Why? Whenever possible, we want the solder to be the weakest link. We want any loading of the joint to cause failure through the solder, rather than through one of the intermetallic structures (or by pad separation from the substrate). This is particularly important, but luckily also easiest to achieve, under thermal mismatch induced loading. However, it may also be important in the more challenging case of mechanical shock loading... More

Problems? Pad finish problems are nothing new. In fact, no common pad finish is immune to sporadic disasters:

• Electrolytic Ni/Au and electroless-nickel-immersion-gold (ENIG) both have numerous potential problems, some unique and some in common.
• We used to think Cu was safer, but severe voiding in the intermetallics may weaken the joints over time, sometimes rapidly and severely. This depends on the Cu, but not on the coating (HASL, OSP, imm. Ag, imm. Sn).
• Immersion Ag coatings may cause 'champagne voiding'.
• There is concern that lead free HASL may cause latent damage to the PCB.

What can you do? Click here for more details on these issues. Or contact our process services team for immediate help with any of them.