Soldering - a "how to"

Here is what I gleaned from extensive reading before I started to solder. I put together everything pertinent that I learnt, in my own words, and went over it afresh before starting on the opto endstop boards. You could call it a tutorial. Unfortunately, it isn't possible to grow a third hand for taking photographs whilst actually soldering, and my photo's aren't perfect anyhow, but they give an idea....

How to....

Check that you have all the right components for the board. It is a good idea to lay them out around the board, each on the respective head/foot/left/right side, to assess sizes and locations of the individual components.

Start with the smallest component on the board.

Firstly, check the component leads for signs of dirt or corrosion (see later), and clean by wiping as necessary. If the component has been shipped stuck onto tape, cut the leads alongside the sticky tape to prevent future issues with glue interfering with the solder joint.


Bend the component leads down to align with the fitting holes in the board. Check which way round the component must be inserted; with some components this doesn't matter, but with others it is critical. Insert the leads, from the top towards the bottom surface of the board, both at the same time, but do not press the component down onto the board, because that may kink and weaken or snap the leads.

For any component that may heat up in use, eg a resistor, leave a small gap so that the component is raised above the board slightly to allow air to circulate and heat to dissipate. For temperature-sensitive components, eg transistors and diodes, where excessive heat from the soldering operation can be harmful, again leave a small gap, so that a small crocodile clip or similar metal item can be attached - during soldering - to act as a heat sink and dissipate excess heat.

Bend the leads outwards away from each other slightly on the underside of the board to hold the component in place. (This picture shows a ferrite bead sat vertically on the board, but most components will be aligned between their fixing holes, known as pads.)

Cut off the leads a few mm (approx 3 mm) away from the board. Do not cut them off flush with the board. Cutting the leads before soldering prevents disturbing or damaging the finished joint.

Repeat with one or two other small components, working from the centre of a big board outwards.

Now heat up the soldering iron. Clean the tip using a dampened card egg-box (my resourceful Dad's method) or a wetted sponge (commercial method). The tip should be shiny.

Apply the tiniest amount of solder, containing flux, to the iron tip, by just touching the solder against the tip, but all around it, to prevent it oxidising. Now wipe the tip on the damp card/sponge.

If the component leads are lightly corroded, and not shiny themselves, use the soldering iron to heat the leads. Without moving the soldering iron, now touch the solder to the lead on the side away from the soldering iron.
Move the solder wire away, remove the soldering iron and check that there is now a layer of solder around the lead. This process is "tinning". "Tinned" parts will solder together well. Discard the excess solder blob on the iron tip by wiping it on the dampened card/sponge. If too much solder is applied to the part being tinned, use desoldering wick/braid to remove the excess by applying the wick to the coating, and the tip of the soldering iron to the wick, gently pulling the wick along under the iron tip as the wick becomes full of solder. Remove both wick and solder together.

On the underside of the board, use the hot iron tip to heat the lead AND the copper connection together, for just a second or two. Now, without moving the iron tip away, add a tiny amount of solder to the side of the lead by touching the solder against the hot lead and copper connection, followed by quickly adding solder, using a dabbing motion, to the side of the lead away from the iron, again down against the copper connection.
Repeat this movement until sufficient solder has been applied to create a good joint. Take the solder wire away, then immediately remove the soldering iron, to avoid boiling off the flux and creating spikes, without knocking the joint. Do not move the board until the solder joint has set.

Now inspect the joint.
The outline of the leads should be jutting out of the solder joint slightly. As the joint cools, it should have concave sides, should be flush against the copper connection, and pulled up around the component lead. The solder should not "bridge" to neighbouring connections. If using leaded solder, the joint should look very shiny; lead-free solder will look a little duller or grainier, but still shiny.
Check the joint from the top side of the board, too; the appearance here should be the same.

If the solder does not look shiny, or has not flowed around the lead well, re-melt it with the soldering iron slightly hotter, and ALWAYS add a small amount of flux, which may be contained in extra fresh solder, as necessary, so that the joint becomes shiny and complete.

Below is a picture of a row of good joints in the foreground, - this was my fourth board ever, so it isn't perfect, but the front left solder-joint is perfect, in size, shape and shininess. The brown marks you can see on some of the others are burnt flux, which can be cleaned off with a commercial cleaner or by scraping gently (eg fingernail), but in this case don't compromise the electrical contact.

Here is a close-up picture of the joint on the left in the background; this isn't good, having too much solder. You can see that the solder is convex instead of concave. However, it has made electrical contact and is a viable join.

Here is a picture showing a bad joint; there are 2 large connecting holes in the middle of the board, and you can see that the top one in the picture has shiny solder in it, whereas the bottom one has dull solder. This would be a bad joint if it all looked like this. In this case, the solder on the other side of the board is shiny and I believe there is a sound connection there. Otherwise this would be a candidate for re-doing the solder joint.


Continue with the other joints, checking each as it is completed, before moving on to the next. Re-clean the soldering iron tip as necessary, probably after every few joins.

When the first batch is soldered successfully, continue with another batch of components, moving up in size and outwards on the board.
Finally, add a tiny amount of fresh solder to the tip, to protect it from oxidation in storage, before switching off. Store the soldering iron covered to keep it clean.
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Testing 1, 2, 3, testing...

Before I went any further, I wanted to test the opto circuits I'd built, so I needed to know which pins were which on the RJ45 connector. I used this, which was the clearest description I found, with a nice easy diagram - so looking at the RJ45 jack socket on the board, with the board the right way up, the pin on the left is 1.
According to the circuit info. in the assembly instructions, pins 4 and 5 are connected together, and this is where the +ve end of my 5V power supply had to be connected, and pins 7 and 8 are connected together, GRND, and this is where the -ve end had to be connected.

Below is a photograph of my testing set-up, using 3 D cells (giving approx. 4.5V) and some alarm wire all blu-tacked together. It took some fiddling to get continuity; too much blu-tak insulated the alarm wire strands!


I stood the battery-tower up and wedged it inside a perfectly-sized cardboard box to hold it all together better. Here is a photo' of the circuit board with its optical sensor blocked with some folded corrugated card (the wire in the foreground is not actually making contact yet) , and below that a photo' with the LED lit.




Believe me, holding the wires to get this working whilst taking a clear photo' was no mean feat!
Hoorah! All 3 circuits work as hoped, with the LED lighting when the sensor is blocked, and going off when unblocked. I am delighted! My first ever soldering was a success!

Silkscreen and solder

Some photographs:

here are all the packages required for the opto endstop board laid out,

and here are the individual components placed around the bare board,

and here are the undersides of the three finished items


I know the photo' is poor, what with being blurred and having terrible reflection off the auto-flash, but you can just about see the scorch mark at the resistor on the first one I did (on the left), before I swapped to a finer tip on the soldering iron.

Now I need to determine which connectors are what on the "ethernet" socket and get myself a 5V power source to check all the opto endstop boards.

Here is a better photo' (new batteries in the camera, daylight (of sorts)) showing the first board:

The slight scorch-mark is (on the middle resistor) just above and to the right of the central fixing hole.
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Tuesday trepidation

I have started assembling and soldering the first opto endstop. These boards are made solely with through-hole components. My first soldering atempt on this PCB left a scorch mark on the board - note Nophead's comment about how the solder pads on the board could do with being bigger.
So I switched off the soldering iron, let it cool and swapped for a finer tip. I'm glad I had bought a set of tip replacements for my iron.

When I got to the LED, I had to ask on the forum what the instructions meant for how to get the orientation correct. The phrase was "Insert the short leg (negative) into the hole closest to the flat side of the silkscreen" - I don't know what that means, nor what a silkscreen is, in this context!
The replies came back that "silkscreen" means the diagram printed on the board (if only they'd written "diagram" instead) so the "flat side" refers to one side of the LED's almost circular diagram, ie the picture isn't completely round - there is a subtle flattening on one side. I'm hoping not all boards are so subtle....

Further information came back that I should not assume that the short lead on the LED is the negative one - it isn't universally true! But that this can be checked by using the lowest resistance range on a multimeter, and touching its black lead against the short LED lead (and the red against the other), causing the LED to light up if the short lead is indeed the negative one.
However, I found this didn't work..... but I found that it did work if I used the triangle (now I know it means a diode) symbol on the multimeter. I only considered trying this setting because I had earlier seen the triangle symbol, labelled LED1, on the circuit diagram for this board.
Looking at information on multimeters, I found that a digital multimeter may not have the right resistance range to check diodes, hence the separate diode-testing setting.
I shall have to try to remember this test before connecting up my other brand LEDs.

My first soldering looked (generally) O.K. on the rear of the board, ie the solder itself looked fairly shiny (I'm using lead-free solder, which doesn't make as shiny a join as the traditional leaded type), concave, although not exactly neat, but it looked dull on the top, and I had used too much solder in places. As far as I can tell, there is, unfortunately, no way of checking the finished board independently of any other boards.

Bank holiday blues

Well, I never did get started on the soldering. Finally we had a dry morning today, so I sorted out the soldering iron - it went outside for a smoke! It took 5 to 10 mins to clear it.
I tried to fit the first resistor into the opto endstop board, starting with one lead and then trying to manipulate the other lead into the right orientation to insert that one through its hole, too, but found that was nigh on impossible - I was in danger of damaging the lead/s. I've been trying to look up better techniques, which turned out to be a difficult task. There is precious little information out there, as everyone starts from just using the soldering iron! It occurred to me that I can't be the only person who doesn't know how to do this.... I did find some in the end.
I've also been refreshing my soldering knowledge, so I have written my own "how-to", starting from absolute basics for those who are utter novices as I am. I shall amend as I go along, and put the tutorial up on the blog when I'm sure I've got it right.
Maybe I'm actually ready to start now.

...three lights; four lights; five lights......

(anyone fond of motor racing will know what my heading means) - false start!

My solder, yes SOLDER, arrived in today's post. So, naturally, I thought I'd have a go.
Oh-oh. As soon as it started heating up, my brand spanking new soldering iron smoked rather more than I expected, and as I was planning to practise soldering (why do the American videos all say what sounds like "soddering"?) in the room housing my stick insects, and stick insects being sensitive souls when it comes to aerosols, vapours, and smoke, I have unplugged and opened the window. I shall have to set up elsewhere until the iron no longer smokes so.

Guess what I'll be doing this bank holiday weekend?

Woo-hoo

The good folks at Farnell, bless their little cotton socks, had refunded £20.75 straight onto my credit card (but fogot to tell me!). They didn't have to do this, as it was my error in the first place, so I am very grateful.
I have now ordered, from Farnell, as it only seems right, some solder wire and solder paste. I'm going for lead-free as an environmental sciency person.

Farnell (second) sub-total £19.26

• solder paste, lead-free, no-clean, 5 ml, 10 g, manufacturer: Edsyn, part number 1521898, £16.11
  
• solder wire, lead-free, 0.7 mm, 2 m, manufacturer: Multicore, part number 9887105, 64 p.

When it comes to adding the costs of everything, I can take off £20.75 for the Farnell refund, but add £1.62 it cost me to post the extraneous parts back!

Back on 11th June, the costs had reached £262.88, excluding a set of washers and screws from B&Q, and the welding tips that got missed off, at £2.
Then on the 21st July came the first Farnell order (less the refund now received), £72.08
and the subsequent return postage of £1.62
the RapidOnline order £12.35
the RS order (less the solder paste refund now received), £3.59
the Maplin further order (including 2 LEDs now not needed) £1.99
today's Farnell second order (as above) £19.26

so the running total now stands at a whopping £375.77

I probably wouldn't have started if I'd thought I'd be spending this much, but hey, still having fun, and it's giving me something unusual to talk about at weddings!