I can do all other SMD connectors just fine right down to 0406 caps and LEDS, and all ICs down to SOIC spacing with no problem at all.
However, when I get to SSOP levels, things tend to get messy due to how accurate you have to be on placement, how easily the pins bend, move or distort, and how close the traces are for home made PCBs.
After a few weeks of doing quite a few I have developed a cool little technique some of you who are also starting out may find useful.
Start by tinning all of the traces, leaving blobs near the end of the traces. Any bridges can be easily fixed as nothing else is on them at the moment. Once you have tinned all the traces, place the IC over it as accurately as possible and then dab your soldering iron on the top left pin to get it stuck to the first trace. Now lift it up to a light so you can see the trace and pin alignment, and move the IC until it is perfectly aligned. Hold it in place by pushing down on it with your tweezers and touch your iron on the diagonally opposite pin to tack down that leg. Check alignment again and if good, go over all pins and allow the solder to flow up to the top of the pins.
The problem I found with that method was solder sometimes got under the pins behind them making jumpers, and then the wick didn’t do much to help.
This way that was never going to happen. I probably just need more practise to do that method, will see how I go on the more I solder, just thought I’d share that method incase anyone else has the same issues I do. I haven’t used flux for any of it though so maybe that would help.
I just use the drag soldering method, but with SSOP I only drag along the surface of the pads at the ends of the pins. I also err on the side of not enough solder and add some more later, instead of putting on too much solder and ending up with a bridge that can’t be dragged away.
angelsix:
The problem I found with that method was solder sometimes got under the pins behind them making jumpers, and then the wick didn’t do much to help.
This way that was never going to happen. I probably just need more practise to do that method, will see how I go on the more I solder, just thought I’d share that method incase anyone else has the same issues I do. I haven’t used flux for any of it though so maybe that would help.
If you end up with jumpers behind the pin, heat it up and feed it more solder until you have a small ball, then use the wick and it takes the lot
under Soldering. For really fine-pitch devices this works very well Having the pcb near vertical and oriented correctly for the row of legs that you are soldering (so that gravity is working for you) makes life a lot easier. Liquid flux, and the right iron tip, are also important. Hmm…, I’m just repeating everything he says.
It’s not for a guy making his first solder joints, but anyone with a bit of experience with smds will benefit. Working vertically is a bit awkward sometimes, but puting down a 100-pin QFP in four strokes of the iron sure beats the time, frustration and damaged pads of removing solder bridges.
I presume the needle tip thing is liquid flux? But what is he doing when he is using a brush, then placing paper over and brushing again? Whats that all about.
The vertical technique looks good, think I will go out and buy a better work desk, a good light and some liquid flux today
I think the biggest difference I have is all the pads I am soldering on my own PCBs, with no resist, no flux, nothing but the copper I etched. All these boards people are showing to solder have the natural solder resist between the pads as well as the overlay, which I presume would help a lot towards soldering?
Also, regarding cleaning the solder tips. Mine only tend to last a week or two at a time, but I do soldering every other night, 50 connections or so lets say. I clean it every few solders using the sponge, and thats about it. What are the best cleaning practises for making a tip last or am I getting good life out of it for how much I’m doing?
I don’t get any benefit out of solder mask other than the leads don’t get stuck between the pads when trying to place the part.
If you are using up tips that quickly I have to assume you are doing something wrong. Maybe the heat is too high or something? I’ve never actually used up a tip on a temp controlled station. I just use the sponge as well. I bought some new shaped tips, though. Not certain about the chisel tip, I still need to practice with it.
This is a 0.4mm lead chip (ya, 0.4mm; only chip I’ve ever seen with this spacing). I did fix the one slightly bent lead afterwards.
angelsix:
The problem I found with that method was solder sometimes got under the pins behind them making jumpers, and then the wick didn’t do much to help.
Are you sure you are getting the wick hot enough? When I use solder wick, I usually start with a small drop of solder on my iron for better heat transfer since you need to heat the wick, pin, trace, and solder all at the same time. For me, solder wick has always been able to pull out bridges that are a result of drag soldering.
TheDirty:
This is a 0.4mm lead chip (ya, 0.4mm; only chip I’ve ever seen with this spacing). I did fix the one slightly bent lead afterwards.
0.4mm pitch is common on the 100-pin varieties of PICs. They are intimidating at first but once you do one, you realize they are only marginally more difficult than drag soldering a 0.5mm device.
phalanx:
0.4mm pitch is common on the 100-pin varieties of PICs. They are intimidating at first but once you do one, you realize they are only marginally more difficult than drag soldering a 0.5mm device.
Thanks. That’s probably why I haven’t seen it, as I usually avoid 80pin or greater packages. The few I’ve had to do have been 0.5mm.
I didn’t find the 0.4mm that difficult. It was only slightly more difficult to do the initial placement, After that it’s straight forward to solder.
I have one of those cheap hobby alligator project holders. My board are almost always pretty small so they hold pretty well in the holder. I use drug store 3X reading glasses for working with these otherwise nothing special. I also have a 10X loop lens and a small 48x magnifier I got from dealextreme.com with LED lights to inspect it afterward.
I’ve been really liking the small QFN’s lately. I’ve been manually applying solder paste and using a cheap hot air station to put them down.
I have to use a cheap stereo dissecting microscope for positioning fine-pitch chips and tacking down the corner leads, but my eyes are over 67 years old.
I have a PCB vice to secure the board. No special magnification other than a 10X eye loop mostly used for identifying the cathode/anode on 402 sized diodes (which I don’t use all that often).
