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May 2002

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Subject:
From:
"Tempea, Ioan" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 14 May 2002 14:34:21 -0400
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Hi Jeff,

where can we buy the stencils you are talking about?

Thanks,
Ioan

> -----Original Message-----
> From: Jeff Ferry [SMTP:[log in to unmask]]
> Sent: Tuesday, May 14, 2002 1:49 PM
> To:   [log in to unmask]
> Subject:      Re: [TN] BGA replacement
>
> Stu,
>
> We have 5 Air-Vac systems and do our share of BGA rework. Although we use
> the flux only method, we apply solder paste more often. We've found fewer
> problems when we apply solder paste. Seems to provide a little extra
> solder
> volume ensuring a more consistent joint.
>
> When we do apply solder paste, we use a new type of adhesive backed BGA
> solder paste stencil. These stencils is made from a flexible material, and
> the adhesive backing seals around each BGA pad preventing the solder paste
> from bleeding under the stencil due to the squeegee action. You get a
> consistent deposit with these stencils, and you can simply throw it away
> after it's used.
>
> Jeff Ferry
> CEO
> Circuit Technology Center, Inc.
> http://www.circuittechctr.com
> [log in to unmask]
> 978-374-5000
>
> Chairman
> IPC Repairability Committee
>
> Sign up for our Free E-mail Newsletter at:
> http://www.circuittechctr.com/general/free_email.htm
>
>
>
>
> -----Original Message-----
> From: [log in to unmask] [mailto:[log in to unmask]]
> Sent: Tuesday, May 14, 2002 10:34 AM
> To: [log in to unmask]
> Subject: [TN] BGA replacement
>
>
> The M.E.s at my company are struggling with replacing a defective plastic
> BGA.
> We have an Air Vac BGA machine. The lead M.E. feels that he needs a solder
> pad
> deposit in place before putting the replacement BGA on the board for
> reflow.
> He
> feels that he will compensate for irregular solder balls on the part and
> also
> possible surface differences on the existing pads which have been wicked
> clean
> of solder.
>
> The problem is in putting down the paste. He is teaching a technician to
> use
> a
> small medium stiff plastic stencil. The paste is applied with a wide
> chisel
> blade x-acto knife looking tool. They are getting uneven solder cakes and
> icicles between the solder deposits.
>
> I ask, is that the best way to put down paste? Is it necessary on a
> plastic
> BGA
> to put down a paste deposit? Will the stringers pull in when heated or
> will
> they
> results in shorts after reflow?
>
> Any info appreciated.
>
> Thanks,
>
> Stu Korringa
> Quality Engineer
> Smiths Industries Electronic Systems
> Grand Rapids, Mi.
>
>
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