Soldering 28pin TSSOP advice needed, one off project, not mass production.

[Buzby]

Hi All,

I've got a pair of 28pin TSSOP chips I need to solder to DIL adapter boards,

There are hundreds of posts on here about soldering SMDs, but I want the definitive solution to my specific situation.

I've only got two chips to fix, so I'm not looking for the 'whole board' solution.

The pins don't look too small. I could maybe solder by hand, with a lot of solder wick at the ready.

( This post is PICAXE related. The two chips are rather cool samples from MAXIM that I hope will fit nicely with PICAXE. )

What does the panel think ?

Cheers,

Buzby

 

[Haku]

You should be ok solldering by hand, when I used to solder those sized chips to proper silkscreened boards I would start by soldering just a corner leg so it gave me the opportunity to precicely align the chip before soldering the rest of the pins, starting with the opposite corner pin still giving you alignment capability. My preferred method once the corner pins were soldered was to put the iron on the ends of the pins and melt solder into it then drag the blob across the pins before the flux completely burns up.

Solderwick is a definite help with multi-pin SMD components but I often find pressing the iron to the excess solder on the pins/board and adding more solder (for the flux) helped pick up the exess onto the iron to take it away.

 

[tony_g]

as haku says hand soldering is definately an option thats not as daunting as it seems, i originally stayed clear of it until i actually gave it a go and was supprised how simple it actually was, and now it seems all of my board designs are smd,slowly working my way towards that 40X2 tqfp lol

i dont have a steady hand and eyesight thats sometimes not at its best but lately i have been soldering SMD 08m2/14M2 chips along with 0805 sized resistors and SOT23 transistors.

i use a fine point tip and i cheat by using solder paste applied to the pads prior to placing the components, then its just a case of getting one corner secured and as long as you are happy with its alignment for the remaining pins its pretty much plain sailing.

i use the solder paste instead of normal solder as it melts the instant the iron tip touches it and for the most part really only needs a second or just slightly more to ensure its fused the pad and i.c leg, i did originally use normal solder both leaded and lead free but for me i found it very tedious and sometimes messy and would often end up killing quite a few of the SOT23 transistors as they did not like the iron on them for anything more than what seemed like almost a couple of seconds

 

[John West]

Put a bit of paste flux on the pads, then solder a couple of diagonal corner pins, then blob solder the whole row. After that, use some solder wick to remover the excess solder. Do that by drawing the wick away from the chip in line with the pins so you don't bend them. Keep clipping off the used wick so you have fresh wick for each draw away from the chip. Then immediately use alcohol to remove the flux. The longer you wait, the harder it becomes to remove.

 

[srnet]

There is not going to be a definitive solution, there are quite a few methods of doing it.

For your first go, I would recommend staying away from the fancy methods and stick to simple hand soldering with a very fine soldering iron tip and very fine solder. Tack the corners first to get the pin\pad alignment right. Then solder each pin in turn.

The only difficulty with the hand soldering method, is that it takes a fair bit longer than other methods.

 

[matherp]

Magnification is key - I use a desk magnifier/light to solder and then a USB microscope to check. Also use very fine solder and a liquid flux, I use 0.25mm solder and can successfully solder 100 pin TQFP packages with pins on a 0.4mm pitch. Use fine solder wick to correct any bridges and soak this in flux before use
See http://store.curiousinventor.com/guides/Surface_Mount_Soldering/101/ for more details

 

[JimPerry]

I use flux paste and two irons. Tack the corners with Needle point Antex XS25 and then run solder down both sides. Then use a Weller 60W with the solder braid to remove the excess.

Easy even with cateracts in both eyes

 

[Buzby]

Thanks for the advice.

It looks like hand soldering is the simplest option, no frying pans or toasters !.

I've got all the stuff, fine tip, thin solder, etc., except flux in a jar or pen.

The chips will be soldered by the weekend, then I can start on the software.

Cheers,

Buzby

 

[Hemi345]

I've had excellent luck with the technique at 1 minute 55 seconds in the following video:
http://www.youtube.com/watch?v=5uiroWBkdFY

I don't have the bevel tip like in video, but a Weller ST1 chisel/screwdriver tip and a Kester flux pen and it works almost just as well. I've soldered quite a few TSSOP/microMax footprints with that technique and only had to use solderwick on the first couple. Like previously mentioned, tack down opposing corners first.

 

[Peter Graat]

For smaller SO-chips I use a normal IC-socked. I can even add a 100nF capacitor across the power-leads. After soldering I use hotmeld glue to strengthen.

 

[Peter Graat]

I tried to add 3 pictures. New attempt....

 

[srnet]

I've had excellent luck with the technique at 1 minute 55 seconds in the following video:
http://www.youtube.com/watch?v=5uiroWBkdFY

And a good video of the simpler technique at about 1:20.

The Videos make these techniques look real easy and quick, but applying just the right amount of solder paste is not so easy at all.

Solder paste in the syringes does not have a long shelf life and is quite expensive, you need to keep it in the fridge really. And you need fresh nozzles to hand, they dont seem to last long.

I have tried most of the methods often shown in videos, ovens, hotplates, I even have a SMT rework station, but I find standard soldering with a fine bit and fine solder so much less hassle.

 

[Hemi345]

Yeah, I agree about the solder paste. My friend and I tried some to solder a DS28EA00 and it was almost a disaster. Nearly one side of the chip was a giant solder bridge that even solder wick and flux had a tough time cleaning up. It's really hard to get a tiny quantity out of the syringe and onto the pad like he did in the video. I prefer my Radio Shack 62/36/2 silver bearing solder and drag technique. I have another TMP175 chip I'll be soldering in the next few days and I think I might try the big ST3 chisel tip instead since it holds the heat better than the tiny chisel I usually use.