doing PCB's but maplins are confusing

[Thunderchild]

I'm thinking of buying the following:
Pre-Sensitised Copper-Clad Board : Printed Circuit Boards : Maplin

but it looks like this tuff needs an extra step in etching, why do I need to put the board in hydrogen peroxide to remove unwanted photoresist before etching ?

what is the standard pcb making process and is this what I'm looking for, unfortunately when i read maplins product reveiws I get the impression they are a bunch of amateurs at best and i can find what I want on RS

 

[gaspode42]

Hi

How are you thinking of making your PCB? There are two methods, the Maplin way (as above) or toner transfer. If you use the Maplin boards then you have to expose the layout with UV which hardens the photo-resist. You then remove the unexposed photo-resist using NaOH. If you use toner transfer or Pulsar film(s) then you just need copper clad board without the photo-resist. Hope this helps.

 

[Thunderchild]

I'm using UV and so far thought thatit was a matter of exsposing end etching, never heard of this intermediate stage, but then so far I've found maplins to be charlies at getting thigs simple, the only thing thats been simple so far with maplins is pay more for stuff than its worth. I think i will go to rapid, I can't find photosensitive boards on RS is it really possible that they do not do them ?

 

[gaspode42]

Yes they do - see here

 

[Thunderchild]

criky their search functions are crap ! I hunted hight and low. so whats the difference between presensitzed and photo-resist ? or is it just two words for the same thing ?

 

[gaspode42]

I think the answer is that they are 'presensitized' with 'photoresist'.
They will still require developing though, I have attached the data-sheet for you.

 

[Thunderchild]

Hi gaspode, yes seems like I was a step behind, I'll have to browse RS a bit and get more stuff

 

[Wp100]

Hi,

Thunderchild I'm using UV and so far thought thatit was a matter of exsposing end etching, never heard of this intermediate stage

A photographer never heard of developing and fixing ? - really ..

As mentioned in my recent UV file, buy quality pre sensitied pcbs from RS or Farnells, use the RS Sodium Met. to develop the uv exposed image as its less aggressive and gives you time to control the process - they wouldn't be selling it if it wasn't any good.

 

[Thunderchild]

well I worked for a printers and oops yes thats right or actually I'm not sure but I remeber the press plates were made by exposure and then developing as in etching but maybe I'm wrong, yes i know how photographic devepment works

 

[Boncuk]

Hi Thunderchild,

there shouldn't be anything confusing about Maplin's.

Basically photoresist behaves like any film material (just being sensitive to UV-exposure).

I've made several thousands of PCBs using photoresist PCB material and no-name material is nothing to suggest because no result is repeatable.

Photoresist can be compared with any optical film. Assume you buy a 1,000ASA film and expose it correctly for it's ASA value it requires processing according to 1,000ASA (not 400ASA for instance).

The same applies to photoresist film. No-name products use different mixtures for the film and also undefined thickness (density), meaning you will have to test each PCB for correct exposure and development time.

Good brands use the same film viscosity and exactly the same film thickness (accurate to 1nm) ensuring the same result even when purchasing material at intervals.

Best results can be achieved purchasing PCB material at BUNGARD (Germany). Check out Bungard Elektronik

To make top quality PCBs you shouldn't use a direct laser print on a transparency to expose the PCB. Make a 1:1 copy of the laser print using positive or negative film (according to etching method - direct etching or differential etching). For extraordinarily good print quality use repro camera equipment (available at book printer's - most of them are willing to help for some bottles of beer. )

The copies have the same function as green TRF for the toner transfer method. Their pixel density is much higher than that of the laser, filling pure black areas purely black (instead of leaving small blind spots)

If the image on the PCB gets underetched the toner (film) is on the wrong side of the carrier. Even a transparency of 0.1mm thickness will allow to expose portions of the PCB caused by refraction, causing traces of <0.3mm to deminish while developing.

As a rule of thumb print the bottom side of a PCB the way you see it on screen (toner on top, which makes it have direct contact with the photoresist). Print top layers inverted for the same reason. (The toner must always have direct contact with the photoresist film.)

Hope that helps you for future projects.

Regards

Boncuk

 

[mvs sarma]

well I worked for a printers and oops yes thats right or actually I'm not sure but I remeber the press plates were made by exposure and then developing as in etching but maybe I'm wrong, yes i know how photographic devepment works

you may see this 30 minute You tube video , Thunderchild !
YouTube - Photo-etching printed circuit board (homebrew PCB)

 

[Thunderchild]

thanks guys very useful info. hopefully next week I will be producing something