Soldering iron tips, how to solder SMD without ruining the PCB

I took a 3x time lap of 3 different irons with IR camera,
I prepared the regulated with some heat shrinks so the thermal image reads right as I recently cleaned them from the burned stuff

2 regulated left and right and in the middle a very old unregulated I found
the unregulated needs far more time to heat up and finally exceeds 385°C my camera supports this is already way too hot
the real heat up of the regulated is shorter than in the video seen

A thin layer of oxidized solder or burnt flux just kills heat transfer. Keeping the tip wet with fresh solder is important especially when using solder wick. Mcpcb’s are best done away from the heatsink with the biggest chisel or knife tip you can fit in there.

Sometimes traces connected to large copper traces suck a lot of heat away from the place you want to solder, ground planes are especially bad. Preheating the board with a heat gun or hot air station helps, making a blob of solder on a big ground pad and burying the solder iron tip in it for a while will also help spread heat through the board. Preheating should be done gently, the board’s fiberglass will burn if you get too aggressive.

Sometimes a component with a low maximum soldering temperature and multiple legs can be difficult because some of the traces are small and heat quickly while other traces traces are large and take a long time to heat up. Flooding the part with paste flux will help spread the heat around reducing thermal stress on the component and keeping air away from the traces preventing them from oxidizing. Make sure the flux is easily dissolved by isopropyl alcohol so cleaning up is easy.

To anyone soldering, before you solder you joint, make sure to clean it well with isopropanol, or in the worst case scenario(or it’s just the solder pad is just full of old oxidized solder), just a very light touch of citric acid that is then to be washed away.

11:11 sales are coming up so finding something should be easy. Youtube is a good resource, maybe try searching through some SGD Electronics videos and keeping an eye on the side thumbnails for anything interesting.

I have a Yihua combo hot air/iron soldering station, when the iron is in the station not being used for a couple minutes it will idle at a lower temperature and then quickly go back to the set temperature once its picked up. Really helps keep the tip in good shape. I like the little Yihua brass shaving ball tip cleaners that come in a little can with flux in the bottom of it. Wave the tip around in the brass and a quick stab into the flux cleans the tip instantly. Lastly find an assorted kit of the good Mechanic brand solder iron tips that fits the iron you buy. They heat up better and the tinned area is smaller so you don’t wind up with solder constantly running away from the point and creating a blob of solder on the shank waiting to run down and solder bridge everything. You’ll probably find yourself using one of the knife tips the most and saving the other tips for special applications.

I also have a KSGER with the T12 style tips. It’s a little quirky to set up when first using it but is in a different league performance wise. The cheap generic tips work ok but I had an end of one of the get stuck in the handle when changing tips one time, quite painful trying to get it out of there. My favorite tips for it are the Quicko XR series with the reduced tinned area.

Why do I always get a tail on the joint when I move the solder tip away from the contact?

For those unfamiliar with isopropanol, it’s the same thing as isopropyl alcohol. Which term gets used is a regional thing. The closer to 100% the better, rubbing alcohol is next to useless.

The different formats for tips have always been a mystery to me. I have seen T12 being mentioned, but I’m not sure what other formats exist or how to figure out which ones a specific iron needs.

I recently saw this soldering iron being recommended (I think by Lightbringer), with this one as a low cost alternative, although I wouldn’t know what advantages the more expensive iron has over the cheaper one. When I search for ‘Yihua’ things become even more confusing, as they have quite a large range of products.

If someone can help me understand these things, it will make the choice (and the determination to get started with soldering) a lot easier for me. I only just found out this year - at the age of 46 - that I’m on the autistic spectrum, which explains a lot about why certain tasks which others can complete with ease have always seemed incredibly daunting to me, while I can easily handle a range of highly complex topics which most people would severly struggle with - it’s just the way my brain is wired. Soldering and electronics in general definitely fall into the first category, but I’d really like to find a way into this exciting hobby!

When I search for ‘SGD Electronics’ on YouTube, the search results only turn up one channel with the name ‘SGD’ which doesn’t have any content. Do you have a link?

I’ve seen mention of T12 soldering stations, and combo soldering / hot air stations.

What is the use case for each and reasons to use one instead of the other?

Some 0603 soldering with regulated iron

First the usual without adding flux at the beginning, the rosin core gets very nice results and perfectly tin first pad,
but 2. Pad is not fully soldered, even when flux added and more soldering time used

2. adding some SMD flux at the beginning the tinning of first pad is a bit slower

I use a relative aggressive form of getting the resistors off, I highly recommend this only when the left side is a solid copper plane that completely surrounds the pad, in very few cases that ripped a pad off with just s small trace connecting it

As a CIS I gotta say, this is pretty good. As someone with an AET, I hope you add a little about ESD.

I just ordered a tube from that supplier. I have not been really happy with my flux, I like the Kester liquid but my paste did not work as well as I wanted. What solder paste do you use? I need to order some as mine is getting old and thick.

Pad soldering

Hardware

- 295°C Weller WSD81

  • Felder 0.5mm Sn62Pb36Ag2 with 3.5% flux (one with relative much rosin core flux, general use not SMD which has less flux %)

Preparations

- clean PCB with Alcohol and cotton swab

- twisting the wires end (helps to prevent splicing while soldering)

  • cleaning tip in sponge

1.

- pre tinning pad and wire

  • heating up pad and stick the wire end into it
  • same as 1. just adding extra flux (for example if you use a SMD solder wire with only 1% flux)
  • directly solder wire to the pad (not recommended but works fine with a solder wire with 2.5% or more flux)

in the video I look without any magnification to the soldering, just the camera records

I use Chip Quik solder paste SMD291AX50T3 purchased from Digikey.
https://www.digikey.com/product-detail/en/chip-quik-inc/SMD291AX50T3/SMD291AX50T3-ND

I generally do not use ESD on the builds I do, the flashlight stuff is pretty ESD safe
I have a silicone mat covering my desk

old and thick can be a few times refreshed with a tiny amount of IPA
if you have to use it every time you open the can it’s time to get new stuff

IPA? You mean 99% isopropyl alcohol? I keep a jug of that around all the time.

yes

At my previous workplace, they had an interesting method for soldering(correcting) smd pcb parts. They main orders were machine assembled, but there were some pieces here and there that must be done by hand, or corrected manually.

The whole pcb was kept on a heated metal plate, which was hot to the touch, but certainly not in the solder melting range. When they installed/replaced a part, a lot less heat input was requied, than heating up everything from room temperature. It worked good as far as I know.

Btw, I also use a KSGER v2.12S soldering station with the black coated tips, and they work awesome. The controller may produce unstable temp readings over 420Celsius depending on the exact tip used, but I almost never had to use that much heat, and the tip still stayed at the set temp, apart from the jumping numbers on the controller.

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Thanks for the videos Lexel. You have very steady hands especially when things are magnified. I love how you guys make it look so easy. :slight_smile: :beer: