PDA

View Full Version : Making / Etching Printed Circuit Boards Supplies



JoeFin
05-28-2010, 06:43 PM
I need to find a good supplier for every thing to make limited runs of Printed Circuit Boards in my shop. I don't have any thing and need to get started ASAP and on a budget.

I don't want to go the "Iron On" route and would preferably use an Ultra Violet Light source and a developer. Any suggestions you guys could make would be fully appreciated

Maybe Evan can chime in on this 1, I'm pretty sure he is making circuit boards in his shop

lwalker
05-28-2010, 07:43 PM
Circuit Specialists: www.circuitspecialists.com

Dragons_fire
05-28-2010, 08:12 PM
I have started moking them using Lye (Drano) as a developer and muriatic acid mixed with hydrogen peroxide for the etchant. works pretty good, the drano needs about 30 seconds to develop the resist, and the etchant can do a board in about 5 minutes.

mechanicalmagic
05-28-2010, 08:18 PM
I'm a user of the "iron on" method. But, the rest of the process is pretty much the same.
I think I got my last bottle of feric chloride at Frys in Milpitas. They sell board stock, both pre-sensitized and bare. I made my own tank out of lucite. Added an aquarium pump to stir (really needs it). Carbide drills I got from e-bay. (Also powdered ferric chloride, NOTE: Mixing FeCl with water generates LOTS of heat).

If there is a Frys near you, that is probably the quickest, although their stock is quite variable. Pacific Valley Electronics in Dublin and Concord says they can get this kind of stuff. Mouser.com has some boards and FeCl online.

No idea who makes light boxes.

My biggest problem was getting from my e-CAD system to a positive (or negative) that I could place over the light sensitive resist.

(PM me if you need to borrow something.)

JoeFin
05-28-2010, 08:29 PM
I'm a user of the "iron on" method. But, the rest of the process is pretty much the same.

(PM me if you need to borrow something.)

Thanks very much

I never used the iron on method and have only done "Resist Pen" method way way back in school. Initially I worry about Iron on smudging or moving a little - is it any problem?

mechanicalmagic
05-28-2010, 10:43 PM
Initially I worry about Iron on smudging or moving a little - is it any problem?

It takes a little practice, and technique.
I use staples. On each layer I put pads exactly .500" apart, OUTSIDE the board perimeter, and .100" from the board edge. After printing, I use a pin to pierce the pads, then manually put staples in the holes. This ensures alignment between the top and bottom traces, and forms a "pocket" for the PC board. That makes it hard for the board to move. I use a "special" paper and iron with about 20# pressure on the iron, and the paper turns a very light brown color. I iron both sides.

Finding the right paper (at a reasonable price) can be challenging. The commercial ones that I tried were poor. The ones that look like transparencies don't hold toner well, and will have holes and light areas. SOME photo papers work well. I found one that was great, bought hundreds of sheets. They changed formulation in the middle somewhere, some is great, some not so. No change of part number, or packaging, very slight color variation.

With a bit of practice, I was getting about 75% good board printing. Defects were obvious, missing trace segments. Acetone removed the toner, and just iron again. If the toner transferred correctly, etch was almost guaranteed success. This was mixed SMT & thru hole, with traces between the thru holes. It sure beat waiting for an outside board house.

One thing to check before using this technique, the printer MUST output an accurate image. My e-CAD allowed me to adjust the size on both axis so I got 6.00" if that's what I wanted. May seem like a minor thing, but if you have a 2" long SMT connector, they don't like the holes to be off by .050".

Fasttrack
05-29-2010, 12:22 AM
At CASL we produced literally hundreds of speciality circuit boards. The whole set-up was purchased from KepCo in St. Louis. We used photoresist and a UV light to expose the boards. The developer and etchant was bought in bulk from KepCo and the etching (which takes a little while for the heavy clad board) was done with their automated sprayer. Afterwards, the boards were washed and silver plated using "cool amp" and drilled with carbide drills.

Although the photoresist is easy, it is important to have high quality artwork. If you just print it out on an overhead, for instance, the UV light will pass through the ink and expose the entire board (don't ask how I know ;) ). For my brake-controller, I actually ended up producing masks by feeding the same transparency through a laser printer about 5 times in a row. Keeping the alignment the same during this hack job was far more difficult than using the iron-on approach ;)


FWIW, circuit boards are best sheared and then drilled with carbide. HSS works, but dulls pretty quick in the epoxy board. Abbrasive saws work but they are messy; a proper shear is the way to go.

mechanicalmagic
05-29-2010, 12:46 AM
Although the photoresist is easy, it is important to have high quality artwork. If you just print it out on an overhead, for instance, the UV light will pass through the ink and expose the entire board (don't ask how I know ;) ). For my brake-controller, I actually ended up producing masks by feeding the same transparency through a laser printer about 5 times in a row. Keeping the alignment the same during this hack job was far more difficult than using the iron-on approach ;)

My experience too.
Don't get me wrong, "iron on" is not going to work the first time out. It's quite a bit of "fiddling"; to get the proper aspect ratio; to get the correct iron temp, pressure and time; and learning to CLEAN the board before hand.

If I could get quick SOLID BLACK images on material that passes light, I would be all over it. Toner doesn't stick to that kind of plastic (that I have found). It's cheaper to go to the China board houses than get a Gerber photo plot locally.

(And I change my designs by the hour, often while a board is being etched.)

EVguru
05-29-2010, 05:04 AM
At work I produce artwork on an Inkjet printer with no problems. We used to use a Laser printer, but the distortion is too much for double sided boards.

Use OHP transparancies and print them using high quality Photo Paper settings. Let them dry on a radiator for a couple of days, or better still bake them. If you don't then they tend to stick to the etch resist and get damaged so you can't use them for more than once. For a top side layer, mirror the image so you end up putting the ink in direct contact with the resist for the crispest image.

We have a double sided exposure box with a vacuum pump to pull a membrane down on to the board so that the artwork is in the closest possible contact with the resist.

Barrington
05-29-2010, 08:16 AM
I get excellent results using a laser printer and '75 micron matt polyester drafting film' - even though it isn't transparent, the UV passes through without a problem, and the extremely fine textured finish really 'grabs' the toner.

In the past I've tried many types of 'transparencies' - all of which resulted in pinholes, oparticularly in large black areas of toner.

Even with good solid laser artwork, for the very best results I would say the exposure and development really needs to be approached in the same way as printing a photograph - i.e. exposure test strips, developer time / concentrations - a bit of trouble initially, but it pays off and once done the results are pretty repeatable.

Cheers

.

JoeFin
05-29-2010, 10:25 AM
1 question fellas

I'm looking over at Allied Electronics selection of MG Chemical's etching supplies and getting a little confused.

They have a "Positive Developer" and "Negative Developer"

AlleyCat
05-29-2010, 10:29 PM
I owned a printed circuit company for many years and may be able to help you. I use a Gerber photoplotter and DuPont photo resist laminator. Photoplotted films will provide the best results. After you fine tune the process it becomes very easy to make boards as long as you don't need plated holes. Send me a PM if you need help.

mechanicalmagic
05-29-2010, 11:04 PM
I owned a printed circuit company for many years and may be able to help you. I use a Gerber photoplotter and DuPont photo resist laminator. Photoplotted films will provide the best results. After you fine tune the process it becomes very easy to make boards as long as you don't need plated holes. Send me a PM if you need help.

AlleyCat,
Where or how can a home shop get Gerber plots output? Is this a service that is hidden somewhere in the phone book?
I can output the file type, but then all I can do is send it to a board house and WAIT.

AlleyCat
05-29-2010, 11:35 PM
AlleyCat,
Where or how can a home shop get Gerber plots output? Is this a service that is hidden somewhere in the phone book?
I can output the file type, but then all I can do is send it to a board house and WAIT.

Almost any company making printed circuits has a photoplotter. I'm sure there are several left in CA although I know many have quit the business in recent years.

I have two plotters left over from the past. One is a Gerber Crescent 30 and the other is a Lavenir RPG-1622. My concern is the availability of photo film since it seems to be a thing of the past. I plastic wrapped the Crescent 30 plotter and put it in storage but still use the smaller Lavenir. There is NO comparison between using photoplotted films and photoresist vs. the various toner and ink jet methods. Contact me by PM if you need help.

lwalker
05-30-2010, 10:58 AM
A long time ago, before laser printers were cheap enough for me to afford one, I used to take PCB artwork to the local copy shop to print on their overhead transparency printers. It was probably HPGL output, not Gerber, but I got pretty good results - nice dark output with no noticeable voids.

These days I send them out. 5 prototypes for $50 is a price I can't beat.


AlleyCat,
Where or how can a home shop get Gerber plots output? Is this a service that is hidden somewhere in the phone book?
I can output the file type, but then all I can do is send it to a board house and WAIT.