The surface finishing methods used in PCB board proofing are different. Each surface finishing method has its unique characteristics.
Taking immersion silver as an example, its process is extremely simple. It is recommended to use lead-free soldering and smt, especially for high precision. The most important thing is to use immersion silver for surface finishing, which will greatly reduce the overall cost and lower the cost. The following are some common surface finishing methods for PCB proofing by the editor of Stariver Circuits.
1.HASL with lead
Spraying tin is a commonly used finishing method for PCB board proofing. It is now divided into lead spray and lead-free spray. Advantages of spraying tin: After the PCB board is completed, the copper surface is completely wet (the tin is completely covered before soldering), suitable for lead-free soldering, mature technology and low cost, suitable for visual inspection and electrical testing, and also belongs to high-quality and reliable pcb boards Proofing processing method.
2. Immersion Gold (ENIG)
Nickelized gold is a widely used surface finishing process for circuit board proofing. Remember: the nickel layer is a nickel-phosphorus alloy layer, which is divided into high-phosphorus nickel and medium-phosphorus nickel according to the phosphorus content. The application is different, and it is not described here the difference. Advantages of nickelized gold: suitable for lead-free soldering; the surface is very flat, suitable for SMT, suitable for electrical testing, suitable for switch contact design, suitable for aluminum wire binding, suitable for thick plates, and strong against environmental attacks.
Electroplated nickel gold is divided into "hard gold" and "soft gold". Hard gold (such as gold-cobalt alloy) is commonly used on gold fingers (contact connection design). Soft gold is pure gold. Electroplated nickel gold is more commonly used on IC substrates (such as PBGA). It is mainly suitable for binding gold and copper wires. However, for the plating of IC substrates, it is necessary to use extra conductive wires to bind the gold finger area before electroplating. Advantages of electroplating nickel gold pcb board proofing: suitable for contact switch design and gold wire binding; suitable for electrical testing
ENEPIG is now beginning to be applied in the field of PCB board proofing, and it has been used more in semiconductors before. Suitable for gold and aluminum wire binding. Advantages of proofing with nickel-palladium pcb board: application on IC carrier board, suitable for gold wire binding and aluminum wire binding. Suitable for lead-free soldering; Compared with ENIG, there is no nickel corrosion (black disk) problem; the cost is cheaper than ENIG and electro-nickel gold, suitable for a variety of surface finishing processes and existing on the board.
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