Silicon Chip – July 2019

siliconchip.com.au Australia’s electronics magazine July 2019 41

conductive inks, but can also apply
solder paste and perform reflow of
populated boards.
You can see a video of the Voltera
V-One in action at: http://youtu.be/
PeW1nURJ5ww
According to the Voltera website, a
complete, unpopulated board can be
ready in around 35 minutes. Compared
to a manufactured board, the Voltera
PCBs will lack a solder mask and silk-
screen layer, and the conductive ink is
not as durable as bonded copper traces.
But the Voltera V-One is not limited
to fibreglass substrates, and flexible
substrates or even glass can be used.
The current listed price is US$4199
for the machine itself, with the cost
of producing each board at around
US$5 each.
If speed is of the essence and price
is not a problem, the V-One is certainly
worth checking out.

Milling PCBs

To form tracks on pre-laminated
board, rather than etching, copper can
be removed by mechanical means.
Open-source and do-it-yourself CNC
(computer numeric control) machines
such as desktop mills, as well as simi-

lar commercial devices, can be used

for this purpose.

A PCB mill routes insulating grooves

in the copper layer to separate the cop-

per into the tracks and islands required

to form a circuit, as shown in Fig.8.

The same machine may be able to

drill holes for the insertion of vias and

through-hole parts.

While such a technique does not

inherently provide the option for silk-

screen labelling or solder masks, the

grooves formed by the routing action

makes it harder for the solder to form

accidental bridges and production can

be very fast, taking just minutes for

smaller designs.

Double-sided boards are possible

with accurate enough registration, al-

though plated holes and vias must be

created manually. Small copper rivets

are available specifically for creating

vias in such boards (they can also be

used to repair commercially manufac-

tured boards).

While it is possible to completely

remove all unneeded areas of copper

from a PCB using a mill, it is usually

unnecessary, wasting time and wear-

ing the milling bits. So PCB mills gen-

erally remove just enough copper to

provide the isolation necessary for

correct circuit operation, and no more.

An extra step is also needed if the

copper needs to be tinned, although

this is generally not necessary for a

prototype board; tinning prevents

surface corrosion, but if the board is

assembled right away, that’s less of a

problem.

Another consideration for this tech-

nique is the waste produced, ie, copper

and fibreglass dust. These are health

hazards, especially glass dust, so a

vacuum system is needed to keep this

under control.

Suitable off-the-shelf PCB mills are

available; the Bantam Tools Desktop

PCB Milling Machine is an example

of this. It is available from Core Elec-

tronics.

See: https://core-electronics.com.

au/bantam-tools-desktop-pcb-milling-

machine.html

Many people are also attempting to

build their own PCB mills, some even

using 3D printers with their extruder

heads replaced by a rotary bit. The lat-

eral forces caused by the milling bit

moving through the material are much

higher than would be experienced

during 3D printing, so not all 3D print-

March 2001: Making photo-resist boards at home,

by Ross Tester. We followed the last

article with a more “traditional” ap-

proach using commercial resist-coat-

ed boards and exposing them to spe-

cial UV lights (or the Sun, which is

very high in UV!) through PCB pat-

terns which had printed on a photo copier onto either

transparent or semi-transparent film.

This is a time-honored method and is capable of very

good results with fine tracks and spacing.

Incidentally, you don’t have to buy pre-coated board

• you can still buy blank board and photo resist, in ei-
  ther a liquid or spray-on form, or even as film which you
  can apply to the board. It’s certainly not as common as
  it used to be but it is available (Google is your friend!).

February, 2012: Homebrew PCB via Toner Transfer

Film, by Alex Sum. This uses a special film

called “Press’n’Peel” which still available

from Jaycar (HG9980). You print your pattern

onto this film via a laser printer and use a

hot laminator (or even a hot iron) to transfer the pattern

to the PCB then etch, drill and cut in the normal way.

The author even used Press’n’Peel to create a compo-

nent image on the top side of the board (similar to the

silkscreen found on virtually all commercial boards).

In this article, we’ve briefly mentioned methods of

producing one-off PCBs yourself – perhaps from a mag-

azine project or indeed a prototype for a new product.

And while we usually take advantage of today’s low

cost, speed and quality of commercial PCBs (which is

why we’ve given up making them ourselves!) there may

well be a time when you want a PCB right now!

SILICON CHIP has published quite a few articles over

the years detailing methods of making one-off PCBs,

using a variety of production processes. We’ll briefly

recap on the most recent articles so if you really want

to make a PCB yourself, you should be able to do so.

February 2001: Toner Transfer, by Heath Young. This

article showed how you can

“transfer” the toner from a pat-

tern reproduced on bond paper

from a standard laser printer to

the blank board You then use

that toner as a resist for etching.

The difficult part is to carefully

remove the paper, which you do by breaking it down,

rubbing it under running water.

We’ve tried it, with mixed results, although we’ve

proved it can be done.

Be prepared for a few misses before you get the sys-

tem to work!

If you really do want to make your own PCBs..