Alternate Circuit Fab Process (For prototyping purposes)

Aims and Objectives

The conventional PCB fabrication process is tedious and expensive, and involves many chemical compounds.

The exposure process takes some time to happen. Then there is the developing, and then etching. Etching probably takes the most time, and expensive etching tanks are required to do the job.

For those working at home, such a process is expensive; the chemicals are costly, toxic and difficult to obtain, and requires most importantly, an etching tank if the etching is to be completed in an appropriate length of time. If insufficient funds are available, as always in the case of self-funded or poorly-funded projects, an etching tank is a painful expenditure. I've been reduced to immersing a nascent PCB in a plastic container, agitating the mixture with my hands and a pair of chopsticks...

Etching is also an environmentally unfriendly process, and the chemical waste generated is not something that should be washed down the sink at home.

These disadvantages of conventional PCB fabrication make it unsuitable for small scale uses, such as those in makeshift labs and homes.

However, there is also a desire to fabricate printed circuits for regular prototyping purposes, because they are more reliable and less tedious to make than soldering them onto prototyping boards. Don't you find flipping a proto-board on one side to insert a component, then flipping to the other side to solder the connections, then flipping back again and getting confused something good to avoid?

Prototyping on printed circuits also means the prototype is more like the possible production version, which makes the prototyping process better.
There're some things breadboards aren't good for too.

with the above, we've come up with a method ourselves. Its by no means a production method. Just meant to make prototyping easier, faster.


Principle
Print out a mask of the circuit pattern on aluminium foil. Electroplate the foil so that only parts not covered by the mask will be plated with a thin layer of metal. Using something sticky, press onto the electroplated aluminium foil, and peel. The electroplated layer will be peeled off from the foil and onto the sticky piece of thing i want my circuit to be on.


The Process

1. Creating the pattern
This can be done with PCB creating software. What should be printed out onto the foil is a negative of the actual PCB circuit pattern.

To do this in PowerPCB:
After creating the circuit pattern, select the "drafting" button.
Click on the "Copper Pour" button on the drafting toolbar.
Create a copper pour outline area along the board outline.
Click on the "Flood" button and click on the copper pour outline.
ALL THESE ARE DONE IN THE SAME "TOP" LAYER, OR THE SAME LAYER AS THE LAYER WITH A CIRCUIT PATTERN.
Then go to File=>CAM
When dealing with the settings, select "Copper" to be printed, in Black colour.
Preview to confirm, and then print.
SELECT PRINT OPTIONS, AND CHOOSE "MIRROR PRINT"! OTHERWISE, THE CIRCUIT PATTERN PRODUCED EVENTUALLY WILL BE LATERALLY INVERTED!!!


2. Printing is to be done on a laser printer. The aluminium foil should be made to be free of creases and stuck to a piece of paper. This will be fed into the laser printer. Printing settings should be set for max toner and darkness and resolution. Parts not meant to have copper MUST be fully covered with toner.

Do multiple passes thru the printer to ensure this, if possible. Otherwise, hand-correct with liquid paper.


3. Trim and clip the masked paper-backed aluminium foil onto a hard flat sheet of material. Immerse and electroplate.
Electroplating was done with "Baker's Soldering Fluid No.3", which is actually zinc-chloride. Or rather contains zinc-chloride. (So what exactly is its composition??) And so we use zinc plate on the other end of the electrolytic cell. well...the zinc plate isn't exactly zinc...contains some iron too. Well that's fine.


4. Once done with electroplating, transfer onto a sticky surface.


Things to note:
If the sticky surface is flexible, do not allow it to flex too much, cos the very thin electroplated layer with break.

Electrical contact is below 20 ohms...but as yet unsure how much resistance there is. And yes i know anything even at 1Ohm and above is rather unacceptable...i know i know.

After soldering, take care that the components aren't pulled off the board. That'll wreck the circuit traces.