This article primarily introduces four specialized plating methods used in circuit board fabrication.
1. **Finger Row Electroplating**
Rare metals are often plated on board edge connectors, protruding contacts, or gold fingers to ensure lower contact resistance and increased wear resistance. This method, known as finger row or protruding part plating, typically involves plating gold on the board edge connectors’ protruding contacts over an inner layer of nickel. The gold plating process for these contacts can be done manually or automatically. Currently, gold plating is used for contact plugs or gold fingers instead of plated buttons. The process is as follows:
1) Strip the coating to remove any tin or tin-lead from the protruding contacts
2) Rinse with washing water
3) Scrub with abrasives
4) Activate with a 10% sulfuric acid solution
5) Apply nickel plating with a thickness of 4-5μm on the protruding contacts
6) Clean with demineralized water
7) Treat with a gold penetration solution
8) Apply gold plating
9) Clean thoroughly
10) Dry the plated components
2. **Through-Hole Plating**
1. There are many methods to apply an electroplating layer to the walls of drilled holes in a substrate. This process is known as hole wall activation in industrial applications.
2. The commercial production of printed circuits involves multiple intermediate storage tanks, each with specific control and maintenance requirements. Through-hole plating is an essential follow-up to the drilling process.
3. When the drill bit penetrates the copper foil and substrate, the heat generated melts the insulating resin in the substrate. This molten resin, along with drilling debris, accumulates around the hole and coats the exposed hole walls in the copper foil.
4. This accumulation can be detrimental to subsequent electroplating. The molten resin leaves a layer of hot shaft on the hole wall that poorly adheres to most activators. Therefore, specialized de-staining and etch-back chemical technologies are needed.
5. For PCB prototyping, a more suitable method involves using a specially designed low-viscosity ink to form a high-adhesion, high-conductivity film on the inner walls of through holes.
6. This approach eliminates the need for multiple chemical treatments; a single application and thermal curing create a continuous film on all hole walls, allowing for direct electroplating without further processing.
7. The ink is a resin-based substance with strong adhesion, effectively adhering to most thermally polished hole walls, thereby removing the need for etch-back.
8. The third type is reel linkage selective plating. Electronic components like connectors, integrated circuits, and flexible FPCs use selective plating to achieve good contact resistance and corrosion resistance.
9. This method can be performed manually or automatically. Selective plating each pin individually is costly, so batch processing is employed. Metal foils, rolled to the required thickness, are punched, cleaned, and then selectively plated with materials like nickel, gold, silver, or various alloys.
10. In selective plating, a resist film is first applied to the copper foil areas not intended for plating, and electroplating is performed only on the designated parts.
11. The fourth type is brush plating. This electrodeposition technique does not involve immersing all parts in the electrolyte.
12. Instead, only a limited area is electroplated, avoiding impact on other areas. Rare metals are typically plated on specific parts of a PCB, such as board edge connectors.
13. Brush plating is often used for repairing discarded circuit boards in electronic assembly workshops. An anode wrapped in an absorbent material is used to deliver the electroplating solution precisely where needed.
1. **Finger Row Electroplating**
Rare metals are often plated on board edge connectors, protruding contacts, or gold fingers to ensure lower contact resistance and increased wear resistance. This method, known as finger row or protruding part plating, typically involves plating gold on the board edge connectors’ protruding contacts over an inner layer of nickel. The gold plating process for these contacts can be done manually or automatically. Currently, gold plating is used for contact plugs or gold fingers instead of plated buttons. The process is as follows:
1) Strip the coating to remove any tin or tin-lead from the protruding contacts
2) Rinse with washing water
3) Scrub with abrasives
4) Activate with a 10% sulfuric acid solution
5) Apply nickel plating with a thickness of 4-5μm on the protruding contacts
6) Clean with demineralized water
7) Treat with a gold penetration solution
8) Apply gold plating
9) Clean thoroughly
10) Dry the plated components
2. **Through-Hole Plating**
1. There are many methods to apply an electroplating layer to the walls of drilled holes in a substrate. This process is known as hole wall activation in industrial applications.
2. The commercial production of printed circuits involves multiple intermediate storage tanks, each with specific control and maintenance requirements. Through-hole plating is an essential follow-up to the drilling process.
3. When the drill bit penetrates the copper foil and substrate, the heat generated melts the insulating resin in the substrate. This molten resin, along with drilling debris, accumulates around the hole and coats the exposed hole walls in the copper foil.
4. This accumulation can be detrimental to subsequent electroplating. The molten resin leaves a layer of hot shaft on the hole wall that poorly adheres to most activators. Therefore, specialized de-staining and etch-back chemical technologies are needed.
5. For PCB prototyping, a more suitable method involves using a specially designed low-viscosity ink to form a high-adhesion, high-conductivity film on the inner walls of through holes.
6. This approach eliminates the need for multiple chemical treatments; a single application and thermal curing create a continuous film on all hole walls, allowing for direct electroplating without further processing.
7. The ink is a resin-based substance with strong adhesion, effectively adhering to most thermally polished hole walls, thereby removing the need for etch-back.
8. The third type is reel linkage selective plating. Electronic components like connectors, integrated circuits, and flexible FPCs use selective plating to achieve good contact resistance and corrosion resistance.
9. This method can be performed manually or automatically. Selective plating each pin individually is costly, so batch processing is employed. Metal foils, rolled to the required thickness, are punched, cleaned, and then selectively plated with materials like nickel, gold, silver, or various alloys.
10. In selective plating, a resist film is first applied to the copper foil areas not intended for plating, and electroplating is performed only on the designated parts.
11. The fourth type is brush plating. This electrodeposition technique does not involve immersing all parts in the electrolyte.
12. Instead, only a limited area is electroplated, avoiding impact on other areas. Rare metals are typically plated on specific parts of a PCB, such as board edge connectors.
13. Brush plating is often used for repairing discarded circuit boards in electronic assembly workshops. An anode wrapped in an absorbent material is used to deliver the electroplating solution precisely where needed.
