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Having issues placing 0603 components on my used Juki 740...

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#75964

Having issues placing 0603 components on my used Juki 740... | 10 July, 2016

hi everyone, new user and noob here.

I've spent the last week getting acquainted with my juki 740, being totally new to placement etc it's been fun to learn!

I've now gotten to a stage where everything is setup in the machine for my board and is placing it (including a qfp144 0.5mm pitch) quite nicely. However, I seem to be having issues with the 0603 stuff, both caps and resistors not landing properly. pick position and placement position is spot on, and I hand measured the resistors and caps with my calipers to input their dimensions into the machine.

There doesnt seem to be a pattern to the way they are being placed wrong, it seems quite random, perhaps they are being dropped before touching the board or something? I'm at a total loss.. I have tried these components on slow speed also which seems to help a little, but not much (and that might even be in my head)

vacuum settings? height settings?

any ideas or things to try would be most welcome.

kindest, Brad

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#75967

Having issues placing 0603 components on my used Juki 740... | 11 July, 2016

I don't know your machine but you are looking at the most likely areas. Some machines define a placement pressure, other may define an overtravel to make sure the device is firmly placed on the board. There are usually also timings for when the vacuum releases,how quickly the head pulls back, perhaps a small amount of blow. Also bear in mind that an 0603 cap can be 3x the height of a resistor, so they will need to defined as different packages. I typically have 2 package definitions for each resistor footprint (normal and chunky!) and at least 3 for caps (thin, normal, thick). Depending how noisy your machine is you should be able to hear it placing each part with a slight tap, if you don;t perhaps it is dropping them onto the board.

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#75968

Having issues placing 0603 components on my used Juki 740... | 11 July, 2016

I have experienced this problem on a number of different machines and have found that it has been one bad nozzle causing the problem. We run Juki 3010 and 3020 and occasionally we have had similar problems. One question, is it bad placements on all 603 parts or just some parts?

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#75969

Having issues placing 0603 components on my used Juki 740... | 11 July, 2016

Other problems on previous machines that we have experienced is that there was not enough board support under the panel or that the panel thickness was inaccurate. Both situations can cause parts to bounce off the PCB or not to be pushed into the paste. (look for indentations in the paste to help analyze your actual problem).

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#75970

Having issues placing 0603 components on my used Juki 740... | 11 July, 2016

thanks for the replies so far.

So far I have been relying on the board clamp on the machine that closes when the pwb is loaded. I have also been doing these tests with double sided tape on the pwb so i can clean them off easier afterwards. I have done 2 so far with paste on them, but still the same issues.

Going to look at what you said there, I have a load of those magnetic pins so just place them under the board arbitrarily?

thanks for teh comment about the nozzle too, it is trying to use nozzle 101 but I think it has a few of those installed, so I'll take one of them out and try again.. also going to move the feeder up to the middle so i can try those parts with the other head.

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#75971

Having issues placing 0603 components on my used Juki 740... | 11 July, 2016

well there you go. I found that trying different values in the "Placing Stroke" had a big effect. I changed it to 2mm and it placed them well, but I could see the board also flexing a little, went to 1mm and the problem came back, so have sat in the middle at 1.5mm and all seems to be well.

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#75976

Having issues placing 0603 components on my used Juki 740... | 12 July, 2016

> well there you go. I found that trying > different values in the "Placing Stroke" had a > big effect. I changed it to 2mm and it placed > them well, but I could see the board also flexing > a little, went to 1mm and the problem came back, > so have sat in the middle at 1.5mm and all seems > to be well.

This is all well and good but what has changed for the placing stroke to go from a normally preset 0.5mm to 1.5mm? Is the BPU motor working correctly, is the table clamp set correctly?

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#75977

Having issues placing 0603 components on my used Juki 740... | 12 July, 2016

I'd start by checking and reteaching the nozzles (this is automatic, it'll measure the nozzle length and vacuum values for each nozzle). After that double check the value you have entered for the PCB thickness as this will impact where the machine thinks the baseline level of the PCB is.

As said previously, changing the placement stroke may get you by, but there's definitely an underlying cause outside of this.

-Phil

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#75979

Having issues placing 0603 components on my used Juki 740... | 12 July, 2016

Brad, have you got any calibration jigs with the machine? This could also be down to laser offset or laser scaling which are both calibrated with different jigs. Where are you based?

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#75980

Having issues placing 0603 components on my used Juki 740... | 12 July, 2016

oh i did not enter the pcb thickness. it is set to 0.0 I thought this was only to be changed for non standard pcb thicknesses.

So, with the pcb being 1.6mm this is probably the answer.

I guess this means I'm dumb..

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#75981

Having issues placing 0603 components on my used Juki 740... | 12 July, 2016

I didn't get any jigs, no. I am based in florida!

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