Electronic Design

Bob's Mailbox

Hi, Bob:
A couple of things I have learned that make working with copper-clad boards much easier are the use of a hot-air soldering tool, and a good pair (sharp point) of tweezers for stripping the foil from the fiberglass substrate. Also, the pc-board prototype routing machines you see in a number of electronic publications are an excellent tool for doing almost any kind of work with copper-clad board—from cutting shaped pc-board pieces, to elaborate double-sided prototypes made for TSOP and SSOP devices.

The routing machine that I use (LPKF) will allow you to use a pointed-tip milling tool to quickly cut very-fine lines through the copper foil. It's much neater and faster than the X-acto knife I have used in the past. The hot-air soldering tool can be used to remove unwanted foil after all the routing and drilling is complete. A drill tool will drill holes, and a second milling tool will cut through the pc board.

Since the routing machine is basically a specialized plotter, controlling it is fairly simple. It came with fairly good software, but I find it easier to export files from the CAD tool I am familiar with in HPGL format. Making multiples of a board is a simple cut-and-paste operation, and making a duplicate board at a later date only requires loading a file. The L-shaped box you mentioned in your article would take about 15 minutes to layout, export, and rout. Two L-shaped boxes would take 16 minutes.
BOB LUTES
Design Engineer
M-tron Industries
Yankton, S.D.

Maybe 15 minutes for you. But 15 weeks for me to learn to drive that computer without crashing. Fortunately big SHEARS, tin-snips, and metal-nibblers still work well—RAP

Dear Bob:
New EE grads are a source of both enthusiasm and comic relief (providing there's not a schedule to meet). Most are of the opinion that "there are 'digital' electronics and 'analog' electronics." Their various instructors never take time to warn them that "there's no such thing as 'digital'—just funny-looking analog with more or less two common states."

Two things have become more common over the years. First, EE students are actually encouraged to treat digital circuits as ideal circuits, ignoring the analog component. Especially at the frequencies we're using today for these components, more circuits do not work as expected. Ah! too bad the world wasn't really a pile of capacitive and inductive elements.

The second problem seems to be in the selection of passive components. Is it my imagination, or are nearly all EE students leaving school with naiveté that nominal value plus tolerance is all that matters? Why has it never dawned on them to ask why there are different materials available for resistors and capacitors? Using other than a ceramic capacitor seems to be thought of not as a possible design need, but a fashion statement <sigh>.

I recently ran across the Passive Electronic Component Handbook by Charles Harper, $89.50, available from: http://www.books.mcgraw-hill.com. Where are texts like this being used in EE courses?
CHRIS ANDERSON
via e-mail

There's also a book by Ian Sinclair on Passive Components, about $30, ISBN 07506 02295, with good insights. But no school is going to use anything practical like THAT in any course. Are they?—RAP

All for now. / Comments invited!
RAP / Robert A. Pease / Engineer
[email protected]—or:

Mail Stop D2597A
National Semiconductor
P.O. Box 58090
Santa Clara, CA 95052-8090

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