For all of you, please be aware that charring along the edges of FR-4 due to laser ablation is somewhat conductive, and if there are power/ground planes nearby the charred edges provide an alternate path. After awhile a short can develop due to increased carbonization over time, leading to catastrophic failure.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Wednesday, June 18, 2014 9:28 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
>
> [cid:[log in to unmask]]
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