Solder Paste recommendation for SMD work

[knifeswitch]

I have most of what I need to start messing around with SMD stuff but wondering if you guys have a standard paste you use. Is quikchip good enough?

 

[Nashou66]

I use it, I thin it down with a little denatured alcohol and put it in a syringe to dispense . It works well
this way for me.

Athanasios

 

[daybreak2350]

Then there's the pen type similar to a felt tip marker. You just rub it on the contact surface. With SMDs being so tiny, applying a paste in tiny dabs could get messy. There are so many variations in solder alloys and paste types, from low cost to really expensive, it gets pretty technical--one for the engineers who have to tailor the specs for a very specific application and environment.
You can also try dipping the solder wire into a jar of paste to coat it a little, the idea being that the flux will run onto the contact pad when you solder the joint.
Anything that works to prevent oxidation and get a nice solid joint is good.

 

[knifeswitch]

We'll start with the QC. Now I just need to remember not to drink coffee before a session.

 

[rcs16]

Been doing smt since the 80’s both in a professional and home setting, never needed to use paste to solder small qty of smt right down to a 0.5mm pitch Dfn or Qfn
I use 15mil eutectic no-clean solder and a temp controlled iron with a small tip.
Suggest to only use paste if you are using a stencil and oven otherwise it’s a mess to deal with, meaning controlling volume is an issue even with a dispensing machine.
A hot air machine is useful for removal and some touch up, that and some liquid flux.
For passive removal I use two irons and heat both lands at the same time, clean the excess solder off pads with solder wick

 

[daybreak2350]

Too lazy to look it up right now, but I think I saw a

Been doing smt since the 80’s both in a professional and home setting, never needed to use paste to solder small qty of smt right down to a 0.5mm pitch Dfn or Qfn
I use 15mil eutectic no-clean solder and a temp controlled iron with a small tip.
Suggest to only use paste if you are using a stencil and oven otherwise it’s a mess to deal with, meaning controlling volume is an issue even with a dispensing machine.
A hot air machine is useful for removal and some touch up, that and some liquid flux.
For passive removal I use two irons and heat both lands at the same time, clean the excess solder off pads with solder wick

Appreciate your "voice of experience" here, Thanks! But you got me thinkin' . . .

• I'm wondering where one might encounter SMDs in hi-fi equipment discussed in Audiokarma--certainly not vintage stuff but maybe more recent designs? In micro stuff like bluetooth earbuds, yea, that I get, but stereo amps etc. I don't know.
• If I were to "tool up" for SMD work, I'd use my 20x Leitz stereo microscope and Weller digital station with small tip. I'd also ask you experts out there if the dual-tip irons like the Weller WTA50 SMD Desoldering Tweezers would be useful for the at-home hobbyist.
• If you can hold two irons in one hand I'll bet you're a whiz with chopsticks--just kidding, most likely use both hands but after melting the solder how do you remove the part before solder hardens again? Just flick it away with the irons' tips, or what?

 

[HPMguy]

SMD stuff started showing up in audio equpment in the 90s along with remote controls I think. Mostly ICs in multipin packages to start with, but now it's all SMD.

A hot air work station works much better than irons for SMD work in my experience.

 

[rcs16]

I recall some of the first consumer use of smt was in VCRs, which was mixed tech meaning smt and tht, one of the basic processes was a glue, place passives, cure on the solder side, place tht top side, wave solder. Once semis were put in smt packages, then processes turned away from wave to reflow soldering processes. You can wave smt on bottom or back side using 50mil pitch but it won’t work for fine pitch due to solder bridging.
Assembly vs rework processes are not always the same. Each part type has its own methods for assembly and rework.

 

[knifeswitch]

Up to now, my hot air has been blown on shrink tube and raising semiconductor temps quickly for trouble shooting. I just figure it's time to learn some techniques and see what pops for me. It would appear there are just as many ways to skin a cat in the SMD world as there are in the through-hole. I have some new tips for the Hakko, some lighter guage solder, plenty of flux and even picked up a decent enough microscope/monitor. I also have a few BPC's complete with quirks or DOA that will make fine subjects. You all brought up useful insight and for that, I'm always grateful.

 

[Guarnera]

I'm retired now, but used to do this stuff for a living. Had a nice hot air station. Dispensed the solder past with a needle and syringe, I liked that better then the power dispenser. Eventually the parts got so small that I had to use such a small needle to dispense such a tiny amount of paste that the little balls of solder in the paste wouldn't flow through the needle. And the supplier had stopped making a paste that had smaller size solder balls in the paste. That was right before I retired. I worked for NASA Jet Propulsion Laboratory. I had a friend that did only flight stuff, space craft type flight stuff. Very strict tight tolerances and specs. Real small stuff, and he never used paste. But he was really good.

 

[daybreak2350]

Just a Thank You to everyone's input above--and it all started with what kind of paste to use... This combined vast collection of knowledge and experience makes Audiokarma worthwhile for me.
So, until they invent a practical laser beam soldering pistol (or pencil, iron, whatever--I just like guns myself) or solder joint nanobots [anyone out there remember Fantastic Voyage?], it appears that there are two basic ways to heat a solder joint:

1. a hot iron tip in direct contact with the joint, and
2. a hot air blast (or why not an inert gas like "submerged arc" welders?).

Whatever the method, I believe the object is to solder a discrete component--in this discussion, SMTs--into a circuit while minimizing oxidation and maximizing "the path of least resistance". Solder on, Karma-ites!

 

[daybreak2350]

I'm retired now, but used to do this stuff for a living. Had a nice hot air station. Dispensed the solder past with a needle and syringe, I liked that better then the power dispenser. Eventually the parts got so small that I had to use such a small needle to dispense such a tiny amount of paste that the little balls of solder in the paste wouldn't flow through the needle. And the supplier had stopped making a paste that had smaller size solder balls in the paste. That was right before I retired. I worked for NASA Jet Propulsion Laboratory. I had a friend that did only flight stuff, space craft type flight stuff. Very strict tight tolerances and specs. Real small stuff, and he never used paste. But he was really good.

So you are a professional with an impressive background in aerospace at legendary employers NASA and JPL. Way cool~thanks for sharing!