OBSERVATIONS FROM SCOTLAND                            28 May 2008                                GM1SXX

Soldering for the Terrified!

Soldering is an art.... no doubt about it. Some might argue that it's a science, and it's that also. At it's best though, it's probably as much art as science.

Soldering strikes fear into the heart of many novices, but it doesn't have to be that way.  In the interests of serious observation, I  thought I'd try summat completely different.  Take a rookie, give them 5 minutes 'training' and have them attempt to build a small CPU based project in a single sitting.

The raw beginner to soldering is apt to make some of the common mistakes, so I tried during the short 'training' period... just verbal training, to explain how to avoid some of the more common pitfalls.  Five minutes of talk is not really adequate to cover everything that the novice will encounter and for someone who has never seen a soldering iron all close-up and personal, it would be quite daunting.

I asked my better half to participate in this experiment. She was very reluctant but eventually agreed, so long as the telly would be left on, so she could watch 'Free Willy' at the same time, you know.... that movie about a marine mammal.... for the kazillionth time.

For anyone who has never seen 'Free Willy', I guess you don't own a TV set.  You can read about 'Willy' at http://en.wikipedia.org/wiki/Free_Willy

I set up shop on the coffee table in the living room, just using the overhead light. A piece of thin ply-board was used to hold the soldering station, a small vice, a pair of diagonal cutters, reel of multicore solder and the parts of the kit she was about to build.  perhaps not an ideal set-up, but one that will be familiar to many.

The kit I chose for her was an ATMEL chip based alarm clock kit from Maplin with a Kingbright multiplexed display, perhaps a little bit complex for the rank beginner.

I  had her identify and stuff all  the smaller parts first, mainly the resistors, small ceramic caps and the like. Her first attempts at soldering had the usual problems... not quite heating the pads enough and of course forgetting to pull the length of solder clear after the solder had flowed.  Amusing to watch. Some of the first few joints she made looked a bit 'ropey' as you might expect but I just left them 'as was' and gave her a few gentle tips (didn't want to start a war of words) as she progressed.  Looking at the finished PCB, there's a noticeable improvement in her soldering style as she progressed with building the kit.

She completed the clock kit in a bit over 30 minutes, quite a respectable performance for a beginner. I deliberately didn't intervene in the actual soldering process... just gave her some advice as she progressed through building the kit. 

This little alarm clock kit uses an ATMEL microcontroller as it's 'intelligence'. I thought it was a wee bit optimistic for a rank beginner but it looked like a kit I could actually use after constructing it... or at least after Sandra constructed it.

She alternated between intense concentration on soldering the joints and clipping the wires... AND watching TV.  Seems women are better than men at multiplexing.  I just sat around and gave her verbal assistance when needed.  I've seen 'Free Willy' about a million times before so for me, the waiting around was a tad boring.

Here's Sandra hard at work on the clock board.  Note that look of intense concentration.

It's interesting that soldering can need so much attention, but of course if it's not something you are familiar with, that's how it is.  After the first 1,000 soldered joints it becomes a conditioned reflex... you don't need to think about it in a concious manner any more. Familiarity DOESN'T breed contempt... it does exactly the opposite.   It turns a task (often complex)  into an effortless conditioned reflex. 

Some of the problems she had are worth mentioning for the benefit of beginners.

#1  Not getting enough heat into the joint.  Beginners seem to be in a big rush to 'get in and get out'. Perhaps they are afraid of damaging either the board or components.  Modern components are fairly tough. You should aim to complete a soldered joint in a few seconds.  As you gain experience, you will discover the ideal sequence and timing to solder efficiently.  It's important to use a properly sized soldering bit in order to transfer enough heat into the job. Beginners are apt to go for the smallest bit they can find. The correct size to use is often one that looks a little bit too big for the job in hand.

#2  Removing the iron before the solder has flowed freely. I noticed early on that although she was applying heat to the parts and feeding the solder correctly, she tended to remove both the iron and solder too early.  You can see the effect of this in the photos below. This is a common thing with beginners and so long as you keep practicing, things will improve and you will get a 'feel' for the best way for you to do things.

#3 Occasionally she managed to form a decent joint but forgot to remove the solder. This of course resulted in the solder remaining 'stuck' to the soldered joint.  Amusing for me.... irritating for her.  Just one of those little things that soon disappears with experience.

And oh yes, she was rather annoyed when she missed the 'best bit' in the 'Free Willy' movie... when the whale gets to swim off to freedom in the sea!  She was not properly multi-tasking at that moment in time.  Perhaps this alleged ability of women to be able to do more than one thing at a time is somewhat over-rated!

The above photo shows some of the early joints soldered by Sandra.  Not at all bad for a first attempt.

She was working from the bottom to the top of the PCB and you can see how her technique was improving as she went.  The joints are the bottom are typical of those made by a beginner while those on the IC are rather better.

This photo shows the joint around the LED display. These are quite neatly executed. She was obviously becoming more comfortable and familiar with the basic techniques of soldering. The photo was taken under fluorescent light using a webcam, so I must apologise for their poor quality.  Her soldering is actually better than it appears in these photos.

I have to say that this is quite good workmanship for a complete beginner and far better than I had expected.

The finished clock.

Sandra was not at all surprised when I connected it up to my variable PSU and it worked first time!  OK, lets keep a sense of perspective.... it's only a clock, but she built it, with her own hand and it works just fine.  I can't take that away from her.  I'm sure that if I can get her to build a few more small kits, she'll be good to solder most things.

SMD?  Well, that's a different ball-game for a different 'Observation'.

 All in all, this was an excellent experiment and a change to watch someone else learn the basic skills needed for soldering. If you are beginner to electronics, I hope it will encourage you to build some of your own equipment. Soldering is like most other things.... practice makes perfect.  There are many companies such as Maplin Electronics where you can buy inexpensive construction kits that will allow you to hone your soldering skills. Perseverance is everything.

Soldering is an alloying process, the joining of two pieces of metal , by a third (the solder) which forms an alloy with both of the metals it is joining.  Cored (or Multicore) solder contains 'cores' of flux, a material whose purpose is to chemically clean the surfaces to be soldered. Solder used to be mainly a 60/40 mixture of lead and tin, but lead is very poisonous so the move is toward lead-free solders that are almost pure tin with one or two percent of copper added.

60/40 solder is really nice to use but the more recent lead-free types take a bit of getting used to. I believe the formulation of the flux used has also changed. Older types used to include colophony, a type of resin, that's not very good to breathe, especially if you are asthmatic. 

So, soldering involves the chemical alloying of two metals with a third. It's important that the parts being soldered are clean, but this is generally not an issue with modern components with plated leads.  When making a soldered joint, you first heat the materials to be joined (usually for a couple of seconds) before you apply the solder wire. The solder should flow instantly and form a little cone shaped joint with a bright silvery surface. . You must keep the parts from moving while the solder cools.

Tempting though it may be, DON'T blow on the joint to 'assist' cooling. This will chill the solder and a 'dry joint' is the usual end result.  A 'dry joint' usually has a 'pasty' appearance and often looks 'blobby'.  Here are examples of a section through a much magnified good and a bad soldered joint.

A good soldered joint and... a bad one.

(Click on images to magnify)

Soldering is a life skill. Like riding a bicycle, once you learn how to do it properly, it's 'programmed in' forever. It's NOT rocket science. All you need is to practise until you are happy with the end results.

When soldering, comfort is essential. On anything larger than simple projects, it pays to have good illumination and to have the board at a comfortable height for working.  The last thing you want is a stiff neck from bending over the living-room table!  At home I use a short angled 'lectern' built for me by a friend.  When sitting at my desk, it places the PCB at a 45 degree angle close to eye level. This may seem too high, but I can assure you that it is very comfortable and convenient to use. It's made from white plastic faced chipboard. just screwed together and it has a ledge at the lowest point to hold the PCB in place. You'll notice that Sandra is using a small vice in the photo. This hold the PCB firmly while the joints are soldered.   I'd strongly recommend using something like this for soldering. I've tried the 'helping hands' type of support but it's inadequate for anything more than the simplest of projects.

Hopefully this short primer will be of help to newcomers to soldering. If I've left anything unanswered you can contact me at...

73 Al.

GM1SXX

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