Subject: Electro-migration
000Importance: normal
200MCB-options: NNYNANAYA
220MCB-type: 0
200o-nw-formtype: n, w
200o-nw-body: 1, 1

I have been running a slightly modified version of the IPC-TM-650 2.6.13
test for dendritic growth.  The pattern has a .010" space between conductors
and I am using .3 volts per mil of space (3.0 volts) with the current
limited to 100 mA.  (These parameters were suggested by a customer).  The DI
water I am using has a conductance of 0.8 micro-mhos/cm.


I have performed this test on samples at different stages of production and
get the same results.  Samples were taken:

 1) Finished product (HASL & OSP)

 2) Print & Etch only

 3) 5 different laminate suppliers - copper clad no processing

 4) Finished product "cleaned" in our ionic contamiantion unit (75%
    isopropyl)

 5) Finished product soaked in acetonitrile (sp?) for 8 hours

So far everything I have tested exhibits dendritic growth resulting in a
current draw in excess of 300 uA in @ about 1 minute.

I also get the same results with copper tape and copper foil on a glass
slide.  Are these results typical?  Will dendrites form even with very low
levels of ionic contamination using this test?

Is there any correlation between this test and ionic contamination and/or
SIR tests?  The samples all passed ionic contamination testing (<1.0 ug/in2)
and SIR testing (> 1.0E11).

Samples were also tested using ion chromatography - bare copper samples
showed < 1.0 ug/in2 for chloride, bromide, and sulfate.  Solder coated
samples were 1.5 ug/in2 for chloride, 22.0 ug/in2 for bromide, and .1 ug/in2
for sulfate.

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