I think we've avoided Ed's original question about pleading for leniency on 
charring.

I, for one, have been "burned" several times by a very small amount of laser 
charring residue providing enough conductivity to fail isolation.  Carbon 
conducts electricity very well!  So even if you can't see the char you should 
be skeptical.

Cleaning off charring is possible, but arduous.  An aggressive oxidizing 
plasma cycle can be qualified to do most of it, but often aggressive 
mechanical agitation with alcohol or some other fluid is also needed.

Wayne

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Wednesday, June 18, 2014 10:28 AM
To: [log in to unmask]
Subject: Re: [TN] Laser depanelization

Hi Ed - we are just starting to investigate and qualify laser depaneling for 
some of our boards. We have not observed the level of charring that you had in 
the photo you provided on our test samples. I recommend talking with your 
laser depaneling provider about their process parameter selections - you 
should not be having that level of burning.

Dave Hillman
Rockwell Collins
[log in to unmask]



On Tue, Jun 17, 2014 at 5:41 PM, Ed Popielarski <[log in to unmask]>
wrote:

> 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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