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December 2006

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Subject:
From:
Wayne Thayer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wayne Thayer <[log in to unmask]>
Date:
Thu, 28 Dec 2006 17:55:32 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (174 lines)
If we need to rework a QFN for insufficient solder/suspected
non-wetting, then we pull the part off and add solder by hand with an
iron.  We visually inspect and rework the deposits, taking care to make
sure the heights are even, then use paste flux and hot air to put the
part back down.

No, its not fun!

Wayne Thayer

>>> [log in to unmask]  >>>
The component is a TI package and the link you show is the type I'm
referring to.  The only difference is the part we are using has 10 pins
with a large thermal pad in the middle.  

How are others inspecting QFN style components?  

How are others reworking QFN style components?  Are you removing the
QFN, or are you adding to the pin that may have insufficient solder?   

If you remove the component, how are you dealing with the fine pitch
issue and getting new paste on the board or solder in general on the
pads so that you can reflow the new component?

We have boards that show the solder paste was insufficient (no solder at
those unprotected lead frames at the sides) and we need to add solder,
we are only visually inspecting with an AOI and manually.  There are no
guarantees that solder will flow to the bottom of the component by just
adding to the outside toe area, so how are others handling this type of
rework?

Thanks,
  


 


Jim West
Engineering Manager
Nexergy Inc.
www.nexergy.com
tel: (614) 351-6216
fax: (614) 324-1979



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--------------------------------------------------------
-----Original Message-----

From: David Greig [mailto:[log in to unmask]] 
Sent: Thursday, December 28, 2006 11:46 AM
To: 'TechNet E-Mail Forum'; West, Jim
Subject: RE: [TN] DRK package

Jim

Have a look at <http://focus.ti.com/lit/an/scba017d/scba017d.pdf>

I'm guessing DRK is a TI package. QFN/DFN are normally plated whilst
panelised, and then sawn or singulated. As a result they have
unprotected lead frame material at the sides. A "toe fillet" is still
useful to get heat into the joint during reflow, and most certainly so
for rework or hand assembly (I have a love hate view on these depending
on whether I'm my minds on electrical/thermal performance or my hands
are on the hot air gun for prototypes!) 


Best Regards
 
David Greig
______________________________
GigaDyne Ltd
5 Albany Business Centre
Gardeners Street
Dunfermline KY12 0RN
United Kingdom
t: +44 (0)1383 624 975
www.gigadyne.co.uk
______________________________

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of West, Jim
Sent: 28 December 2006 14:27
To: [log in to unmask]
Subject: [TN] DRK package

Hi,
 
Looking for some help with the package shown within this email.  The
package virtually sits flush with the PCB, and the pads are directly
under the body of the part.  The pads are exposed on the side, but by a
very small amount.  I have a lot of questions regarding the processes
from the beginning to the end, but wanted to see if anyone else runs
this type of package and what your experiences have been like?  Some
questions would be stencil apertures design guideline, paste height,
after reflow inspection method, and reworking.    
 
Best Regards,
 


Jim West
Engineering Manager
Nexergy Inc.
www.nexergy.com
tel: (614) 351-6216
fax: (614) 324-1979



This email message and all attachments transmitted with it are intended
solely for the use of the addressee(s) and may contain legally
privileged, protected or confidential information. If you believe that
you have received this message in error, please notify the sender
immediately by email reply and please delete this message from your
computer and destroy any copies.

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