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Old 7th Sep 2018, 8:50 pm   #1
David G4EBT
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Default UV Dry Film Photoresist PCB production info in 'Chinglish'!

For the last couple of years I've been successfully using the 'dry film process' for homebrew PCBs, the method of which I described at post 24 of this now closed thread:

https://www.vintage-radio.net/forum/...UV+PCBs&page=2

There are lots of helpful youtube videos on youtube which illustrate the process, which uses negative resist UV film. Hence, the resist of any clear parts of the artwork mask remain in place after exposure and developing, and any masked areas are washed away when developing the board, so the artwork needs to be a negative. It isn't difficult to master the technique and neither the exposure time nor the developer concentration are too critical. The UV film is very cheap and the developer is 'soda ash' which is also cheap and readily available. (Only two level teaspoons of the white powder are needed in 200ml of water).

As I'm coming to the end of the roll of UV film that I bought, I've just ordered another roll. It can be bought from UK suppliers on e-bay, or more cheaply from China. By 'cheaply' I mean a 5 Metre long 300mm wide roll for £2.85 post free! Way cheaper than pre-sensitised boards, and if a board doesn't turn out to your liking when exposed, just clean it off with acetone and apply new film. The only downside to anyone who has never used the film before, is that they may struggle to understand the 'Chinglish instructions, which are probably the most baffling example that I've seen:

Quote:

‘Photoresist for Dry Film for PCB production’

Description:

• Operating steps:

1, grinding CCL, this simple, using the finest polished clean water frosted paper on the line
2, removing film, photographic film is sandwiched between two layers of film, the first side can make use of transparent tape tear torn, try a few on the line
3, and then foil, copper clad laminates can look a little cleaner, pasted, try not to have bubbles.
4, good paste membrane used presses, not too hot, about 100 degrees from the fixing.
5, the printed circuit board film, suggestion is to use film, the fine could reach the highest degree of accuracy if you did not ask for the paper to print it with sulfuric acid trip.
6, the printed circuit on the photographic plate (Note: Dry film is negative, so to highlight the print, which we usually use photographic plate opposite) with ordinary energy-saving lamps 10 or so, if there is exposure Machine 1 minutes on the line, the sun not tried, it should be 30 seconds -60 seconds, the exposure process Obviously, since the photosensitive film will change color when exposed to light, the light becomes dark blue. You will easily see your circuit diagram appeared on the board.
7, developing and tear the protective film on the front panel, into the developer (developer according 1:100,10 gram Total 1L of water) to be used when developing a little harder stick cotton wipe board.
8, etching, this goes without saying (ferric chloride etchant environmental For protection, hydrochloric acid + hydrogen peroxide, etc.) is recommended environmental etching shop, fast, clean, no odor.
9, after a good CCL etching, stripping, from film watered by 1:60 or 70, the board bubble like a few minutes
10, after the completion of the board, very pretty good, most dense line spacing is 0.1mm, width 0.1mm, 0.1mm lines do know though is very easy to do, but do 0.1 lines and 0.1 line spacing dry film can easily do it.

End quote.

It probably all makes sense in Chinese.

All the really matters is that the UV film is great product, and at only 18 pence a square foot, experimentation won't break the bank.

Below is a recent example of a PCB that I've made using the dry film process.
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Old 8th Sep 2018, 2:54 pm   #2
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

David- your next project( if you accept it, in mission impossible terms,) is to turn the chinglise into English. I did get a roll from a similar supplier with almost similar instructions, but more, fortunately, I did have a course or four at a well known Japanese communications HQ and now know how to translate Oriental lingo, the only difference is that my experience is of Jingloenese.
My UV roll was of a similar price (thanks to you ) and the few times I've used it makes it easier to use.
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Old 8th Sep 2018, 3:19 pm   #3
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

This happens because many Chinese companies simply put the Chinese text through very basic translation software. It is never seen by a competent English speaker so nobody is aware that it's incomprehensible. There are umpteen examples of this on the net - my favourite is the restaurant proudly named "Translate Server Error".

https://en.wikipedia.org/wiki/Chinglish
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Old 8th Sep 2018, 3:35 pm   #4
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

Not just Chinese, but in the early day's Japanese firms. I was sent on a large Jap comms firms course on a small product and learned HOW to translate the terms in the manual. After that working on and programming any of the range was child's play.
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Old 8th Sep 2018, 7:56 pm   #5
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

this is for a " tube " amp of a well known site : Sound review

Overall all frequency are balanced, with the full tube flavor characteristics, the full sense and intensity of low frequency, IF is warm mellow, and it has a special advantage in high-frequency. The high-frequency structured throughout, with great accuracy, but did not split at very high frequency, sound details, stretch and bright high-frequency controlled well.
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Old 8th Sep 2018, 8:41 pm   #6
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

I suspect that any attempt I ade to convert English text into Mandarin, using any automated translator or whatever would be even funnier to any native Mandarin speaker. So I'm disinclined to criticise errors in translation or idiom too strongly.

Native English speakers are a bit too thin on the ground in some areas of China, so getting one to look over the finished work might not be feasible.

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Old 8th Sep 2018, 9:36 pm   #7
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

I’m glad you’re doing well with this. Honestly I have given up making my own PCBs now. I was having such a hard time getting everything right in the production phase and the results were starting to make some of the more complex designs I was putting together really hard to pull off.

But did some reasearch and I have discovered two wonderful things in the last 6 months: cheap Chinese board houses (JLCPCB) and cheap Chinese SMD parts (LCSC). I can now have ten double sided boards with niceties such as solder mask and plated vias up to 4 inches down each side for £11. Think I spent £8 last time and got about 3000 parts to fill them up with.

The boards are actually only $2. The rest is delivery which takes 10-12 days from ordering.

And if it goes wrong you get some nice coasters
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Old 9th Sep 2018, 5:36 pm   #8
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

For anyone who does have a UV light box and would ordinarily use pre-sensitised laminate, regardless of the Chinglish, I can certainly recommend the dry film process. The exposure time isn't critical, nor is the (cheap!) developer concentration. When developed, the film leaves a much thicker resist layer than does pre-sensitised positive resist laminate. The film Is so cheap that a few mishaps are irrelevant.

True - it makes no economic sense to make one's own PCBs, and if we factor in our time, it makes even less sense. Except for one thing: hobbies are about the enjoyable use of scarce leisure time on such activities as interest us most, and from which we derive most satisfaction. For me, I enjoy designing and making PCBs for simple projects as part of my home-brew activities, so neither the time nor the costs enter into it.

To maximise my chances of success, there are a number of things I avoid:

I don't do any SMD work and I don't do double-sided PCBs though I guess I could if I wished. As far as I can, I only make PCBs that I've designed myself. If designed by someone else - eg, magazines of yesteryear - I adapt the artwork if need be. For example, if I think the tracks are too narrow or the pads too small, which I've found is invariably so with free design software such as Express PCB, (not really intended to be for home PCB production, but to be uploaded to a PCB pool for commercial production). That said, I know some constructors get along nicely with it.

About the most complex PCB I've made in recent times is for the Radio Bygone Wobbulator (which later featured in the BVWS Bulletin some years ago). It was a nicely designed PCB as with all R.F. Haigh designs, but even so, I still beefed up the tracks a little and slightly enlarged the pads. The PCB turned out fine. Colin Armstrong, (who isn't active on the forum these days), designed a little 'sawtooth generator' for the 'Wobby' and the PCB for that too was a success. (See pic below).

However much we may try, we can't attain commercial standards but that's never been my aim or yardstick. All I've ever tried to do in my homebrew activities is to attain as good a standard as can be achieved by any hobbyist within the limitations of a home workshop, in both workmanship and appearance, externally and internally.

I use a decent mini-drill in a good quality drill stand and a home-brew speed controller (constructed on a home-brew PCB!). I use 0.8mm HSS drill bits and to obviate the risk of 'skidding' I discard the bits after each PCB except if the PCB is small. HSS bits are so cheap from China, it's not worth trying to make them last.

I couldn't get my PCBs made commercially in any event as they call for 'Gerber Files' whatever they are.

I'm too far down the food chain for that malarkey! I try to aim for low tech/high skill as best I'm able.
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Old 9th Sep 2018, 6:37 pm   #9
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

Quote:
Originally Posted by Oldcodger View Post
Not just Chinese, but in the early day's Japanese firms. I was sent on a large Jap comms firms course on a small product and learned HOW to translate the terms in the manual. After that working on and programming any of the range was child's play.

Many years ago I went for a job with a UK arm of a Japanese manufacturer of ophthalmic equipment. As the interview progressed, it become obvious that a core part of my work would be to re-write the "English" manuals supplied by Head Office such that the UK sales force and customers could understand them - I didn't proceed with the application as at the time I was looking for something more "hands on" than a technical author role.
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Old 10th Sep 2018, 3:03 am   #10
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

Years ago, we could only get the dry film in 300m rolls and it was expensive if you weren't buying large quantities.

It was cheaper to get a local pcb production house to supply pre-laminted 12" x 18" pcb sheets (I used to do the things they weren't interested in - hobbyists, small jobs etc).

OT - David, which issue was Colin's Sawtooth project in please, I'll have to see if I can get a back issue.
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Old 10th Sep 2018, 11:35 am   #11
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

Quote:
Originally Posted by Terry_VK5TM View Post
OT - David, which issue was Colin's Sawtooth project in please, I'll have to see if I can get a back issue.
It wasn't a published design - I think Colin probably designed it himself, and the associated PCB.

It was back in 2009, when the Radio Bygones wobbulator was being built by several forum members, myself included. Colin hadn't wanted to use his 'scope timebase, so he built a sawtooth generator into the wobbulator and redesigned the front panel to add a timebase control. To quote Colin:

"The circuit for this used a couple of discreet transistors, a 555 timer IC and two Op Amps from a Quad LM324. I used the other two spare Op Amps in this as high impedance buffers for the output of the wobbulator. They also serve to invert the output so the ‘peak’ on the scope is up rather than down".

Colin kindly sent me the hand-drawn circuit and PCB layout, along with the re-designed front panel for the wobbulator. He's not been active on the forum for quite some time and I'm not in touch with him, but I don't think he'd mind if I posted the circuit in the homebrew section of the forum, acknowledging that it's his work - not mine, so rather than take this thread off topic, I'll do that.

As to the RB Wobbulator, as has been mentioned several times, the four Toko coils required have been unobtainable for some years, and the varicap diode is also difficult to source, so for anyone wishing to homebrew a wobby, they'll need to look for another design.
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Old 10th Sep 2018, 12:20 pm   #12
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

I've emailed Colin to seek his permission to place the circuit for the sawtooth generator on the forum.

If that's forthcoming, I'll add a thread in the homebrew section.
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Old 10th Sep 2018, 12:51 pm   #13
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

Random completely off topic, but I found this design for a wobbulator a while ago: http://www.intio.or.jp/jf10zl/csg.htm (probably replace the FETs with J113 / BF245 etc fine and varactor with 1SV149 from aliexpress, FB801 with trifilar wound FT37-43
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Old 10th Sep 2018, 2:07 pm   #14
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Default Re: UV Dry Film Photoresist PCB production info in 'Chinglish'!

Thanks David
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