Another PCB issue with developing.

[therecordingart]

Ok...right now I'm only getting one good board out of 10! When I place the PCB in the developer it is removing half of the traces before the rest of the board is finished developing. I've tried many different exposure times to UV and many weaker....extremely weaker mixes of sodium hydroxide...still no dice. One good board out of ten isn't cost effective!!!

Does anyone have any suggestions? Does PNP Blue work well?

 

[peterc]

How warm is your developer? I've found that room temp or slightly warmer gives the most even developing result. If it is too warm, it develops way too quick & a lot of the tracks disappear before yer' mince pies.

If it is cold, it can take forever or just not develop fully.

Do you have the recommendations from the PCB manufacturer? Is it pre-coated PCB? They should give developer details. And also etching details.

My boards take about 90 sec to develop, & then I leave them in for an extra 30 secs or so to make sure all the un-required covering is removed.

Peter

 

[therecordingart]

Thanks, Peter. What I'll do is leave my water and my bottle of developer in the same room for a few hours before I decide to mix them.

Has anyone had luck with Press n Peel?

 

[gyraf]

If traces are being eaten before development is finished, there are four possibilities:

1) Too long an exposure time.

2) Too strong a developer.

3) Printout is not dense enough, allowing light through where it shouldn't come through. I most often use colour-laser transparant printout from the local printshop - that's the best contrast printout available around here. Not b/w laser!

4) Poor contact between PCB and layout - allowing light to sneak in under layout. I use some mouse-mat like foam, and 3-4kg (transformer) weight distributed over it to make good contact.

Jakob E.

btw: RecordingArt - it's best to continue related questions in the same thread - that way topics gets much easier searchable for similar questions later..

 

[mcs]

[quote author="gyraf"]3) Printout is not dense enough, allowing light through where it shouldn't come through. I most often use colour-laser transparant printout from the local printshop - that's the best contrast printout available around here. Not b/w laser![/quote]
Or find a place with an image setter. You will get a perfect film with great density. And it doesn't have to cost a lot (or anything, if you know the right people... :grin.

Best regards,

Mikkel C. Simonsen

 

[Svart]

i use 10:1 water to sodium hydroxide with cold water. warm water will develop these too quickly.

I usually leave my exposures for hours under a UV lamp with no ill effects. i make the developer a little weak and over expose the PCB for best effect.


i also use a mouse pad under my PCB and heavy polycarbonate sheet over the art/PCB then place the UV lamp over it.

 

[smallbutfine]

Ok...right now I'm only getting one good board out of 10!

Sounds pretty expensive to me...perhaps you can try out toner transfer methods if you can't get the right parameters (and there are plenty of it) for the photosensitive methods. There are plenty of good descriptions and it's very easy to start over with the same pcb material if the transfer is not as good as you want it, so you have nearly no waste. PNP transfer sounds like a no brainer from all i read, but it's not cheap. Personally i have very good results using the paper from the Reichelt catalogue with toner transfer...that's pretty cheap, fast, and gives fairly good results. I described it over at the midibox wiki, but i think it's only in german so far....

Hope this helps.

Martin