About a year ago I bought some solder paste expecting to use it before now.
Well, I’ve just used it on my very first SMD board …a complete disaster - I had thought it would melt/flow easy enough using a hot air gun - it didn’t - it laughed in my face.
Now I don’t know if this is because…
It’s old.
My technique is wrong
The paste is not suitable (crap)
Something else.
So fellow sparkfunners…I seek recommendations for a DIY friendly solder paste which will allow me to melt the solder by hovering a hot air gun over it (I have a gun like this http://www.lashen.com/vendors/CooperToo … /6966c.jpg ) - if it’s available in a syringe so much the better (I imported a timed dispenser from China).
Is there one brand/variant that the majority stick with on here?
I’ve bought a cheasp toaster oven, but haven’t pushed the boat out to convert it yet…I’d be grateful for opinions on whether even the most basic of toaster ovens beats trying to reflow with a handheld gun.
Solder paste has an expiration date, so it’s likely that paste has gone after a year of storage.
You’re supposed to put it in the fringe. Personally I have had good results with the cheap dealextreme paste using my hot air station. I do not store the paste in the fridge and the first jar I bought has lasted a few months now and it still works. I have kids, and I’m not going to put the paste in the fridge. I figure it’s cheap enough that I can just reorder every few months. I also ordered syringes and syringe tips from there, but syringes ship really slowly.
Apropos of nothing, but I just decided my syringe of 2 1/2 year old solder paste is finally worn out. I had some Edsyn CR44, I’ve found it lasts a long time at room temperature (I suspect it’s designed for prototyping where the syringe is probably going to lie around on the workbench for a long time). It still works even now for certain values of “work”, it’s just become increasingly hard to dispense, probably due to the solvent disappearing/chemical reactions.
Since I want to use stencils, I need rather more bulk of solder paste than a minuscule syringe full of it. The trouble is my favorite electronics supplier either has syringes or 500g tubs, the former way not enough and the latter far too much!
I have been buying the “Lodestar” paste from DealExtreme about 10 jars a time, for about 4 years and I love the stuff. I DO keep it cold and it lasts me well over a year that way.
As for soldering with it, I have been using the $30 Target hot skillet method for a couple of years now and I love it. However, when I first started using paste, I was using a Wagner paint removal gun (two settings) and heating the boards from the bottom side, never the top. Heating from the bottom allowed for decent transfer of the heat, good flow of solder and prevented the air flow from blowing the parts all over the place.
If you have a large amount that seems unusable, scrape it out of the tube, add a little flux and clean the container it was in. Then put it back in and carry on using. I have done this a few times and it works fine. I find gel flux works best, but the contents of my flux pen have also worked before now.
There are 2 basic kinds of solder paste: Lead free and Tin Lead. Both oxidize over time. If you store it in a refrigerator you reduce the rate of oxidation, but a year old paste is trash. If you want, I will send you a tube of solder paste.
TheDirty:
Solder paste has an expiration date, so it’s likely that paste has gone after a year of storage.
You’re supposed to put it in the fringe. Personally I have had good results with the cheap dealextreme paste using my hot air station. I do not store the paste in the fridge and the first jar I bought has lasted a few months now and it still works. I have kids, and I’m not going to put the paste in the fridge. I figure it’s cheap enough that I can just reorder every few months. I also ordered syringes and syringe tips from there, but syringes ship really slowly.
wanted to update this post w/ my testing of the “solder-it” silver solder - doesn’t melt until the board actually changes color from a regular color brown to a dark toast - i wouldn’t use it for solder paste.
i have used the deal extreme lodestar paste and i really don’t think it is rohs but it does work good and flows at a relatively low temp. i have made a couple smt boards w/ it and a solder stencil and will continue to use it. i have enough wrong w/ my health to worry about a little bit of lead
Solder paste likely to be used after a year there is no need of keeping in fridge,just the process of oxidation decreases in fridge.its like silver paste,its work very well.there are two types of solder paste
