Short Version on Making Things
Jed Margolin 6/20/2024
I love making things. That is why I became an engineer. This way I can design the things I make. And I can make the things that I want.
If you are new to making things I have written a tutorial for you: www.jmargolin.com/making/jm_make1.htm
This is a very short summary:
A. Soldering
1. Wear protective glasses when you solder.
2. Use a temperature-controlled soldering iron. I use a temperature of 350 degrees Celsius for most things electronic. (For copper plumbing I use a propane torch.)
You can get temperature controlled soldering irons on eBay for a good price. The one I use looks a lot like this:
There are three buttons and a small LCD display. One button turns it on and off. The other two buttons set the temperature. The LCD displays the temperature. If it doesn’t have an LCD it isn’t temperature controlled.
Make sure it is for 120VAC. The Chinese still call it 110VAC. Apparently they didn’t get the memo that it was standardized in the U.S. to 120VAC in 1967. https://electronics360.globalspec.com/article/10511/how-the-u-s-came-to-adapt-120v-while-others-are-using-230v
And for some reason the Chinese don’t call it “soldering”. They call it “welding”. Soldering is not welding. From https://en.wikipedia.org/wiki/Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing fusion, which is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal.
Soldering is similar to brazing but brazing uses a higher temperature which produces a stronger joint.
Soldering (AmE: /ˈsɒdərɪŋ/, BrE: /ˈsoʊldərɪŋ/), is a process in which two or more items (usually metal) are joined together by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Soldering differs from welding in that soldering does not involve melting the work pieces. In brazing, the filler metal melts at a higher temperature, but the work piece metal does not melt.
The melting temperature of tin is 231.9 degrees Celsius. The melting temperature of lead is 327.5 degrees Celsius. The melting temperature of Sn60Pb40 solder is 183-190 degrees Celsius. The melting temperature of copper is 1,085 degrees Celsius. My soldering iron does a good job soldering copper at 350 degrees Celsius. How is it that you can solder tin/lead to copper when the copper isn’t melted during the process? I found the answer at https://www.howcast.com/videos/504745-how-does-solder-get-inside-copper-soldering/
Soldering and brazing are two techniques of joining metals where the base metal, in the case of electronics which is copper, the base metal doesn’t actually melt and it’s natural to ask how does the solder get inside of the copper if the copper doesn’t melt?
Now, copper is a metal that’s not made of a pure single crystal but is formed of lots and lots of small micro crystals. We call it a polycrystalline material. And in between these crystals are little spaces where the tin and lead from solder can diffuse into cracks and crevices, microscopic crevices and useful to form the bond. So the tin lead doesn’t really get into the crystal structure itself of copper but gets in between the crystals. And the same is true for brazing as well.
So if you were to look at the material under a microscope you’d see lots and lots of little grains of salt, if you will. And if you were to look at a microscopic image of soldered copper you’d see that the solder flows in between the crystals and leaving little islands of copper in between.
Much of the soldering takes place at the microscopic scale. Things like these oxides that disrupt solder are little particles that get in between the solder and the copper and prevent this diffusion of lead and tin into the crevices of copper. So there’s a lot going on at the microscopic scale. It’s very important to the features that we’re interested in at much larger scales.
And you can look at a piece of soldered material. If you were to cut it you’d see a layer of tin lead and a very sharp line where the copper begins. But look closely at that layer and you’ll see the that the tin and lead are actually intermingling with the copper and so there’s a boundary layer where the tin and lead have flowed into the copper a short distance but you’ll see that there’s actually a zone where the two metals exist but the three metals exist all together.
3. Although the EU has banned the use of solder containing lead I don’t live in an EU country so I still use Sn63/Pb37 solder. That is 63% tin, 37% lead. I use that because that is the eutectic alloy of tin and lead which means it melts at the lowest temperature of the alloy. It is only a little better than the standard Sn60/Pb40 solder. For a chart of the melting temperatures of different solder alloys Click Here.
Note that lead-free solders have a higher melting temperature than leaded solders. That is important because electronic components (especially ICs) can be damaged by excessive heat.
Because of the EU’s ban on leaded solder most ICs and other parts today are tinned with lead free solder. Otherwise companies would have to maintain two separate product flows and two separate inventories. Because they are tinned with lead free solder they require a higher temperature if you are soldering them to a board. If you use a socket it is not a problem. Just something to think about. (If you use a socket use a socket with machine tooled pins, not the leaf-spring crap.)
For PC Boards I use solder with a 0.5mm (0.020”) diameter.
4. Keep the tip of the soldering iron clean and tinned. This is necessary to efficiently transfer the heat to the work. A dirty (oxidized) tip won’t transfer heat very well. Don’t use a damp sponge to clean the tip. The best way to clean the tip is to use 0000 steel wool. By using steel wool you also avoid the problem of cooling the tip when your sponge is a little more than damp. And the tip lasts longer since, when the sponge doesn’t work well enough, you have to use sandpaper.
5. Don’t inhale the fumes from soldering.
From: https://hackaday.com/2017/02/23/what-the-flux-how-does-solder-work-anyway/
Electronic solder usually has a flux made of rosin. Rosin is a natural product derived from pine trees, notably the loblolly and longleaf pines for US-made rosin. It has the advantage of being more or less inert at room temperature but highly acidic when liquified, and has a melting point slightly lower than solder. The rosin core of electronic solder will therefore melt before the solder, flowing into and around the joint. The acidic liquid reacts with metal oxides, exposing clean metal for the solder to wet into. The acidic liquid flux converts the metal oxides to metal salts and water, which are typically locked up in the flux when it solidifies. The reaction products are generally harmless at that point, but some processes still require the used-up flux to be removed.
If you don’t have a fume hood use a fan to suck the fumes away from you.
6. After soldering a board clean the flux off of it. The recommended agent is isopropyl alcohol. Use a brush like this:
Its technical name is “horsehair bristle acid shop brush.” You can get them really cheap at Harbor Freight Tools: https://www.harborfreight.com/36-pc-12-in-horsehair-bristle-acid-shop-brushes-61880.html . I take one and cut the bristle leaving about 1/4" of bristle left on the brush. That makes it very stiff so it can brush off the rosin. I use an uncut brush when I just want to put a lot of cleaning agent on the board.
Don’t tell anyone but I am old school and still use acetone (in my ventilated area) to clean my PCBs. Acetone dries faster than alcohol especially if you use 70% isopropyl alcohol which contains 30% water. You should use 90% isopropyl alcohol. (If you use acetone don’t inhale the fumes.)
B. Desoldering
Sometimes you have to desolder a joint. For years I used solder braid or a manual desoldering pump. They don’t work very well.
The best way to unsolder a joint is where a vacuum pump (producing a continuous vacuum) sucks the solder through the heated soldering iron. They are expensive. The next best way is where a mechanically armed pump sucks the solder through the heated soldering iron. They cost a lot less but you have to keep arming and triggering the pump.
You know how they say: Measure Twice, Cut Once? To that I will add: Check Twice, Solder Once.
C. Making Things
1. Solderless breadboards. They suck.
2. Soldering wires point-to point. Very time consuming.
3. Wire Wrap. The easiest way to wire circuits other than using a PC Board. I am afraid Wire Wrapping is becoming a lost art.
4. Using a Printed Circuit Board. You can design your own. Like most things, the more you do it, the better you get at it. There are a number of good PCB Design programs that have free versions. (I use DipTrace.)
I have posted several of the projects I have done in the past several years. I have included the zipped Gerber files so you all you have to do is select a PCB fabricator and upload the zipped Gerber files to them.
D. Getting the boards fabricated.
This is a good Web site for finding board fabricators. https://pcbshopper.com/. You enter the size of the board and the number of boards that you want. It gives you the price and shipping options from a number of fabricators all over the world. It isn’t perfect. You have to go to the companies’ Web sites to get the exact prices. Well, you have to go to a company’s Web site anyway to order boards. Shipping costs more than the boards. You can sometimes spend less on shipping if you are willing to wait longer to get the boards.
For the past several years I have ordered boards from these companies. They all make excellent boards.
JLCPCB: https://jlcpcb.com They are the fastest to make boards.
PCBWAY: https://www.pcbway.com/ If you order boards from them using the links I provide they will give me a small royalty.
ALLPCB: http://www.allpcb.com/
ELECROW: https://www.elecrow.com/ The last time I ordered boards from them (March 2024) they were very slow to make them.
E. Buying parts.
I frequently buy parts from eBay. But there are some parts that I have bought on eBay that have consistently been Bad Parts: TL062, TL064, TL082, TL084, ICL7660.
For these parts I recommend Tayda Electronics (www.taydaelectronics.com). They don’t sell everything but the parts they do sell are reasonably priced and their parts have always been good. Their shipping charges used to be very reasonable, now they are high. So now I wait until I have a large order before I buy from them.
AliExpress (https://www.aliexpress.com) A warning about buying Chinese Picos. Everything else I have bought from them has been good and less expensive than anywhere else.
For other things I use the standard distributors. All of them charge too much for shipping.
Digikey (https://www.digikey.com/)
Newark (https://www.newark.com/)
Mouser (https://www.mouser.com/) Their shipping charges are slightly lower than Digikey and Newark but their Web site is excruciatingly slow.
F. Now go out and make something splendid.
Jed