Colleagues,

In building the IPC-6012B we are making changes to Table 3-2 for Final Finish Requirements - your disposition on the following is requested:

At Expo, at the request of the 4-14 Plating Subcommittee chaired by George Milad, it was recommended that for Class 1, 2 and 3 product, the maximum allowable thickness of gold on areas to be soldered (identified in the table as Row GS) would be 0.45 µm [17.72 µin].


More recently it has been recommended that the Class 3 maximum allowance be increased to a value of 0.8 µm [31.5 µin].


The con's offered against this indicate that in the usage of electrolytic gold plating finish on solderable areas, heavier thickness may not be better as it can lead to embrittlement of the solder joint.

The pros offered for the increase indicate that in many cases involving military product, there are two main issues, solderability and embrittlement.  Some task group members contend that solderability can be a major issue since military product may not be used for 1 -2 years after product has been manufactured, whereas many commercial products built are potentially used right away.  The second issue of embrittlement, however, many not be so much of an issue - some task group members have calculated that the percentage of gold in solder, in cases of 30 µin depositions, is less than 4% and that gold embrittlement is not really a problem.  Hence an increase in thickness, in favor of long term solderability, is desired. 

What maximum thickness value for Class 3 can this task group agree is appropriate for IPC-6012B?

Thanks,

John Perry
IPC