OK
>Date: Fri, 19 Feb 1999 10:32:45 GMT
>Reply-To: "TechNet E-Mail Forum." <[log in to unmask]>,
> Edward Brunker <[log in to unmask]>
>From: Edward Brunker <[log in to unmask]>
>Subject: Re: [TN] TechNet: confirmation required (6F2282)
>To: [log in to unmask]
>
>ok
>
>______________________________ Reply Separator
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>Subject: TechNet: confirmation required (6F2282)
>Author: "L-Soft list server at IPC (1.8c)" <[log in to unmask]> at
INTERNET
>Date: 19/02/99 04:21
>
>
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>------------------ Original message (ID=6F2282) (91 lines)
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>Date: Fri, 19 Feb 1999 10:19:56 GMT
>From: "Edward Brunker"<[log in to unmask]>
>To: <[log in to unmask]>
>Subject: Re[2]: [TN] Squeegee Speed
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>
>>The factorinfluencing this effect is how stencil gaskets to the board
and
>>you may need to look as points such as : Board finish
>
>>Regards
>>Edward Hale
>
>
> I find this aspect intersting. Resist height is always more than
the
> plated copper height. For all alternative finishes with LPI, in my
> experience. The resist over traces leading to pads brings the
resist
> up even more. The dome on HASL boards will protrude above, but
only
> for a portion of the pad, the edges still remain lower.
> Does anyone spec the resist height to be less than the pads?
> So stencils rest on the resist leaving 10 - 30 microns of free
space
> underneath.
>
>
> Regards
> Edward Brunker
>
>
>>Evenin' all!
>>
>> My question is this: My stencil printer operator has said
that he
>>has to
>>wipe our 6-mil stencil each pass to get the paste in the 20-mill pitch
>>aperatures for a QFP to release well. We are using Amtech NC-559 type
3
>>paste with 89.5% metal. The paste is not old. I considered using
type 4
>>paste, which has a much finer powder in it. I was told by Amtech that
this
>>finer powder paste will pack more densly into the aperatures and I
could get
>>some bridging, unless I order a new stencil with aperature reductions.
Our
>>squeegee speed is 0.6 inches/s, or 15mm/s. Is this too slow? Amtech
>>suggested that at this slow speed, the paste could be rising out of
the
>>aperature, as if someone pressed on a wet sponge and it rose back to
its
>>original shape. What is a good squeegee speed for 20 mil pitch parts?
>>Thanks all!
>>
>>Ryan Jennens
>>TelGen Corp.
>>
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