Thanks for your good suggestion.
There are few questions:-
How is the module soldered to you board? Manually (unlikely), reflow
oven, wave soldering or others?
RE: reflow oven with 12 zone.
a) Is there a thermal pad at the center of the QFN?
RE:YES
b) Is the solder fillet evenly across the terminals (align good)?
RE:YES
a) It seems to me that the solder volume is not enough to hold the part
in it original position. Evaluate by adding solder/ touch on the terminals.
RE:Yes, we are trying it.
b) The module came in SnPb alloy while your process calls for Lead-free
process?
RE: our process is snpb process,but QFN solder joint is lead-free alloy
but the module's terminal is snpb solderball.
c) Try to add thermal relief/ small piece of heatsink on the QFN to
prevent it from re-melting
RE:a good idea, we are just trying to do it like what you said.
Min Jun
H3C process engineer
Tel:+86-010-82774234
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-----邮件原件-----
发件人: Tan Geok Ang [mailto:[log in to unmask]]
发送时间: 2008年5月8日 8:53
收件人: [log in to unmask]
主题: RE: [TN] QFN's open in SMT power module after second reflow
There are few questions:-
How is the module soldered to you board? Manually (unlikely), reflow
oven, wave soldering or others?
a) Is there a thermal pad at the center of the QFN?
b) Is the solder fillet evenly across the terminals (align good)?
a) It seems to me that the solder volume is not enough to hold the part
in it original position. Evaluate by adding solder/ touch on the terminals.
b) The module came in SnPb alloy while your process calls for Lead-free
process?
c) Try to add thermal relief/ small piece of heatsink on the QFN to
prevent it from re-melting
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Min Jun
Sent: Wednesday, 7 May 2008 9:36 PM
To: [log in to unmask]
Subject: [TN] QFN's open in SMT power module after second reflow
We recently qualified a SMT power module which has a small QFN part on
the
board bottom side （the QFN package is intersil ISL6522 5mm×5mm）.
After the module was soldered to our board, We often found solder
jointer
open in QFN terminal for remelting
We also find one doubtful point, in general, if the standoff of QFN has
obviously height and the solder jointer has beautiful fillet,
The module will easily have the open issue after reflow.
So we think the problem reason is caused from the incoming parts PCBA
process control and DFM design although the incoming is good,
Also we think the standoff of QFN in module should be controlled,
otherwise
the solder jointer will have open issue in our PCBA.
Who have encountered the same issue or could give me any idea? Thanks in
advance!
Min Jun
H3C process engineer
Tel:+86-010-82774234
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This e-mail and its attachments contain confidential information from
H3C,
which is intended only for the person or entity whose address is listed
above. Any use of the information contained herein in any way
(including,
but not limited to, total or partial
disclosure, reproduction, or dissemination) by persons other than the
intended recipient(s) is prohibited. If you receive this e-mail in
error,
please notify the sender by phone or email immediately and delete it!
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