IPC-4556 - Amendment 1 : 2016

Replace all of Section 1.4.1 Solderability with the following:

1.4.1 Solderability

One of the two primary functions of ENEPIG is to provide a solderable surface finish capable of providing a coating durability rate of B, per the IPC-J-STD-003. Coating Durability B is defined as: Intended for boards likely to experience multiple soldering processes and/or other process steps using SnPb or Pb-Free assembly profiles. The solderability requirement is for all ENEPIG plated SMT features tested to wet with solder covering at least 95% of each feature. Non-wetting and dewetting of the remaining 5% of the feature is allowed, provided no individual defect accounts for more than 1% of the feature area. For through-hole solderability, the requirement is to wet to the knee of the hole. However, it is noted that board thickness, feature hole aspect ratio, number of internal copper planes, etc., will have an impact on solderability testing results if a static solder float test is utilized. For challenging designs, it is recommended to use the manufacturing assembly soldering method for solderability testing.

The use of electroless palladium as a diffusion barrier between the nickel and the gold mitigates the potential for hyper corrosion of the electroless nickel deposit, thus enhancing its solderability and solder joint reliability. The minimal thickness of the electroless palladium and of the immersion gold deposit make the possibility of embrittlement of the solder joint by palladium or gold, negligible. It is the responsibility of the user to calculate the percentage of both gold and palladium in the resulting solder joints where mounting pad sizes associated with 0201 or smaller components are encountered and compare these calculated levels of gold or palladium to the 3 wt.% threshold values believed to give rise to solder joint embrittlement.