At 10:08 AM 1/6/97 -0500, you wrote:
>I am interested in the reasoning in selecting point geometry used to
>contact gold over nickel pads on SMD boards. In some cases customers are
>requesting  (high spring force, hardened steel pointed probes) and
>others are requesting round gold pleated moderate spring force probes. 
>
>The application is the same SMD pads with gold, what are the
>considerations in testing these pads.
>What are the different considerations for point geometry for different
>surfaces.
>
>I am most interested in why sharp hard points, rather than domed gold
>contacts, are used for gold pads?
>
>Is pad damage not an issue?  Is the problem simple related to dirty
>boards?
>
>Thanks in advance.
>
>---------------------------------------------
>Edward G. Shea          |  Tel (909)981-1810
>Test Connections Inc.   |  Fax (909)981-3015
>Upland CA. 91786        |  [log in to unmask]
>---------------------------------------------
>

1) For tight SMD pads I have seen some people run higher continuity (100ohm)
with a dome headed pin to fight registration problems but will generally
fight false shorts with this approach.

2) For fingered (Tip) pads, pad damaged is allowed outside the "sweet" spot.
People that don't stagger off the "sweet" spot will tend to use domes.

3) Headless pins most people are preferring a "blunt" ("bull") nose pin
instead of a conical point.  Doesn't get trapped under top plate, and on
tight pitch will not expose Cu, or break the pad.


 
Jeff Garland 
Lavenir Technology, Inc.
[log in to unmask]
603-431-6279
FAX 603-431-6578

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