5 Types Of Pcb Surface Finishes
These pass the federal government RoHS laws and after process growth to reduce the expansion of tin whiskers have turn into the mainstay of the trade. Since the world business has moved further towards RoHS many circuit board manufacturing vegetation have standardized on Pb-free HAL and not value that surface at a premium. Indeed some have scrapped HASL completely and subcontract that finish resulting in a value premium for leaded solder.
If your boards need to be RoHS and have fine pitch elements together with BGA’s we recommend ENIG or immersion silver. The transfer to RoHS in Europe and later in the US resulted in improvement of lead-free SnAgCu solders based on tin with additions of silver and copper and with traces of bismuth, indium, zinc, and antimony.
While every finish has its personal advantages and downsides, in most cases, the method, product or setting will dictate the floor end that is finest suited on your software. For example, if your printed circuit boards don't need to be RoHS, Sn/Pb HASL may be the best choice.
Once these traces are fashioned, however, there’s extra work to be carried out. Bare copper is famously reactive stuff, and oxides quickly kind that can make the traces difficult to solder later. There are tons of of different ways to prevent this, and PCB surface ending has become nearly an art form itself. Depending on the necessities for the circuit, traces can be coated with tin, lead, gold, nickel, or any combination of the above, using processes ranging from electroplating to immersion in chemical baths. And the traces aren’t the one finishes; solder resist and silkscreening are each important to the usability and durability of the finished board.
Subsequent introduction of a nickel controller into the ENIG line had been the carried out countermeasures. Price, availability, shelf life, reliability and the assembly process are key factors when selecting a PCB floor finish.