solder paste for manual stencil printing

[flasonsmts]

normally the solder paste need to store at the 5℃-10℃, and it need to be used in 24 hours. too long time don't use it will make the tin alloy be oxidated, and there will be too many water come into the solder paste. if you really need open it, then it's better save it in  5℃-10℃ and sealed it's very good and need a longer preheating time, and maybe you can add some flux into the solder paste to got better activite of the solder paste.

[rx8pilot]

normally the solder paste need to store at the 5℃-10℃, and it need to be used in 24 hours. too long time don't use it will make the tin alloy be oxidated, and there will be too many water come into the solder paste. if you really need open it, then it's better save it in  5℃-10℃ and sealed it's very good and need a longer preheating time, and maybe you can add some flux into the solder paste to got better activite of the solder paste.

This is true....but some paste is more durable than others. When I switched to GC10, I immediately found that its lifespan is MUCH longer than others. I purchase in tubes, push out what I need and store the leftover in a thick, small bag at 5C. So far, I have not needed to dispose of any paste even after considerable abuse.

[D3f1ant]

I have a pot of GC10 that is used for hand printing and occasionally used to fill a syringe for dispensing, it is two years past it's expiry date and it seems to perform fine...it doesn't seem to have dried much, if at all. It gets very abused, I even put surplus paste straight back into the pot. I wouldn't trust it for production, but so far it hasn't given me any problems for protoype use.

[jmelson]

Loctite GC10

Thanks to all who recommended the GC10.  I had heard good recommendations before, but at that particular time it was hard to find in the US.  Now, it is pretty easy to get online.  I just did some boards with it, and the results look quite good.  So far I have not done anything with fine lead pitch, but see a few good indications that it will do nicely.  My stencil got out of alignment, and I printed a few boards with the paste going between the pads before I noticed the problem.  Since the parts were already placed, I ran it through the oven, expecting some rework.  But, you couldn't even tell which boards had the misaligned solder paste -- NO bridges at all.

One issue, I dropped one of the boards before getting it in the oven, and most of the parts (all the chips) flew off.  I have done this a couple times in the past, and usually only a few of the largest parts flew off.  But, I'm not complaining at all if the soldering goes better than with other pastes.

Thanks again!

Jon