Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

If you are using through hole components, and if you are planning on etching or machining your own PCB, and you do not have the capability to incorporate plated through holes, then the easiest method I have found is to use a single sided board if you can afford the larger size. I place all the traces on the bottom layer of the PCB and all the components on the top side of the board. This makes soldering components simple since the solder pads are not beneath a component where they are hard to access, especially true for items such as DIP sockets, connectors, and such. There is no need for solder mask in this situation. I usually use my soldering iron to coat all the copper on the PCB with solder before mounting any components to assist with solderability and reduce corrosion problems later. Of course you can also use electroless tin or gold to accomplish the same thing, but the solder is cheaper. One word of caution, it is fairly easy to get solder
bridges between traces with this method, but they are fairly easy to spot and correct before the components are placed.

If I find that I need to make a double sided board in order to be able to complete all your connections then I make all connections to items such as sockets and connectors on the bottom side of the board only, with a short trace to a via (pass through hole) located far enough away from the socket to allow easy soldering of a short length of wire (scrap resistor lead, etc) on both sides of the board at the via. This ensures a good electrical connection between top and bottom layer. If you do not place any conductive components on the top of the board, or avoid running top layer traces under the metal items, then solder mask is not required.  I frequently use a combination of through hole and surface mount components on double sided boards using this method, since surface mount are easy to lay out, smaller, and less expensive than through hole components. The attached image (latch PCB.jpg)is a recent double sided PCB that I machined using the combination
of surface mount and through hole components.

Where you really need solder mask is if you want to use solder paste and an oven to solder a bunch of surface mount components at one time. In that case, the solder can easily bridge between traces unless you have the solder mask to only expose the metal where you want solder. The second attached photo (dual charger PCB 2.jpg) shows a commercial built PCB that I designed and soldered using solder paste and a toaster oven. If you have the boards made commercially they usually come with a solder mask plus nice silk screened designators for the components. Double sided boards with plated through holes on all holes and vias is common, and is a very nice feature. When I was designing lots of different boards, I usually placed several different prototype boards on a single panel which I then had fabricated. The cost for a panel was usually under $100, and I often had 5-10 different circuit boards on a panel. I would sometimes order several panels to have
enough boards of each type for a prototype production run. The cost for extra panels of the same layout is quite small since much of the cost is in setup and producing the artwork for etching the boards. I found it was not cost effective to try to etch or machine my own boards for most prototype projects when my time was costing the company money. Now that I am retired, I have more time, and the money comes out of my pocket, so that makes it slightly different. I also seldom have more than one or two designs to build at a time.

Bob Butcher

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