Seriously Newb question about soldering

seeclear

I got the BR-1 speaker kit from Parts Express to put together with my son (age 9), because he likes anything with wires and I thought he would love to do something with a circuit board that actually works. As it is, he takes apart toys like RC trucks, etc and is fascinated by the PCBs, wires them up all funky and keeps asking me, "Dad, do you think it will work?" I tell him that you have to understand the circuit in order to make it "work", but he is undeterred. So, anyway, the instructions with the speaker kit gives good instructions on what to do, but not enough detailed instruction on exactly how to do it, and I don't want to screw up the PCB, not having soldered on one before.

So, the "front" of the board has the layout of all the components printed on it, with the little holes for the corresponding wires to go through. I plan to use hot glue to attach the components on the front, with the full length wires sticking through to the "back". Once that is secured and turned over, there are little copper circles which I am thinking is where the wire will be soldered/connected.

First question, should I leave the wires from the components full length until soldered, then trim, or trim to a shorter length before soldering?

Next question, do I need to prep the wires or the circuit board in any way to make the solder "stick" properly? The instructions that came with the soldering gun say to "clean" the parts to be soldered thoroughly. I'm familiar with that when sweating plumbing joints, but I don't want to overdo it with this small/fine stuff.

Next question, do I use the soldering iron to heat the little copper circle and just touch the solder to it to melt it, or will that damage the PCB? Or do I melt the solder with the hot tip and let it "drip" onto the connection? Do I need to use a heat sink clamp between the joint and the component, or is this process quick/cool enough that it won't endanger the component?

I think that is all the questions I have for now, but if you gurus who do this a lot have any other tips to make it work smoothly, I would really appreciate it. Thanks in advance!

treitz3

Hello, maybe I can help. I personally would not worry about using hot glue to place the components on the board first, but that's just me. Making sure the soldering iron is hot enough to make a good solder joint, I would install the component and solder one side at a time leaving only what is necessary to come out of the other side of the board. As quickly as you can, heat up the wire leading through and dab solder on the wire until the hole completely fills up [without moving the component]. Quickly remove the soldering gun and repeat this process until the other side of the component is installed. Then move on to your next component until the board is done.

I take it that you have the appropriate tools to get this done correctly?

treitz3

You want each solder connection to look like ^^^this^^^ ideally. What you don't want is a cold solder joint as shown below.

seeclear

Thanks, Tom, that is very helpful.

treitz3

You are welcome. If you have any other questions, don't hesitate to ask. Have fun!

ShinAce

seeclear wrote: »

1) First question, should I leave the wires from the components full length until soldered, then trim, or trim to a shorter length before soldering?

2) Next question, do I need to prep the wires or the circuit board in any way to make the solder "stick" properly? The instructions that came with the soldering gun say to "clean" the parts to be soldered thoroughly. I'm familiar with that when sweating plumbing joints, but I don't want to overdo it with this small/fine stuff.

3) Next question, do I use the soldering iron to heat the little copper circle and just touch the solder to it to melt it, or will that damage the PCB?

4) Or do I melt the solder with the hot tip and let it "drip" onto the connection? Do I need to use a heat sink clamp between the joint and the component, or is this process quick/cool enough that it won't endanger the component?

1) full length and then trim once soldered
2) new components are pretty clean, but I've learned to either sand down old dull leads or even wipe with alcohol. Also a good idea to use a toothbrush and clean up a joint after soldering. That core of rosin has a habit of eating away at joints, over a long time.
3)yes, heat both parts with the iron and then touch the solder to both parts without the solder touching the iron directly. As you learned in plumbing, if the metal is hot enough, the solder will get there. It will climb metal to cover the hot spot.
4)no

A typical joint should have the iron touching for 2-5 seconds. I personally solder one leg of a resistor and then move onto another component. Let the resistor cool down before soldering the second leg. It's not mandatory, but I like to play it safe.

ViperZ

Look in Section 6:

http://workmanship.nasa.gov/lib/insp/2%20books/frameset.html

This is NASA Workmanship Pictorial Reference for soldering, wiring and everything else. The best picture reference I have ever seen.

Tater

seeclear wrote: »

First question, should I leave the wires from the components full length until soldered, then trim, or trim to a shorter length before soldering?

>>With leaded components and backside soldering I like to install several while bending the leads over so they stay in, then solder in batches, then trim the leads off.

Next question, do I need to prep the wires or the circuit board in any way to make the solder "stick" properly? The instructions that came with the soldering gun say to "clean" the parts to be soldered thoroughly. I'm familiar with that when sweating plumbing joints, but I don't want to overdo it with this small/fine stuff.

>>If the circuit board is bare copper you should pre-tin it. It doesn't hurt to clean the leads, especially if they appear dirty. A quick swipe with steel wool works well too, just do that away from the board so no wool fragments end up on the board.

Next question, do I use the soldering iron to heat the little copper circle and just touch the solder to it to melt it, or will that damage the PCB? Or do I melt the solder with the hot tip and let it "drip" onto the connection? Do I need to use a heat sink clamp between the joint and the component, or is this process quick/cool enough that it won't endanger the component?

>>A variable temperature iron is best for this. It's worth the extra cost. The heat (watts) is proportional to the amount of metal you're heating. Yes, heat the circular copper pad (about a second at 6-700 watts for something that size) and touch the solder elsewhere on the pad for just an instant. If you overapply the solder, slurp it off with some solder wick. A good solder joint should not have bulges or bubbles of solder. It should hug whatever you're soldering pretty tightly.

Ricardo

I found these videos very helpful.

http://www.tangentsoft.net/elec/movies/