As more and more DIP ICs are being fazed out, some of them are now only available as surface mount devices. Creating a custom printed circuit board for each one is impractical for the amateur robot builder or experimenter. Pre-etched Breakout boards which adapt a surface mount IC to the standard .1" spacing of breadboards are available. Unfortunately, they often cost more than the IC itself. Below are some techniques for making your own breakout board using standard copper traced stripboard or perfboard. Also included below are some techniques for fairly easily mounting other surface mount components.
Breakout board
This Breakout board works well with SOIC sized ICs. This technique can also be used to mount several SOICs on a project perfboard for more complex circuits. It requires two specialty items--special solder and magnet wire--to make it easy. Low temperature solder was used for all the connections in the picture shown. Because it melts at a lower temperature, you can solder a joint almost twice as fast as with regular solder, so the chances of damaging the IC are greatly reduced.
Since I made this breakout board, I have started using thin solder instead of the low temp solder. When components are very close together, it can be difficult to solder them without blobbing over and shorting nearby pads and wires. The best solution is to use a small tipped adjustible heat soldering iron (1/32") and the thinnest solder you can find. Standard solder and low temp solder is usually .032" in diameter which works fine for most things. Using thinner .015" diameter solder allows you to easily control the amount of solder on the joint. If you use the least amount of solder neccessary, it not only takes up the smallest volume, but it also allows you to solder a joint as quickly as possible. Even faster than with the low temp solder. This reduces the chance of overheating and damaging delicate components like ICs and surface mount LEDs. You can find the low temp solder and the .015" solder at: Mouser.com
I also use 30 AWG heat strippable magnet wire available at: Mouser.com. You can also use regular magnet wire, but it does not strip as easily, so I prefer the heat strippable magnet wire. This wire has a coating that can be stripped by soldering it with enough heat to melt the insulation. It takes up to 10 seconds to strip the coating while soldering. For some delicate components such as soldering to LEDs or ICs, this can be a damaging heat. The best compromise for me, is to use this heat strippable magnet wire. I take a sharp knife and slide it across the magnet wire to peal off the coating and then rotate the wire around until it is stripped fairly well around its diameter. Then I solder the stripped wire end until it is well tinned. Then, you can solder it quickly to any delicate component without heat damange.
Step 1
Cut your perfboard to size and then use a 1/8" drill or a Dremel tool to remove the copper traces where the IC will eventually be glued on.
Step 2
Insert the edge of a small square of heavy duty aluminum foil underneath the pin you are going to solder and over the pins on either side. This will prevent the solder from flowing on to the adjacent pins. It will also act as a heat sink. Clamp the IC and foil onto a sheet of FR-4 fiberglass or perfboard.
Strip and tin enough magnet wire to go to all the pins. If you are using heat strippable wire, you can strip it by soldering a large blob of solder onto some scrap copper traced perfboard. Stick the end of a 1-1/2" length of magnet wire into the molten blob and hold it down with the hot soldering iron. Keep it immersed for 10 to 20 seconds and then slide it out. The insulation should melt away leaving the end of the wire nicely tinned. If not, repeat the process. Cut the tinned part of the wire to about 1/8" long. Tin the length of wire again about 3/8" to 1/2" from the tinned end of the wire.
You can now clamp the wire to the board holding the IC and aluminum foil shield and using the low temperature solder, solder the end of the wire to the IC pin. Move the foil and repeat the process for the rest of the pins. When you're done, you should have something which looks about like this:
Step 3
Solder some .1" header pins to the perfboard you drilled out. Glue the IC to the perfboard. When the glue is dry, bend and solder the tinned wires to the header pins. Try to avoid getting the wires to close to each other as that can cause crosstalk or stray capacitance in some circuits.
You could of course forget the magnet wire and simply use shorter pieces of #30 uninsulated tinned wire. The advantage of leaving the magnet wire long and insulated is that it allows you to solder to the header pins without reheating the solder joints on the IC pins. This reduces the chance of damaging the joint or the IC. After you have tested the circuit, it is probably a good idea to coat the wires with liquid tape to increase their insulation value, reduce the chance of crosstalk, and protect them from accidental damage from handling.
Attaching other Components
Other surface mount components can be soldered with magnet wire and then mounted almost anywhere on your project circuit board. As before, pre-tin the magnet wire. It is also advisable to first solder a blob of low temp solder or thin solder on the contacts of the component. Then you can solder the tinned wire to the component.
Gluing Components
You can also use conductive glue or Wire Glue, to glue some components such as very small LED's that are a pain to solder. Keep in mind that any kind of conductive glue has some resistance and each joint can add 5 to 9 ohms to the circuit. In the case of low current LED's, it doesn't much effect the overall circuit and whole arrays of LED's can be glued in this way. Buff the copper well with steel wool to eliminate oxidation and finger oils before you glue the components. The led above was glued and then left continuously on for six weeks and it held up fine over time. Excess glue, after it dries, can be scraped off with a knife. I would recommend coating the top surface around the LED's with liquid tape or clear contact cement to insure a solid, long term mechanical connection to the board.
Here is a link that will show you how to make your own conductive glue that has a lower resistance and greater flexibility than Wire Glue: Make Conductive Glue
You can send Questions or Comments to:
Copyright 2008, Inkless Press