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From [log in to unmask] Tue Jul 30 12: |
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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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