I meant to say 35-gram syringes...

Steve

From: Steve Gregory 
Sent: Wednesday, February 22, 2012 7:51 PM
To: [log in to unmask] 
Subject: [TN] Air Bubbles in Syringes of Solder Paste...

Hi All,

I have a question about syringes of dispensable solder paste. We purchase 10cc syringes of Type-4 dispensable solder paste for work that we do. It’s used much of the time to dispense paste for the stacked capacitors that we do, much of the time it’s for 0402 caps, so the dispensing has to be very precise.

Recently our operators have complained about the paste, they said they’re having a hard time being consistent with the dots they’re trying to dispense. One of the operators showed me the syringe that she was using, and I was surprised at the air bubbles I saw inside the syringe. The photos below are pictures I took under a microscope through the side of the syringe:

http://stevezeva.homestead.com/AirBubbles.jpg

http://stevezeva.homestead.com/AirBubblesClose.jpg

I can see why she was having trouble. As I said, we buy these syringes pre-filled, they come to us packaged in a cool pack, and we store them immediately in the refrigerator until they are ready to be used. They are taken out and allowed to come up to room temperature before they are ever attached to a dispenser. We use EFD dispensers BTW.

I looked at the syringes that were un-touched and stored in the refrigerator, and they had the same sort of bubbles. So our dispensers are not introducing them, and it seemed like the bubbles were only associated with one lot of of syringes. There was another lot in the refrigerator that did not have the bubbles.

So my question is (not being a solder paste vendor), how are these syringes filled ? Do they centrifuge them to eliminate the bubbles ? I know I did that in the past when I filled syringes with chip bonder for our Fuji dispenser, in fact, the centrifuge was sold to us by Fuji. But I’m not sure about solder paste. How do you go about making sure there are no bubbles in syringes of solder paste ? Is there anything we can do with the paste that we have to eliminate the bubbles or should we just send the paste back ?

Steve

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