Home made PCB using light to transfer...

Hi Im making my up my own PCB (oneside) I haven't tryed to make double side yet.

What im doing is im Taking a copy of the circuit layout
(or making it on the computer) in the sice 1/1 the Photocopy it on overheadprojector plastic. I take 2-4 copy's
and put them on top of eachother, it have to be done very pricise. them I put the copys of the circuitlauout on top of a light sensitive PCB. And use an old artificial sun lightbulp to light the Board.
then I put the Board in a small basin with Ironcloride.

Where the Board had get light the ironcloride move the copper. and the nice Circuitboard Is then ready. Take care it dosen't be in the acid to long.

I wan't to know If anybody is making PCB like this?

I was thinking that It woud be nice if there could be a place on this page where people can put the PCB schematics
they have make for other people to save some time.
there is so maney circuit on the page, but very time I have to build something I have to use a lot of time to make up a smart circuit board first.

why not make a circuit (schematis arcive) ?
 

hifi

Member
2001-03-06 3:07 pm
sweden
no f*cking gerber files...sorry about my language but it would be much simpler if people just used regular jpeg / gif / bmp and specifyed the measurments of the boars...maybe not i dont got any program for gerber files....can acad hadle it ?.....then it would be fine but not as is atleast not for me....i usualy uses acad photoshop and good ol´d paint =) when making and remaiking circit boards...

i use HCl and H2O2 in a 1/3 1/3 and the rest water mix for etching what do u call these chemucals in english? ....


/micke
 
hifi,
it's always nice with an openhearted debate, and I'm sorry I didn't make my intentions clear from the start. My idea was, that uploaded gerberfiles should be made visible/usable to everybody, but that might be to big a task for our kind host, since there are a lot of gerber formates out there.
JPEG-formates tend to get a bit smudged at the edges, and paint usualy makes it look like a jig-saw's teeth, but of cause it can be made in JPEG or GIF, if thats the prefered formate.

And to Karsten/km.
You ask: <home made boards?? why?? >
I answer: because some of us are true DIY-people, who like to Do It Yourself. It's true that if someone has gone through making a layout, and paied the start-up costs to the PCB-manufacturer, each PCB won't be expencive, but still, personly I find it a lot more interesting to DIY.
Another idea would be to make a forum, perhaps even within this, where people/companys can sell their PCB. Just an idea.
 

hifi

Member
2001-03-06 3:07 pm
sweden
hmmm.....it is also way easier to make prototypes at home it would be expencive to get every single board manufactured proffecsionally....

i got rather good facilities to make circuit board ...uv lightbox and etch tanks. a real nice drill with an xy table

only problem is when it needs to ble plated through holes and really really smal SSOP devices...otherwise homemades works great!
-------------------
yes that is a problem with jpeg (bluring edges) but PDF?... it would be nice to have a format that saves board meassurments ....

/micke
 
Hi,

The way I proceed:

I always work on a computer, with Ultiboard or an old program called ezboard. Then I print it on a fine coated paper with an inkjet printer at 720dpi. The print is reversed (view from the component side).
I use two actinic UV 25W tubes (this was a kit, very afordable), I use white spirit on the paper to reduce exposure (it dries quickly but it is usable). Inked side is directly on the photoresist to avoid blurry edges. It takes about 8min to expose well, precision is very good.
Then I use the standard ironcloride (in a low cost eching machine).

another solution is to print with a laser printer on a semi transparent paper (this paper is very difficult to find). retroprojection film are not very good: not enough contrast and very poor precision and high cost.

For distribuing the files. The best way is to print it with a postscript driver on a file (there is one free driver at http://www.adobe.com ) then using the ghostscript program to convert it to pdf (see http://www.pdfzone.com for more info). In this way there is no problem with dimension or exotic file format.
 
Home made PCBs

Home made PCB can be very OK, if done the right way...

Making artwork-:
PC printouts can be OK, but normal transparent printing film does often give insufficient dying to be used for films, and thus have to be printed with several layers. This will usually give rather blurry edges, but this is OK if the leads and solder lands are at least 1mm and 2 mm dia resp. (appx. 40 and 80 mils ). There is a film product on the european market called LASERSTAR, which gives excellent results with laserprinters. I use it for prototyping down to less than 10 mil leads and ICs in QSOP, .62 mm ( 25 mil )pitch. This looks very much like the semitransparet plastic drafting film that was used earlier, very smooth but matte surface. Special permanent ink pens will also do the job for very crude projects.

Exposure can be done by sun tanning lamps, black light tubes etc. but lamps with a "blue actionous" output ( appx 380 nm) works best. Even sun light will do..... On the european market, there is a fluorescent tube from OSRAM called TL20/05. Two ore more of these ( appx 10-20 EUR each ) i a proper lamp will do an excellent job for the advanced hobbyist. Exposure time will have to be determined by trial and error, 2-3 mins at least with normal positive resist PCB materials.

Developing for the common positive resist PCBs in Europe will be done in a solution of sodium hydroxide of 12 grams to the litre. Common caustic soda does an excellent job, but stick to the recipe and use exact weight.

Etching can be done by a saturated ferric(3)chloride solution, or by sodium peroxide at appx 200-250 g pr. litre. Both solutions works best elevated to appx.45 deg C. and even better if air is injected in the solution. Aquarium heaters and pumps can do a good job, in lack of Pro equipment. A tall and slim tank, glass or plastic, with heat and air, will make an excellent hobby etching machine.
Clean the boards well and dry..
Another recipe calls for 40% Hydrochloric acid ( HCl, and 40% hydrogen peroxide ( H2O2) and water in a mix of 1-1-2. This is also an excellent way, but be accurate with the mixing ---but-- the process releases a little bit of chlorine gas, so operate only in good ventilated areas. This solution cannot be stored and must be mixed prior to use.
**ALWAYS PUT ACID (CHEMICALS) INTO WATER,--NEVER the other way round...
Have fun........

BTW- the idea of a file server is excellent, and I think postscript or PDF files is a good idea, even if I would like to se Gerber's myself.....

[Edited by AuroraB on 06-27-2001 at 09:02 AM]
 
I've almost finished my first PCBs I made myself.......not sure how much I just would've rather paid but it worked perfectly up until the actual etching part.....Because I didn't have an adequate way at the time to heat the etching solution to the specified 110-130 degrees farenheit it took a long time. Adding to that, I was using 2oz copper and I basically spent 3 hours with very little of the board actually clear of copper, but wow are those traces thick!! I feel a VERY noticeable bump in the board where the copper is so I guess it has to remove a lot of it.

Anyway, going to finish it again today with some heat in the solution!
 
Hiya All :)

2 Comments:

1. I agree with all those people who have suggested printing to the "purpose" inkjet OHT films. Inkjet works better than a laser for this purpose, but only if you use the correct plastic film (polycarbonate, not polyester).

Even so, always check the tracks against a strong light before burning the boards!

2. Regarding file formats. If you use JPEG at standard compression there will be "bleeding" at the track edges. The best solution is GIF or TIFF using LZW compression (same as Zip = no data loss). This will produce a perfect image - all you need to specify is DPI for printing, which could be done in the filename. If you want to use JPEG then some of us will be able to store these as "low-compression" JPEGs and these will be nearly as good as GIF/TIFF. If you choose PDF you must remember to change the image storage options in the writer, because the standard is medium-compression JPEG at 150dpi !!! Fortunately, this can be changed to Zip at higher DPI as required. The later would also be fine as a "standard".

Lastly ...... "why make home PCBs?" ...... well, if you are somewhere where you can get milled boards cheap I am envious, for many of us these are much more expensive than etched boards.

cheers, mark
 
Hello all,

i have to second: yes, inkjet is bettre than laser. And inkjet OHP films can give incredible good results. Provided the right brand is used. If you do not have satisfactory results with one brand, try the next brand until you arrive at the right one.

A friend of mine (hoping fervently he will find his way to diyaudio, too, he curretnly builds an electronic church organ unsing sampled sonic patterns digitally recorded from an ancient church organ) makes SMT artwork with pad grid of 0.5 mm only and trace spacing of 0.18mm. I saw PCBs he made from those artworks printed on OHP film which are simply flawless. No under-etching, no holes in traces, just perfect. He reported he had to switch from HewlettPackard films to those made by Zweckform (German manufacturer) to reach that standard.

I went thru all those differnt artwork procedures out there , had failures with OHP film (HP brand) and settled on thin paper (1:1 inkjet-printed) having a weight of 50grams per square meter. Flawless results also. but expose times of 26 minutes with my Philips UV face tanner using six actinic UV 25W tubes. Having the the printed side touching the photoresist is essential.

But this Zweckform film my friend recommends will be my next experiment, i want to get rid of this 50gr paper.

Etching:
FeCl is unspeakable, moreover it causes nasty wounds (contamination not noticed at once) and it causes unremoveable yellow-brown spots in clothing, on the floor, everywhere. And it needs to be warmed which makes it more agressive not only to the etched copper. A mess. And heavily underetching.
Ammonium-Persulfate ( (NH4)2S2O8 ) and its enhanced versions like Seno Feinätzkristall doesn't work at room temperature, it has to be warmed. And it tends to starve during etching, no way to boost it then. And it etches way less than "promised on the package". Tried it out. But it causes no peripheral nastinesses and messes ad etches fine. Moderate underetching. Not good enough in total.

For etching i only can recommend the Hydrochloric acid process using HCl and H2O2 .
Mixture:
HCl ~35% ("smoking"): 200ml
H2O2 30%: 30ml
water: 770ml
use more H2O2 for boosting (careful !!)
Use of a rather fresh mixture recommended (else the H2O2 will degrade), but up to 4 weeks of age are not a problem. Keep all stuff away from light when not in use.
Most efficient, this process etches atleast as much as "promised on the package" and it is adjustable to your needs by changing temperature. It doesn't suddely stop if too much copper already is dissolved. It can be boosted if weak by adding H2O2.
During etching i have the water tap running, noo problem with human skin or eye if HCl exposure is below 5 seconds, no permanent damage then. Been there, done that. During school and university i used HCl (and a running water tap within short reach) to get my hands really clean (after painting or repairing machinery).
H2O2, makes it a bit more tricky, admitted, as the peroxide has the oxidating potential the hydrochloric acid has not (human skin get permanently damaged by oxidating acids only, of course also non-oxidating acids have to be washed away at once)
Ok, back to PCB etching, this process etches faster with increasing temperature but it works already at room temperature. Then there is no observable under-etching. Even at 50°C underetching is way lower than with Ammoniumpersulfate. At 90°C under-etching is higher than Ammoniumpersulfate at 50°C and etching goes very fast: 70µm copper within 10 seconds. Provided you dare to have almost boiling hydrochloric acid on your oven :)

Moving/stirring the etching bath is essential with HCl but not as essential as with the other processes mentioned above. I mainly used transparent etching bags with HCl/H2Os inside and warm water outside for waming the etching bath. This is very safe but has 2 strong drawbacks:
1st
etching is way stronger at the PCB edges so underetching occurs near edges but not in the middle of the PCB. Stirring is too unequal. This is natural as the acid is streaming not laminarly but turbulently over the edges and so the acid movement is way higher there.
2nd
the edges of the PCB have to be ground very smooth, otherwise they cut through the etching bag.

Stirring the bath:
I do not recommend strring up the etching bath with air bubbles blown in at the bath's bottom. They tend to kill the etching process and they are a sure way to kill if toomuch air is used. I made 1st tries with an upright etching cell and a sled on its top with two parallel downwards oriented glass rods. During etching i moved this sled manually back and forth: the glass rods were parallelly moved over the PCB in constant distance without touching it. Very satisfying results; i will settle on that.
 
Alternative to etching.

At a recent convention, I was introduced to an Irish company that will make proto-type (or hobbiest quantity) PCBs

pcb-pool.com

Very attractive pricing. (low minimum. Just email your files, and they return you board(s). Plated through, soldermask, silkscreem, 4 layers.

They accecpt many type of PCB CAD files. At the prices quoted, it is not worth dealing with the chemicals.

I have no connection to this business. I am just passing on what seems like an excellent option.
 
PCB Board on Yahoo

at www.groups.yahoo.com there is a diy PCB forum started up by one of the guys on PICBasicPro mailing list, the URL is:
http://groups.yahoo.com/group/Homebrew_PCBs/ there are over 200 members in this forum.

I use positives PCB's which I generate using Ultiboard, develop the boards in a 3% solution of NaOH, and etch in FeCl. The only problem I've had with Ferric Chloride is that it will stain anything. I use a kodak darkroom syphon to stream a 130 degree water around the corningware that I etch in.

I have also used the direct printing method using an HP 7475a plotter and adapted Staedler waterproof markers-- for those of you who remember how to use a serial plotter! The plotter method requires a little software skill with the output generated by Ultiboard, but it yields quick clean results. HP 7475a's go for ten to twenty bucks on EBay.
 
I just hope none of you lets the finished solution of copper salts run down the drain. In Germany, most community wasteyards will accept "household" chemicals in small quantities.

Small projects that can be printed with the trial versions could be posted as original files. For example, Eagle will let you make up to 100x80 mm² with the freeware version.

Dice:
One used to be able to buy hydrocloric acid in hardware stores (Baumarkt), but I haven't checked recently. But where do you get hydrogen peroxide solution outside of a pharmacy and at pharmacy prices?

If you have problems with the pcb piercing the bag, try freezer bags. Aldi has a nice quality, but only one size. For larger bags, look at the Melitta products in any supermarket.
 
This is may method, proven hundreds of times:
Doing the layouts at home (Eagle, www.cadsoft.de), printing PDFs using Acrobat PDF Writer at 600dpi (no compression), mail it to the office, searching the best printer; It still seems to be that very old apple laserwriter (600dpi). Printing is done on 100g/m² transparent paper.
Exposing takes 4 minutes with a diy solution using 4 8w uv-tubes, chemistry starts with 10g NaOH on 1l water.
The greatest etching tool I ever used comes from www.radixgmbh.de, uses a special kind of FeCl and takes only about 2 - 3 minutes to achieve excellent results.
 
PCB's and plotters

I forgot to mention, I scanned, OCR'd and put most of HP's manual on the HP PCL/Graphics Language on one of my websites www.tech-diy.com (along with a bunch of other stuff, of course.) As indicated, these plotters go for about $10 - $20 on EBay, you can easily affix a copper board onto a piece of mylar with scotch tape and let it rip! It is necessary to modify a Staedler waterproof marker to fit into the caracass of a plotter pen -- not that difficult.

The advantage of the plotter method is that you don't have to go through any photographic process to generate traces.

I had also mentioned that there is a modification necessary to get the plotter to plot quickly -- this involves modifying the Arc Absolute command (AA) to cut a circle with a 15 degree arc, instead of the 1 degree arc which Ultiboard specifies -- this is easily done using "Find and Replace" in MSWord.

Replying to the poster who uses a 1% solution of NaOH, I found that this was too slow in developing positive boards, 5% is much too concentrated and develops off everything in a matter of seconds. I did try to use Drano, but didn't find it satisfactory compared to laboratory NaOH.