SMD Soldering Tips

[jmsigler]

Hello Everyone,

I was wondering if anyone had tips for soldering SMD components, specifically microcontrollers/FPGAs in TQFP/QFP packages (or even BGA)? For example one tip I think I've seen is to extend the last pin on each row to act as a reservoir for excess solder.

[suicidaleggroll]

For high pin count leaded packages (TSSOP, SSOP, SOIC, QFP, etc.) I find it easiest to just load it up with solder, making sure every joint has been soldered but completely ignoring bridges, then going back with wick to clean up the excess.  It's very fast and the result is clean and consistent.

BGA needs an oven or hot air with a stencil/paste or very careful manually balling.

[CrashO]

I mostly use (a lot of) flux and a regular (0,2 x 3mm or something) shizzle tip. Apply a small bit of solder and slightly touch each pin (and pad) (I can do about 12 pins before needing to re-apply solder again).
I tried the dragging technique before, but mostly ended up spending more time on cleaning up with wick, then to do it one pin at a time.

[suicidaleggroll]

I tried the dragging technique before, but mostly ended up spending more time on cleaning up with wick, then to do it one pin at a time.

Could be your temp was too low or tip too small.  You need heat for wick to work well, even on small packages I use a fairly large chisel at 750 F (400 C).  I can sweep an entire side of a 100-TQFP with wick in just a few seconds.  Just did a board a couple of days ago with a 100-TQFP and a 44-TSOP, took just a couple of minutes to completely solder and clean up both of them.  It took longer to do the handful of 0402 caps than those big ICs.

[tggzzz]

Try the "skillet pan" method; I add some sand to act as a thermal buffer. FFI: https://entertaininghacks.wordpress.com/category/homebrew-pcbs/

I've used it without problems on ICs with 0.5mm pitch leads, 0603 and larger components, and 100-way connectors with 0.8mm pitch.

[jmsigler]

I actually have access to a reflow oven. Would you guys recommend learning how to use that? or keep using the soldering iron? I haven't gotten great results with the reflow oven, but I think I also just need to work on applying the paste more consistently.

[tggzzz]

I also have access to a reflow oven at my local Backspace. I find a saucepan at home is more convenient and perfectly satisfactory for my boards.

Nobody masters any technique at the first go, but I found the saucepan method easier and better than I expected. YMMV.

[MarkF]

Here are many Hakko videos show various soldering tips and techniques for SMD parts.

[KL27x]

I actually have access to a reflow oven. Would you guys recommend learning how to use that?

As you have discovered, applying paste is not automatic. Even with a stencil, getting good results is not automatic. There's a 20 page thread on manual solder paste dispensers in the "other equipment" forum, and mike58's dispenser looks pretty darn good. I try to avoid leadless parts, but if I have to do any on a large scale, I will be giving one a whirl.

For any SMD with exposed leads, meh. I took a long walk down that path and even bought my own reflow oven. The oven works fine. But it's in storage. Unless I need to do a lot of leadless parts, it wastes my time.

For high pin count leaded packages (TSSOP, SSOP, SOIC, QFP, etc.) I find it easiest to just load it up with solder, making sure every joint has been soldered but completely ignoring bridges, then going back with wick to clean up the excess.  It's very fast and the result is clean and consistent.

You can drag solder with any tip, but I swear you can do it just like this. And then clean up the results with the iron, no wick. If you use a large CF tip. Simply like magic. Once you get the hang of the tip, you can progress to tilting it to adjust for the amount of solder and not even make the bridges to begin with. It's impossible to describe the difference between it and all other tips and to do it justice.

For example one tip I think I've seen is to extend the last pin on each row to act as a reservoir for excess solder.

You would not even necessarily want to do this with a CF tip, because that would just be extra wasted solder, and you would need to pick up solder more frequently. I can often solder all the QFP/SSOP IC's on a board without stopping, just picking up a little solder from the decoupling caps.

With a CF tip, solder is your bitch, and you control it like a puppet on a string.

[jmsigler]

Okay, I think I'm going to look into getting mike's solder dispenser or the kingzer pnumatic dispenser. On mike's website, he recommends heating up the paste with a hot air gun or hot water before using it. Does this affect it's storage life at all? I've had problems with viscosity of my paste before and I think this might help a lot. 

[KL27x]

You keep solder paste in the fridge to increase the life. This increases the viscosity, reducing the rate of separation of the suspension. This also reduces the vapor pressure, reducing evaporation of the solvent.

Heating it does the opposite.