Copper Clad Boards:
The most common type of board is the copper clad board. It is most often a 0.062" thick sheet of fiberglass with a thin layer of copper deposited on one side (single sided) or both sides (double-sided) of the sheet. The entire surface is usually covered with copper although there are production processes which can deposit solder, or gold to a bare board to form the circuit traces. In all cases of using copper clad board to makes PCBs at home, you must produce a "mask" exactly matching the circuit pattern you wish to create and put that pattern on the copper surface. Once the mask is in place, you use a liquid etching fluid to remove the unwanted unprotected (unmasked) copper from the board, revealing your circuit pattern. When etching is complete, the mask pattern must be removed with a chemical stripper or steel wool.
Perfboards or Wirewrap boards:
These are protoboards have a grid of pre-drilled holes and copper pads or strips. Some have tinned copper. Some are double sided. Some have special features like an edge cut and plated to plug into a PC 8-bit ISA slot. The copper patterns vary so you can choose what you like. I prefer having all the holes with separate square pads on one side because it is easy to cut the board to any desired shape or size and you can arrange components any way you like.
Solder method:
All you do is plug in all your parts are solder them in & route wires from point to point. Most beginners rush this process and do not consider their layout or component mounting methods before starting and make a mess of it. The best thing to do is use sockets for all the chips. Plug them all in without soldering first to plan the layout. That way, you won't get half of them installed before finding out you didn't leave enough room for something. I also prefer to plug component carriers into dip sockets as well. That way, you can solder resistors, transistor, capacitors, etc. to the component carriers first and then plug them into the socket. Believe me, this makes changing a resistor or something later much easier. Also, by using all DIP sockets, you can refer to ALL component pins by "socket#.pin#" notation on your schematic. This alone will help you a great deal. Consider that trying to solder multiple wires to a single point is difficult and messy. Add your wires from the component side, not the solder side, and this won't be a problem because the holes will help hold the wires in place while you are soldering. Why some people add all the wires on the bottom is beyond me, especially considering they probably first assembled circuits on breadboards!
Wirewrap Method:
I greatly prefer this method but it depends on the person. Wirewrapping typically makes the assembly much thicker and you may not like it. Wirewrapping is almost a lot art. There was a time when highly sophisticated machines were completely wirewrapped even in production, using thousands of connections. Of coarse, CNC wrapping machines did this job, not people. All DIPs, and most components must be plugged into wirewrap sockets which have long square pins (about 0.75"). These long pins are used to wrap wire (30 gauge) around to form connections. To add a connection, you use a simple hand-tool. Wirewrapping tools, wire and sockets are available at Radio Shack and many other suppliers. You simply cut a wire, strip the ends to 0.5" or so, insert the wire end into the side hole/slot of the tool, place the tool's center hole over the pin you want the wire connected to, and turn the tool several times. This wraps the wire around the pin in a tight coil. Up to about 3 connections can be added to a typical ww-socket pin. One neat feature of wirewrap sockets is that you can "un-wrap" a pin to change a connection. You can also purchase plastic "ww-socket pin-labels" which are very useful in grouping & identifying all the pins.
Breadboards:
Breadboards are sometimes called solderless perfboards. These are great for beginners and students and I recommend them highly for experiments and if you plan to build lots of temporary circuits. The board has many rows of holes (usually 5 holes per row which are internally connected) arranged side-by-side from one end of the board to the other. There is always 2 groups of holes separated by about 0.3". All you do is plug all your chips into the holes such that the chip has one row of pins on one side of the separation between the 2 groups of holes and the other row of pins on the other side. Plug resistors and capactors etc. into other holes such that each pin is in a separate row-of-5. Pins plugged into holes in the same row are connected. Use 22 ga. solid wire to make connections between pins buy just plugging in the stripped ends. The great thing about breadboards is how easy they go together and come apart. Most school labs use them extensively.
Ferric Chloride Etchant Fluid:
This is a common etchant for hobbyists because it can etch without being heated (works better heated though) and you by it premade so you don't have to mix anything. You just put your board into a tray (glass or plastic, not metal) and pour the etchant fluid over it gently until it is about 1/4" deep over the board. Swish it around a little for about 1/2 hour. Stop when the pattern is completely etched. You can use it over and over until it stops working. It picks up a black precipitant as it works so it gets darker as it works. Also, the smell is pretty harsh, and it gets worse if you heat it. At room temp, it won't stink up the room though. It also stains, even some plastics and ceramics. Ferric Chloride is a base, not an acid, so don't think you can use baking soda which is also a base to neutralize it should you spill it. Use lots of water to wash it off if you get it on yourself.
Amonium Persulphate Etchant Crystals:
This is a common etchant for hobbyists. It smells a lot less than Ferric Chloride, starts out clear, and turns blue as it etches. You buy it in crystal form in 1kg containers. 1kg makes 1 gallon of etchant which will etch about four or five 8"x10" single-sided boards. It must be heated and well agitated to work well, so it helps a great deal to have an etching tank with built in heaters and pumps. DynaArt Designs has exactly this kind of etching tank. Amonium Persulphate is a base, not an acid, so don't think you can use baking soda which is also a base to neutralize should you spill it. Use lots of water to wash it off if you get it on yourself.
Dry Etch Transfers - DETs:
DETs are like the the little rub-on decals you get inside cereal boxes. They are made in the shapes of DIP pads, single pads, traces, etc.. Use a pen or pencil to rub them onto a copper clad board to create a circuit pattern or mask pattern, then etch the board. They are very cheap but very time consuming to use. Also, there's no way to use them with your computer. Personally, I used them a lot before computers came along to make images on clear sheets, then used a positive photographic process to make my boards. Before that, when I was very young and just getting started with very limited resources, I used DETs on copper with great success. |
