Homebrew PCBs

> I have made some boards using the toner transfer
> method with fairly
> good results. Something closely related is the
> matter of getting
> cables connected to a printed circuit board. I would
> very much like to
> hear of good ways to build nice cables and
> connectors that are "clean"
> and approach the looks and durability of commecial
> cables.
> 
> I work with amateur (ham) radio and many of the new
> radios use RJ45
> plugs for the microphone. I do have a good crimp
> tool for RJ45 use and
> make my own cables for home networking. I have
> constructed a couple
> cables to connect to such radios, ending up with a
> short stub of cat 5
> wire coming from the RJ45 plug then converting to
> some shielded wire
> for audio and flexible cable for the other signals.
> I end up with
> something that works, but is nowhere near as nice as
> the commercial
> cable.
> 
> I suspect that there must be some injecting molding
> machine (at a cost
> of a few million, no doubt) that creates all these
> nice cables that
> come with commercial equipment. My current solder
> and heat-shrink
> methods don't approach the quality of my PC boards
> and seem the "weak
> link" in the homwbrew process.
Vertical insert molding machines and molds are
actually not that spendy. $100K for a used machine,
and a mold would set you up real well, up to a few
hundred thousand/year.

Book molds are yet another way to go, figure on under
$10K tooling. But the piece part cost is higher, and
you are limited to the upper ten thousands/year. A
friend had his molds made for $3K, but its a really
simple connector.

As far as DIY, its time consuming.... but cheap

1. create a nice looking master (wood, clay, or wax)
2. create a silicon rubber mold from the master
3. create a clamping arrangement to hold the silicon
rubber mold onto the cable and connector
4. cast the connector/cable assmebly

Your biggest expense will be a vacuum system to degas
the casting material. If you don't mind a few bubbles
here and there, some materials are more forgiving and
work find without degassing. Silicon rubber molds are
good for 5 pieces if you are not careful, and you
might even be able to make 30 or 40 if you are
careful.

If you need more than 30 or 40, it pay be cost
effective to have a casting mold machined from
aluminum. I've got thousands of products in the field,
some of which were medical using aluminum casting
molds for the connectors. However for prototypes and
proof of concept, the silicon rubber works fine. Much
of the time, we installed small circuit boards right
within the connector assembly (the first few of course
were home brew).

Do not however try to use hardware store silicon. Its
not for casting, and does not work very well.

Ron

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