One good method is to utilize the electroless copper deposition coupon with
some modifications.

I/we have used a coupon that has a series of 4-8 holes drilled prior to
deposition. The operators plate the coupon along with their basket of work.
The drilled holes are such that you snap a short end piece off which leaves
the half hole plating still intact on it and the rest of the coupon is used
to determine the plating rate and/or thickness.

The snapped off end section(not the hole side) is then ground down on
x-section preparation equipment.
The remaining piece is then micro-etched and rinsed and dried. Now it is
ready to place on a x-section microscope and shine a light source through
the back of the coupon and view the half hole side for light pin points. The
test is subjective because some(italics) pin points can/will plate up in the
electrolytic baths and pose no problems.

Also, I/we used to micro-etch the coupon for 3 times the actual plating line
preclean cycle. This was done to assure that the eless copper thickness was
sufficient to allow for a hoist/program snafu or a rework process if
necessary.

The testing must be done on the material specific product to be helpful.
Also, there is some debate on how much light can pass though the holes and
still cause no problems. These are best answered by the production hose
engineers after some monitoring of the process has been performed.

My last comment here is that at my previous employer we did the above
monitoring and could not identify a failure in plating (voids in the
electrolytic copper) over a one year period due to poor backlight results.

Hope this helps. I can speak off line on this topic if anyone is interested.

520-745-8515


>From: Robert Coburn <[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] Backlight testing / Electroless copper
>Date: Thu, 24 Jul 2003 13:41:47 -0400
>
>Hi Technetter's;
>
>Does anyone have any info (website, standard, company, etc) regarding
>backlight testing, evaluation and rating of electroless copper processed
>holes?
>
>Thanks in advance.
>
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