I agree. We are modifying the 6012 requirements by specifying that non-functional lands must have evidence of annular ring. We don't believe they need to meet the full annular ring requirement for a functional pad. We do this to both maintain the dielectric spacing, and on plane layers to prevent the possibility of resin cracks which can propagate to the surrounding plane for polyimide resins. I fear these cracks might also be possible for the new hi-temp lead-free epoxy resin systems which, from all accounts, seem to be more prone to CAF and pad cratering than older epoxy resins, so I don't want to take a risk of resin cracks with them.
Bill
-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Francis Byle
Sent: Tuesday, August 17, 2010 4:57 PM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Non-Functional Land Registration and Annular Inspection
IMO, the boards are not compliant to the strict letter of 6012, only
because 6012 does not differentiate between annular ring requirements
for functional vs. non-functional.
In practice, it's an area that I believe must be AABUS. The customer, by
designing with the smaller non-functional land, is incurring higher
costs if they demand compliance, and the fabricator is incurring risk if
they agree to compliance without adequately understanding the risk of
the smaller lands. The risk level is of course highly design-dependent,
and thus should be something that is worked out between supplier and
customer, per design.
Regards,
Fritz
-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Reed,
Randy
Sent: Tuesday, August 17, 2010 15:33
To: [log in to unmask]
Subject: [IPC-600-6012] Non-Functional Land Registration and Annular
Inspection
IPC-6012 has no guidance on the management of non-functional lands (that
I can find) concerning registration and annular ring limits.
The scenario causing problems is designs where the non-functional pad
size is smaller than the functional pad size. I am not trying to debate
whether this is a good design practice.
What is the intent of IPC-6012? Should boards with registration and/or
annular ring failures on non-functional lands, with the smaller pad
size, be considered non compliant?
Randy
Randy Reed, CQE
Reliability Lab
Viasystems Group Inc.
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