careful etching enhances the post-polish view -- but you need careful
control -- sloppy etching can 'enhance' the effects of smear residue --
but a well controlled etch is preferable to the raw polished sample as
this can contribute many more artifacts -- the photos in the report are
embarrasinly similar to sections i have prepared myself in previous lives,
and i would not question their veracity -- the quality of the polish and
etch looks very good -- ian
From:
"Rivera, Raye" <[log in to unmask]>
To:
<[log in to unmask]>
Date:
26/08/2011 11:46 AM
Subject:
Re: [TN] Is Desmear or Etchback Optional?
Sent by:
TechNet <[log in to unmask]>
Hi Victor,
I actually tried twice to reply to you, but the message didn't post.
(Maybe because I sent HTML format instead of plain text?) I'll try again.
The sample was etched. I asked our lab about their etch process, and here
is their reply.
"We use ammonia hydroxide 10 parts to 1 part hydrogen peroxide. It is only
applied for 3 seconds and washed off and dried."
I am sorry, but I no longer have this sample. The lab report has good old
fashioned Polaroid photographs. I rescanned the originals to IPC
groupsite. They are the same photos, but perhaps they will be a little
clearer.
http://ipc-technet.groupsite.com/uploads/files/x/000/06a/2ef/SmearVert.jpg?1314122607
http://ipc-technet.groupsite.com/uploads/files/x/000/06a/2ed/SmearHoriz.jpg?1314122565
Best regards,
Raye Rivera
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Friday, August 26, 2011 4:43 AM
To: [log in to unmask]; Rivera, Raye
Cc: [log in to unmask]
Subject: RE: [TN] Is Desmear or Etchback Optional?
Raye,
I saw the additional photos you posted. Again, I ask if the sample
were chemically etched. When searching for IP sep or drill smear I don't
etch the sample so as not to jeopardized the interface. Once the sample
has been etched the area of interest is exemplified by the chemistry. Even
Ray Charles can see the anomaly.
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rivera, Raye
Sent: Monday, August 22, 2011 11:11 AM
To: [log in to unmask]
Subject: Re: [TN] Is Desmear or Etchback Optional?
Hi Victor,
I agree the root cause is probably a drilling issue. Re-reading my earlier
post, I see I used the term "insufficient desmear" rather casually. What I
meant to say was that the desmear process did not remove all the resin the
drill left behind. I cannot tell from the photos whether this was caused
by excessive smearing due to a dull drill or some deficiency of the actual
desmear process.
Best regards,
Raye Rivera
QA Manager * Canoga Perkins * 818-678-3872 * [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Monday, August 22, 2011 5:00 AM
To: [log in to unmask]
Subject: Re: [TN] Is Desmear or Etchback Optional?
Raye,
I finally got to see the 2 photos that you shared. I would like more
clues as to which this is a desmear process anomaly. At first glance I
see what appears to be rough drilling.
Victor, Cell: 512.736.6817
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rivera, Raye
Sent: Friday, August 19, 2011 2:46 PM
To: [log in to unmask]
Subject: Re: [TN] Is Desmear or Etchback Optional?
Hi Victor,
Certainly! I uploaded a copy of the lab report to groupsite. Here is the
link.
http://ipc-technet.groupsite.com/uploads/files/x/000/069/daa/SmearRept.pdf?1313782786
Best regards,
Raye Rivera
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Friday, August 19, 2011 10:31 AM
To: [log in to unmask]
Subject: Re: [TN] Is Desmear or Etchback Optional?
Can you so kindly share the above stated desmear artifact on a cross
section. A picture is worth 1000 words.
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rivera, Raye
Sent: Friday, August 19, 2011 11:29 AM
To: [log in to unmask]
Subject: Re: [TN] Is Desmear or Etchback Optional?
Hi Bob,
We have seen insufficient desmear here and it does create an unreliable
connection. A properly prepared microsection will show the defect clearly,
which is how we (or rather, the lab we contract) caught it.
I suppose it is possible that some shop might entirely skip desmear to
save money, but any shop with that attitude would not last long. It is a
key part of the process and skipping it would absolutely result in
defective and rejectable boards.
Best regards,
Raye Rivera
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Friday, August 19, 2011 6:59 AM
To: [log in to unmask]
Subject: Re: [TN] Is Desmear or Etchback Optional?
Would NO DESMEAR result in connection of barrels to planes (perhaps
un-reliable connections) or would many internal connections be open?
Is it the case that some low cost shops would NOT DESMEAR to reduce costs
and get away with it?
Thanks,
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Pete
Sent: Friday, August 19, 2011 9:37 AM
To: [log in to unmask]
Subject: Re: [TN] Is Desmear or Etchback Optional?
It's not actually "kissing away 2 mils"
When you start adding up tolerances for drill hole size, location, layer
registration, process allowance.... you can easily come up with 2 mils
difference from one shop to another. 10 mils hole to copper shouldn't be
difficult at all for a good fab shop.
Not that it's really possible, but any shop so particular with their
drilling that they wouldn't require some sort of desmear would be
particular enough to desmear anyway.
Pete
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