Try one of the Kester product (Flux 979) for better SIR test performance. Maybe cost you more but solves your problem.

SUPRAPTO SANTOSO

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From: NG ENG GUAN [mailto:[log in to unmask]]
Sent: Friday, September 26, 2008 4:33 PM
To: [log in to unmask]
Subject: Re: [TGAsia] 转发: The effect of Flux residu e on PCB

Hi Leo,

No doubt , this is caused by the flux. We had faced the same problem before .Our solution is to clean up the flux.  

From: TGAsia [mailto:[log in to unmask]] On Behalf Of Leo Yang
Sent: 26 September 2008 13:03
To: [log in to unmask]
Subject: [TGAsia] 转发: The effect of Flux residue on PCB
Importance: High

FYI

B/R

Leo Yang

IPC WOFE

21-54973435-616

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From: charles.lee [mailto:[log in to unmask]]
Sent: Friday, September 26, 2008 11:51 AM
To: 'Asia Committe Task Group Forum'
Subject: The effect of Flux residue on PCB

Dear All,

Our customer complained us that flux residue resulted in dielectric resistance reduction between two pads on PCB (From 10Mohm to 3Kohm), please refer to the attached picture.

The flux we have been using is No-clean type supplied by Union Soltek.

We are now puzzled with below questions:

1) What is the chemical substance around these two pads? Is it only flux residue?

2) Will the flux residue be able to occur chemical reaction with solder mask after elapse of a long time?

3) What is the root cause which results in dielecric resistance variance?

We look forward to your expertised explaination, thanks!

Best reagrds

Charles Lee