Also look at IPC 7095 and 7094, there is a lot of good information on
reliability issues with using soldermask-defined pads. Paymon, this is
where soldermask is considered to encroach into the solder joint. Read
particularly IPC 7095 section 8.4.3, and again Werner Engelmaier also
has written some excellent articles on the influence of soldermask on
reliability of BGA solder joints.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Friday, March 30, 2007 12:54 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Resist Encroachment onto BGA pads
I suspect a lot since all of the work on solderability/reliability in
regard to wetting angles was done many years ago.
Is Werner on the forum?
John
John Burke
(408) 515 4992
-----Original Message-----
From: Paymon Sani [mailto:[log in to unmask]]
Sent: Friday, March 30, 2007 10:15 AM
To: TechNet E-Mail Forum; John Burke
Subject: RE: [TN] Solder Resist Encroachment onto BGA pads
Thank you John, is there any studies on this?
Paymon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: March 30, 2007 12:45 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Resist Encroachment onto BGA pads
Actually yes.
If you put solder resist over the lands for the BGA you have by
definition a joint defined by the resist system.
Effectively this will give you a 90 degree wetting angle which is - you
guessed it a stress riser.
So a joint with solder mask defined joints will be more liable to crack
under stress.
John
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani
Sent: Friday, March 30, 2007 9:02 AM
To: [log in to unmask]
Subject: [TN] Solder Resist Encroachment onto BGA pads
Hello All,
Does anybody know why IPC does not allow any solder resist encroachment
onto the BGA copper defined lands for PCBs?
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