Porosity test - IPC has a test procedure 2.3.24 - TM 650 and also ASTM
B-799.

We have used these tests for Gold porosity over pure Nickel for more than
0.5 microns testing. They are OK if no condensation occurs on the test
piece. At higher RH the chamber air gets easily bumped to dew point by
moving air draughts in the room as also within the chamber resulting in
condensation on the test part. The test procedures in ASTM advise  room
ambient below 55% RH and this is very sensible.

Brian is more clear than most I know - as to why this happens - Water in a
closed chamber condenses on the walls and suspended parts in it.

However subsequent absorption of So2/HNO3 vapor in this condensate corrodes
any test piece and results are meaningless. Hence the new caution in test
procedures that test area, the chamber the test pieces are all at control
temp and below 55% RH.

We found the gel porosity tests most reliable but a little tedious unless
you get all. Here you can count the spots and evaluate. We have done this a
few times as we could not get ready supplies of the inputs required.

On line we regularly use a drop of fuming Nitric acid on the gold are for 30
secs. Wash/ wipe dry. Peel with a black color peel tape. Inspect for gold
spots peeled off. ( does not work if underlying is Ni/P alloy) This is very
fast and reliable

 Caution - test chemistry has to match the substrate i.e. bare substrate
should corrode for e.g. Ni/P alloy used in ENIG resist most standard tests
as its reactivity to Nitric acid is low (pure nickel just dissolves).

Revert in case you need more data

Anil Kher




-----Original Message-----
From: Scott Westheimer [mailto:[log in to unmask]]
Sent: Wednesday, July 19, 2006 12:30 AM
Subject: Re: Porosity Testing

I remeber a test performed in the 1980's using nitric acid, a glass chamber
and some type of paper. A part with gold plating was placed in the glass
chamber with the nitric and after some time the part was taken out and the
paper was laid across the gold plated area and you could see an pattern
developing on the paper. May be if you check the IPC archives or military it
might be in there.

Scott B. Westheimer
CREE, Inc.


>From: "Victor G. Hernandez" <[log in to unmask]>
>Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
>[log in to unmask]
>To: [log in to unmask]
>Subject: [TN] Porosity Testing
>Date: Tue, 18 Jul 2006 10:45:10 -0500
>
>Fellow TechNetters:
>
>Can someone shares their experience with porosity testing of gold,
>Pd/An, Pd/Ni, etc.
>What are the Pros and Cons of this test and how effective.
>
>
>Victor,
>
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