I am looking for some solder past, the stuff below that I found does not look like it has solder in it but says solder past. So is this what I need, just need a small quantity as I don't do a lot of sm. If someone could recommend something good, could you shoot me a link. Thanks



https://www.ebay.com/p/2pcs-Amtech-...aste-10cc/17013724403?iid=263909447533&chn=ps

 

No, that's flux (useful but not solder), this is solder: https://www.ebay.com/itm/AMTECH-Sn63-Pb37-T4-No-clean-Solder-Paste-35g-SynTECH-N/173309757941

It may seem expensive, but it's quite a lot and should last a long time. It is also a very good alloy, though it is not lead free (a good thing unless you need lead free for some reason).

You might want the flux as well, if you are doing rework.

 

I think this is only flux - no solder.

 

Cool, thanks, mine said past and flux....but just looked like flux. Thanks again.

 

Cool, thanks, mine said past and flux....but just looked like flux. Thanks again.

It's "solder flux", that is, flux for soldering. You will need some most likely, but a pen is probably best. Get a Kester no clean pen for maximum joy.

 

If you are only doing a little bit of surface mount, you can tin the pads with solder (using extra flux makes this easier) then remove as much as you can using fluxed braid, leaving only a think film of solder on the pads. Components can be reflow soldred to the pads using a soldering iron, usually without the need for additional solder. Yes, flux during this procedure makes it go quicker and reduces the chances of creating bridges that short pads.

 

How small are the parts you need to solder? I generally stay with 805-size components and have never needed solder past. A few weeks ago, I did a 0.5 mm pin spacing for an FPC connector. Again, no solder paste, hand held iron, and fine (0.015) leaded solder.



The smudge at the bottom is some flux I failed to clean completely. I usually use the method described by Dick C., but only tin one pad and don't remove excess. Just a tiny drop of solder, then reflow with the iron.

If I have a whole lot of parts to do or when positioning is critical (as with the connector), I use a microdrop (<0.1 uL) of cyanoacrylic adhesive (CA, super glue) to fix the part(s) to the PCB, do not pre-tin, and solder away as usual. The nice thing about cheap CA is that it evaporates at solder temperature, so if a little gets on a pad, it doesn't interfere. Industry uses a similar adhesive in manufacturing some boards.

Several years ago, I tried solder paste. I found that the amount you put down is fairly critical, and the shelf-life is relatively short. I found no benefit to using it on a hobby scale. Clearly, if my project requires a lot of parts, then paste would be preferred.

 

I really recommend getting solder paste with some silver in it. It really helps the solder flow with small SMD components and pads.
I use ALPHA UP78 - 62Sn/2.0AG/36Pb (which i found from a chinese supplier) or ALPHA CL-78. Its always good to have a small syringe + needle of flux also, in case you have to reworks something, or if you have been a bit heavy handed with the paste and need to remove a solder bridge between some pins.

I use the solder paste in a small 25ml syringe with 26 or 28Ga dispensing needle which I use with an air driven dispensing unit. I keep the syringe and paste in the fridge and push some fine stiff (tungsten) wire I had laying around into the needle between uses to minimize wastage. Ive actually been using the same syringe of paste for many years now!

 

The pins are .5 and already did 3 sides of the chip. I can't get to the back side of the chip so was going to use past. I ordered some and will be here tomorrow. Thanks for all the advice, not did a lot of sm.

 

Another approach to soldering to the back side, if it needs it, is to put a relatively large diameter PTH under the chip. and solder through that. With larger chips, I have put a puddle of solder on the center. Then heated from the rear until it settles in to place. Pins are done last.

Good luck with the solder paste. I wish it were sold in smaller, sealed packets like some repair packets of epoxy are sold.

 

The pins are .5 and already did 3 sides of the chip. I can't get to the back side of the chip so was going to use past. I ordered some and will be here tomorrow. Thanks for all the advice, not did a lot of sm.

Put the unused portion in the refrigerator, it will last much longer.