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May 2008

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Thu, 8 May 2008 10:53:44 +0800
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¡¡¡¡George,
¡¡¡¡1). What is the surface finish on the pads of the QFN?  Is it PdNiAu?
¡¡¡¡RE:I don¡¯t directly contact with the QFN's supplier(intersil),but
judging from the intersil website info, it maybe matte tin with exposed
copper side. As I know, the pdNiAu is the TI patent.
¡¡¡¡2). Have you made any transmission x-ray images of the QFN's soldered on
the PCBA to see the number and size of voids on the pads and heat sink.?  
¡¡¡¡RE:Yes, I have found many voids with big size under the thermal paddle
and the peripheral pads by X-ray, we also complained about this issue to the
module supplier.
¡¡¡¡Best regards!
¡¡¡¡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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¡¡¡¡
¡¡¡¡-----ÓʼþÔ­¼þ-----
·¢¼þÈË: Wenger, George M. [mailto:[log in to unmask]] 
·¢ËÍʱ¼ä: 2008Äê5ÔÂ8ÈÕ 10:21
ÊÕ¼þÈË: [log in to unmask]; [log in to unmask]
Ö÷Ìâ: RE: [TN] ´ð¸´: [TN] QFN's open in SMT power module af ter second
reflow
¡¡¡¡
¡¡¡¡Min Jun,
¡¡¡¡
¡¡¡¡I have two additional questions.
¡¡¡¡
¡¡¡¡1). What is the surface finish on the pads of the QFN?  Is it PdNiAu?
¡¡¡¡
¡¡¡¡2). Have you made any transmission x-ray images of the QFN's soldered on
the PCBA to see the number and size of voids on the pads and heat sink.?  
¡¡¡¡
¡¡¡¡
¡¡¡¡
¡¡¡¡Regards,
¡¡¡¡George
¡¡¡¡George M. Wenger
¡¡¡¡Andrew Wireless Solutions
¡¡¡¡Senior Principal FMA / Reliability Engineer
¡¡¡¡40 Technology Drive, Warren, NJ 07059
¡¡¡¡(908) 546-4531 [Office]  (732) 309-8964 [Cell]
¡¡¡¡[log in to unmask]
¡¡¡¡ 
¡¡¡¡
¡¡¡¡-----Original Message-----
¡¡¡¡From: TechNet [mailto:[log in to unmask]] On Behalf Of Min Jun
¡¡¡¡Sent: Wednesday, May 07, 2008 9:41 PM
¡¡¡¡To: [log in to unmask]
¡¡¡¡Subject: [TN] ´ð¸´: [TN] QFN's open in SMT power module af ter second
reflow
¡¡¡¡
¡¡¡¡¡¡¡¡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
¡¡¡¡¡¡¡¡ 
¡¡¡¡¡¡¡¡
¡¡¡¡
****************************************************************************
¡¡¡¡***********
¡¡¡¡¡¡¡¡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!
¡¡¡¡¡¡¡¡
¡¡¡¡
****************************************************************************
¡¡¡¡************
¡¡¡¡¡¡¡¡
¡¡¡¡¡¡¡¡-----ÓʼþÔ­¼þ-----
¡¡¡¡·¢¼þÈË: Tan Geok Ang [mailto:[log in to unmask]] 
¡¡¡¡·¢ËÍʱ¼ä: 2008Äê5ÔÂ8ÈÕ 8:53
¡¡¡¡ÊÕ¼þÈË: [log in to unmask]
¡¡¡¡Ö÷Ìâ: 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¡Á5mm£©. 
¡¡¡¡¡¡¡¡
¡¡¡¡¡¡¡¡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
¡¡¡¡¡¡¡¡
¡¡¡¡¡¡¡¡ 
¡¡¡¡¡¡¡¡
¡¡¡¡¡¡¡¡
¡¡¡¡
****************************************************************************
¡¡¡¡¡¡¡¡***********
¡¡¡¡¡¡¡¡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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