Backround

I am presently in the evaluaton stage of identifing the processes and
techniques required for OSP boards.  I have seen several samples of boards
that exhibit what I would describe as a Tee-Pee effect on un-populated fine
pitch pads.  By this I mean that there appears to be a pointed center, not
the typical rounded conical shape I would expect.

                  II
                 I  I                                  xxxxxxxxxx
                I    I                              XXX          XXX
              I        I                            ________________
            ________________                       |________________|
                 Pad
               Tee-Pee effect                            Conical Shape

Also, my understanding has been that in addition to the geometric benefits
of coplanarity, I should expect to see a reduction in solder bridging.

Basics:
 
The boards were manufacturered using Enthone Plus 106A.  Reflow was done in
a multiple range controlled convection oven without the use of nitrogen.

Questions:

1)   Can you tell me of other paste (Brand Names and Types) you would
recommend for evaluation in the assembly process.

2)   Can you suggest a stencil thickness, aperature to pad ratio, and
geometry (ie trapezoidal) that you have had some success in using.

3)   Should we require the use of nitrogen in the reflow of our boards and why.

4)   How does the process and process controls differ from HASL boards.

5)   Is there an archive repository in TechNet where I can find more details
on this topic.

         Thanks in advance for your suggestions.

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