Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


pcb board deflection when mounting component

paul

#22160

pcb board deflection when mounting component | 27 October, 2002

Does any expert here know the specification of board deflection when we mounting component by pick and place machine?

That is when the nozzle place the chip on the pcb, the board will have some deflection. And are there any requirment that we need to add support pin or support jig if the board deflection over certian level?

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#22162

pcb board deflection when mounting component | 28 October, 2002

It has been my experience that when all conditions are as they are supposed to be there should be zero or very little deflection. When you start placing components with pick and place equipment that does not have a Z pressure sense, you run the possibility of damaging nozzles and components if your PCB's are not nice and flat. Lets take an 0805 for example. We are a contract shop and we run thousands of different 0805 pn's, well the part thickness varies with different component manufacturers even though they are still 0805's. It is important that you verify Z size of the part before you run a job. It is also very important that you have maximum support under the board as well.If the board is "concave", instead of smashing parts your machine will drop them before they are in the paste or glue.

There may be an IPC spec. If there is I am sure Dave F. will hop in to help you.

Hope that is a little help to you anyways. Its early Monday and my brain is still on weekend mode.

Best Regards

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tkenny007

#22166

pcb board deflection when mounting component | 28 October, 2002

Specs for Bow and Twist for PCBs (IPC-A-610C, 10.6. There may be an update by now). I also have a note in our quality guide referencing (IPC-TM-650, 2.4.22) and (MIL-STD-105D). In summary, a PCB should not bow more than 0.040" with all four corners touching a flat surface (constraining if necessary) and the twist should not exceed 0.040" when holding down only 3 corners to a flat surface.

As far as deflection when in the pick and place equipment, I like to set it up with about 0.005"-0.020" max. This is just in case the tombstone detecting feature does not work and it tries to put a 0603 down on its side. This prevents too much damage to nozzle tips. Then again, my machine has a Z pressure sensor.

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#22181

pcb board deflection when mounting component | 30 October, 2002

Normally warp max 1% of diagonal board measurement is acceptable. What's your p&p like? Some will not experience problems at all! reg Jasper

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#22182

pcb board deflection when mounting component | 30 October, 2002

> It has been my experience that when all > conditions are as they are supposed to be there > should be zero or very little deflection. When > you start placing components with pick and place > equipment that does not have a Z pressure sense, > you run the possibility of damaging nozzles and > components if your PCB's are not nice and flat. > Lets take an 0805 for example. We are a contract > shop and we run thousands of different 0805 pn's, > well the part thickness varies with different > component manufacturers even though they are > still 0805's. It is important that you verify Z > size of the part before you run a job. It is > also very important that you have maximum support > under the board as well.If the board is > "concave", instead of smashing parts your machine > will drop them before they are in the paste or > glue. > > There may be an IPC spec. If there is I > am sure Dave F. will hop in to help you. > > Hope > that is a little help to you anyways. Its early > Monday and my brain is still on weekend > mode. > > Best Regards

Normally warp max 1% of diagonal board measurement is acceptable. What's your p&p like? Some will not experience problems at all! reg Jasper

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#22293

pcb board deflection when mounting component | 6 November, 2002

Check out one of the board suppport that are currently available: Grid-Lok, Formflex and others. These systems are available for many models of printers and P&P. They automatically set up to any board, first or second side, and provide excellent support. www.grid-lok.com www.dek.com

Good luck, Charlie

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