At 06:43 AM 1/25/2002 -0600, Bryn Wolfe wrote:
>Actually, though, Hot Air Leveling should not cause the burst unless there is
>soldermask on both the top and bottom, or if it is a blind via. However, I 
>think of a way in Protel to tell it to tent only the component side. You'd 
>have to do some editing in the gerber file.

Well, it's easier than that. But still a nuisance.

>This sounds like a feature that should be added to Protel, that is, 
>selecting which
>side of the board tenting of through-hole vias occurs on: top, bottom, or 

The feature is there, but it doesn't work. A solder mask expansion design 
Rule with top layer and via scope would, one would think, apply only to top 
layer masks. But the rule is not working that way, it seems. I think that 
vias are considered to live on Multilayer, which causes problems in many 
ways (such as with blind and buried vias, which are displayed only if 
Multilayer is on, regardless of the actual layers they affect -- but in 
this case the gerber routines do appear to correctly identify the layers 
for plotting).

I'm hoping that how vias are handled is fixed in Phoenix; it is one of the 
current serious shortcomings.

In this case, there are two ways I know to selectively tent vias (top vs. 

One has been mentioned: make the top plot with vias tented and the bottom 
with them free of mask. This, however, is a manual operation, easily 
overlooked next rev....

Another would be to select all the vias, copy them to the clipboard, and 
unselect All. Then paste the vias using the same reference location. There 
are now two vias in each location, one of them selected. Convert the 
selected vias to free pads, leaving them selected so that you can now 
globally edit them to the layer where you want solder mask to appear. You 
can also give them a distinctive padname, such as "topvia," if you put them 
on the top layer. This layer is the layer which will have solder mask 
openings. Tent all vias. You may, if you wish, set very tight, even 
slightly negative solder mask openings for Free-topvia.

Be sure, in the global edit, to eliminate the hole, the holesize should be 

The down side of this method is that editing will be a slight nuisance, 
since the topvia pads. But before doing the next rev, you could delete all 
Free-topvia pads. At least you will have been reminded....

Note that there seems to be, similarly, no simple way to directly control 
solder mask expansion on *pads* according to top or bottom. The problem is 
not just with vias. Actually, when you look at the solder mask expansion 
rule dialog, it is fairly obvious that it has not received proper 
programming attention: all copper layers are shown, not just top and bottom....

Note to Protel programmers: we don't put solder mask on inner layers! Ditto 
paste mask...


I wouldn't really complain if the rule scope dialogs allowed more 
flexibility than could actually be used; but there are other desired scope 
possibilities that are missing. The whole system needs more attention, 
again, we have hopes for Phoenix....

Abdulrahman Lomax
Easthampton, Massachusetts USA

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