Hi Sarah,

 I would like to ask the following questions  on separation problem:
 1) what is the difference between IL separation and post separation?

        There is no difference - post separation is a term used to describe the more
proper term - inner layer separation.  Sometimes you will hear it referred to
as T Joint separation too.

 2) what causes the occurrence of such kind of defect?

        There are numerous causes depending upon where the separation occurs.  Can
you determine if it is between electroless and inner layer, within
electroless, or between electroless and electrolytic?

        At one time when I was building boards - we had it every fall when our
ambient rinse tanks became cooler than they were in the summer.  Heated rinses
made it go away.

        Once you determine where the separation is located, we can help with the
processes that are involved.


 3) how can we prevent this type of problem from occurring?

        First you have to determine what step in the process is causing it.

 4) at what layer does this problem usually occur?

        Traditionally it appears at layers 2 and N-1, due to their seeing more
movement during thermal stress testing and any other thermal excursion.

 5) how can you distiguish separation from resin smear?

        When you look at microsections the separation is filled with resin and not a
"hole" that is present from actual separation.  This is sometimes easier to
see with polarized light.

        If you suspect drill smear, you can run your board through an oxide process
immediately after desmear and then examine the inner layers.  Copper inner
layers will be black, but any smear will not be coated with oxide.

 Hope this helps to get you started on solving the problem

Susan Mansilla
Robisan Lab

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