[CoAMarcus]

Jeff,

No, JB-Weld will not be used on anything aside from the first few. We needed some adhesive real fast, I was at Home Depot and saw that, and decided to try it. We have a lot of PCB adhesive on the way, but its not here yet and we were stuck without it. We get that Monday, and then we can begin production testing with the adhesives as soon as it arrives.

-Marcus Freimanis

[phomann]

What we are using is JB-Weld. This is an easy mixing epoxy, strong as anything you can find, cures at 150F, and is good up to 600F. Just put a spot on the board, stick the MOSFET down on it, run it through the oven at 150F, and you are good to go. Make sure the leads aren't sticking above the panel and you can just stencil it like normal.

As I type this the machines are being set up to run the G250s. We get the stencil tomorrow, and if everything looks good we will run limited production some time very soon. As promised, there will be lots of pictures. ;-)

-Marcus Freimanis

Hi Marcus,

My question was to do with the paste stencils used. How do you determine the apertures size for the THC? The apertures need to be large enough to apply enough pate to fill the hole space wit solder. I don't know how to determine this other than trial and error.

Cheers,


Peter.

[tooManyHobbies]

Today will be spent programming the Juki pick-and-place machines with G250/G251 component data (tedious hand-entered data keyboard work)

Hand-entered? Doesn't your PCB software generate a Pick-&-Place file for that? Or is the Juki so low-end that it can't take this info (which I can't imagine)?

tom

[Mariss Freimanis]

tooManyHobbies,

We use AutoCad for everything including board layout. That means schematics, logic timing charts, 3D-modeling, etc. We use Autogerb, a 3rd party .arx application inside ACAD to convert pcb layouts to gerber files.

During board layout, we generate a PARTS layer in ACAD that has tiny circles at the geometric center of every SMT component. We have AutoGerb produce a .drl file from this layer to get the X/Y coordinates of every SMT component relative to the prime fiducial mark on the board. We then use a little .exe I wrote in C+ to output component name, value, rotation angle and X/Y coordinates in .txt format. This is printed out and some poor schmuck here (sometimes me) has to then enter it into the Juki FS-750s or FS-740 machines. It's not as bad as you think; it takes a few hours to enter and verify the data. After that the machines may run for years with only minor program editing as new drive revisions come out.

The Juki machines place 10,000 parts per hour, are 5' by 5' by 5', weigh 3,000 lbs and cost about $50K to $70K now for 10-year old machines. We have 3; we will be 'retiring' our oldest one soon and replace it with a newer one.

Mariss

[Mariss Freimanis]

phoman,

What I did was calculate the thru-hole volume minus the component lead volume to know what volume of solder is needed to fill the thru-hole. Then calculate the volume of your solder paste tub (we use 500 gm tubs). Divide the calculated density of the paste (gm/mm^3) into the known density of solid solder to know the multiplier needed to account for volatiles and flux. Multiply it by the fill volume to know the volume of paste required. Subtract away the fill volume because squeegeeing the paste will pack the hole. Make your stencil aperture diameter equal to the volume of paste needed (pi times radius^2 times stencil thickness). Top and bottom meniscus volume is adjustable by squeegee pressure and technique. We stencil our panels with a manual machine.

Mariss

[phomann]

phoman,

What I did was calculate the thru-hole volume minus the component lead volume to know what volume of solder is needed to fill the thru-hole. Then calculate the volume of your solder paste tub (we use 500 gm tubs). Divide the calculated density of the paste (gm/mm^3) into the known density of solid solder to know the multiplier needed to account for volatiles and flux. Multiply it by the fill volume to know the volume of paste required. Subtract away the fill volume because squeegeeing the paste will pack the hole. Make your stencil aperture diameter equal to the volume of paste needed (pi times radius^2 times stencil thickness). Top and bottom meniscus volume is adjustable by squeegee pressure and technique. We stencil our panels with a manual machine.

Mariss

Mariss,

Yes, I have read a couple of papers that provide the formula for determining the volume of paste required and hence the stencil aperture sizes. I guess I was after a bit of advice from practical experience, which is what your 2nd last sentence refers to I guess.

I have a few old stencils around with enough spare area to experiment with. I can create circular apertures by drilling, and can do tests on say an IDC 10 pin connector. It should provide practical results that are suitable to determine what size apertures will be needed for the stencil.

Cheers,


Peter.

[tooManyHobbies]

The Juki machines place 10,000 parts per hour, are 5' by 5' by 5', weigh 3,000 lbs and cost about $50K to $70K now for 10-year old machines.Mariss

I only worked at one place that purchased an SMT line, and that was in 1991. That equipment placed around 10k parts per hour too, but they cost $750K+ and were MUCH larger than your Juki's! How times have changed!

Hmmm. I wonder if I can make an X2 place paste, and smt's. :idea:

tom

[Mariss Freimanis]

Most important, they are reliable and accurate too. Our first P&P was a benchtop belt-drive contraption. You were lucky to have it place an 0805 within +/-0.025" of the programmed position. Slow too at only 2,000 pph. You would only have 150 drives at the end of a grueling 12-hour production day, all of which needed manual rework.

Mariss

[the4thseal]

ok,, now that this thing might be close, my drooling is getting out of control, i thought now is the time get power supplies motors,break out boards ,controllers, ect. so what component are people going to use? i want to be prepared to get MOVING right away.so lets hear it......

[skmetal7]

all i need are three g251s and my conversion is DONE!!!

[the4thseal]

so what sre the components that you are linking to it then?

[skmetal7]

c10 BoB ----> g251 ----> keling 282 oz/in steppers

[jalessi]

WHERE'S THE BEEF?

[jalessi]

THE NATIVES ARE GETTING RESTLESS!

[the4thseal]

c10 BoB what is this? a break out board?

[skmetal7]

http://www.cnc4pc.com/Store/osc/prod...products_id=45 i dont know if the link works, but yeah its a breakout board from cnc4pc.




i think jalessi has teretts....

[the4thseal]

so what made you choose it, i am finding it hard to tell which one to get....performance ect and this new driver is making me think of the whole.

[Kipper]

http://www.cnc4pc.com/Store/osc/prod...products_id=45 i dont know if the link works, but yeah its a breakout board from cnc4pc.




i think jalessi has teretts....

It's tourettes not terretts...I should know....I fricken got it too...<<Joke btw.......Or nearly?

[wolfdagon]

so what made you choose it, i am finding it hard to tell which one to get....performance ect and this new driver is making me think of the whole.

So why not just get he G540 when it is availabe? I think that we can be sure that the drivers and break out bord will work very well together since they are being designed to do so.

[keebler303]

Its also harder to let out the magic smoke in a package deal. If you can wait, I would definitely hold out for the G540.

Matt