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June 2011

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Mon, 27 Jun 2011 07:32:03 -0500
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Good morning Luan,
It sounds like a design issue where the SMT chip pads directly connected to the PTH next to it are sent into reflow during contact with the molten solder from the selective solder machine. Attempting to coat the SMT chip solder joints with temporary soldermask does not work, because underneath the maskant the solder is still able to go into reflow as a result of direct contact with the molten solder from the PTH part and the surrounding heat through the board itself. Solder can easily flow away from the chip cap solder joints underneath the temporary solder mask. 
It is possible that the only way to fix this would be a design change. Another possibility would be to identify the particular PTH parts that cause this to happen and hand solder those.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Luan Nguyen
Sent: Sunday, June 26, 2011 10:18 PM
To: [log in to unmask]
Subject: [TN] Chip insufficient by Selective soldering

Dear TechNet,
We have been facing the insufficient solder at Chips from Selective soldering. 
When we solder Through hole components, solder volume of Chip pads next to PTH component is reduced, cut-down and these chips are insufficient solder. Although we have applied solder stop material (Pn: 700-1603-000-V, Wondermask 2207-5G, Techspray Solder Stop) to cover these chips but the problem have been happening. We understood that temperature to solder PTH component caused to this problem but we don't know what action for them.

Would you please help us to understand the principle of this insufficient and have any related documents or any advice. We thank advance!

Luan Nguyen.


***************************
Nguyen Hoang Luan
QA Supervisor - IPC Trainer
Spartronics VietNam Co, Ltd.
No.3, Street No.6, VSIP
Th An Dist., BDuong Prov., VN
Tel: (84-650) 784 890
Fax: (84-650) 784 891
Mobile: 090.3.667448
Email: [log in to unmask]
***************************


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