Cory&Lise: Response to your questions.
 1. Yes most board fabricators are using thermal masks. However they are
using PISM (photoimageable soldermask). The mask you are using, SR1000 is
not photoimageable. The image for this mask is defined by the image created
in the screen it is printed with. It does not have the resolution required
for tighter spacing higher density boards. It requires about 8-10 mils
clearance per side. Most new generation PISM's are down to 2-3 mils per side
because the image is photo defined..

2. Again, if we are talking about screen imaged thermal masks such SR1000
the answer is yes they are moving away from them due to the above mentioned
issue with resolution.However they have replaced the screen imaged thermal
masks with PISM not UV mask.
The reason your board fabricator would like to have you change to a UV mask
is that it it is probably cheaper for them to process, no long baking step.
Also they probably don't do much screened image thermal mask and would like
to minimize the number of process and materials they have.

3. I don't know if there is a heavy matte UV available. I would suggest you
have them provide you with a matte PISM. This would more closely match the
polymer chemistry and surface characteristics of the SR1000 than a straight
acrylic UV.


Regards

Michael Barmuta

Staff Engineer

Fluke Corp.

Everett Wa.

425-356-6076






 -----Original Message-----
From: Cory & Lise [mailto:[log in to unmask]]
Sent: Friday, January 28, 2000 7:03 PM
To: [log in to unmask]
Subject: [TN] Wave soldering SMD and Matte finish mask



Hi Technet

We have been using Hysol SR1000 mask on single sided boards.  The boards
contain bottom side SMD parts and are wave soldered.  We are having
excellent soldering results with the mask - near zero defects.  Our process
is spray fluxer, no chip wave of any sort, and no nitrogen.  We attribute
the low defect rate in part to the mask's ability to carry flux to the exit
side of the wave - helps prevent bridging.  Our PCB vendors are constantly
pushing us toward UV cured mask, however, we have yet to see one with as
matte a finish as the SR1000.

My Questions:
Are many manufacturers using thermal cure mask?

Why are fabricators moving away from thermal cure?

Is the a UV curable matte finish mask available that offers comparable
finish to the Hysol SR1000?


Thanks in advance.

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