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Prototype PC Boards

If you're a small manufacturer, design lab or college without in-house PC board prototyping facilities, who do you turn to? It's a problem a lot of organisations face - even SILICON CHIP - but there are answers out there . . .

By Ross Tester

Commercial prototyping services are not new – they’ve been around pretty much since PC boards started being used extensively in, what, the 1960s? By and large, they’ve concentrated on the one-off board as an adjunct to their main game – commercial PC board manufacture.

A potted PC board history

When PC boards first came out, producing artwork for the pattern was a labour-intensive and exacting process. First of all, the pattern had to be worked out by the designer or engineer, then hand-drawn by a skilled draftsman (yep, very few girls back then) using black ink on either film or paper.

I well remember one such draftsman where I worked who had all-but finished such a drawing – a rather large one at that – and then knocked over his bottle of ink (guess where!). A week’s work, literally in the bin . . .

Once the drawing was finished, checked and checked again, a photographic negative had to be produced, usually involving a trip to a photo lithographer. Then the board had to be produced using one of several photo-sensitive processes.

Later came drafting tapes and pads, which allowed the board pattern to be laid out on film and used directly with positive photo resists. However, track widths (or more specifically track gaps) had to be kept quite wide so that the photo resists (and production processes) of the day could handle them.

Another memory from way back then is the late Ron Bell, founder of RCS Radio (and one of Australia’s early PC board gurus!) complaining bitterly to the project designers at Electronics Australia when we used "25 thou" tapes and spacing instead of his minimum of "35 thou"!

"No-one in Australia can produce boards with that spacing," he said. Imagine how Ron would be today with 5-thou tracks and spacing over multiple layers!

PC board PC software

It must have been the late 1980s or early 1990s when software for printed circuit board design started appearing (remember Autotrax?)

Since then, there have been lots of board layout packages brought out – some excellent, some average and some, well . . . Some were so expensive they were way beyond the home constructor but believe it or not, some were actually freeware or shareware.

OK, so you’ve designed your masterpiece on the computer and even had the software check it out to make sure there are no mistakes. Where to from here?

As you might imagine, SILICON CHIP faces this dilemma with just about every project we design, as the vast majority are based on PC boards.

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