Mike H. -

Black pad is related to electroless nickel gold. 
This discussion is about electrolytic nickel gold.

John - Did those who indicated there was no problem with electrolytic
gold thickness
Of ~30uInches have data supporting their position?  I think that
17uInches recommended
By George's team makes more sense unless there is data to review which
indicates otherwise.

My $.02,
Robyn

-----Original Message-----
From: IPC-600-6012 Mail Forum [mailto:[log in to unmask]] On Behalf Of
Mike Hill
Sent: Monday, September 30, 2002 11:32 AM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Max Allowance of Gold on Areas to Be
Soldered


All,

I have seen the responses to the immersion gold thickness Question and
have read them with much interest.


I have a customer that insists that any readings over 5 microinches is a
indication they will get black pad. Certainly the 17 microinch limit
proposed by the committee is much greater than the limit of 5 by my
customer.


Does anyone have a comment about the relationship to black pad if gold
is over 5 microinches?

Thanks
Mike

-----Original Message-----
From: IPC-600-6012 Mail Forum [mailto:[log in to unmask]]On Behalf Of
John Perry
Sent: Friday, September 27, 2002 6:59 PM
To: [log in to unmask]
Subject: [IPC-600-6012] Max Allowance of Gold on Areas to Be Soldered


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