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Leon
02-12-2012, 06:34 PM
PCBs with tracks as narrow as 8/8 mil (8 mil width with 8 mil spacing) or even less are easy to make at home with inexpensive equipment. I use an HP 9540 printer to print transparencies that are used with positive pre-sensitised PCB material in a simple UV exposure unit. After exposure the board is developed, etched and then drilled.

Printing

I use the HP 5940 printer because it is comparatively cheap, it can deliver 1200 dpi output directly from the Pulsonix PCB software I use, and it works well with the JetStar Premium film available from Mega Electronics (UK).

I print on an ordinary sheet of A4 paper initially, cut a piece of film a bit oversize (it's expensive), and stick it to the A4 printout with a piece of masking tape. The matt surface of the film must be uppermost. It goes into the paper input tray with the film on the underside, and the tape towards the back of the printer, in the feed direction.

Print the artwork using the best quality setting, and cut it to size. I mainly make single-sided boards, the artwork has to be reversed for a through-hole board with the copper on the bottom.

Exposure

Cut the PCB laminate to size and remove the protective black film. I use Mega Electronics FPC 16 material as it's very easy to cut and drill, unlike the more usual FR4.

Place the sensitized side of the laminate in contact with the transparency (ink side against the resist) and put it on the exposure unit. Switch on the lamps and leave it for the required exposure time. This needs to be established beforehand using test strips, as was done with photographic enlargers.

Remove the laminate, and develop it.

Development

I use caustic soda (sodium hydroxide) solution (about two teaspoons to a litre of water), and it takes about 30 seconds to remove the exposed resist with constant agitation in a small plastic container at room temperature. Wear rubber gloves.

Etching

I use warm ferric chloride solution for etching, it lasts a long time and can be used until it is exhausted. It's usually supplied in powder form. Follow the instructions when making up the solution.

Put about 1.5 cm of ferric chloride solution into a suitable plastic container, and place the container in an old washing up bowl with about 2.5 cm of very hot water in it. I use boiling water straight from the kettle. Put the laminate into the ferric chloride and rock the container, wearing rubber gloves. The board should be etched in about 5 minutes.

Remove the board from the solution, rinse thoroughly in clean water, and dry. It's now ready for drilling.

Double-sided boards

Double-sided boards can be made by sticking the top and bottom transparencies together along one edge, ensuring that the two sides are properly registered. The double-sided laminate is then placed between the two transparencies, and each side exposed in turn. With care, reasonable results can be obtained. I prefer to make single-sided boards, with a few wire links on the other side.

UV exposure

Here is a photo of my home-made UV exposure unit:

http://www.leonheller.com/Photos/UV%20unit.jpg

A sheet of ordinary window glass cut to size rests on the wood strips.

It takes 12 minutes to expose the laminate I use.

Removing ferric chloride stains

FeCl3 stains clothes, and anything else, badly. Oxalic acid deals with the stains quite well - make a solution with water and soak the stain. Wash the item. Oxalic acid is available on Ebay, it's used for whitening wood. It's rather toxic, don't drink the solution.

Suppliers

Mega Electronics (UK) supplies JetStar and JetStar Premium film, as well as LaserStar film for laser printers:

http://www.megauk.com/artwork_films.php

I also use their FPC 16 laminate:

http://www.megauk.com/pcb_laminates.php

I actually buy it from ESR, as they don't have a minimum order charge:

http://www.esr.co.uk/

Farnell sells something similar, but I don't find it as good as the material sold by Mega. Farnell also sells the film:

http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=WZBJEPFICXA44CQLCIQZMMQ?N=0&Ntk=gensearch&Ntt=jetstar&Ntx=mode+matchallpartial&suggestions=false&ref=globalsearch&_requestid=453190

Please ask if anything needs clarification.

ElectricAye
02-12-2012, 07:21 PM
Just make sure the kiddies know that sodium hydroxide and ferric chloride are kinda nasty things. You probably don't want to just dump them down the drain as-is, especially if you have your own well.

http://upload.wikimedia.org/wikipedia/commons/thumb/a/a1/GHS-pictogram-acid.svg/200px-GHS-pictogram-acid.svg.png

Leon
02-12-2012, 07:23 PM
Sodium hydroxide is OK down the drain, it's used as a drain cleaner. Ferric chloride is used by the water companies, but they won't like the copper.

Duane Degn
02-12-2012, 10:11 PM
How does one dispose of the copper solution?

My concern about disposing of the waste chemicals has kept me from making PCBs at home.

BTW, it's now very difficult to purchase NaOH(in USA). They used to sell it in the grocery store, now I have to by it off eBay.

Leon
02-12-2012, 10:23 PM
Here in the UK it can be taken to the local council rubbish dump, they have a collection point for toxic waste. Small amounts can be poured down the drain with plenty of water, the copper content will be minimal.

The solution can be regenerated with hydrochloric acid and hydrogen peroxide, or by bubbling air through it, and will gradually become cupric chloride, which is a good etchant in its own right.

Developer which doesn't contain NaOH can be bought, but it's expensive.

tonyp12
02-12-2012, 10:45 PM
Can not someone come up with inkjet graphene, so you can print your traces.

Leon
02-13-2012, 12:00 AM
Do you mean printing directly on the copper?

tonyp12
02-13-2012, 12:35 AM
No, I mean printing the traces directly (maybe a few passes) on a substrate.
A google search shows that is not far fetched.
http://www.extremetech.com/extreme/106599-first-inkjet-printed-graphene-computer-circuit-is-transparent-flexible

Erik Friesen
02-13-2012, 02:31 AM
http://techref.massmind.org/techref/pcb/etch/c84-st.htm

tonyp12
02-13-2012, 02:48 AM
I'm not talking about printing a mask on copper and then etch.
I'm talking about printing the “copper trace” itself, actually graphene that is electrically superior to copper.

Leon
02-13-2012, 03:19 AM
I've never heard of anyone using that technology at home. Additive processes using copper deposition are used for fine-line PCBs (< 5/5 mil), but require lots of processing steps and aren't suitable for home-made PCBs.

lardom
02-15-2012, 09:47 PM
My guess is that you would have to make a few mistakes before you get a two sided board right.

Leon
02-15-2012, 10:38 PM
I've made a few, it isn't difficult.

Bean
02-16-2012, 12:14 AM
If you are going to drill after you etch, make sure you have a large ring. Otherwise the bit will tear the ring off the board.
I try to drill before I etch if possible.
Bean

Erik Friesen
02-16-2012, 12:51 AM
I have done some double sided boards using the inkjet method similar to described above. It isn't that hard, especially compared to the toner method. You can line up your artwork before hand, and then tape it to the board.

@Leon, some links to known good products could be useful.

I suspect that roughed up laser transparencies would work.

Leon
02-16-2012, 02:28 AM
I've added some links.

Bean,

I use tungsten carbide drills, running at 15,000 rpm, and don't have any problems with pads coming off, even with small annular rings. I often use teardrops for added support.

Leon
04-08-2012, 05:00 AM
Here is one of my boards. It's part of a high-performance direct-conversion radio receiver.

average joe
04-08-2012, 05:16 AM
I just read graphene and had to post on this because I was thinking about that a while ago! I read a few things on the way people are producing it, and it seems like a GREAT idea.. Someone should work on that!

Leon
04-08-2012, 05:28 AM
I don't see the relevance of graphene to PCBs. Do you have a link?

Leon
04-08-2012, 05:45 AM
Here is another board of mine:

http://webspace.webring.com/people/jl/leon_heller/msp430.html

It was made a long time ago, using a laser printer and tracing paper.

average joe
04-08-2012, 06:36 AM
Sorry if it's not relevant but Graphene and Graphyne have AMAZING properties. If we can make transistors and capacitors out of the stuff, why not entire systems.
http://physics.aps.org/articles/v5/24
http://hardware.slashdot.org/story/11/11/26/0439205/uk-university-creates-first-inkjet-printed-graphene-circuit

jmg
04-08-2012, 08:17 AM
Exposure
Place the sensitized side of the laminate in contact with the transparency (ink side against the resist) and put it on the exposure unit.

Has anyone tried this sort of UV exposure box, using LEDs ?

http://s.eeweb.com/members/circuit_projects/blog/2012/01/26/ultraviolet-exposure-box-using-LED-1327597271.jpg

or this
http://www.electronics-lab.com/projects/mcu/018/index.html

and I see Mouser has UV LEDs at tolerable prices ?

VAOL-5GUV0T4 405nm 160mcd 30deg 100: $0.438
( 2,910 In Stock)
VAOL-5GUV8T4 385nm 80mcd 30deg 100: $0.571
( 2,579 In Stock)

Leon
04-08-2012, 08:24 AM
I know of people who use them and they work OK. UV tubes are cheaper (they were when I checked a few months ago, at any rate) and less work is involved in mounting them. I've got a feeling that UV tubes are better for narrow tracks because of the increased collimation, but I could be wrong.

pik33
04-08-2012, 08:47 AM
In "good old times" (30 years ago) I made my boards at home like this:

- draw a board scheme on a paper with pen
- wrap a board with this paper and drill holes
- get a waterproof lacquer and a pen (old kind of pen used to write with ink on drawing paper in these times) and draw lines on board with this pen
- treat a board with FeCL3
- use a solvent, then a home cleaning detergent to clean PCB
- ready :)

FeCl was hard to get (Poland, 198x) so I experimented with solutions made from h2o2, vinegar and salt, it worked :)

average joe
04-08-2012, 09:09 AM
I have a couple boards someone bought from RS for me. I have never done anything with them and they are wasting away. A process I was PLANNING to use and read a bit on involves printing schematic on !*MATTE*! photo paper with LASER... Then iron onto board to create resist. Dampen paper and continue applying heat until ink separates from paper. I did a test transfer and it worked. Never did etch the board though. Not the most elegant but should work. Eventually I would like to do photo-resist work, but need a darkroom first :(

Leon
04-08-2012, 09:10 AM
pik33,

I made my PCBs the same way when I started playing about with electronics at home. I used to paint the tracks with cellulose paint and a fine paintbrush.

Joe,

A darkroom isn't required for photo-etch.

average joe
04-08-2012, 10:04 AM
Very true, but a workshop would be a big help. A one bedroom apartment makes a poor lab. Especially with a 3 month old. Soldering is done in the bathroom, and any chemical work is done outside in the dirt with spill collection procedures.
I have seen examples of people using simple CAM machines using stepper motors and a dremel. I've thought about one of these quite often, but do nowhere near the volume necessary to justify the price of one. Could be built DIY IMO.
http://youtu.be/gZFvra3kXEs

Leon
04-08-2012, 10:10 AM
They are slow, compared to the photo-etch technique, and don't produce very good results unless one spends a lot of money. The Pulsonix PCB software I use supports the LPKF prototyping machines, and they are very expensive.

Leon
04-08-2012, 07:53 PM
This (rather poor) photo is my latest board. It's a prototyping board for the DIP28 NXP LPC1114 ARM Cortex-M0 chip. They aren't officially available yet, NXP supplies me with samples of new devices in return for running the LPC2000 group. I've also attached the layout, and the schematic.

I need to remove the resist and drill the board. I'll see if I can get a better photo when I've removed the resist.

jmg
04-08-2012, 11:00 PM
It's a prototyping board for the DIP28 NXP LPC1114 ARM Cortex-M0 chip. They aren't officially available yet...

The problem with these DIP offshoots, is they do not cover the newest variants, so the LPC11A14 / LPC11U14 for example, are not showing anything even planned in DIP.

Also, being wide body, they really have chosen just the hobbyist niche; a SDIP might have more volume but perhaps the die just will not fit ? Lack of wide-supply is another drawback in NXP devices.

I can also see part codes for DIP24, but no road map mention of these, so do we guess they are pruned for the DIP28 ?
Not such good news for someone who designed-in a DIP24 ?

Leon
04-08-2012, 11:19 PM
It is a bit odd. I prefer the PIC32, which is in a narrow 0.3" package.

I also asked for some of the SOIC and SSOP ones, but they are having some problems with them.

.

User Name
04-08-2012, 11:35 PM
Just as an OT comment: I often wonder why NXP offers nothing but M0 chips in DIP or PLCC. The M3 family delivers remarkably better performance - so much so that I can't get enthused about the former. (Clock rates don't tell even half of the story.)

Leon
04-08-2012, 11:42 PM
It's probably because the M0 parts compete with 8-bit devices, which are available in DIP.

jmg
04-08-2012, 11:43 PM
Just as an OT comment: I often wonder why NXP offers nothing but M0 chips in DIP or PLCC. The M3 family delivers remarkably better performance - so much so that I can't get enthused about the former. (Clock rates don't tell even half of the story.)

Good question. DIP packages have to be a niche, and not really that price sensitive, so sensible would be the 'largest die; in SDIP28 and another (larger?) sibling in DIP28 ( or even SO28) - M4 in SDIP28 anyone ? ;)

jmg
04-08-2012, 11:44 PM
It's probably because the M0 parts compete with 8-bit devices, which are available in DIP.

Really ? Which 8 bit parts come in Wide Body DIP28 ?

Leon
04-09-2012, 12:01 AM
Not many, but the point is that they are available in DIP.

average joe
04-09-2012, 12:22 AM
There has been more than once I settled for a chip that I didn't want, just because it was not available in dip. Adapters can be very expensive, and just like shields, they waste too much space IMO. I have done some amazing things with no resources before, but I'm getting too old for this nonsense. I've been watching the PCB threads and wondering the best way for me to get printing. This is the ONLY way I'll be able to move into SMD like I desire..
The board looks very nice. The one thing I HAVE been wondering. How the heck do you guys do solder mask?

Leon
04-09-2012, 12:52 AM
I don't bother with solder-mask. Some people do: film has to be applied and then the process is similar to the actual PCB production, with artwork, UV exposure, etc.

Wa_Mo
04-11-2012, 02:39 AM
Today I received my order of Press-and-Peel sheets.

I just had to try this out, since the toner transfer from glossy photopaper did not work.
And the result after one hour of mucking about,

http://i.imgur.com/bCnit.jpg

I found some etchant and silver plating liquid from about 30 years ago. Still did the job. Not perfect, but acceptable.
Now drilling all those holes should be fun.

Leon
04-11-2012, 04:16 AM
That looks very good. I've never been able to get on with toner-transfer.

I've just drilled lots of holes on my latest board.

Tubular
04-11-2012, 06:41 AM
@Wa_Mo, thats a really good Press n Peel result. I usually get more pits than that, though it generally works well enough, and its easy to fix any minor breaks.

I've never really optimized the temperature of the iron etc. Perhaps I should invest an hour like you and inject some science into the process...

Wa_Mo
04-11-2012, 08:47 AM
I don't know if there are different types of Press and Peel available. The sheet which I used was Press and Peel Blue (http://www.techniks.com/) and I just followed the directions which came with the sheets. The important step seems to be the temperature of the iron (ca 300 deg F).

I wonder if the peeled sheet could be reused for a presensitized board.

91610 91611

Leon
04-11-2012, 09:42 AM
It probably could, but you'd be better off with a transparency done on an inkjet printer.

Leon
04-14-2012, 05:30 PM
Setting up my equipment takes about two minutes and involves:

Putting the UV exposure unit on the kitchen table, placing the transparency and sensitised laminate on the glass, plugging it in, and switching it on for the requisite time.

Pouring the developer into the container in the kitchen sink, and adding the exposed laminate.

Pouring very hot water into an old washing up bowl in the kitchen sink, adding the etchant container, pouring the etchant into the container, and adding the laminate.

Putting the equipment away takes about four minutes and involves:

Removing the UV exposure unit from the kitchen table and putting it away.

Pouring the developer back in the bottle and rinsing the container. Putting them away.

Pouring the etchant back in the bottle, rinsing the container and the old washing up bowl. Putting them away.

The developer, etchant, and two plastic containers are kept in the old washing up bowl, and take up very little space. The UV exposure is very compact, also.

The only item I built was the UV exposure unit, it took me about one hour. I could have purchased one quite cheaply.

Everything is done under normal lighting - daylight or artificial lighting. A special table isn't necessary with my process.

:) :) :)

Leon
04-23-2012, 04:19 PM
Here is my latest PCB, fully assembled. It's a simple prototyping board for the new NXP LPC1114 ARM Cortex-M0 in a DIP28 package. I can't test it properly because the device isn't supported yet by the Rowley CrossWorks ARM tools, and the loader won't work. They are working on it. I can access it via the ARM SWD debug interface, so there can't be anything wrong with the PCB design.

I extracted the chip ID from the LPC1114 using the debug I/F, and Rowley has used it to modify their loader. I was able to test my hardware properly with the new version.

Leon
04-25-2012, 05:37 PM
Here is my test program:



/* Flasher.c
** LED flasher
** LED on PIO1_0 (pin 9)
**
*/

#include <LPC11xx.h>

void delay(void);

int main(void)
{
LPC_IOCON->R_PIO1_0 = 0x0041; // Select PIO1_0, Mode inactive, no hysteresis, ADmode digital, standard GPIO output
LPC_GPIO1->DIR = 0x00000001; // Make PIO1_0 output
LPC_GPIO1->DATA = 0x00000000; // Start with it low

while(1)
{
LPC_GPIO1->DATA = 0x00000000; // LED off
delay(); // Wait a while
LPC_GPIO1->DATA = 0x00000001; // LED on
delay(); // Wait a while
}
return 0;
}

// Delay routine
void delay(void)
{
volatile long i;
for (i = 0; i < 500000; i++)
;
}


ARM's CMSIS - Cortex Microcontroller Software Interface Standard - makes accessing peripheral registers quite straightforward. Cortex peripherals are rather complex, and would otherwise be rather difficult to use.