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March 2006

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Subject:
From:
Graham Naisbitt <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Graham Naisbitt <[log in to unmask]>
Date:
Thu, 9 Mar 2006 11:20:48 +0000
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Hi Joyce

There is a new IPC-TM-650 2.6.3.7 spec due to be released soon that
introduces a far more relevant test protocol to help characterise a process
rather than a single material (e.g. Flux).

This includes a recommended bias of 5v based upon a gradient of 25v/mm. The
reason for this is based upon science research led by the NPL that showed
lower voltage actually increased the effects of electro-chemical migration.

The measurement voltage is also recommended to be at 5v with no reverse
bias.

The purpose is to try and test under conditions that most accurately reflect
what your product is doing in real life.

Testing using the old standards may well yield unrealistic results. As a
further example, no-clean fluxes tested at 85/85 would be volatilised off
the surface at this elevated temperature. New recommendations now under
consideration are to test no-cleans at 40C/93RH - that way we can better see
if there are any ECM issues.

The dielectric withstand in CC-830 requires the coating to be tested to
TM-650 2.5.7.1 and "there shall be no disruptive discharge evidenced by
flash-over (surface discharge), sparkover (air discharge) or breakdown
(puncture discharge). The leakage rate shall not exceed 10 microamperes."

I hope this helps

--
Regards Graham Naisbitt

[log in to unmask]

GEN3 SYSTEMS LIMITED (Formerly Concoat Systems)
Unit B2 Armstrong Mall
Southwood Business Park
Farnborough, Hampshire GU14 0NR

Phone: +44 (0)12 5252 1500
Fax: +44 (0)12 5252 1112

www.gen3systems.com




On 8/3/06 19:49, "Joyce Koo" <[log in to unmask]> wrote:

> Dear SIR,
> could you kindly provide the update info regarding the maximum bias for the
> conformal coating SIR test?  Is it still 333 V/mm?  assume I use read out at
> 100 Vdc and bias at 50 Vdc for the B-25A, am I right that bias max is
> 333V/mm and read out is at 666V/mm spacing?  Thank you very much.
> Best regards,
>                        jk
> ps.  I know Concoat recommend low voltage bias, but the current test method
> 650-2.6.3.4 is still high voltage.  (50Vdc bias)... by the way, anyone has
> table regarding the dielectric withstanding voltage per IPC-CC-830?  Many
> thanks.)
>
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