In a former life we laser cut FR4, usually because routing wasn't adequate
or forgotten. Often on populated boards in emergency time.
We were primarily a ceramics house using CO2, so it was not a mainstream
activity. But tapes and ribbons were.
It is possible to cut laminate with minimal to no charring but you need to
pulse relatively slowly (compared to ceramic) and with a ferocious gas flow.
Properly set up the laminate is not merely oxidised but goes direct to
plasma without char.
[It works very well at the bottom of a v-score. The question then "Do you
want the cut to drawing or at the bottom of the V?"]
I would say the photo is not indicative of the best that can be achieved.
I would say occasional edge discoloration, depending on adjacent tracking,
resist, legend etc. should be achieved. Other laser types would work OK but
would be slow. Water jetting is theoretically good and probably practical,
but I never saw it. Probably a cultural thing - water on my PCBs no way!
Nearest for electronics type products as routine production I would say is
thermal interface shapes.
Regards
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Wednesday, June 18, 2014 5:11 PM
To: [log in to unmask]
Subject: Re: [TN] Laser depanelization
I agree - charring has the potential to become a "conductive trace the
product design team didn't plan" so any amount of charring needs to be
understood from a potential failure location.
Dave
On Wed, Jun 18, 2014 at 10:02 AM, Wayne Thayer <[log in to unmask]> wrote:
> 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
> >
> > [cid:[log in to unmask]]
> > 970 NE 21st Ct.
> > Oak Harbor, Wa. 98277
> >
> > Ph: 360-675-1322
> > Fx: 206-624-0695
> > Cl: 949-581-6601
> >
> > "It's one kind of victory to slay a beast, move a mountain, and
> > cross a chasm, but it's another kind altogether to realize that the
> > beast, the mountain, and the chasm were of your own design."
> >
> > https://maps.google.com/maps/myplaces?hl=en&ll=48.315753,-122.643578&s
> > pn=0.011188,0.033023&ctz=420&t=m&z=16&iwloc=A
> >
> >
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