Avoiding solder blobs on 0603 when handsoldering.

[hamster_nz]

Does anybody have any hints on avoiding 'blobby' joints on 0603 passives?

I'm currently using 0.71mm leaded solder, a 0.5mm conical tip, iron set to around 310 C

Problem seems to be that when the wire melts, it melts too much, giving approximately twice the solder that I really need.

I find paste in a syringe is pretty messy to work with, and don't like the idea of having little balls of solder smeared over my projects.

I have looked for thinner solder  maybe 0.5mm, but it doesn't seem common, so I assume I am doing something wrong. I would include a photo, but am too embarrassed. 

[JustMeHere]

More flux will help.

I use paste.  Just brush the extra balls away.  You could try using a bevel tip.  It's good at removing extra solder across it's broad face.

[james_s]

I use thin solder, and I just touch it to the tip of the iron for a moment so it only melts off a little bit.

[TheHolyHorse]

I use 0.38mm solder for all my SMD soldering, never soldered anything smaller than 0805. Finding 0.38mm solder shouldn't be an issue.

Combine the previous tips with thinner solder and you'll probably be good. Of course practice will refine your technique so that's not a bad idea either.

[ataradov]

I solved this problem by not overthinking it. I do get more solder than I want on 0603 parts, and I simply don't care. It looks meh under the microscope, but looks fine to the naked eye.

It obviously depends on what you understand under more solder than you want. I'm talking about solder joints like this

[Siwastaja]

0.71mm solder, IMHO, is a bit on a thick side for 0603 soldering work. It's usable, but requires careful feed.

0.5mm, or even thinner, allows you to better regulate the amount of solder.

Note that shiny blobs (opposed to dull cold joints) on 0603 passives are mostly an aesthetic problem. While a large blob can, in theory, hide a poor joint, if you have recently purchased passives, with recently manufactured HASL, or ENIG board, and your solder has proper flux in it, it will connect just fine under the blob. I sometimes have these blobs in my prototypes and just go on instead of spending time to fix them.

[TheHolyHorse]

"Perfectionism is bullshit ...." -Louis Rossman

[james_s]

Another technique I've used at times is just apply some flux and use only the solder that's on the tip of the iron, not feeding any additional solder into the joint.

[ataradov]

Another technique I've used at times is just apply some flux and use only the solder that's on the tip of the iron, not feeding any additional solder into the joint.

Yes, I only do that. How do you even feed the solder and keep the part in place and solder at the same time? You would need 3 hands for that. A good soldering iron tip is key here. And what constitutes good is very individual.

[ModernWires]

0.7mm solder is way too thick for delicate SMD work IMHO. I use 0.3mm solder even for 1206 parts. They should be quite common these days. I can even get 0.2mm solder leaded or lead-free pretty easily.

[james_s]

Another technique I've used at times is just apply some flux and use only the solder that's on the tip of the iron, not feeding any additional solder into the joint.

Yes, I only do that. How do you even feed the solder and keep the part in place and solder at the same time? You would need 3 hands for that. A good soldering iron tip is key here. And what constitutes good is very individual.

Tin the pad, solder one end of the part, heat the other end and brush the solder against the tip to add just enough. I've used both techniques.

[Jeroen3]

Buy and use flux.
Syringe flux.
Use lots of it.

If your joints are blobby or spikey, or you drag solder with the tip away, use more flux!
You can never use too much flux.
You easily clean flux in an ultrasonic cleaner. Especially water* soluble.
Place in an oven for 15 minutes to dry.

Perfectly clean nicely soldered board.

*use demineralized water

[JDubU]

Here is what I do for the best (and easiest) way to solder 0603 sized smd parts (assuming that leaded solder is permitted for the project):

Use a chisel (not conical!) 700 degree (F) soldering iron tip that is closest to the same width as the terminal or lead of the part that you are soldering.  For 0603 passives, this would be 0.032".
I use a Kester #186 flux pen and the smallest diameter leaded solder.
Cover the PCB pads with flux using the flux pen.  Use lots of flux!  Do not put any flux on the leads of the parts yet.
Place and hold the part on the fluxed pads using fine, right angle tweezers.  The leads of the part will slightly stick to the flux, helping hold the part in position.
Wipe the soldering iron tip on a damp soldering sponge to clean as much old solder and oxidation off as possible.
Touch the soldering iron tip with the solder wire to make a very small drop of liquid solder on the very end of the tip.
Touch the pad/lead junction with the tip of the iron.  When it hits the flux, the solder drop on the tip will flow smoothly into a fillet between the lead and the pad.
Now that the part is locked down with the first joint (or first two joints, on a diagonal, for ICs), Use the flux pen to cover all leads with flux (including the ones that were just soldered but only had flux on the pad).
Solder the remaining lead(s) using the same technique.  Go back and reflow the initial joints now that there is added flux on their leads.
Do not use solder wire directly on the leads.  It is very hard to control the amount of solder that will melt and will cause blobs that would need to be removed with solder braid.
After all parts have been soldered, thoroughly clean off the flux with anhydrous IPA (I use MG Chemicals 99.9%).
Inspect all joints and reflow (flux/solder/clean) any joints that you aren't happy with.

[Mechatrommer]

if you need perfectionism, you can suck excess blob with solder braid + flux. but as many suggested, small solder diameter is the better thing to begin with.

[Kasper]

Thin solder helps but I usually use thick because it requires less feeding and has more flux in it.

I almost always use a big chisel tip.

I sometimes add flux but usually don't bother because its sticky, smelly and waste of time.

For small amount of solder in joints:
Hold solder to joint then press iron onto solder, and pull solder away a moment later. Goal is to pinch off a bit of solder and pull it away before too much melts.

Its like doing a burnout, stomp on the gas and then a moment later drop the clutch.  Gas being iron and clutch being solder.

[Kasper]

by "pinch off" I meant "melt off"

[rstofer]

Flux both ends, put a dab of solder on the iron tip, hold the component with pointed tweezers and 'drag' solder the connection by just placing the iron  on the joint.  The solder will flow by 'auto-magic'.

There are many 'drag solder' videos on YouTube but they usually deal with pins on packages but the same concept will work for SMD resistors and capacitors.  Flux is the key ingredient.

[KL27x]

There's a perfect amount of solder for the lowest fail rate. For oven reflow. For soldering by iron, I am in Atarov's camp. A good connection is a good connection.

1.6mm solder is all I've used in over a year.

If you want less solder on the pads, make your pads smaller?

[TheHolyHorse]

If you want less solder on the pads, make your pads smaller?

Sure you'll get less solder but it will still "blob".

[jackthomson41]

Practice makes you perfect but I think getting perfect in soldering won't pay much ....  Btw if I got into blob thing, I simply de-solder it with heat gun. https://www.theengineeringprojects.com/2018/08/esp8266-pinout-datasheet-features-applications.html