Clarence,
In IPC-A-600G, under para 2.9.6 (page 45), "There are no wrinkles,
waves, ripples, or OTHER DEFECTS in the solder resist coating---etc".
The cracks could certainly be considered "other defects". Rather than
trying to specify IPC-A-600G, the soldermask should be specified to meet
IPC-SM-840C. Paragraph 3.4.8 (page 5) "Visual Requirements---The
material shall be uniform in appearance and free of foreign materials,
CRACKS, inclusions, peeling, and roughness---etc"
These two specifications, and their intents, would justify rejecting the
boards with cracks. Better yet, would be to rework the boards by
applying another coat of SM over the cracks, as is recommended in the
new IPC-HDBK-840 for SM. This would only work if there are no
components installed. Alternatively, if the boards are conformally
coated after assembly, the conformal might wick into the cracks enough
to provide protection.
Dennis J. Cantwell
R & D Liaison
Printed Circuits, Inc.
1200 West 96th Street
Minneapolis, MN 55431-2699
952-888-7900
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-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Knapp,
Clarence W.
Sent: Thursday, August 03, 2006 5:26 PM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Inspection of Solder Resist
Sounds good But under what criteria of IPC600 are you rejecting the SM.
Note, I do not have the IPC600G
Clarence W Knapp
M&P Engineering
Ph 818 715 2478
Fx 818 719 7769
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-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Denny
Cantwell
Sent: Thursday, August 03, 2006 3:09 PM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Inspection of Solder Resist
If I may inject my opinion into this discussion, from the photo shown,
this should be a rejectable condition to EITHER IPC-A-600G or the
IPC-610. These cracks will absorb solutions by capillary action, and
lower the insulation resistance to probable failure in field usage. Not
knowing the supplier of the product, nor the type of soldermask used, my
opinion may be biased, but the cracks pictured are common when a certain
soldermask is used. If the panel is "flexed" (during photo development
of a LPISM), these cracks are common, if the flexure occurs prior to
baking to full cure. The SM does not develop any flexibility until
after the bake cure. I cannot state whose SM does this, out of respect
for the supplier of the SM, but a change to a different supplier's LPISM
eliminated this problem when we had a similar cracking problem. We
learned the hard way, by losing an entire production lot for cracks, but
since changing suppliers, we have not had any problems.
Dennis J. Cantwell
R & D Liaison
Printed Circuits, Inc.
1200 West 96th Street
Minneapolis, MN 55431-2699
952-888-7900
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-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Knapp,
Clarence W.
Sent: Thursday, August 03, 2006 4:16 PM
To: [log in to unmask]
Subject: [IPC-600-6012] Inspection of Solder Resist
I just run into a problem between IPC-A-600 and IPC-A-610. In the IPC
600 Solder Resist cracking is not addressed with the waves and wrinkles
so it is not inspected for and generally ignored. However, IPC-A-610
states that crack of the resist is a rejection. The enclosed picture is
an example of the crack on bare board.
<<DSCN2423.JPG>>
Clarence W Knapp
M&P Engineering
Ph 818 715 2478
Fx 818 719 7769
[log in to unmask]
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