In your message dated Monday 9, September 1996 you wrote :
>     with respect to above mentioned problem i wud like to clarify that the
> said defect is being noticed only in ML boards.The said problem is not
> noticed to such an extent in DOUBLE SIDED RIGID boards for the same
> complexity of the Product. Therefore we suspect strongly the ML lamination
> process as a POTENTIAL CAUSE.Could any one throw some light on this
                          ---------------------------
We have not had this problem on ML boards since we always place a layer of 1080 
or 2113 under the foil to get a flatter surface finish.

However, we have seen the problem on 0.5oz laminate both on inner layer print 
and etch, and pth boards. With print and etch you get a regular matrix of cut 
tracks and with plated panels you get 'spiky' tracks.

Dry film lamination is a key area. We found results were good with our old hot 
roll laminators provided roller temperatures are high enough to flow the resist, 
and the speed slow enough to give the resist time to flow into the contours of 
the foil. The defect can be seen as voids after lamination if you get the right 
angle with magnification but are difficult to make out until you know what to 
look for.

Check the consistency of your laminator across the rollers top and bottom and 
you may be surprised at the variation. If you look for the problem and see it on 
the left, right, or trailing edges, or just on one side, then you have a problem 
with lamination.

An exit temperature monitor is a must and speed must be set to give the highest 
exit temperature specified by the resist supplier. Board input temperature 
should be within recommended limits also. 

Hope this helps,

Paul Gould
Teknacron Circuits Ltd
EMail [log in to unmask]

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