of palladium chloride; 0.5-1 ml/L of 37% hydrochloric acid. 1-2S. And (5) normal temperature. Or: 15-30 mg/L of palladium (palladium sulfate); 5-10 ml/L sulfuric acid. Normal temperature: 20-40S, preferably the latter formula in environmental protection.

The needle tube is chemically plated with palladium-P alloy. The formula is as follows: 2g/L of palladium chloride; 4ml/L of 37% hydrochloric acid; 160-164 ml/L of 28% ammonia water; 25ml/L (or 32-40 g/L ammonium chloride) of ethylenediamine; 50mg/L of bismuth nitrate; 10-15 g/L (12 is better) of NaH2PO2. H2O; the temperature is 48-55 degrees (51-52 degrees is the best); PH 9.8 ≥ 0.2(9.6 is preferred), plating speed: about 1um/H, the obtained plating layer is compact and uniform, and has no obvious defects and pinholes. Generally, the P content is within 3.2-5%. (more than 2%) hardness value is more than 165HV, and is suitable for the inner wall coating of the needle tube (preferably the sliding contact combination of the needle head plated with hard gold coating); contact resistance is guaranteed OK. In addition, the chemical palladium-P coating has solderability, corrosion resistance and wear resistance which are comparable with those of the hard gold coating. The chemical palladium process has high plating solution stability. The stress of the plating layer (hydrogen evolution) is fully reduced, and the crack phenomenon in the plating process can be effectively prevented. Therefore, the formula of the chemical palladium-P is adopted.

The plating layer before electroless palladium-P plating is electroless copper HV160 type. Weak corrosion is required after electroless copper plating. The process is to treat 4% sulfuric acid water at normal temperature for 3-5 seconds. Then the pre-palladium activation is removed after flowing water washing.

When the needle head and the needle tube are treated corresponding to the copper alloy base material, the surface pretreatment process comprises the following steps: (ultrasonic dewaxing-) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -.

The chemical polishing process corresponding to the copper alloy base material comprises the following steps: the cost of the environment-friendly (40 g/L of oxalic acid, 18 g/L of sodium hydroxide, (30%) of hydrogen peroxide is 120-150 ml/L, 0.1-0.15 g/L of BTA benzotriazole, 4-8 ml/L (can be in the range of 2-10.5 ml/L) of ethanol, 3-4 (3.58) [ caustic soda particles/glacial acetic acid adjustment ], normal temperature, 20-40S.) is higher, but the environment-friendly type hydrogen peroxide is mainly applied to electronic elements with strict requirements on processing size; non-environment-friendly (40 ml of nitric acid, 60ml of glacial acetic acid, 5g of potassium dichromate, 3g of copper chloride, 1L of copper chloride, normal temperature, 10-15S).

The needle head is prepared by adopting a high-stability electroplating process. The preparation method is roll electroplating. The matching plating layer matching suitable for the common-goods high-stability electroplated needle head is as follows: substrate + matte nickel + hard gold. The general thickness is: nickel is 2-4 microns, and the gold layer is less than or equal to 20u "(0.5 micron). For higher stability requirements, a single or multiple barrier layers are added between the nickel layers. Examples include nickel silver palladium gold 4 combinations, nickel (ruthenium rhodium) gold 3 "big combinations", nickel (PNP/PCP) gold 3 "small combinations", etc. Besides gold color, the surface layer can also be used as a plating layer (decoration) with high stability. Such as platinum, ruthenium-rhodium alloy, ruthenium white, grey ruthenium, black ruthenium, tin cobalt gun, etc. If the process needs no nickel, a silver electroplating layer (Rohm and Haas 3KBP additive) cyanide silver plating method can be adopted as a bottoming layer; furthermore, if nickel-free and silver cyanide-free processes are desired, silver plating of 5, 5-dimethylhydantoin with the hayman additive system without cyanide (but with the care of a reasonable pre-silver on copper process- -an environmentally friendly thiourea) can be used to prime the surface. For products with simpler shapes, the quality requirement can be met by plating cyanide-free alkaline copper (environmental protection) on the copper as a bottom layer.

And electroless plating copper HV160 as the bottom plating layer of the needle tube. The chemical copper plating layer is used as an intermediate structure layer, and the fit between the needle tube base material and the surface layer palladium-P is effectively adjusted. The thickness of the electroless copper plating layer is about 1.5-3 microns, and the specific process comprises the following steps: 12g/L of blue vitriol; KNaC4H4O 613 tetrahydrate/L; 20g/L of disodium EDTA dihydrate; 11ml/L of 37% formaldehyde; 4-12 mg/L (5) of potassium ferrocyanide; 100-150 mg/L of C6H14O2N4.HCl (arginine hydrochloride); 80-140 mg/L of vanadium pentoxide; adjusting pH to 12 with potassium hydroxide; the temperature is 35-40 ℃. The coating hardness of 60um is measured, and HV is 165, so the coating is named HV 160.

The modified ammonia nickel stainless steel direct plating formula (barrel plating/rack plating) is as follows: nickel sulfamate 80 g/l; boric acid 40 g/l; 10-15 g/L of nickel chloride; a modified nickel (matte) additive (50-70 ml/L or a proper amount) (such as MP-200SE) (Ni286 modifier); 30g/l of sulfamic acid; the temperature is 45-55 degrees (the initial preparation slotting temperature needs 60 degrees so as to be convenient for boric acid to dissolve); pH 1-2 (1.5) [ pH regulator (formic acid or sulfamic acid) ]; Dk0.1-8A/dm 2 (barrel plating 0.1-2.8A/dm 2), which can be directly pre-plated with a bottom layer; then, nickel sulfamate under normal acidity (PH4 +/-0.5) is removed to electroplate (thickly plate) matte nickel or semi-bright nickel or bright nickel. In particular: the maintenance is timely and good, and the direct plating by using the modified nickel-ammonia tank can meet the requirement of spring surface treatment.

2 formulas can be adopted for the barrel plating acid gold formula. First [ code AG 1# ]: potassium aurous cyanide non-Rosh formulations. Gold 1 g/l (with human potassium aurous cyanide); cobalt 0.2g/l (cylinder opened introduced by cobalt sulfate); be is 13-15 degrees; PH is 4.3 plus or minus 0.4; the barrel plating Dk is 0.1-0.4A/dm 2 (0.2). Temperature: 40 degrees. 1ml of the barrel plating additive and 1ml of the cobalt gloss agent are required to be supplemented for every 1 g of the gold salt (the cobalt metal concentration can be increased by 0.01 g/L for every 1 ml/L). Second [ code AG 1-CM # ]: an environment-friendly formula/gold potassium citrate system of a Rohm and Haas CM type supplementary additive system. The specific formula is as follows: 2-4 g/L of gold potassium citrate, 140-150 g/L of potassium citrate, 20-30 g/L of citric acid, 4.0-4.6 of PH and 0.3-0.5 g/L of cobalt (0.4 of cylinder opening); 1ml of the barrel plating additive plus 1ml of the cobalt gloss agent is required to be added for every 1.22 g of the gold salt. The temperature is 35-40 degrees; dk (barrel plating 0.1-0.4A/dm 2).

The chemical deposition palladium-P coating is arranged on the inner wall of the needle tube (with a cavity and the inner layer needing electroplating). The design is more reliable and stable; the gold plating can be continued on top of the palladium plating to harvest the multi-decorative requirements. The most ideal environment-friendly high-binding force gold immersion process comprises the following steps: no electrolysis and environment protection. 2g/L of gold (potassium/sodium aurous L-cysteine and the amount of gold introduced by mass); dipotassium phosphate 30 g/L; 40-60 g/L of sodium gluconate; DMAB 5-10 g/L (10); NaH2PO2.H2O 3-7 g/L (4); 8 g/L of borax; l-cysteine 40 g/L; 40g/L potassium sulfate; the additive is 1mg/L of 2-mercapto benzothiazole. 0.5-2 g/L (1) of hydroquinone. 0.3-0.6 g/L of saccharin sodium. (50 mg/L nicotinic acid; cerium (introduced by cerium acetate) 2 PPM; adjusting acidity pH value to a range pH of 6-7 by KOH; temperature: normal temperature and 25-30 (heating control 30 ℃), treatment time of 15-25 minutes; film thickness of about 0.08-0.14 um.; production thickness of plating layer is controlled by X-RAY spectrometer (XRF). The plating speed needs to be increased a little bit, and can be performed according to 5g/L (and can be increased by 5 ℃), sodium gluconate probably has action on the stability of palladium. kinetic theory analyzes that the stable constant of palladium equilibrium electrode potential 0.915 v.Au (Cys) 2-complex is power exponent 10(30 exponent) level, which is between that of KAu (CN)2 (10-38 exponent) and that of Na3Au (SO3)2 (10-28.7 exponent level), for example, the stable power exponent is calculated according to K of 1 × 10(30 ℃), at normal temperature, gold equilibrium potential-0.29 v. since palladium is autocatalytic, gold is catalytically reduced after palladium has been precoated on chemical copper. NaH2PO2 was slightly previously reacted with a mild reducing agent, DMAB; when the gold is thick enough and fully coated, gold is autocatalytically reduced by DMAB (growth continues). The redox potential of NaH2PO2 was slightly minus 0.2V DMAB. The main agent DMAB is environment-friendly after being oxidized and is friendly to gold plating solution (process). Heating at 45 degrees, measuring and calculating: gold equilibrium potential-0.45 v, at equivalent reductant concentrations: : due to the more negative potential, the nucleus atoms will be small; however, heating causes the crystal nucleus to grow more rapidly and larger; this requires finding a balance point to control the particle size of the immersion gold. The better advantage is also that the reaction temperature of gold is low; the temperature is much lower than that of displacement gold plating on a nickel base or catalytic reduction gold on the nickel base (gold potassium citrate is adopted for introducing gold) at 85-93 degrees. Is expected to become the next generation of mainstream (replacing high-temperature gold plating; expanding in PCB and multiple fields). In particular: removing reducing components DMAB and NaH2PO 2; the PH is controlled to be 8-10, and the formula is suitable for electroplating (charged electrolytic plating) environment-friendly gold and hard gold (hard gold needs to be added with a hard nonmetal such as tellurium/selenium) patent applications, wherein DK is 0.05-1.2A/dm 2 [ gold (by L-cysteine aurylidene potassium/sodium and introduced mass gold amount) is 2 g/L; dipotassium phosphate 30 g/L; 40-60 g/L of sodium gluconate; 8 g/L of borax; l-cysteine 40 g/L; 40g/L potassium sulfate; the additive is 1mg/L of 2-mercapto benzothiazole. 0.5-2 g/L (1) of hydroquinone. 0.3-0.6 g/L of saccharin sodium. (50 mg/L nicotinic acid; 2PPM cerium (introduced by cerium acetate) pH value is adjusted to 8-10 by KOH, the temperature is 20-45 degrees (30 degrees), and the method can be used in the field of Pogo Pin needles and probes (in addition, the preparation method of cysteine aurylidene potassium is provided, the following steps are that gold chlorate is reduced to 1-valent gold liquid by using sodium sulfite as a reducing agent, L-cysteine is added (the pH of the solution is controlled to be weakly acidic), and mixed water liquid of precipitation phase AuCys is prepared, and solid AuCys is adjusted by KOH, so that KAu (Cys)2 clear liquid is obtained.

Providing an environment-friendly silver plating scheme: 120-140 g/L (120 cylinder opening) of 5, 5-dimethylhydantoin; 30g/L of silver nitrate; 50g/L of sodium carbonate; 40g/L of potassium pyrophosphate; 10g/L of borax; 0.4g/L of 2-butyne-1, 4-diol; piperonal 0.2 g/L; triethanolamine 0.2 g/L. (sodium saccharin 0.5g/L may be added) pH: 9-10. temperature: and (5) 20-25 degrees at normal temperature. Barrel plating Dk is 0.1-0.6A/dm 2 (preferably 0.3-0.4A/dm 2).

The invention combines the above contents and can really realize a completely environment-friendly (non-toxic process electroplating) qualified electroplated layer.

Example 1: the stainless steel spring is rolled with hard gold. [ all environmental protection ] stainless steel spring spiral rock degreasing- - -water washing- - -descaling [ 37% hydrochloric acid (V/V) 20% -30%; 20-30% of 30% H2O2 (V/V); 420-30 g/L of NaH2 PO; 5-10 ml/L of absolute ethyl alcohol; PH is less than 0.8 and normal temperature is achieved; treatment time: 1-3 min or H2SO 4200-240 g/L replaces hydrochloric acid (more environment-friendly)/needs to be protected, water washing, barrel plating of modified nickel ammonia, barrel plating of nickel ammonia (semi-optical) -barrel plating of hard gold (gold potassium citrate system) Dk is 0.2A/dm2 to thickness (the general film thickness is gold 4 u-20 u ", the thickness can reach 30u at most). The thickness of the coating was controlled using an X-RAY spectrometer (XRF).

Example 2: and (4) barrel plating hard gold on the beryllium copper spring. [ all environmental protection ] beryllium copper spring ultrasonic wave wax removal- - -water washing- - -descaling [ sulfuric acid 5% + OP emulsifier ] - - - -water washing- - -barrel plating ammonia nickel (half light/(full light) - - - - - - -barrel plating hard gold (gold potassium citrate system) Dk 0.2A/dm2 to thickness (general film thickness is gold 3u 'to 5 u', thickness can reach 8u at most), and X-RAY spectrometer (XRF) is adopted to control the plating thickness.

Example 3: (copper alloy) needle roll plating hard gold [ non-environment-friendly gold ] (roll grinding/ultrasonic wave wax removal- -) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -.

Example 4: (copper alloy) needle roll plating hard gold [ all environment-friendly ] (roll grinding/ultrasonic wave wax removal- -) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -.

Example 5: (copper alloy) needle head plating surface layer platinum/ruthenium white/ruthenium black/rhodium ruthenium alloy (one) (all environmental protection/severe environment increasing application (hard core support sweat electrolysis test pass)) (rolling/ultrasonic wave wax removal- -) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (1-2 u' Pd (PDP) and its alloy (PNP/PCP)) - - - -Pt/Ru white/Ru black/Rh Ru alloy this example 5 item and flow are one of the protection clauses of the patent.

Example 6: chemical palladium (chemical gold) (all environmental protection) (roll grinding/ultrasonic dewaxing-) -ultrasonic degreasing-chemical polishing-, -water washing-, -sulfuric acid activation (4-5% m/m sulfuric acid bright membrane activation) -, -water washing-, -chemical copper plating (HV160#) -pre-palladium nuclear treatment-, -chemical palladium plating-P (thickness control is XRF): X-RAY spectrometer (electrolytic-free environment-friendly gold).

Example 7: the method comprises the steps of barrel-plating a large ternary plating layer (all environment-friendly) (barrel-grinding/ultrasonic wax removal-) -ultrasonic oil removal-, - -chemical polishing-, - -water washing-, - -sulfuric acid activation (4-5% m/m sulfuric acid bright film activation) -, - -water washing-, - -nickel sulfamic acid electroplating-, - -rhodium ruthenium alloy (1-10 u') -, - -hard gold AG 1-CM #.

Example 8: the method comprises the steps of barrel-plating a small ternary plating layer (all environment-friendly) (barrel-grinding/ultrasonic wax removal-) -ultrasonic oil removal-chemical polishing-water washing-sulfuric acid activation (4-5% m/m sulfuric acid bright film activation) -water washing-nickel sulfamate electroplating-PNP/PCP (1-5 u-) -hard gold AG 1-CM # (copper alloy) on a needle head.

Example 9: the Pogo Pin was constructed and tested in part of the "Artificial sweat + Electrolysis test" test method: 1) charge test for Pogo Pin plus sweat (PH4.7) for 1 hour, applying sweat every 10min (to ensure pad is wetted by sweat, but not flowing around) 2). After the step 1 is finished, carrying out high temperature and high humidity for 2 hours under the test conditions of 55 ℃ and 95% RH, wherein 3 hours in total are taken as a round of test; 3) after all tests are finished, the test piece is cleaned by clear water and then placed for more than 12 hours to observe results, and a microscope is required to be used for photographing before and after the tests to compare the test results. [ judgment standards: after the test is finished, the pogopin surface is required not to have the abnormalities of coating falling, color change, corrosion, verdigris precipitation and the like. "C (B)

Example 10: the Pogo Pin is configured and tested in part under the Low Power impedance test.

The test method comprises the following steps: the resistance of the terminal is measured by four-line measurement. Testing current: 100mA max. test voltage: the lower the impedance, the better 20mV max. The resistance requirement is as follows: within 30-50 milliohms.

Example 11: pogo pins were constructed and tested in part of the electrolytic corrosion test.

The test method comprises the following steps: 1. before testing, Pogo pin presses 1500 times (to the lowest working height); 2. after the samples are connected in parallel, 1pcs is used as Vbus (connected with the positive pole of a power supply) and 1pcs is used as GND (connected with the negative pole of the power supply), the distance is required to be 5mm, and the samples are connected to a constant voltage source for supplying power by 5V; 3. putting the sample into a beaker containing 5% NaCl solution, wherein the connecting line direction of the Pogo pins is parallel to the bottom surface of the container when the sample is placed, and sweat is immersed in the needle head part of the Pogo pins; the method comprises the following steps: the electrolysis time is 5min, and the corrosion condition is observed under a 40-time microscope and fed back. Evaluation: the appearance is not damaged; the corrosion point meets the requirements: 1. the maximum diameter of the corrosion point is less than 0.05mm without calculation; 2. no more than 1 corrosion site for a single sample; before and after testing, the contact impedance meets the specification requirement; the plating layer can not be peeled off and the bottom can not be exposed, and the charging and data transmission functions are normal.

Example 12: some special (electroplating combination layer) Pogo Pin accelerated electrolytic corrosion test experiment and result:

the special coatings applied were: CFE- (Pt + Au &) Rh-AP; the specific matching thickness is as follows: pt2u "+ Au0.35um + Rh4 u". Accelerated electrolytic corrosion test (5V; PH 4.7; Pitch ═ 5 mm): effective time of resisting electrolysis is 5 ~ 10Min [ contrast experiment: CFE- (Ni &) Au plating; i.e., ni1.4um + au1.25um. (5V; PH 4.7; Pitch 5mm) ═ 10-30 seconds ].

Example 13: barrel plating the needle with the small ternary plating of example 8); the needle cannula was coated with "example 6" electroless palladium plating as an inner wall (facing). The catalyst is stainless steel spring gold plating. Riveting integrated test: low power impedance test — result OK.

Example 14: electroless barrel plating of needles "example 6)" electroless gold plating; the needle cannula was coated with "example 6" electroless palladium plating as an inner wall (facing). The catalyst is stainless steel spring gold plating. Riveting integrated test: low power impedance test — result OK.

Example 15: vacuum extraction treatment of deep hole and blind hole piece- -minus 0.1 MPa.

And (3) implementing link quality control: use and method for manufacturing production link quality control instrument jig

1) Noble metal (silver/gold/palladium/rhodium/ruthenium) bath metal concentration monitoring-a machine (AA240FS-GTA120 atomic absorption spectrometer).

2) Coating thickness monitoring- -FISCHERPOPE X-RAY, Germany.

3) Crystal phase microscopic and thickness measurement-Leika gold image silver thickness measuring instrument.

4) And (4) testing the concentration of the plating solution by conventional chemical operation, namely, titration analysis.

5) And (4) adjusting the technological property of the plating solution, namely, conducting Ha's groove slicing.

6) NSS spraying experiment and electrolysis experiment of the coating product.

The invention can expand and prosper the application field of the Pogo Pin electric connector (Pogo Pin); continue to lead electrical connector (or probe) mainstream and current. An intelligent environment-friendly 3C electronic domain, an intelligent charging and discharging domain, an intelligent signal transmission domain and the like are arranged; promote higher development and prosperity. The caliber of the Pogo Pin transmission is expected to be 60A at the maximum; the environmental temperature rise is 30 degrees, the capacity is expanded, and a new area is developed in the safety field and is applied to more new fields.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (10)

1. The preparation method of the high-stability low-impedance spring pin electric connector is characterized by comprising the following steps of: the discrete components are assembled after independent quality treatment, and the needle head is prepared by adopting a high-stability electroplating process; the SUS stainless steel fitting is electroplated with hard gold in a rolling way, the needle tube is prepared by adopting a method of chemical polishing activation and electroless deposition special coating, and a chemical surface plating process is adopted, so that the surface coating hardness HV can exceed HV 165.

2. The method of claim 1, wherein the outermost plating layer is selected from the group consisting of electroless palladium-P, electroless hard gold, and electroless ruthenium, depending on the desired grade of the parts.

3. The probe electroplating process of the high-stability low-impedance pogo pin electrical connector as claimed in claim 1, wherein electroless copper deposition is used as an intermediate structure barrier layer on the base material copper alloy, referring to the hard gold index HV 140; the better chemical copper plating needs to ensure HV 150-165.

4. The process of claim 3, wherein the spring roll is electroplated with hard gold, and the SUS material is treated with hydrochloric acid, urotropine and surfactant, and then underplated with nickel sulfamate pre-plated to modify the pH system; the method ensures good plating quality, the barrel plating hard gold can adopt an environment-friendly formula or a formula of a aurous cyanide citric acid system, the environment-friendly formula can adopt a gold potassium citrate system of a Rohm and Haas CM supplementary additive system, and the specific formula is as follows: 2-4 g/L of gold potassium citrate, 140-150 g/L of potassium citrate, 20-30 g/L of citric acid, 4.2-4.5 of PH and 0.3-0.5 g/L of cobalt; the gold plating intermediate additive is suitable; the temperature is 35-40 ℃.

5. The process of claim 3, wherein the tube is plated with an electroless palladium-P alloy, which is activated after electroless copper plating: 0.05-0.1 g/L of palladium chloride; 0.5-1 ml/L of 37% hydrochloric acid, 1-2S, normal temperature, or: 15-30 mg/L of palladium sulfate; 5-10 ml/L sulfuric acid, normal temperature: 20-40S.

6. The process of claim 3, wherein the tube is chemically plated with a palladium-P alloy, and the formulation is: 2g/L of palladium chloride; 4ml/L of 37% hydrochloric acid; 160-164 ml/L of 28% ammonia water; 25ml/L of ethylenediamine; 50mg/L of bismuth nitrate; 10-15 g/L (12 is better) of NaH2PO2. H2O; the temperature is 48-55 degrees; PH is not less than 9.8 plus or minus 0.2, plating speed: about 1um/H, the obtained plating layer is compact and uniform, has no obvious defects and pinholes, and contains P within 3.2-5%.

7. The probe electroplating process of the high-stability low-impedance pogo pin electrical connector according to claim 3, wherein the plating layer before electroless palladium-P plating is of electroless copper plating HV160 type, weak corrosion is required after electroless copper plating, the process is 4% sulfuric acid water normal temperature treatment for 3-5 seconds, and then pre-palladium activation is removed after flowing water washing.

8. The probe electroplating process of the high-stability low-impedance pogo pin electrical connector of claim 3, wherein the surface pretreatment process when treating the needle head and the needle tube corresponding to the copper alloy substrate is as follows: ultrasonic dewaxing, ultrasonic oil removal, chemical polishing, water washing, sulfuric acid activation and water washing.

9. The probe electroplating process for the high-stability low-impedance pogo pin electrical connector of claim 3, wherein the chemical polishing process corresponding to the copper alloy substrate is: environmental protection: 40g/L of oxalic acid, 18 g/L of sodium hydroxide, 120-150 ml/L of 30% hydrogen peroxide, 0.1-0.15 g/L of BTA benzotriazole, 4-8 ml/L of ethanol and 3-4 of PH (adjusted by caustic soda grains/glacial acetic acid); normal temperature, 20-40S, non-environmental protection: 40ml of nitric acid; 60ml of glacial acetic acid; 5g of potassium dichromate; 3g of copper chloride; mixing 1 liter; and (5) at normal temperature for 10-15S.

10. The probe electroplating process of the high-stability low-impedance pogo pin electrical connector of claim 3, wherein as a bottom plating layer of the needle tube, an electroless copper plating layer is used as an intermediate structure layer, the fit between the needle tube substrate and the surface layer palladium-P is effectively adjusted, the electroless copper plating layer has a thickness of about 1.5-3 μm, and the specific process is as follows: 12g/L of blue vitriol; KNaC4H4O 613 tetrahydrate/L; 20g/L of disodium EDTA dihydrate; 11ml/L of 37% formaldehyde; 4-12 mg/L of potassium ferrocyanide; 100-150 mg/L of C6H14O2N4.HCl (arginine hydrochloride); 80-140 mg/L of vanadium pentoxide; adjusting pH to 12 with potassium hydroxide; the temperature is 35-40 degrees, and HV is 165 after the coating hardness measurement of 60 um.