NetNews Usenet Archive 1992 #16/NN_1992_16.iso/spool/sci/electron/13333

Text File | 1992-07-25 | 3.4 KB | 78 lines

Newsgroups: sci.electronics
Path: sparky!uunet!munnari.oz.au!uniwa!gude
From: [e-mail] (David J W Emrich)
Subject: Re: 0.100" spacing
Message-ID: <[e-mail]>
Organization: University of Western Australia
References: <[e-mail]>
Date: Sun, 26 Jul 1992 06:50:31 GMT
Lines: 67

[e-mail] (Allen Williams (co-op)) writes:

.... stuff deleted....

> Now, I have another question! Previously, I've been drilling holes for my
>IC's with a drill press, which isn't so bad for the small 16 pin IC's.
>I can usually eyeball where the drill press will drill with reasonable
>accuracy, and any variation can be compensated by bending the pins of the
>IC socket or IC to fit.

> However, I have a 64 pin IC that I want to put on a circuit board. I don't
>wish to have to get a stronger eyeglass prescription after drilling the holes.
>So does anyone have any techniques or equipment that they use to drill these
>types of things?

.... more stuff deleted ....

Sorry, can't help you on your fantasy drill press accessory (if you get
one, send me a catalog and a price list!).

Several years back I got into PCBs in a fairly small amateur way, and,
like you, I got sick having to line up ICs by sight.  Also, the drill
bit didn't always stay in line, causing horrid problems trying to insert
the DIPs later on.  My solution was to make up several jigs to use when
drilling the IC holes.

First, get hold of an old commercial PCB that you don't want any more,
with lots of DIPs on it.  Preferrably at least a 22-pin and a 48-pin DIP
(I think 22 is the longest .3" wide DIP and 48 is the longest .6" wide
DIP).  The idea is to find the longest available DIPs at whatever widths
you use.  You can use the 22pin jig to drill anywhere from 8-pin up to
22-pin DIPs.

Then, carefully remove the ICs from the board, without damaging the
holes.  (The method I use to do this is quite barbaric, but if you
don't need the chips, it is easiest on the board.  Just use a pair
of side-cutting pliers, to clip the leads off the chip, right up
at the casing, and then desolder the stumps of legs, one by one!).
Grab a scrap piece of soft steel about 1/16" thick, and cut it to
about 1/8" wider than the dimensions of the DIP,  and about 2" longer
(at one end).  This leaves a convenient "tag" on the end of your jig,
that can be clamped to the PCB while drilling, so that it doesn't move
around.  Then, carefully line up the blank that you just made, with the
holes in your commercial PCB, and drill them through the steel.  Make
sure that you don't apply too much pressure until the drill has centered
itself properly, because if the drill drifts in the steel, it will cut
the commercial PCB, and the whole won't be in line.

Once you have the steel jigs made, you can get them hardened (if you have
a friend in the steel works industry!), but I haven't found this to be
necessary.  You just have to be a little careful when you line up the
press.  Generally, I don't clamp the PCB, so I can move it around
slightly, letting the drill bit center the board exactly in the jig.

To use the jigs, just line them up with the copper pads, by holding the
PCB up to the light, and clamp the jig (parallel clamps are the best,
but G-clamps are quite OK).  Then drill away!

It's still fiddly, but it is quite a bit quicker than eye-sight
guessing, and a lot less optically stressful!

Hope this is of some use.

[dav]    a.k.a.
David Emrich
[e-mail]