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April 2003

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From:
"d. terstegge" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 2 Apr 2003 09:52:54 +0200
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Hi Carl,

For a twisted board I wouldn't know how to measure it after assembly,
but for warp (bow) you can do it like this: Hold a steel ruler against
the edge of the board, perpendicular to the boardsurface, in such a way
that there is an equal gap between the boardsurface and the ruler at
both ends. Now use shims of various thicknesses to measure the gap.
The value that you get, times hundred, divided by the lenght of the
measured side gives you the percentage of bow for this side of the
board. The highest value for the four sides of the board is the one to
compare to the spec limit.

Daan Terstegge
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net

>>> [log in to unmask] 04/02/03 12:14am >>>
 Any of you guys know how to measure board warpage after the unit has
been completely process?

Process:
SMT Bottom
SMT Top
PTH Axial and Radial
Hand loaded
Wave Solder
Post wave processing

 At my Incoming receiving area I can detect board warpage but after the
wave process (sometimes SMT Top) the boards start to warp. All the
profiles have been verified and validated.
 We know we have a vender issue but the problem is our customer will
not accept the unit we have in process (around 500). So if anyone has
any suggestions it would be greatly appreciated.

Carl Ray
Sr. Manufacturing Engineer
Huntsville, AL 35807
Phone: 256-882-4800 ext. 8845
Cell: 256-990-1990

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