PCB Fabrication

Common Solder Mask Issues With Pcbs

by:A-TECH      2020-12-20

As a end result, solder paste is not applied uniformly, resulting in solder shorts on excessive lead count elements similar to QFPs and BGAs. The different finishes in this class have all been formulated to solve this downside, a lack of flatness of the soldering surfaces. Solder mask enlargement may be outlined for pads and vias on a person foundation, within the related properties dialog. Options can be found to follow the expansion defined within the applicable design rule, or to override the rule and apply a specified growth directly to the person pad or by way of in query. Options are also out there to pressure full tenting of the pad/via on the highest and/or backside.


The black material will cause the solder joint to be weak and fail. This drawback is simply found after the PCB is absolutely assembled. I even have seen entire packages ruined as a result of somebody decided to save lots of a few dollars by using this end on a complex, double-sided assembly PCB only to find that every board had failed solder joints. Sure, $30 was saved per bare PCB, however all of them have been scrapped at tons of of times the apparent savings. The downside with HASL is that the solder top on the pads of very nice pitch SMT parts isn't always uniform.


My view on this is very like the expertise we had with ENIG. Slowly, we began to expertise failures from black pad, till one day, many people had disasters on our arms.


As a result of this expertise, I select to attend and see how this works for some time before jumping on to the immersion silver band wagon. After all, most of us nonetheless have to go through the lead free solder transition and don’t want a floor end problem on top of every little thing else.


This finish is applied with two chemical baths which are very complex. The chemistries have been formulated so that nickel deposits onto the copper adopted by gold on high of the nickel. Again, the target is to get a skinny layer of gold onto the pad for corrosion protection. As lengthy because the chemistry is properly monitored and contemporary, this finish works very properly. The problem with the end stems from the truth that when the chemistry will get out of balance a skinny movie of black materials is deposited on the nickel just earlier than the gold is deposited.

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