The amount of charring depends, somewhat, on the laser settings (and
laser). You can optimize for minimum charring and HAZ (heat affected
zone), usually at lower power and frequency settings and slower
throughput. Other modifications that help reduce charring are increase sm
pullback from laser path, use depth route or scoring opposite so as to
reduce the thickness of FR4 cutting through and relieve the tool holding
the board in the laser path so as to reduce backsplash or blowback from
the backup material or fixture.
Doesn't really help you if the boards are already fabricated and sm is in
the laser path, but you can also try plasma clean after laser ablation.
Jana Carraway
____________________________________
Jana Carraway
Staff Engineer, Future Technologies
Advanced Technology Group
Micro Systems Engineering, Inc, an MST Company
6024 S.W. Jean Road
Lake Oswego, Oregon 97035
503.744.8547
email: [log in to unmask]
Ed Popielarski <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
06/17/2014 03:46 PM
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Subject
[TN] Laser depanelization
Hi all,
One of our aerospace customers is requesting boards depanelized from
support frames.
I looked into router, but the conformal coating tends to smear and will be
a significant FOD issue later.
We are willing to invest in laser, however, the result is a bit of
charring on the edge, not much of a surprise. Unfortunately, this example
http://stevezeva.homestead.com/Capture.JPG was rejected on IPC-A-610-Rev E
Para. 10.7.4 "Solder Mask Coating-Discoloration" "Burned or charred solder
mask material.
In my opinion, this is not within the "spirit of the law" since there are
no specific provisions for laser depanelization, only marking.
Anyone know of some way around this?
Ed Popielarski
Engineering Manager
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