An interesting test I have seen performed no clean flux as an indicator of
reactability (new word) is to print the no clean product on the comb
pattern and then relfow.  Apply power across the comb pattern and the
current should be zero with a good no clean (lets hope!).  Place a drop of
DI water on the comb pattern.  If the power does not change it is probably
a good sign that the product does not absorb moisture and cause EM.  If the
circuit breakers blow and the emergency lights come on then you want to be
more critical about the product.  This is not intended as a replacement for
the longer moisture and temp tests but it is reported to provide a short
term indicator of the long term results.  The theory being that DI water is
so starved for ions that if any are present they will readily go into
solution and cause a circuit path with the water.



At 03:31 PM 8/18/97 MDT, you wrote:
>     Hello,
>
>     Based on my literature research, my preliminary plans would be:
>
>     1. Obtain SIR comb pattern coupons, run them through the assembly
>     process w/o components. Use interested flux and solder wire, reflow.
>
>     2. SIR test  OR
>
>     1. Run the product board through the assembly process w/o components.
>     Use interested flux and solder wire, reflow.
>
>     2. Ionic test like Omagemeter
>
>     Definitely, the second plan is simpler for us. But I am not sure it
>     can work. Could someone provide some advices on a simple workable
>     qualification procedure for no-clean rework?
>
>     Another related question:
>
>     I am aware of 2 options to make test coupons: one is to get coupons;
>     the other is to get Gerber file of the test pattern and generate it on
>     the product board. Which one is better?
>
>     Appreciate any help.
>
>     Regards,
>
>     Yuan
>
>
Denis Meloche
Technical Sales Engineer
Heraeus Cermalloy
24 Union Hill Rd.,
W.  Conshohocken Pa., 19428
610-825-6050
Fax 610-825-7061
Email "[log in to unmask]"