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February 2000

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Subject:
From:
Brunker Ed <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 8 Feb 2000 17:00:39 -0000
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I couldn't agree less.
If your pad geometry is correct and if your stencil apertures are correct
then there should be no problem. I have run quite happily without dams on 25
and 20 thou pitch. If you print solderpaste in 12 thou strips on 25 thou
pitch then the 13 thou gap is more than ample with a 6 thou stencil.
Regards
Edward Brunker


-----Original Message-----
From: Ed Valentine [mailto:[log in to unmask]]
Sent: Tuesday, February 08, 2000 4:45 PM
To: [log in to unmask]
Subject: Re: [TN] Solder mask dams between fine pitch parts


Barbara -

From a manufacturability viewpoint, you definitely want solder mask between
fine pitch parts as a major factor in controlling bridging.  In the '89-'90
timeframe, we ran many tests on in-house designed test boards that had both
the "open window" and LPI mask between the fine pitch pads, even on the same
part layout, using dummy components.  The results were dramatic.  Mask
between the fine pitch pads made a huge difference in first pass yields on
QFP's down to 16-mil pitch.  We rarely ever had bridging.

Ed Valentine
Electronics Manufacturing Solutions
Phone: (919) 270-5145
Fax: (919) 847-9971
www.ems-consulting.com
[log in to unmask]
----- Original Message -----
From: Barbara Burcham <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, February 08, 2000 10:04 AM
Subject: [TN] Solder mask dams between fine pitch parts


> What is the assembly industry take on the advisability of solder mask dams
> between the pads on fine pitch parts - 25 mil?
> To have or not to have?
> What is the fabrication industry take on the maunfacturability of solder
> mask dams between the pads on fine pitch parts - 25 mil?
> To fab or not to fab?
>
> Barbara J. Burcham, CID
> PCB Designer
> Fairfield Industries
> Sugar Land, TX 77478
> 281-275-7687 Work
> 281-275-7550 Fax
> [log in to unmask]
>
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