Scott,

I had one board shop give me samples trying to convince me to accept
DIG.  I told them I have zero interest!  However, since I already had
the samples (in two gold thicknesses), I figured it didn't hurt to put
the samples through some of the same tests I was doing for an immersion
silver qualification.  One such test was to bake the boards for 48 hours
at 150C and see how they solder.  I wasn't concerned about the
solderability of the immersion silver but I figured the DIG would have
horrible solderability without a copper diffusion barrier.  To my
surprise, the DIG samples soldered beautifully; even better than the
immersion silver.  (My OSP 'control' samples were unsolderable).

I didn't pursue the DIG, largely because it is still a 'newcomer' and
I'd prefer to let someone else to break their teeth on it.  But
apparently, the concerns of copper diffusion seem to be somewhat
unfounded.

Thanks,
Ryan Grant

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Scott Lefebvre
Sent: Monday, April 30, 2007 6:51 PM
To: [log in to unmask]
Subject: [TN] ENIG vs. IG over Copper DIG.

Currently I have been using ENIG as my primary lead free solder finish
but I've been reading about Direct Immersion Gold "DIG".  Direct
immersion gold is deposited directly on the copper surface to a
thickness of 1-2 uins.  I want to know if anyone in Technet has any
experience with this finish.

 

I use both water soluble solder and no clean solder flux in our current
process.  The lead free solder is SAC305 for both SMT and through-hole.

 

One of the drawbacks I could think of is copper dissolution when
soldering the boards with SAC305 solder.  I have not had any issues
using our existing ENIG solder finish but one of our new PCB shops have
asked if we could switch.

 

Scott Lefebvre


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