Homebrew PCBs

Just joined this list, but I've made PC boards (of varying degrees of crudeness)over most of my nearly 50 years as a ham.   My interests are primarily fairly simple single-sided board prototypes, but with the ability to fight SMT gradually ebbing I figured it was time to get serious, as the Dremel tool etcher has its limitations ;-)

I've been practicing with the toner transfer method and quit digging through the recycle bin in search of the right free paper and made my first board using the Pulsar material today.   The image transferred completely and it was MUCH easier, as the dextrin paper came off easily.  But the quality of the image wasn't much better than what I've been getting and certainly nothing like the examples I've seen.   Mostly, jaggy traces, uneven edges, pinhole voids in the groundplane areas, etc.   It will make a usable board, but I thought I'd seek some advise that might hasten my trip up the learning curve.

The key variables I see are repeatability of the heat source and the toner.   I'm still using a household iron, and I'm sure my application process couldn't be much more inconsistent in terms of temperature, pressure, pattern, time, etc.     My printer is an HP-5000 with everything cranked up to max, but it probably could use a new toner cartridge (which I'll just go ahead and do).

I'm not sure which variables in the process are causing the issues I'm seeing, but would the GBC hot roll laminator would be the next logical step toward better results? 

Thanks and 73,
Bob W9RAN

Hi Bob,

In my quest to find a repeatable and accurate imaging and to make a reasonable PCB, I've tried numerous photographic paper with toner transfer.

I've also used Pulsar paper.

First of all, HP toner has a melting point (commonly written as MP###) of around 95C to 105C. The toner transfers very easily from the Pulsar paper onto the copper so you do not need to heat the iron to max. Doing so causes the toner to liquify too much and the edge of the image will bleed. 

Set the iron onto silk to see if it will transfer. if it still bleeds then set it to a lower temperature. if it didn't transfer set it to a higher temperature. Iron are not accurate at all so you will have to play with it to get the right temperature.

Don't need to press it crazy hard. Transfer happens within 20seconds of heating and moderate pressure. Again trial and error.

If the image transferred to the copper but manages to peel off or lift off, then carefully bake the board in a oven at 200F for about 10 minutes. This will soften the transferred toner, make it sticky and will cause the toner to stick to the copper on your PCB. Make sure the toner is not touching anything else, touch only the copper. My two sided board is held up only on the edges while it is in the oven and during cooling. You can think of this as anealing the film and it helps to reduce the porosity of the toner. 

I didn't find the green TRF film all that helpful. 

If you do these things, and etch, your traces should look plenty good. I've managed to get a clean footprint for PLCC.

If you really want to get a manufactured grade look, then use a photo resist.

Still have some pulsar but mostly going with photo resist.

hope this helps.

smilingcat

> I've been practicing with the toner transfer method and quit digging through the recycle bin in search of the right free paper and made my first board using the Pulsar material today.   The image transferred completely and it was MUCH easier, as the dextrin paper came off easily.  But the quality of the image wasn't much better than what I've been getting and certainly nothing like the examples I've seen.   Mostly, jaggy traces, uneven edges, pinhole voids in the groundplane areas, etc.   It will make a usable board, but I thought I'd seek some advise that might hasten my trip up the learning curve.
 
> 
> Thanks and 73,
> Bob W9RAN
>

--- In Homebrew_PCBs@yahoogroups.com, "smilingcat90254"  wrote:
> 
> First of all, HP toner has a melting point (commonly written as MP###) of around 95C to 105C. 


Thanks very much for sharing your experience and suggestions.  Just knowing the melting point puts a different light on things -- I'd mostly been concerned about not having enough heat, when it's pretty clear now I had way too much.

Today I made two attempts with a simple little board.  I wasn't able to use my IR thermometer to measure the temperature of the iron (too shiny) but a meat probe thermometer did the job, and on the "Silk" setting my iron runs right at 250 deg. F., which seemed about right based on the MP of the toner.   The first attempt was for 60 seconds with moderate pressure, and while the toner transferred, a large area flaked off.    The second time I kept the iron set on Silk but increased the time to 90 seconds.  In each case I moved the iron around 3-4 times but didn't "iron it", just held steady pressure.   

The result of #2 can be seen here:
http://img849.imageshack.us/img849/5864/tonertest90secsilk250de.jpg

The traces transferred well and are much clearer, but some areas of the ground plane didn't transfer too well as can be seen by the exposed copper areas.   Seeing this, I followed your suggestion and baked the board in the oven at 200 deg. F for 20 minutes, which seems to have helped adhesion.    Since it doesn't affect the operation I'm going ahead and etching this one, and next time I will vary the temperature or time a bit and see what effect that has.

Overall - much improved!   And to answer my own original question, I can see how the hot-roll laminator could help insure equal heat and pressure all across the board.

73, Bob W9RAN