4 Layers Multilayer Electronic OEM PCB
The process/technology requirement of circuit board production is a very important factor, it directly decides the quality and positioning of the board. Like HASL, gold plating, ENIG.In relative terms, ENIG is for high-end PCB boards.Because of the good quality for ENIG, the cost is also high.So many customers choose the most commonly used HAL technology.Generally HAL is divided into lead HASL and lead-free HASL.Here's the difference:
1. Lead HASL is lighter for the tin surface, and the lead-free HASL(SAC) is rather dull.Lead-free infiltration is less than lead.
2. Lead HASL is harmful to human health, but not for lead free. Lead eutectic temperature is lower than unleaded.The content is depend on the composition of unleaded alloy.For example, the eutectic of SNAGCU is 217 degrees, and the welding temperature is eutectic temperature plus 30~50 degrees.It depends on the actual adjustment.Lead eutectic is 183 degrees. Such as mechanical strength, brightness and others lead are better than lead-free.
3. The lead content of lead-free tin is no more than 0.5, while lead can reach 37.
4, Lead can improve the activity of tin line in the welding process, tin line with lead is easier used than unleaded, but lead is toxic, long time using is bad for body.For melting point leaded tin will be higher than tin with lead, thus the welding point strong more.
Compared HASL with ENIG,the difference is below:
1. In terms of cost, HASL price is low and gold plating is high.
2. In terms of color, HASL PCB is gray and the gold PCB is golden.
3. In terms of anti-oxidation and corrosion resistance,gold board is stronger than HASL board, and the shelf life of gold board is longer than the HAL board.The active order of common metals is potassium, calcium, sodium, magnesium, aluminum, zinc, iron, tin, lead, copper, mercury, silver, platinum and gold. So tin is just a little bit more anti-oxidative than iron, and we all know that iron is easy to rust.Gold is the lowest activity, the most stable chemical property, so it is not suitable for oxidation and corrosion.
4. In terms of conductivity, from high to bottom: Ag, Cu, Au, Al, Na, Mo, W, Zn, Ni, Fe, Pt, Sn, Pb.The conductivity of tin is much smaller than that of gold.
5. The tin pcb is better than the ENIG pcb in terms of solderability.
6. The gold plating pcb is much smoother than the tin pcb from the surface smoothness of the welded pads. As the IC integration is higher and higher,IC feet are more dense;however, the vertical spray tin process is difficult to smooth the welding pads, which brings difficulty to SMT's pasting, and the defective rate is high. Therefore, whole pcb plating is easily be seen in high density and super small SMT process.