Marie,
Welcome to TechNet!
Although no expert, my reaction is that voids in the goldplating would not,
in itself, cause poor vertical fill in the holes. The gold should burn off
during soldering and wetting should be to the underlying Nickel (presumably
this is an ENIG board). It seems to me that the problem is either with the
underlying copper plating or else the Nickel layer plated onto that. Have
you done any cross-sections of affected areas?
Some questions:
1. What are the diameters and aspect ratios of the affected holes? If the
aspect ratio is too great and/or the hole diameter too small, plating
thickness half way down the hole is affected, especially with
small-diameter holes.
2. What is the target gold plating thickness? If it's too thick, that may
have some bearing on the problem you're seeing. If it's too thin, and you
have Nickel plating underneath, you may have porous gold that has allowed
the Nickel to oxidise. This would cause poor wetting and so the solder
might not rise properly.
3. What flux was used to assemble the boards? Maybe you need to try a
slightly more aggressive one. I'm not well up on fluxes, so can't make any
recommendations, but I'm sure others can.
4. Is it only the holes that are affected, or is the soldering quality of
other parts of the boards less than ideal also?
We need a few more clues to give a better answer.
Peter
Marie Magnin <[log in to unmask]> 13/01/2003 10:01 PM
Sent by: TechNet <[log in to unmask]>
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cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: [TN] voids in gold plated holes
Dear TECHNETers,
It is my first post to this list, please forgive me if I ask an already
posted question, but I could not find any answer to my problem.
We have received, populated and soldered a set of 50 boards which have
voids in the gold plating layer into holes (either PTH and via holes). We
have discovered the problem because of a poor vertical fill of the holes at
wave soldering.
Is there any standard for this parameter ? Neither IPC nor PERFAG mention
anything about this, they just state on copper plating.
Is there any risk of corrosion in the future for these boards ? (they will
be installed in factories, means in "standard" environnement in terms of
humidity and temperature )
If yes, how would you prevent it ? ( we cannot post solder the holes,
because of the large quantity of these and also because many of them are
hidden under SMD part; I would personnaly would use conformal coating)
Many thanks for your help and kind regards
Marie Magnin
QA Manager
FIRSTEC SA
Rue du Grand Pr¨¦ 70
CH 1211 Gen¨¨ve 2
T¨¦l : +41(0)22 918 36 85
Fax : +41(0)22 918 36 93
mailto:[log in to unmask]
http://www.firstec.ch
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