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Determining keepout for an SMT part?

BrotherTheo

Hi,

 

The library part for an 0603 resistor has a rather large keepout. I am trying to find out if it can be made smaller. I already found out the pads can be smaller, but all the datasheets I looked at said nothing about keepout. How does one determine this? Is it a function of the machine doing the placement?

 

Thanks!

 

--Tim Ressel

  • 0

    Tim Ressel wrote:

     

    Hi,

     

    The library part for an 0603 resistor has a rather large keepout. I am

    trying to find out if it can be made smaller. I already found out the pads

    can be smaller, but all the datasheets I looked at said nothing about

    keepout. How does one determine this? Is it a function of the machine

    doing the placement?

     

    Thanks!

     

    --Tim Ressel

     

    Keepout can be dependent on the PnP (pick-and-place) machine if it uses

    mechanical grippers that need a certain amount of space for grabbing.

    However, many placement machines these days use vacuum pick-ups on the part

    centers. In that case you're more likely to have trouble with short

    components too close to tall components. It depends on who is doing the

    assembly and what machines they have. Another use for keepout is to make it

    simpler to guarantee sufficient space between component arrays to allow

    trace routing. For example, with 8/8 mil trace/space a keepout of 12 mil

    would guarantee you could route a trace between two identical parts placed

    on a 12 mil (or more typically 12.5 mil) grid. Yet another use for keepout

    is to allow room for rework if necessary, which typically requires hot air,

    a vacuum, and makes a mess of surrounding components that are too close. I

    suppose keepout may also be useful if a PCB is being milled out mechanically

    with a router bit.

     

    I've noticed the rather large keepouts in some of the RCL libraries myself.

    I don't know how those sizes were picked, maybe it's an IPC standard thing?

    I'd be curious to know myself. In any case, I copy them to my own libraries

    and reduce them if necessary. Hasn't caused any squawks at the assembly

    houses I use.