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1. PCB plating process: pickled → full board electroplated copper → pattern transfer → acid degreasing → secondary countercurrent rinsing → micro etching → secondary countercurrent rinsing → pickling → tin plating → secondary countercurrent rinsing → countercurrent rinsing → pickling → pattern copper plating → secondary countercurrent rinsing → nickel plating → secondary washing → citric acid → gold plating → recycling → 2-3 pure water washes → drying.
2. Remove the oxide on the plate surface, activate the plate surface, and maintain the concentration generally at 5%-10%. This prevents instability in the sulfuric acid content of the tank solution caused by water introduction. The acid leaching time should be brief to prevent PCB board oxidation. Replace the acid promptly when turbid or excessively copper-laden to avoid surface contamination of the electroplated copper cylinder and plates.
3. Also known as “primary copper,” it shields freshly deposited thin electroless copper to prevent acid erosion post-oxidation. The tank solution chiefly contains copper sulfate and sulfuric acid, with a high acid and low copper formula ensuring uniform PCB surface thickness distribution and effective plating of deep holes and small apertures. Sulfuric acid content is maintained at 180-240 g/L, copper sulfate around 75 g/L, and trace chloride ions are added for gloss enhancement. Typically, 3-5 ml/L of gloss agent is used per cylinder, adjusted based on production outcomes or 1,000 ampere-hours.
4. PCB full board plating current is typically calculated at 2 amps per square decimeter, multiplied by the board’s platable area. For full board plating, this equals board length in dm × board width in dm × 2 × 2A/dm². Copper cylinder temperature is maintained around room temperature, preferably not exceeding 32 degrees Celsius, often controlled at 22 degrees Celsius. In hot weather, a cooling temperature control system is recommended for the copper cylinder.
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I’ve refined the language for clarity and coherence, maintaining the technical details of the PCB plating process and associated considerations.
Remove oxides on the copper surface of the trace, ink residue, and ensure adhesion between primary copper and graphic electroplating of copper or nickel.
Clean the copper surface of the roughened circuit to ensure adhesion between graphic electroplating copper and primary copper. The micro-etching agent uses sodium persulfate, with a stable and uniform roughening rate and effective water washing. Typically, sodium persulfate concentration is maintained at about 60 g/L for approximately 20 seconds, with an addition rate of 3-4 kg per 100 square meters. Copper content should be controlled below 20 g/L. Other maintenance cylinders are micro-etched with copper sinking.
Remove oxides on the circuit board surface and activate the board surface with a general concentration of about 5%-10%, to prevent instability due to water introduction in the sulfuric acid tank solution. Acid leaching time should be controlled to prevent surface oxidation. Replace the acid promptly when it becomes cloudy or copper content is too high after prolonged use.
It is also known as “secondary copper”. To meet the rated current load of each trace, both trace and via copper must achieve a certain thickness. Line copper plating aims to achieve this thickness promptly for both via and trace copper. All other aspects are identical to full panel plating.
1. The metal resist layer, composed mainly of pure tin, is essential for graphic electroplating to protect the circuit during etching. The bath solution primarily consists of stannous sulfate, sulfuric acid, and additives. The stannous sulfate content is carefully controlled at approximately 35 g/L, with sulfuric acid maintained at around 10%. Tinning additives are typically added based on a 1,000 ampere-hour method or adjusted according to actual production board requirements.
2. Current calculation for electroplating tin is generally set at 1.5 amps per square decimeter multiplied by the plate’s electroplateable area. The tin cylinder temperature is kept at room temperature, not exceeding 30 degrees Celsius, and often controlled around 22 degrees Celsius. In summer, due to elevated temperatures, it’s advisable to install a cooling temperature control system for the tin cylinder.
3. Nickel plating serves primarily as a barrier layer between the copper and gold layers, preventing diffusion between them which could otherwise impact board solderability and longevity. Additionally, the nickel layer acts as a primer, significantly enhancing the mechanical strength of the subsequent gold layer. Process parameters for copper plating across the entire board include the addition of nickel plating additives, typically managed through a 1,000 ampere-hour approach or adjusted based on actual production outcomes, with an addition rate of approximately 200 ml/KAH.
4. Graphic nickel plating is generally calculated at 2 amps per square decimeter, considering the plate’s electroplateable area. The temperature of the nickel cylinder is maintained between 40-55 degrees Celsius, ideally around 50 degrees Celsius, necessitating the use of a heating and temperature control system for the nickel cylinder.
Divided into electroplating hard gold (gold alloy) and soft gold (pure gold) processes, the composition of the hard gold plating and soft gold tanks is fundamentally similar. However, the hard gold tank contains trace amounts of metals such as nickel, cobalt, or iron. As a precious metal, gold exhibits excellent characteristics including good weldability, oxidation resistance, corrosion resistance, low contact resistance, and high alloy wear resistance.
The gold plating on circuit boards primarily uses a gold citrate bath. In the case of soft gold, the gold content is maintained at approximately 1 g/L with a pH around 4.5, operating at 35 degrees Celsius, and a specific gravity of about 14 Baumé. The current density typically reaches around 1 ASD. Key additives include salts for pH adjustment, conductive salts to regulate specific gravity, gold-plating enhancers, and gold salts.
To safeguard the gold plating, a citric acid immersion bath is recommended prior to the gold plating process. This step effectively reduces contamination risks and stabilizes the gold plating. After electroplating, rinsing with pure water is essential for wash-off and recovery purposes, also replenishing the evaporation losses in the gold tank.
