Why don't use Spray Tin for PCB surface?

As the integration of IC is getting higher and higher, the IC pins are getting denser and denser, and it is difficult to blow the thin pads flat by the vertical tin spraying process, which brings difficulties to the SMT placement. In addition, the tin spraying board The standby life is very short, and the gold-plated plate just solves these problems.

1. For the surface mount process, especially for the ultra-small surface mounts such as 0603 and 0402, because the flatness of the pad is directly related to the quality of the solder paste printing process, it has a decisive impact on the quality of the subsequent reflow soldering. Therefore, the whole board Gold plating is common in high-density and ultra-compact surface mount processes.

2. In the trial production stage, affected by factors such as component procurement, it is often not soldering the circuit board immediately after production, but often waiting for several stars to wait for the components to arrive before soldering. The standby life of gold-plated plates is longer than that of lead-tin alloys. It is many times longer, so everyone is willing to use it. Besides, the cost of gold-plated PCB in the plating stage is almost the same as that of lead-tin alloy plate.

However, as the wiring becomes denser, the line width and spacing have reached 3-4MIL, which brings the problem of short circuit of the gold wire.

As the frequency of the signal becomes higher and higher, the transmission of the signal in the multi-layer coating due to the skin effect has a more and more obvious influence on the signal quality.