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Hitachy QFP 256 leads problems

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Hitachy QFP 256 leads problems | 18 March, 2007

Hi there,

I want help on the following issue.

Where I work, we place a component QFP 256 terminals (20 mil pitch)from hitachi (renesas), we use a MPM UP-3000 screen printer, IP-III placement machine and Vitronics 8 zones reflow Oven. lead plating is 90-10 SnPb and solder paste is Indium NC-SMQ92J

We have had two different problems with this component. 1.- No wetting.- Actually we tried with a lot of things (solder paste, different pad finish -hasl, gold- reflow profile optimization, reflow on nitrogen ambient) and Run with nitrogen ambient has the best results, but is about $40K yearly and Management is looking to avoid using nitrogen. Also, since we're an automotive supplier, get approval is not so easy...

2.- Component placed Skewed (shifted). This issue we cannot control it, is being placed at last in the sequence and with the lowest speeds on all movements, the compontent is not placed accurately all the time. The component tends to place skewed on the pre-rotation direction. is there a way we can calibrate the placement for a IP3? we currently use a glassplate, but I think only X&Y is being calibrated. other thing is all other components are being placed well, we place another 20 mil pitch component (but less pins) with which we do not have the same problem.

Thanks in advance for your help

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Hitachy QFP 256 leads problems | 19 March, 2007

is the component placed off all the time or does it vary? if the placement offset is consistent then there is every chance that the machine requires calibration (providing your program is correct) If it varies then there could be lots of things causing the issue.

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Hitachy QFP 256 leads problems | 19 March, 2007

When you say "No wetting" you mean the paste looks the same as it did going in but dried out? Or is it that you are not getting toe fillets?

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Hitachy QFP 256 leads problems | 20 March, 2007

Some causes of skewing. If you have exhausted all mechanical problems for that head.

Pickup data from tray is incorrect. If you aren't picking up in the exact centre it is possible that the component is being skewed after vision adjustment i.e. centrifigul force is moving the component after vision if the component is being rotated or xy movement. If the tray pitch data is incorrect then you will slowly move from the centre of each component at pickup as you move along the tray. Also pre-rotate the component to placement angle before vision check.

Vision data is incorrect and the component is being offset from its true centre. Check the vision data and ensure that the crosshairs are actually centred on the component. Ensure that there are no objects outside the component that may be recognised as being white. eg. solder paste or dust on back of nozzle or dust etc on camera. Ensure your component data is correct, i.e. height etc.

Wrong size nozzle, deformed nozzle. If the nozzle is too small or leaking vacuum you will have problems

Try different rotations of mount angle 0, 90, 180, 270. If the results are all the same then you would normally have a head offset problem. If the offsets are all different but make "sense" according to the placement angle then you may have a bent nozzle/spindle/shaft or the vision file is offset.If the results are all random then you may have a faulty R axis driver, motor or encoder or combinations of all of the above. Z axis driver, motor or encoder could also be faulty. Your God may be angry with you.

Place the component with a different head and see if you still have offset. What result you get from this may help to eliminate some of these other causes OR it may not. Let us know how you go.

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Hitachy QFP 256 leads problems | 20 March, 2007

is not getting toe fillet, you can se like a "paste dome" on the pad so the paste is not flowing to the pin...

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Hitachy QFP 256 leads problems | 20 March, 2007

Hi to all, thank you very much for your feedback.

The part is rotated before inspection; and also tend to be shifted to the same direction of pre-rotation so i think is not correcting misalignment or maybe some settings on shape data are not correct.

Someone is familiar with Fuji Flexa so can take a look on shape data?

The clue about motors seem to be interesting...

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