SMD Soldering Question

[vigilante397]

So I'm trying to get into SMD, I have some lovely boards acquired from the amazing Dave (pickdropper) and have begun the journey. Being my first experience on the journey, the first IC I soldered in turned out rather sloppy, with unseemly globs of solder on several of the legs. I figured out the tack-and-reflow technique for the other components on the build, but the first IC still looks dreadful. I've heard of people without a hot air station putting the board on a spoon and heating it with a lighter "meth addict style" to reflow unseemly joints, but I wasn't sure if this would damage sensitive semiconductors or whether it was just a joke to begin with. Advice?

Thanks!

[Govmnt_Lacky]

I have seen some videos of people using solder braid (with solder pre-tinned into it) and using it to draw away excess solder from between IC legs. Wicking??

Could be a solution!

[vigilante397]

I have seen some videos of people using solder braid (with solder pre-tinned into it) and using it to draw away excess solder from between IC legs. Wicking??

Could be a solution!

Excellent idea, not sure why I didn't think of that. I know I have a spool of the stuff lying around somewhere......

[knutolai]

Are you using solder flux?

[vigilante397]

Are you using solder flux?

I'm using flux-core solder, but otherwise no

[slacker]

A tip I saw recently to get rid of excess solder is hold the PCB vertically heat the joint up then smack the edge of the PCB on your work surface. Allegedly the excess solder flys off, no idea how effective it is.

[vigilante397]

A tip I saw recently to get rid of excess solder is hold the PCB vertically heat the joint up then smack the edge of the PCB on your work surface. Allegedly the excess solder flys off, no idea how effective it is.

Oddly enough I have been doing that with through hole components for years, except that instead of hitting the board itself on the desk I let my hand hit and the impact through my hand is enough to knock off melted solder. This has been effective for smaller SMD components, but when I tried it on the IC in question (a PT2399) the only thing I succeeded in doing was knocking solder blobs onto adjacent pins

[bloxstompboxes]

Solder wick does work wonders for working with ICs that are SMD. I do so all the time at work. Sometimes it's easier to do the drag method and just wick away whatever bridges I create. Point to point is a good process but only with fine diameter solder. I've used solder wick when doing V850s and not had any issues. Just remember to take the wick and the iron away at the same time. Otherwise, your wick will be stuck to the legs and much harder to remove. I've had to redo replacing an IC because of that when I was new to it. Solder wick is harder to use though when working in crowded areas. You could remove the component with the wick if your not careful. Be sure to use a narrower wick then you might normally use when doing hand insert work.

[knutolai]

how about a solder-sucker? Those syringe looking devices.

[Tony Forestiere]

Are you using solder flux?

BIG difference as I have read.

[Transmogrifox]

Solder suckers don't do much for surface mount stuff.

I +1 the solder braid.  I also do this all the time at work... And solder flux is wonderful stuff.  Really helps transfer heat where it counts and really helps avoid bridging and general mess-making -- even with flux-core solder having flux really helps.

The biggest tip is to get a magnifying lamp.  Just an extra bit of focused light and some magnification helps a ton to guage the amount of solder you add to begin with.

Second, a chisel tip or small hoof tip is a great help.  The nice and pointy conical tips look like they would be great for little devices, but sometimes I find it easier to apply solder with a chisel tip large enough that it could touch 4 pins at once.  The key is to just pulse the solder quickly onto a really hot surface right where you want it.

For an IC (seveal pin device), I usually put a little solder on one of the corner pads, hold the IC  with tweazers in one hand while holding the soldering iron on the edge of the pad with the other.

Place the part, let go with the tweazer, then push it around into perfect alignment if needed and then clamp the ends of the tweazer together and push right in the middle of the IC to hold it in place.  Then remove the soldering iron from the pin and let the solder solidify.

Then tack the opposite corner pin by holding the chisel tip on the side of the pin while also touching the pad.  Pulse a small amount of solder and pull back.

When you add too much solder, the copper braid (wick) cleans it up nicely.

Another technique I have seen used for tighter-pitch ICs is to glob solder on the iron tip and just drag it across a row of pins.  If done well, there is no cleanup left to do.  If too much solder is applied, clean the tip and drag it across again, repeating several times until all pins are clear of globs and bridges.  If you really made a mess, then the solder braid to the rescue.

At work we have the luxury of microscopes so I don't cringe at the idea of working with size 0402 parts and IC's with invisibly tight pin spacing because it all looks huge in a microscope and it's amazing how steady you can hold when you have that kind of visual feedback.

With only a magnifying lamp I think 0603 and SOIC footprint IC's are about as small as I go comfortably.

[bloxstompboxes]

I too use the tweezer method to hold the IC in place and tack a leg or two to hold it in place and then finish it up. I also try to drag the solder across the pins to remove solder bridges rather than the wick, unless there is just too much. My favorite tweezers are these tiny anti-static and anti-magnetic little suckers. I can hold and place the smallest breadcrumb size resistor there is with those things. We use "no clean" flux pens at work. I forget the name of the manufacturer. I use the crap out of that stuff since we have jugs of 99% alcohol there too. It and a horse hair or even a hogs hair toothbrush cleans it right up, even though you don't have to clean it off.  Helps to have an air hose to blow the alcohol dissolved residue right off the board too. The hogs hair brush leaves a nice brushed look while the horse hair leaves it shiny. Just depends on what you like to use really.

[Jdansti]

Here's an excellent video:

[vigilante397]

how about a solder-sucker? Those syringe looking devices.

I was wondering if there were special ones made for SMD soldering, but the ones I have are much too large.

The biggest tip is to get a magnifying lamp.

Second, a chisel tip or small hoof tip is a great help. 

I definitely should look into a magnifying lamp.

And I have a chisel tip for my iron which I use 100% of the time with surface mount stuff, but I guess I rationalized that a smaller tip was necessary for smaller pads and smaller devices so I had been using the thin conical tip.

I have a 90 minute break between classes tomorrow (dropped my least favorite class ) which will be spent in the engineering lab, so I will definitely be trying out the solder wick to clean up my botched IC soldering and the chisel tip for further soldering. I also finally got my SMD resistors and capacitors I had been waiting for, which look like they will be miserable to work with, so more excitement ahead!

This has been added to my "watch later" list on youtube as the wife has been coming in every few minutes to make sure I'm doing my homework and not "looking at more of that pedal stuff"

[J0K3RX]

water soluble liquid flux, apply with a syringe then use your iron and just glide down one side of the IC and up the other... done, and perfect looking solder joints that shine like diamonds with no bridges. Sizzles like bacon frying as your iron travel down the IC. You can flow an entire 304 pin quad pack in 30 seconds with a standard hand iron, rinse it off with water, blow with compressed air and you're done. So, all you really need is the flux which you can get for around $50 for a gallon, this should last you for a long long time and you already have an iron I would assume. You can use it for touch up also and you really never have to add any solder, it will re-flow what is already there perfectly. This is how large board manufacturers do it for everything except for special contracts like medical, military that have super strict regulation etc..

Get "Kester Water Soluble Flux 2331-ZX, 1 Gallon" a syringe, apply one tiny drop to a solder joint and just touch it with your iron and you will see the magic.. Also, you will be able to remove solder bridges without any effort.

Removing parts is another thing but can be done relatively fast without damaging the part or the board. If you have hot air you can just squirt the water soluble flux on a surface mount component,hit it with the hot air and it will straighten up all by itself when the solder wets. If you don't have hot air you can get a heat gun, I think harbor freight has a 1500watt for like $15. You can use this but you have to know what you are doing and make sure there are no plastic parts, connectors or anything sensitive to heat in the general vicinity of the part you want to flow. I have seen people use those plastic welders with really good results and they are dirt cheap also. A handy tool to have is a stainless steel probe, like a dental pick or something like that. You can use it to clear holes in through hole boards after you remove a part, just heat up the hole with the solder in it then slip the probe in the hole and wait a second for it to solidify, then just turn the probe a couple times and pull it out. The hole will be cleared and you can insert the new part and solder it up... solder doesn't stick to stainless   

[bluebunny]

A handy tool to have is a stainless steel probe, like a dental pick or something like that. You can use it to clear holes in through hole boards after you remove a part, just heat up the hole with the solder in it then slip the probe in the hole and wait a second for it to solidify, then just turn the probe a couple times and pull it out. The hole will be cleared and you can insert the new part and solder it up... solder doesn't stick to stainless    

If you're not a dentist, use a wooden cocktail stick.  It doesn't burn and solder doesn't stick to wood.

[italianguy63]

solder doesn't stick to wood.

Not so sure.  I can make solder stick to wood.  I have made it stick to my pants, and my skin before too...

[bluebunny]

I should have said to keep the cocktail stick moving.  And I dread to think what you're doing soldering stuff to your pants, Mark...

[CodeMonk]

A tip I saw recently to get rid of excess solder is hold the PCB vertically heat the joint up then smack the edge of the PCB on your work surface. Allegedly the excess solder flys off, no idea how effective it is.

It works.
I've been doing it for years.
Can also effective in getting stubborn solder out of holes.
Although I usually use a 2x4 on the desk. Keeps those little solder balls from being all over the floor.

[vigilante397]

If you're not a dentist, use a wooden cocktail stick.  It doesn't burn and solder doesn't stick to wood.

Good idea, I think I'll use that. I always have the brilliant idea of sticking a clipped lead into a hole I'm trying to clear, and I just end up with said lead soldered in there

Not so sure.  I can make solder stick to wood.  I have made it stick to my pants, and my skin before too...

While I am worried about why you would solder something to your pants, I worry more about why you would want to solder something to your skin