PCB surface treatment process affects the quality of soldering.
PCB surface treatment is the key and foundation of SMT patch quality. The treatment process of this link mainly includes the following points:
(1)Except for ENG, the thickness of the plating layer is not clearly specified in the relevant national standards of PC. It is only required to meet the solderability requirements.The industry can generally require the following.
OSP: 0.15 ~ 0.5 μm, not specified by IPC. Recommended to use 0.3 ~ 0.4um
EING: Ni-3～5um; Au-0.05～0.20um (PC only stipulates the current thinnest can be required)
Im-Ag: The thicker the 0.05~0.20um, the more severe the corrosion (PC not specified)
Im-Sn: ≥0.08um. The reason why we want to be thicker is mainly because Sn and Cu will continue to develop into CuSn at room temperature, which affects solderability.
HASL Sn63Pb37 is generally formed naturally between 1 and 25um, and the process is difficult to accurately control. Lead-free mainly uses SnCu alloy. Due to the high processing temperature, it is easy to form Cu3Sn with poor sound solderability, and it is basically not used at present.
(2) pcb surface treatment
The wettability to SAC387 (according to the wetting time under different times of heating, unit: s).
0 times: im-sn (2) florida ageing (1.2), osp (1.2) im-ag (3).
Zweiter PLENAR SESSION Zweiter PLENAR SESSION Im-Sn has the best corrosion resistance, but its solder resistance is relatively poor!
4 times: ENG (3)-ImAg (4.3)-OSP (10)-ImSn (10).
(3) The wettability to SAC305 (after passing through the furnace twice).
ENG (5.1)—Im-Ag (4.5)—Im-Sn (1.5)—OSP (0.3).