Q.DIL? SIL? DIP?

ADual In Line. Single In Line. Dual In-line Package.

Q.What is a "Thou"? Is a "Thou" the same as a "mil"?

A. A "Thou" is one thousandth of an Inch, 0.001". A "mil" is the same quantity, a milli-inch. I prefer the term thou because it is less likely to be confused with millimeters. Since there are 25.4mm to the inch, 1mm = 39thou. All components originally used imperial measurements, so the thou are a good unit to work with. For example the pins on a normal DIL package are 100thou apart.

If you haven't seen it used before, a single quote ' is an abbreviation for feet, and a double quote " stands for inches. So I could write my height as 5'10".

If you are working in metric, just use millimeters for everything. E.g., I am about 1800mm high. DON'T use cm!

Q. What size grid should I use? How close can my tracks be?

A. Short answer - 12 thou tracks on a 25 thou grid is preferred.
Long answer. Well the old capabilities of most PCB manufacturers were 12 thou tracks with 12 thou clearances (gap between tracks). These are called 12/12 design rules. If you use 12 thou tracks on a 25 thou grid then you have a guaranteed 13thou gap between adjacent tracks. You can run one track between the pads of a DIP and meet the clearance rule if you use 62 thou diameter pads, or at least 62 thou wide anyway. Almost everyone can manufacture to 10/10 rules these days. Some can do 8/8, even 6/6, but you will start to pay for the privilege. Stick to 12/12 rules unless you have a reason not to. With 10/10 rules you can run two 10thou tracks between 50thou wide DIP pads on a 5thou grid.

Q. What clearances and track widths should I use?

A. On a standard (1 Oz. Cu) PCB, a 0.010" track will carry 0.8A with a 10 degree C rise. Plenty for you. But remember to use thicker tracks anyway for power supply traces etc, just in case you short them.

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