To all Curtain Coat Skip Sufferers: I know of three ways to get around a skip problem, and neither is without some risk. 1. You can increase your coat weight. Going from 11 g/sqm to 13 g/sqm will get coverage over some skips. There are limits to what can be attained, and there is the material cost increase. 2. You can reduce your viscosity. Going from 60 seconds to 50 seconds will dramatically increase the fill of small skips. If you only do that change, you will find the thickness of mask over conductors and especially the corners of conductors will drop. I recommend increasing temperature in conjuction with reducing viscosity. This has the net effect of keeping solids the same and minimizing the thickness loss over conductors. For example, increasing the Probimer 52M curtain temperature from 24 C to 27 C and reducing the viscosity from 60 seconds to 50 seconds results in no change in solids content (but you will see a different ratio of coverage on conductor to coverage on laminate). 3. You can increase the temperature of the boards as they are coated. This has the same effect as raising the temperature and lowering the viscosity. The downside to this is that you may see an increase in mottling and runback, with some thinning of mask over pads. Any of these conditions will help unless you have channels that are too narrow. As a rule of thumb, any channel that is not at least twice as wide as it is deep will get a skip. Good luck! Bruce Guttman HADCO Corporation [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: SM SKIP IN CURTAINCOAT PROCESS Author: JMONAGHAN Date: 7/24/95 7:31 AM Hello, Our company largest DS PCB manufacturer in Malaysia.We are encountering the soldermask skip problem.I give below the parameters used. M/C Burkle Curtain coater Ink Peters GL2469sm Viscosity 60to65 Beltspeed 78m/mim web weight 6.4to 6.8gms/600sqcm We use pattern plating process and plating thickness 40to 60 microns. The Sm skip is random and happens near closely spaced tracks(most of the times). I Shall be highly grateful if anyone can give info to minimise the sm skip problem. Thanks R.Srinivasan Likom PCB SDN BHD Malacca Malaysia E-mail :[log in to unmask]