On Fri, 26 Jul 1996 14:33:28 -0700 Bill Dieffenbacher wrote:

> From: Bill Dieffenbacher <[log in to unmask]>
> Date: Fri, 26 Jul 1996 14:33:28 -0700
> Subject: Re: Solderability of Electoless Ni
> To: [log in to unmask]
> 
> We have been starting to have solderability problems with some electroless
> nickel plated pwbs.  Nickel has always been a challenge to solder... but we
> have been successful until recently by simply doing a pumice scrub prior to
> solder stenciling, and by minimizing the time through assembly and into reflow.
> 
> There have been a large number of Technet communications on Electroless Ni
> and Immersion Au over the last few weeks.  We are tying to learn from those
> who are having similar problems.
> 
> A few topics which were not fully addressed and would be of great value are:
> 
> 1. Does anyone know of a good test coupon or test method which can be used
> to evaluate pwb surface solderability?
> 
> 2. What role does surface finish play in solderability and will a rough
> plated Ni finish have more solderability problems than a smoother finish?
> 
> 
> Any help would be appreciated.
> 
> Bill Dieffenbacher,  Lockheed Martin Control Systems
> [log in to unmask]  Phone 607-770-2961  Fax 2056
> _______________________________________________________________
> 
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> 
Bill,
	I hope the following information meets your need:

FROM MIL-S-13949/4D (16 August 1993):
MILITARY SPECIFICATION SHEET FOR GF BASE MATERIAL (I.E. FR4)

Dimensional Stability (for base material thicknesses less than .020 inch (0.51mm)).

	After bake:  Class A, 0.00075 inch/inch (0.00075 mm/mm) maximum;
		    Class B, 0.00050 inch/inch (0.0005 mm/mm) maximum

	Same values are given for the 'after stress' condition.

Typical (nominal) values given in Laminate Suppliers' Product Data Sheets are:

< .0030 in/in (for thin cores <= .028"
< .0035 in/in (for thicker cores between .028" and .062")



Fred J. Paul, Sr. Process Engineer
PCB Operations, FLUKE CORPORATION
direct:  206 356-5734  fax:  206 356-6070
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