Can someone explain some PCB manufaturing processes?

Lets assume I have generated a number of boards via a PCB CNC/milling machine...

I would like to know in laymen terms what is involved in the process of the following...

tinning the traces
plate through holes
solder mask
and silk screening...

I know there are tinning solutions out there etc... but I guess what im wondering is what do the smaller (commercial) PCB fabricators use?

im trying to avoid chems as much as possible though im sure some processes will require it.

can anyone enlighten me?

:green:

This is definitely a question for Gustav - I just saw his manufacturing plant yesterday - :shock: - really amazing..!

Jakob E.

"im trying to avoid chems as much as possible though im sure some processes will require it"

Most metal plating is nasty.

If you are milling the board the dust is bad. One it might be fiberglass and two any fine dust is bad for your lungs sand,paper dust,thread dust, coal dust etc.

I would think that milling PCB's turns out better traces than etching?

or is this not true...

what exactly is involved in masking?

This is one thing that I have wondered

https://www.cs.tcd.ie/Ross.Brennan/mystuff/PCB_Fab_Wallchart.pdf

Bri

[quote author="Scenaria"]I would think that milling PCB's turns out better traces than etching?

or is this not true...

what exactly is involved in masking?

This is one thing that I have wondered[/quote]

Id be more than happy to answer any fabbing questions, but Im having a little language problems here . What exactly do you mean by milling ?
What I understand by milling is the final process of cutting the PCBs out of the production panel.

Masking? You mean applying solder mask?

Gustav

Gustav, jag tror att han menar fräsa (=milling) själva mönstret, inte kortkanterna.

http://www.pcbmilling.com/

Milling away the copper is an intriguing idea. With a little x/y mill, you could prototype right from the computer.

Copper is a bitch to cut, though. It plugs the mill bit easily; a lot of oil would be needed to keep it clean and cool, I think.

Also, you would probably want to start with a material that's thicker than the standard 0.062" as you'd want to go a little deep into the material to account for thickness variations.

How about a laser?

Hi scenaria,
with tinning there's a kind of "chemical tin" involved. (german "Chemisch Zinn"). It's a liquid sold in litres or gallons and quite a poison on it's own...
Once you get your hands on this, usage is pretty simple and fairly cheap and reliable.
Sure you can "wave bath" the pcb with tin as well.
There are some electro galvanic systems available but i heard nothing good for now in home usage, meanly because of the costs...
Personally i tin by hand with collophonium in alcohol applied to the boards before. to get a fine look you can work with hot air to let the tin flow even.

Plate through holes:

Plated through holes are done by first sensitizing the inside of the
hole using stannous chloride which leaves a tad of divalent tin on the
surface. This is followed by a treatment with a palladium solution.
The adsorbed divalent tin reduces some palladium in solution to
palladium metal which sticks to the PCB (in the hole). The PCB then
goes into an electroless copper plating bath where the palladium
catalyzes the reduction of copper in the electroless plating
solutions. The result is a thin conducting layer of electroless copper
through the hole. Too thin to use as is. (Of course this plating
through is done before any of the copper on the circuit board is
exposed. i.e. the mask has not been developed)
Finally the board goes into a conventional plating bath to produce a
thicker coat and make contact with the copper on the circuit. This is
a rough outline without the gory details.

Click to expand...

Definately no option at home...even for the commercial pcb factories this is a pain in the ass ( not to mention your drilling has to be first class quality). Another practice is the use of plate thru rivets with a special rivet press, but i don't know if the results are nearly as good (weaks at the rivet-copper connection). However the most ugly part.

Solder mask is easier, there are some readily available systems based on a photo sensitive layer fairly usable at home. another option is screen printing the laquer. For rapid prototyping the pro's use a liquid latex solution alot...

Silk screening: well, just what it says... :grin:
Just needs a screen printing frame, a photosensitive laquer system and paint...
Personally i'm very happy with toner transfer from paper right to the pcb right now, very fast and easy (around 5 minutes incl. printing on my ole laserwriter). if the board is too dark (FR4 sometimes) i just leave it...

From all i heard pcb milling is a pain in the ass and two times slower than toner transfer and etching (and in the end much more expensive on a per piece basis, not to mention the cnc mill). Only an option for big size single pcb prototypes...but for this application it's cool.
i heard most people use their cnc for drilling only. :grin:

Hope this helps.
Maybe take a look http://groups.google.com/group/rec....ching+insubject:photo&rnum=1#1b6dd9f3e97c0edb
Kind regards

Martin