Soldering Question

[Tenorikuma]

I've never soldered anything before, but I'm about to try making some LED-lit vending machines and need to solder an LED, resistor, and connector to fit a very small space.

 

Can I just glue these down, "dead bug" style to a small piece of styrene and solder the leads together? If any solder drips on the styrene, will it damage it? (My research says that 60% tin solder melts at 190° and polystyrene at 240°, so there is some margin there.)

[Martijn Meerts]

I would solder things before glueing them to the styrene. Unless you have a soldering station with adjustable temperature, your soldering iron will be a lot hotter than 240 degrees. Dripping solder shouldn't be a problem though. It's hard to get the stuff to drip in the first place, and it cools down fast.

[Tenorikuma]

I would solder things before glueing them to the styrene. Unless you have a soldering station with adjustable temperature, your soldering iron will be a lot hotter than 240 degrees. Dripping solder shouldn't be a problem though. It's hard to get the stuff to drip in the first place, and it cools down fast.

 

What's a good way, then, to hold the components in place and keep them from moving while soldering?

[Martijn Meerts]

Get a "helping hand", something like http://www.amazon.com/Helping-Hands-Soldering-Holder-Magnifying/dp/B000YC2GM4

 

Just make sure it's a decent one with a large/heavy base for stability, and you don't really need the magnifying glass either.

 

Of course, it also depends on what you're soldering. Are the LEDs and resistor regular types or SMD types. In case of SMD it works to just use double sided tape to hold the component in place temporarily.

[Tenorikuma]

Thanks for the advice. They're just standard components in this case (I have chip LEDs too but am going to try the normal 3mm kind first). The trick is I need to make sure they're arranged in a space smaller than 11x7 mm before I solder; maybe I'll just tape them to my work table with masking tape and then solder away.

[Martijn Meerts]

I tend to use an experimental circuit board, one of those that has lanes running across them on 1 side (there are some that have lanes of 3 "holes" length, or just dots)

 

I try to fit everything on as small a space as possible, and then just cut off what I need. It works great for SMD components actually.

[Tenorikuma]

I tend to use an experimental circuit board, one of those that has lanes running across them on 1 side (there are some that have lanes of 3 "holes" length, or just dots)

 

I try to fit everything on as small a space as possible, and then just cut off what I need. It works great for SMD components actually.

 

There's a parts shop nearby that sells an 11x16 mm (4x6 hole) universal circuit board, which I can probably just fit into two side-by-side vending machines.

 

What do you use for cutting the boards?

[Martijn Meerts]

Usually a small jewelers saw with very fine teeth

[Tenorikuma]

I went to the store and found circuit boards built on flexible plastic stickers you can cut with scissors, so I'm going to give that a try.

[Bernard]

Once you get used to it, soldering is actually a lot of fun. You will feel that the electrical connection you just made is secure.

Oh, and clean the tip after you finish using the iron, I have a damp sponge that that I wipe the tip on after use, it helps prevent the solder from building up.

[Tenorikuma]

My first solder is a success! (I think.) I managed to solder an LED, a resistor, and two wires to a very small piece of flexible circuit board. It just squeezes into the 12x6x8 mm vending machine I made earlier today. And it works! (Now I just have to finish the vending machine window and paint it.)

[Martijn Meerts]

There are a few things to keep in mind while soldering, some of them I learned the hard way (by ruining a lot of soldering iron tips amongst other things).

 

When you first use a new tip, make sure you get some tin all over it, it'll help in the long run with heat dissipation. If you don't do that, you might end up with a tip that has cold spots here and there, which is immensely annoying. I also always tin the tip like that after I'm done using it and before cleaning it.

 

I don't use a sponge for cleaning, but some device which is really like a metal ashtray with very course sort of copper wool in it. The "wool" will scrape off the tin.

 

Use the correct tin for the correct metal/tip. There are lots of version of tin, some work better for certain things. I can't quite remember what is what, I would have to check that out again.

 

Try to avoid soldering liquids as much as possible. A soldering flux will make soldering a lot easier, but if you don't clean it very carefully afterwards, it'll start eroding. I made my own (functional) catenary poles and wires at some point, using a flux to make things easier (and especially faster). The flux ended up eating away the pantographs of my test train =)

 

 

There's lots of other stuff, best to look up some soldering primer / how-to's on the internet =)

[Tenorikuma]

Thanks for the tips.

 

Most soldering irons here seem to come with a little yellow sponge, so I moistened mine and used it to wipe the tip when I was done. I'll try to remember to tin it next time. I'm using basic 60% tin solder, which the package recommended for basic electronics and circuit boards. I'm not using a separate flux, but I believe the solder may have some flux in it.

 

I did find one or two basic soldering how-tos online, which helped a lot. No screw-ups so far is a good thing, I suppose.

[Martijn Meerts]

The good thing is, even if you do screw up (which, inevitably you will at some point), the components used are cheap and it really doesn't matter if you fry a couple of them.

 

Except when you're soldering decoders of course, that can get expensive fast =)

[cteno4]

Tenorikuma,

 

hey welcome to the soldering world! it can be great fun once you get a feel for it. first thing to do is find some wires and old electronic components if you can and just practice soldering on those some. this will really give you a feel for how the whole process works. it really is a bit of an art.

 

a few tips:

 

if you are soldering small parts get a small tip for your iron. this will make your life much easier. also use thin solder, not big fat stuff, again will make life easier

 

best to use good solder that has a little flux built into it. a martijn mentions using liquid flux is a mess and usually ends up putting way to much flux in your joints and can cause corrosion later unless you clean it off well (hard to do on little parts like this). for little joints like this you wont need much solder at all so see if you can just buy a small amount, some stores will sell a couple of feet coiled up in a ziplock bag or bum a little from a friend ;-)

 

when you solder small critical joints make sure you tin and wipe your point first. this means just put a small amount of solder on the tip (tinning it - called tinning as solder is mostly tin based) then wipe it in cotton rag fast to give it a nice shiny smooth coat of solder. a copper cleaning pad is great also, but fast wipes will work on a cotton rag if you are cheap (not synthetic as itll melt on your tip!)... using a cotton rag can leave a bit of carbon on the tip, but i have never had a problem using it in a pinch.

 

start the soldering by putting the tip down at the joint and apply just a very quick tad of solder to the tip right at the joint. this will make a little solder flow into the tip and release a bit of flux on the joint, then quickly move the solder over to the other side of the joint and apply it at the joint. the heat will melt the solder on the other side and wick all around the joint quick and quickly remove the iron tip. if you try to just put all the solder onto the tip/part joint what usually ends up happening is the tip will just keep sucking up the solder and not the joint so much and you can end up with a big blob of solder on the tip which can then at times flow in fast to the joint leaving a huge blob of solder on your joint and a mess...

 

for tiny surface mount leds (chip leds) you might also see if you can buy them with wire leads attached if you find it too nasty to solder the tiny ones.

 

another technique to soldering small parts is to tin each part. ie apply a small amount of solder to the smLED pads and tin the ends of the wires. then put the two together and quickly apply a clean iron tip to the joint and the two parts will join very quickly. pre-tinning your parts can make for very clean joints and will usually mean less solder on the joint so not take a huge stress, but gives good electrical connection and you can then have your solder hand free to use to move a part into place which is helpful with tiny stuff that may be hard to get in place or in some awkward angle. also means you need to apply a bit less heat and for a shorter time than soldering it w/o pretinning. on small parts overheating can end up destroying the component if your iron is really hot. again as martijn mentions a variable heat iron is a good idea as small solder joints can be done at a lower heat. you only need a really hot iron when doing larger parts that end up sucking up a lot of heat.

 

again its practice that will help the most. practicing and experimenting on some junk stuff really helps a lot. even though i picked up a soldering iron and started using it when i was 4yrs old i still will do a few joints before starting on something tricky to just get my touch back!

 

its a good idea to wear goggles or glasses. i didnt for many many years with no problems and finally about 10 years ago i had a bit of solder splatter across my eyes when a wire popped loose and i had my face too close. while the solder hardens really fast its was a nasty sting and made me realize it would be stupid to hurt my eyes over a solder joint...

 

Post pictures of these, I want to see them. I was thinking of using some styrene rectangular tube stock cut off thin in cross section to make some vending machines by then cutting out a small picture of a machine and recessing it in the hole some (i wanted a bit of a lip around the edge of the machine sticking out. did not think about putting an led behind it to make it light up! fantastic idea! groan, you made a new project for me to fiddle with!

 

have fun, great idea!

 

cheers

 

jeff

[Tenorikuma]

Thanks for the tips Jeff. I have a bunch of chip LEDs I haven't dared solder yet (I couldn't find any with leads pre-soldered), but your pre-tinning technique sounds like something I should try.

 

I have one teensy LED-resistor unit soldered and ready to go, but my first attempt at the vending machine itself was unsatisfactory, so I'm going to try a new method. (Tiny bits of styrene are just so finicky when it comes to positioning and gluing, and it doesn't help that a single coat of paint takes a week to cure in this humidity.)

[cteno4]

Tenorikuma,

 

its all about getting in there and trying it! thats why practicing on some scrap really help a lot! pre-tinning is a great cheat way to make things solder fast in those awkward positions.

 

trainaidsa.com has some smds with leads attached for $1 ea, not bad! only place i have seen with them pre wired like this for those that hate micro soldering. hes a good guy with nice little inexpensive products to missing things you need in train modeling! hes also open to ideas for other products that you just cant find to itch that scratch in your modeling.

 

http://www.trainaidsa.com/shop-leds.shtml#smd3528

 

cheers

 

jeff

[veejo]

I work in the electronics industry, and also used to teach soldering to new workers.

Before tackling fine work, or expensive work, buy some bigger resistors, or find an old PCB and practice a bit.

The trick is the flux has to melt, to clean the surface (melts at low temperature), to allow the solder flow and form a "heat bridge", and raise the temperature of the surfaces you are soldering so that they "fuse" together. Soldering is a molecular bond.

You'II get the hang of how quickly the heat is transferred  etc,etc.          You'II get the feel for it, it's not hard.

It's an investment that will also serve you well when you do trains that aren't DCC ready into DCC.