Dear Inge,
Thanks for your feedback.
Myself have verified the process, during SMT reflow soldering, there's no
warp issue.
How did you fix the issue?
Best Regards
Willis Tam
-----原始邮件-----
发件人: TechNet [mailto:[log in to unmask]]代表 Ingemar Hernefjord
发送时间: 2005年11月12日 3:24
收件人: [log in to unmask]
主题: [TN] SV: [TN] urgent issue BGA fall out
We have seen same. Are you sure the BGAs did not warp during the
soldering process? Furthermore, in what part of the BGA do the
interrupts occur? In our case, we got normal function again when we put
a finger on the BGA and pressed a little.
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För WTSJ-Willis Tam
Skickat: den 11 november 2005 07:31
Till: [log in to unmask]
Ämne: [TN] urgent issue BGA fall out
Prioritet: Hög
> Dear All,
>
> Recently, we found a very strange defect with the BGA IC.
>
> Here's our process flow: SMT---> De-panel (by V-cut machine)--->
> Functional test--->final inspection
>
> We found around 10 pcs BGA falling out either at the process of
de-panel or
> functional test, defect rate less than 0.1%. The defect only happened
in 2
> days, It's very strange, all the solder balls adhere to PCB. there's
no
> solder ball adhere to the BGA substrate.
>
> Investigations from our side:
> 1. We have been built the same product since April 2004. no issue
before.
> 2. Since May 2005, the SMT process was converted to RoHS, BGA also has
been
> changed to green type since then, monthly output around 200K.
> 3. The BGAs were 100% baked under 110 degreeC for 24 hrs before SMT.
> 4. We use Loctite LF318 solder paste for SMT, the time between 70
degreeC
> to peak 245 degreec is around 250 seconds.
> 5. The BGA only subjected to 1 time reflow (only 1 side with
components)
> 6, We have reflow fixture to support the board during reflow. there's
no
> warpage issue.
> 7, Use Vcut machine to separate the units from a 6 up-panel PCB, no
extra
> stress to the board.
> 8. Use pogo pin to make connection for functional test fixture, no
extra
> stress.
>
> Information of BGA.
> 1. It's a solder mask defined substrate. with ENIG surface finishes.
> 2. 0.8mm pitch, pad size 0.35mm.
> 3. IC supplier apply solder ball with flux only, without solder paste.
>
> Would anybody give me some advices, what shall be the most possible
root
> cause? it's a BGA IC issue or a SMT process issue? How to improve?
>
>
> Thanks
> Willis Tam
>
>
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>
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