At 12:00 AM 12/9/01 -0600, you wrote:
>Date: Sun, 9 Dec 2001 00:00:11 -0600
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>Subject: TechNet Digest - 7 Dec 2001 to 8 Dec 2001 (#2001-766)
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>There are 2 messages totalling 54 lines in this issue.
>
>Topics of the day:
>
> 1. BGA Rework Equipment
> 2. Plating and Resin Recession
>
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>Date: Sat, 8 Dec 2001 05:23:36 -0600
>From: Earl Moon <[log in to unmask]>
>Subject: Re: BGA Rework Equipment
>
>I really echo Warren's message. When first developing HP's BGA rework
>process, using SRT, it took three months to get everything almost right.
>Then, there were surprises needing rectification. It never really ended as
>new boards and components were designed and built plus CPI.
>
>The process first must be developed. It must be transferred to manufacturing
>including all procedures for everyone and all parts involved, or those
>perceived to be, it must be validated for each part on each board type, and
>operators must be trained for each shift. Though most all operators great at
>their jobs, some definitely caught on quicker and did consistently better
>jobs than others.
>
>Profiles alone can take much development time, and they're long themselves,
>no matter the paste or original assembly profile. Parts must be removed and
>sites cleaned and touched up and thoroughly inspected. A costly supply of
>nozzles must be bought as well. Micro stencils must be purchased and
>processes developed for their use. Part replacement and reflow processes
>must be right on. X-ray inspection is a must for rework, as it is for
>prototypes, before final test, and on it goes.
>
>This is a good one to "farm out." I think you already knew this or are an
>excellent rework engineer yourself.
>
>MoonMan
>Date: Sat, 8 Dec 2001 17:45:23 EST
>From: Werner Engelmaier <[log in to unmask]>
>Subject: Re: Plating and Resin Recession
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>
>Hi Roger,
>Thicker copper deposits have indeed greater (but not better) elongation
>values than thinner deposits. This, however, does not mean that thinner
>deposits have less ductility; the lower elongation value is an artifact of
>using a test method which is inappropriate for sample geometries like plated
>copper foils. Elongation tests work well for specimen for circular and square
>cross-section; foil specimen have a cross-sectional aspect ratio of 500 to
>1000, which creates this type of artifact.
>This is the reason test methods specific for foils (ASTM E 796 "Standard Test
>Method for Ductility Testing of Metallic Foil," IPC-TM-650, TM 2.4.2.1
>"Flexural Fatigue and Ductility, Foil" ) were developed. These test methods
>show there is no difference in ductility for thin or thick foils from the
>same batch.
Hi,
I will be back on 12/17/01.
Regards,
Jong
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