Nice piece of work, Stefan, getting the time / temprature curing curve. have
you tried it in your smt oven? Can't wait for the photos!
What kind of pcb material were you using? thickness and oz of copper?
Myc
On 8/1/06, Stefan Trethan <stefan_trethan@...> wrote:
>
> Hi,
>
> It seems i finally cracked it! Made PCBs with no more through-etching and
> ink so tough not even acetone can take it off!
>
> I spent a few hours cooking PCBs today. The curing was definitely my
> problem.
> Had to make a more scientific mechanism to carry out some experiments.
> Basically an old electric hot plate with a aluminum plate on top and a
> temperature meter attached. This way i could adjust the temperature within
> +-10C and more evenly than with the hot air gun or the stove.
>
> Then i printed many test PCBs and heated them to different temperatures,
> from desiccation to delamination. It turns out that around 230C is the
> sweet spot. keep that for several minutes (at least 3 i'd say for now but
> more research needed). This incidentally is exactly the point where the
> copper will start to go from just minimal yellowish oxidation to a purple
> one (This is probably what Volkan is using to judge the temperature). It
> is well away from damaging the PCB.
>
>
> If you are much below or above this temperature the ink will not resist so
> well. Round about 225C the ink starts to change somehow and can no longer
> be cleaned off with acetone.
>
> Anyway, that's what i can tell you today: cure on a 230C hot metal plate,
> +-10C, for about 4 minutes and it will work.
>
> I will make photos of the PCBs tomorrow, i need daylight my camera does
> not make useable flash photographs.
>
> There is definitely much more to be discovered here, but i finally found
> repeatable parameters that so far work every time, all the time. There may
> be other or even better ways to do this, but i finally have something that
> works for me, and that's great!!
>
> James, let me know what exactly would be required to qualify for the $50
> prize ;-)
>
> Below a writeup i started a few days ago while waiting for a PCB to etch,
> mainly concerning the work on the printer. I want to put this on
> <http://dipcb.schtuff.com/>, because i think a wiki might be a good way to
> help further development of this process. If we write a wiki together it
> will allow newcomers to get up to speed (and help us to remember).
> Suggestions for that welcome.
>
> Any my thanks again to Volkan!
>
>
> Printer Modification:
>
> ∗)Stripping down
> First all plastic is removed around the C84 that is not required for
> printing. This is the side caps, the main body, and some smaller loose
> bits. At this point the printer will still print normally.
>
> ∗)Preparation
> make sure the printer is in good working order, and the parking station is
> clean. With all used C84s you will find a badly clogged parking
> station/vacuum mechanism that MUST be cleaned. Do a nozzle check to make
> sure the head is working on all nozzles. I opted to disable the vacuum
> mechanism by removing the small gear on the rough transport roller and
> instead manually provide vacuum with a syringe. You can leave the pump
> engaged if you do not mind unnecessary cleaning.
> This is also the best point to install spongeless carts with auto-reset
> chips and test them on paper. Fill yellow MSIPRO ink in the black cart
> (you may also use the yellow cart the C84 can not tell which cart is where
> as long as all are present). Add a few drops of black mispro ink for
> better visibility.
>
> ∗)Rear Paper path
> The paper feeder is removed from the back, taking out the optical paper
> sensor.
> This sensor is glued to the side of the paper slot (in the metal chassis),
> so that the material passing through here will activate it.
>
> ∗)Front Paper Path
> Remove the pizza wheels from the output. You may also remove the black
> plastic paper guide and that ink sponge at the front. Rip out the whole
> spiel, you only need to keep that greased sheetmetal rail where the head
> rides on. It is easier to leave the shaft with the rubber output rollers
> in place since it carries a pulley for the belt. It has no further
> function and you could remove it if you tension the belt some other way.
> Now a flat sheet will pass through the printer.
>
> ∗)Central Transport Roller
> Remove the middle pressure roller assy. Now a small PCB will fit through
> the middle. If you cut it in half and replace the outer pressure rollers
> with the half sections you get even larger PCBs through. You must hold the
> springs up with something like a strip of metal or PCB to make up for the
> cut-away half. If one needs full with even narrower wheels could be
> attached at the very outside, but usually it will not be needed.
> If you go for a rail under the carrier for 2-sided PCB alignment you need
> to take out the rough transport roller and grind it down in the middle to
> allow this rail to pass. Works well with a bench grinder. Don't grind it
> too thin you need some strength.
>
> ∗)Head Height
> To allow for the increased media thickness we must adjust the head height.
> The easiest method i found is to cut through the chassis just over the
> paper gap. You could cut exactly through the paper gap, but that would
> lift the pressure rollers as well and require a change there. The chassis
> can be cut in place with nibbler pliers.
> On the left (stepper/belt) side of the printer you need to add a small
> piece of sheetmetal (ideally an angle piece around the rear edge) that
> holds the cut-off part at about 3mm higher than it originally was. On the
> right (head) side you can simply put nuts or washers under the two
> mounting screws (and use longer screws) to achieve the same increase in
> head height.
> You also need to raise the head parking station, lift up the plastic over
> the screw mount on the inside and again use a piece of plastic or
> sheetmetal with screws to raise it on the outside. There was a snap-in
> mechanism originally not allowing you to simply put something under a
> screw. The inside in not held as firmly now, but that's fine and you could
> use a longer screw and some strip of metal to clamp it down if you really
> like.
> Lastly you need to raise the front head rail by the same amount. Simply
> put spacers (nuts) under where the screws attach the piece and use longer
> screws.
>
> ∗)Carrier
> You need to make a carrier for your PCBs, any rigid material like
> cardboard will work. It should not be too heavy. I used a sheet of formica
> and glued thin cardboard to the bottom for traction (probably not needed).
> If you want a rail for alignment you can glue a piece of aluminum to the
> carrier. It must be low in height to fit in the gap in the transport
> roller, but high enough to provide alignment between plastic guiderails.
> If you do not need the rail a simple piece of cardboard will do.
> The C84 will expect a short delay between the start of the feeding
> mechanism and activation of the paper switch, so you need to make a cutout
> of (edit) on the carrier to faciliate this delay. That is with the sensor
> right at the metal, if you place it further outward you need a longer
> cutout. The C84 is quite tolerant, a tolerance range of about +-4cm or so
> was found to work. (Procedure for finding the valid range upon request if
> you can't work it out yourself).
>
> ∗)2-sided Alignment
> If you need to align printing on the second side of the PCB it would be
> good to be able to print in the same spot each time. To ensure that you
> can put a rail on the underside of the carrier which rides between plastic
> guides on both the input and output of the printer. To mount these plastic
> guides it is easier to cut out the plastic bottom of the printer to allow
> for wooden mounting blocks. I have not yet installed this fully as aligned
> doublesided printing is not a priority.
>
> Printing:
>
> ∗)PCB Preparation
> Sand the PCB with 600 or 1000 grit paper so that he surface appears
> scratched everywhere. You may also use a abrasive plastic pad sold for
> cleaning copper pipes before soldering. Then wipe with acetone, twice, the
> first pass should take away the copper dust. The PCB must be grease free
> now and stay that way.
>
> ∗)Printing
> To print you must insert the carrier manually into the printer. Turn the
> printer on, and wait until it has completed it's dance. Now feed the edge
> of the carrier into the printer so that it jsut protrudes a few mm from
> the traction/pressure rollers. Make sure it is straight so it will not run
> against an edge when the printer feeds.
> Now rint the artwork on your carrier to find the right position (stick
> some tape or adhesive backed plastic foil on it or you may end up with
> permanent marking of the carrier). You can use low resolution for this
> print since you only need to know where it will end up. If you use the
> fastest draft setting watch out, the printer virtually shoots it through.
> Now place the PCB over this position and stick it down with tape. You may
> delay the acetone cleaning of the PCB until this point if you prefer.
> Again feed the carrier and print the artwork.
>
> ∗)Printer Settings
> When printing a purely black test pattern i found the transparency setting
> does not use any ink from the black cart at all.
> The other settings use ink in varying amounts, the most ink is used for
> matte paper and the least for glossy or durabright setting. You need Photo
> or Best Photo resolution. The "fast" setting, which prints in both
> directions of travel, produces better results for me. No edge smoothing
> needed.
>
>
> ∗)Curing
> -- see top of message --
>
>
> ∗)Etching
> I suspected Ferric chloride is less agressive to the ink than CuCl, so i
> set up a test. I cut a test PCB in half after curing to get identical
> samples, and put one in CuCl and one in ferric chloride. If anything the
> ferric chloride showed more agressive under-etching.
>
>
> Be sure to visit the group home and check for new Links, Files, and
> Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> If Files or Photos are running short of space, post them here:
> http://groups.yahoo.com/group/Homebrew_PCBs_Archives/
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>
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