UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Hints, Tips and Solutions (Do NOT post requests for help here)

Notices

Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

Reply
 
Thread Tools
Old 16th May 2020, 12:20 pm   #1
Wendymott
Octode
 
Wendymott's Avatar
 
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,112
Default One off PCB's

Hi Peeps..... When I am making / designing various electronic apparatus, often several prototypes are required, my usual M O, is to use the photo sensitive pcb material, but its getting a bit expensive..and at the moment my supplier CPC has vastly reduced its stock holding..of photo resist material....thus I reverted to the Hot Iron transfer method...I think it is worth recording my successes and failures to you.
There has been many articles / posts in the past recounting using glossy magazine paper and the like, of which I had several failures, however one of our members suggested glossy photo paper. At the time.. I bought some and had varying results.... thus it was shelved... till now.
I had reason to make 3 different pcb's, and the photo resist method was too expensive... thus I tried the hot iron again.
One of the pit falls is the spacing of pads and tracks.... the resolution is not great.. thus MINI SMD IC's are not worth attempting... however discreet SMD components, and leaded devices are OK.
When designing the artwork, ensure there is reasonable spacing between tracks and pads, otherwise bridges may occur.
At first I was cutting the pcb material nearly to size..WRONG..you should leave about 10mm on each edge oversize.
I often print at least two artworks, as if one fails you have another to use nearly straight away
Clean the substrate (pcb copper) very thoroughly... I use brillo pad...I did try Acetone...... which was NOT to be recommended, as it has some chemical effect on the toner.
I then use masking tape to hold the pcb to the work surface, this is done at each end of the pcb but NOT in the area of artwork.
I mark the back of the art paper with a felt tip pen, the outer limits of the artwork, so you can judge that it is in the right place... then masking tape the artwork to the bench.
I then apply the heat from a domestic iron for about 3 minutes, working to all corners etc. Leave to cool.... do not rush this..
remove the masking tape and the artwork should be well adhered to the copper.
Place in a bowl of water for 10 mins to allow the paper to soften... remove carefully working the paper away from the copper...
When the backing is removed gently remove the residue... I use a soft sponge pan scrub as the toner is quite hard.
When it looks clean, look again under a magnifier, to remove any residue left, usually in drill holes and between SMD pads, I use a sharp craft knife for this.
If any of the toner has been removed, it is usually around the edges, thus black marker can be used to make up any errors.
If it is ok, then etch..........mine usually takes about 10 mins at 25 deg C with air agitation
The pcb shown took about 30 mins in total. Remove the toner residue with brillo pad, and check under the magnifier for any bridges...
IF you do not have success first time.. clean the copper with the brillo pad and start again..not like photo resist where its lost...
I hope that my experiences are of use to some.
Attached Thumbnails
Click image for larger version

Name:	PCB.jpg
Views:	135
Size:	24.9 KB
ID:	205976  
__________________
Should get out more.

Regards
Wendy G8BZY
Wendymott is offline   Reply With Quote
Old 16th May 2020, 3:42 pm   #2
radioman
Hexode
 
radioman's Avatar
 
Join Date: Apr 2003
Location: Ayr, Ayrshire, UK.
Posts: 494
Default Re: One off PCB's

Thanks Wendy - very useful information.
I'll be trying this method for my next one-off PCB.
One question though : What temperature setting is best on the iron ?
(Hope this isn't a stupid question !)

Andy
__________________
G-QRP #12697
radioman is online now   Reply With Quote
Old 16th May 2020, 7:11 pm   #3
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 4,227
Default Re: One off PCB's

One issue with using very abrasive material like steel wool etc to clean plain PCB is that it can leave tiny surface scores and scratches which provide a kind of capillary route by which the etchant can flow in underneath the etch-resist, sometimes resulting in a nearly invisible etched break in the track where the etchant has followed the line of the scratch.

I would try to use something less aggressive for initial cleaning of the PCB, maybe a cleaning 'rubber' specifically made for the purpose.
SiriusHardware is online now   Reply With Quote
Old 16th May 2020, 8:27 pm   #4
Wendymott
Octode
 
Wendymott's Avatar
 
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,112
Default Re: One off PCB's

Andy.. NOT a stupid question... as HOT as you can..just remember though.. the copper and board will retain heat for a while so do NOT burn yourself.
I forgot to mention that I only use this method on scrap Phenolic board.... Fibreglass seems to have an unwillingness to co operate.
Yes Sirus... but these pcb's are for prototypes not the finished article..if I get any under cutting.. its a small price to pay..for final boards I always use Photo resist material... but thanks for the "Heads up"
__________________
Should get out more.

Regards
Wendy G8BZY
Wendymott is offline   Reply With Quote
Old 16th May 2020, 11:03 pm   #5
Oldcodger
Octode
 
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 1,613
Default Re: One off PCB's

Wendy- I did try this with sort of paxoline PCB and with normal iron temperatures i had no joy, but with higher temps had the copper come away from the pax. I now use a (home made ) light box and negative resist.
Oldcodger is offline   Reply With Quote
Old 16th May 2020, 11:27 pm   #6
Wendymott
Octode
 
Wendymott's Avatar
 
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,112
Default Re: One off PCB's

Hyas Mr Codger... I still use photo resist pcb's but as I say for odds and sodds now..its getting too expensive..the clear film I use is getting difficult to obtain.. I use NOBO Laser film and it is difficult to buy now..obviously there will be alternatives.. but we like what we know. We all know.. what works for one.. may not work for another.
__________________
Should get out more.

Regards
Wendy G8BZY
Wendymott is offline   Reply With Quote
Old 17th May 2020, 12:34 am   #7
Terry_VK5TM
Octode
 
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 1,326
Default Re: One off PCB's

Look up 'photo resist film' on ebay etc.

Very cheap (although you have to wait for shipping) and you can make your own photo resist board in much the same manner as using the iron on technique.
__________________
Terry VK5TM
https://www.vk5tm.com/
Terry_VK5TM is offline   Reply With Quote
Old 17th May 2020, 10:28 am   #8
David G4EBT
Dekatron
 
David G4EBT's Avatar
 
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 4,099
Default Re: One off PCB's

Quote:
Originally Posted by Terry_VK5TM View Post
Look up 'photo resist film' on ebay etc.

Very cheap (although you have to wait for shipping) and you can make your own photo resist board in much the same manner as using the iron on technique.
In the UK, negative photoresist dry film is actually quite cheap from UK suppliers.

EG: 4.59 post free for a 1 metre roll 30cms wide.

https://www.ebay.co.uk/itm/UK-1Roll-...UAAOSwY5pen-OU

It comes in a black light-proof wrapper and if kept in that wrapper it doesn't seem to degrade over time. I'm still using a roll that I bought in 2016 when I first started using this technique. I keep the roll in a desk drawer, unwrap it in subdued light (curtains drawn to keep out UV), cut off what I need and pop the roll back in the drawer.

I only buy genuine fibreglass FR4 laminate - not SRBP laminate, which is sometimes wrongly described on eBay as 'FR4'. The copper on SRBP has poor adherence to the substrate.glass-reinforced epoxy laminate material. FR-4 is the NEMA designation for composite material composed of woven fiberglass cloth with an epoxy resin binder that's flame resistant (self-extinguishing), which is why it's terms 'FR'.

https://en.wikipedia.org/wiki/FR-4

I clean the laminate with 0000 grade wire wool and wipe it dray with methylated spirt (known outside the UK as 'de-natured alcohol') and the film adheres really well.

There's no doubting that for occasional one-off PCBs the iron-on technique wins hands down. It obviates the need for a UV light box, creating a UV mask, applying the UV film, getting the correct exposure duration, the correct developer concentration, and all the associated costs. But if a UV light box is to hand, or if anyone wants to make a cheap UV exposure light, the negative resist film technique has much to commend it.

In the four years since I started using negative dry film, I guess I've successfully made more than fifty boards, (though none this year as my interests are developing elsewhere).

Whatever technique is used, at the design stage it will pay dividends to make the tracks as wide as they can be and the pads are large as they can be. Thin tracks will be undercut at the etching stage, and even if a PCB drill in a drill stand is used, small pads can easily be mis-drilled by the drill bit skidding or can tear off the pad. The more copper that can be left on the board, the shorter the etching time and the less the risk of undercutting. Many PCB CAD programs are intended for use in commercial PCB production and don't entirely lend themselves to DIY PCBs unless the tracks and pads are beefed up.

In all that I do, I aim to attain as good a DIY result as I can, but at the end of the day, even if a DIY PCB wouldn't win a beauty competition, if it's functional and we enjoy doing what we do, it's mission accomplished.

And yes, it makes no economic sense to go through all the rigmarole when we could send a Gerber file to a PCB house and get top quality commercially produced PCBs, but if we applied a cost/benefit analysis to any aspect of this or other hobbies, it wouldn't stand close examination. Except of course that we can't put a price of the enjoyment we derive. If it's not enjoyable, we wouldn't do it.

A couple of past forum threads on PCBs here might be of interest:

https://www.vintage-radio.net/forum/...//www.vintage-

https://www.vintage-radio.net/forum/...d.php?t=149574
__________________
David.
BVWS Member.
G-QRP Club member 1339.
David G4EBT is offline   Reply With Quote
Old 17th May 2020, 11:12 am   #9
Wendymott
Octode
 
Wendymott's Avatar
 
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,112
Default Re: One off PCB's

Hi Terry and David. I bought some of that Negative film..... not used it yet..I wanted "Quick and dirty"....which the above method suits....The reason for the original posting was..it had been mooted many times and I had had very varying non success ... so I decided to have another go.. this time the process seemed ok..so I commented on it...as the methods previously were a bit scant...when I get to the full blown project it will be Positive photoresist as normal... Thanks for your inputs ALL of you
__________________
Should get out more.

Regards
Wendy G8BZY
Wendymott is offline   Reply With Quote
Old 17th May 2020, 11:18 am   #10
stuarth
Hexode
 
Join Date: Feb 2010
Location: Heysham, Lancashire, UK.
Posts: 438
Default Re: One off PCB's

If you're only producing a one-off, what about MEPads and Manhattan construction. Excellent for RF, especially if using the underlying board as a ground plane. You can get quite neat results, and it can be modified or added to at any time. They produce tiles for DIP and SOICs, and even for some valves (B9A, B7G, Octal and Acorn, I think).

Stuart
stuarth is offline   Reply With Quote
Old 17th May 2020, 11:33 pm   #11
Oldcodger
Octode
 
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 1,613
Default Re: One off PCB's

Quote:
Originally Posted by Wendymott View Post
Hyas Mr Codger... I still use photo resist pcb's but as I say for odds and sodds now..its getting too expensive..the clear film I use is getting difficult to obtain.. I use NOBO Laser film and it is difficult to buy now..obviously there will be alternatives.. but we like what we know. We all know.. what works for one.. may not work for another.
Wendy- lots of years ago (when my eyes were a lot younger, and my hand a lot steadier) I used marker pens to produce my PCB. But some time ago I noticed that nail polish pens were available. This might be a better alternative for one offs .I've used "not wanted" pots of Swimbo nail polish to produce a keyboard, and it was a no problem job, so prrhaps if found, these nail polish pens might be better. Not a blokkie topic, but Swimbo does like to help me out in my hobbie
Oldcodger is offline   Reply With Quote
Old 18th May 2020, 12:33 am   #12
Terry_VK5TM
Octode
 
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 1,326
Default Re: One off PCB's

Quote:
Originally Posted by David G4EBT View Post

It comes in a black light-proof wrapper and if kept in that wrapper it doesn't seem to degrade over time. I'm still using a roll that I bought in 2016 when I first started using this technique. I keep the roll in a desk drawer, unwrap it in subdued light (curtains drawn to keep out UV), cut off what I need and pop the roll back in the drawer.
I bought low UV output flouro tubes for the workshop so that I could have decent light while making pcb's, saved squinting in the dark to see what I was doing.
__________________
Terry VK5TM
https://www.vk5tm.com/
Terry_VK5TM is offline   Reply With Quote
Old 18th May 2020, 9:50 am   #13
Wendymott
Octode
 
Wendymott's Avatar
 
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,112
Default Re: One off PCB's

Hi Mr Codger......Hmmmmm it would certainly help in repairs to any artworks damaged in the pre etch part. After lock down I will venture into town to buy a couple from the market. Terry.. thats the trouble with some processes...I made my UV light box with about 100 UV leds.............. then to add to the box I added white leds between the rows of UV ones ... selectable.... and On / Timer...to aid registering my two copies of positive arts. Great this hobby... so many views and persons willing to advise
__________________
Should get out more.

Regards
Wendy G8BZY
Wendymott is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 9:35 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.