[RnB180]

up

 

[saab]

Here I am starting my first cmoy from tangent's site. This is my first experience with solder and need some comments. Does it look o.k.? I know I have yet to snip the wires, but everything feels firm and I don't see any bridging. Sorry about the focus, but my camera's macro setting is not that great.

 

[The Monkey]

looks pretty good for your first time. It may be easier for us to see after you snip the legs. I think you could be using a bit too much solder, but someone with more experience should confirm. Overall, much better than my first attempt.

 

[shiggins]

Here's a pic of the PCM2702 on one of the Guzzler's USB DAC's I built.

I was impressed with the soldering, but the pro's may have something to say about that. It was a right pain in the arse to solder (tiny bloody pins). I did the flood and suck technique; flood one side with solder then remove it with braid/sucker to leave a nicely soldered chip. Well, that was the idea. Flood - easy. Suck - erm, yeah. I used approximately 1 mile of desoldering braid only managing to remove the solder one particle at a time. A stiff back, dizzy head (desoldering braid smells rather nice) and a few hours later I was done. The DAC itself is still sitting there uncased (another one of those half-finished projects) but atleast I get to post a picture of my handy work!

Edit: Before any smartass says, I am aware the two pins on the far left are shorted but I gave up with them and they're connected on the PCB anyway.

 

[bryman79]

Quote:

Originally Posted by shiggins I did the flood and suck technique; flood one side with solder then remove it with braid/sucker to leave a nicely soldered chip. Well, that was the idea. Flood - easy. Suck - erm, yeah. I used approximately 1 mile of desoldering braid only managing to remove the solder one particle at a time.

I've had excellent results with the flood-and-suck technique using a basic de-soldering pump and iron. What exactly did you have trouble with?

The main reason I posted is because I've run across several threads lately that have expressed how agonizing soldering small ICs is, especially with the flood-and-suck technique. And most of these posters resort to the de-solder braid technique. I'm afraid that when a newbie runs across these posts, he/she may be deterred from even trying.

So to all you newbies, I first want to point out that the flood-and-suck technique has a couple of advantages: 1) cleaner-looking joint; 2) faster (it takes me about 5-10 minutes to do a 28-pin IC); and most importantly 3) it puts far less heat into the part. So how do you do this successfully? Here are the basic steps I use:

1. Obtain a basic soldering pump
2. Obtain a low-wattage soldering iron, preferably with a small-diameter, pointy tip that will allow you to solder a pin or two on the small ICs if necessary... I use a Radioshack iron and grind my own tips (i.e. chuck them in a drill and place against a bench grinder/sander), which allows me to make them any shape I want
3. Place your IC on a bare board (preferably) and temporarily secure it with a strip of scotch tape whose width is less than that of the body of the IC (i.e. so that you don't touch it with the iron)... this will allow you to get the IC perfectly placed, centered, etc.
4. Tack each corner of the IC (i.e. solder the four corner pins)
5. Remove the tape
6. Flood 3-5 pins at a time, working your way along that side until all pins are flooded (work quickly so you don't introduce too much heat into the part)
7. Suck 3-5 pins at a time, working your way along that side until all pins are sucked
8. Invariably, a few adjacent pins will be connected, which is where I presume most people give up and go to the de-soldering braid... I have found two basic techniques that get the job done: 1) with the soldering pump nearly horizontal to the PCB, use the tippy-tip of the iron to just heat the two pins that are soldered together, and work the solder out away from the IC; or 2) with the soldering pump roughly 90 degrees to the PCB, place your iron on the legs of the IC touching the PCB and work the solder vertically off the pins
9. Once there appear to be no pins connected, check your work with a magnifying glass and a high-power flashlight shining up from the bottom of the board (I use a Brinkmann Legend LX lithium/xenon flashlight that is brighter than hell)... if I remember right, there were some areas that I was questioning, so I slid the dull-side of an x-acto knife along the PCB between the pins to make sure there was no solder connecting the pins (make sure not to bear down and damage the solder mask or traces beneath the IC)
10. Repeat steps 6-9 for the other side of the IC
11. Use some kind of flux remover to make it look pretty

Hope this helps.

Regards,
Bryan

 

[shiggins]

Quote:

Originally Posted by bryman79 I've had excellent results with the flood-and-suck technique using a basic de-soldering pump and iron. What exactly did you have trouble with?

Just the desoldering braid. Couldn't for the life of me get it to work properly. I have desoldered succesfully with a pump before, but this time I did not have one available. I'll pop one on the shopping list... <scribble>

 

[RnB180]

this thread deserves a bump

 

[Dreamslacker]

A little point-to-point soldering work..

 

[DaKi][er]

Quote:

Originally Posted by shiggins Here's a pic of the PCM2702 on one of the Guzzler's USB DAC's I built. http://img.photobucket.com/albums/v165/shiggins/Head-Fi/IMG_0905-small.jpg[IMG] I was impressed with the soldering, but the pro's may have something to say about that. It was a right pain in the arse to solder (tiny bloody pins). I did the flood and suck technique; flood one side with solder then remove it with braid/sucker to leave a nicely soldered chip. Well, that was the idea. Flood - easy. Suck - erm, yeah. I used approximately 1 mile of desoldering braid only managing to remove the solder one particle at a time. A stiff back, dizzy head (desoldering braid smells rather nice) and a few hours later I was done. The DAC itself is still sitting there uncased (another one of those half-finished projects) but atleast I get to post a picture of my handy work! Edit: Before any smartass says, I am aware the two pins on the far left are shorted but I gave up with them and they're connected on the PCB anyway.[/i] [/td] [/tr] [/table] What you need is FLUX!!!! Soldering SSOP shouldn’t take more than a few minutes at most When the flux is burnt out of the solder it becomes real brittle and tacky and is very prone to bridging when it shouldn’t like in your picture, put some flux and reflow the joints will make the solder very smooth and liquidy and it will only stick to what it is meant to and leave you with professional joints every time Using extra flux I can easily solder those SSOP size chips without any use of desolder braid or suckers at all, the solder just doesn’t want to bridge in the first place

 

[nleahcim]

Quote:

Originally Posted by shiggins Here's a pic of the PCM2702 on one of the Guzzler's USB DAC's I built. http://img.photobucket.com/albums/v165/shiggins/Head-Fi/IMG_0905-small.jpg[IMG] I was impressed with the soldering, but the pro's may have something to say about that. It was a right pain in the arse to solder (tiny bloody pins). I did the flood and suck technique; flood one side with solder then remove it with braid/sucker to leave a nicely soldered chip. Well, that was the idea. Flood - easy. Suck - erm, yeah. I used approximately 1 mile of desoldering braid only managing to remove the solder one particle at a time. A stiff back, dizzy head (desoldering braid smells rather nice) and a few hours later I was done. The DAC itself is still sitting there uncased (another one of those half-finished projects) but atleast I get to post a picture of my handy work! Edit: Before any smartass says, I am aware the two pins on the far left are shorted but I gave up with them and they're connected on the PCB anyway.[/i] [/td] [/tr] [/table] IMHO you didn't use enough solder on that chip.I like for the edges of the pins not to be visible - for the solder to just round down so there's no real corner, if you know what I mean. Should work just fine though. And it shouldn't take you that long for a single chip... I think it took me maybe 3 minutes when I built my usb dac... I'm wondering if your iron might be too weak? Not sure.

 

[mono]

Quote:

Originally Posted by DaKi][er What you need is FLUX!!!! Soldering SSOP shouldn’t take more than a few minutes at most When the flux is burnt out of the solder it becomes real brittle and tacky and is very prone to bridging when it shouldn’t like in your picture, put some flux and reflow the joints will make the solder very smooth and liquidy and it will only stick to what it is meant to and leave you with professional joints every time Using extra flux I can easily solder those SSOP size chips without any use of desolder braid or suckers at all, the solder just doesn’t want to bridge in the first place

Agreed. It seems there's some tendency for most starting out to use too much solder and not enough flux.

 

[1UP]

I thought flux is already in the solder? Do you have to use extra?

Re: soldering ICs - can you not just do this leg by leg using an itty bitty tip (instead of the flood/suck desoldering)?

 

[mono]

Quote:

Originally Posted by 1UP I thought flux is already in the solder? Do you have to use extra? Re: soldering ICs - can you not just do this leg by leg using an itty bitty tip (instead of the flood/suck desoldering)?

Because the primary goal is to get solder to flow as much as possible, for it all to wick/around under the leg-pad junction, it helps to have the flux already down around the area. When one depends on the flux IN the solder, they're already melted a lot of solder onto the area before the flux is there to help spread it. Presuming the legs are uniform still, as is the copper or tin plating, there really isn't much solder needed to connect these, while the flux content in most solder may be considered more optimal ratio for different soldering tasks.

You could just use a really fine point a leg at a time, if the part isn't really tiny and you have really steady hands- though it may take a long time and the results may not be as good. I'd still pre-flux the area first though.

Practice makes perfect. One way to practice is to find an old computer motherboard. Take it outside and put a heat gun (or mild blowtorch) on the opposite side of the PCB from the chip. heat the area some then slap it against something quickly. Well, "slapping it against something" may only be necessary if you don't have the heat gun for the front-heating of the board, as manipulating a hot board quickly while the solder is still melted to get off the chips is harder. With the heat gun you can just do it better and grap the chip itself.

The chip(s) will fall off so you have a chip and mating pads to practice with. It'll be a little harder than a clean board due to some solder residue, but it may still be better than risking good parts to hone a technique.

 

[DaKi][er]

Quote:

Originally Posted by 1UP I thought flux is already in the solder? Do you have to use extra? Re: soldering ICs - can you not just do this leg by leg using an itty bitty tip (instead of the flood/suck desoldering)?

Extra flux is extremely useful, I got a pot of the stuff that was meant for lead lighting and general stuff like that but it works very well on electronics

Soldering smd chips one pin at a time is fine for SOIC sized parts but it is not practical at all with SSOP and smaller and there are far easier ways
This is a sure way to do them that will get you perfect results everytime in minutes -
Coat pcb pads in flux paste
Sit chip in position, the flux will help hold it there a little but you will still need to hold it down
Flow some solder onto your iron tip
Tack one corner pin down
Square the chip up and do the opposite corner
(now the fun part) with your iron still wet with a small amount of solder, wipe it across all the pins of one side, with the flux there it will make the solder only stick to the metal and it wont bridge as long as you don’t overload your iron
Repeat for the other side, done

Comparing this to the solder braid method, this has worked far better for me and I wouldn’t do it any other way

 

[1UP]

Have you got a camcorder?