Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Solder Clogging

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Solder Clogging | 4 June, 2010

I am running a cemelot 5000 and I am having trouble with the solder clogging up the needle. When the solder is removed it almost appears if it has reflowed. I am using a 22 guage needle, and the problem occurs with both type 3 and type 5 solder paste(Alpha CL-78 Dispensing Solder Paste, and Alpha OM-325 fine feature lead free solder paste). We are dispensing with an auger.

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Solder Clogging | 5 June, 2010

It's a common problem. Try using a different needle diameter. Paste type||Suggested needle size II||21 or larger III||23 or larger IV||25 or larger V||27 or larger VI||30 or larger

Additionally, improper clearance between the auger pump screw and the cylinder wall can cause solder paste to clog.

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Solder Clogging | 15 June, 2010

You also need to consider the total metal load in your dispensable paste. You'll need a slightly higher flux content and less metal, say around 87% total metal, in a 4 or 5 mesh size.

We had to have some special mixes made in order to do fine pitch and micro dot dispensing using an auger type dispenser, but it was certainly possible to do this consistently with the right paste formula.


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Solder Clogging | 3 July, 2010

Hege, can you share more info on the formulation you ended up using for the micro dot dispensing? I'm trying to find the proper metal load and viscosity for the auger valve dispenser that we are developing and it looks like the regular low viscosity (400KCPS) SAC pastes with 85% load are not very suitable for microdots. The biggest problem is with the feed pressure. There is a very fine line between pressure being too low and too high and when the pressure is too low, the cavitation occurs (under 3PSI). When the pressure is set too high (over 3PSI) then excessive drooling takes place. At this point I'm tempted to order a custom formulation with 600-700kCPS wiscosity and 85% load of Type-5 paste. The goal is 0.25mm dots.


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Solder Clogging | 4 July, 2010

Hi for you question we may can hlep you.

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Selective Solder Wetted Nozzles

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