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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Package tilting during assemly

Viswanath Valluri

#13760

Package tilting during assemly | 20 October, 1998

Hello : Some of the recent FBGA (a Chip Scale Package) packages that I am looking into have body sizes having aspect ratio's 2:1. In particular, body sizes of 14x8mm, 15x8 mm etc. The ball count for this particular package is around 40-68 I/Os. My question is how are packages with these aspect ratio's picked up during assembly? Some kind of a vacuum pick up? If so does it pick it up in the center ? The reason I am asking this is because the location of the solder balls plays a critical role in the board reliability of the package. If the ball matrix is concentrated around the center of the package, will the package be tilted during assembly, giving rise to non - uniform solder joints ?

Any thoughts would be greatly appreciated.

Thanks and regards

Vis Valluri

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Stefan Witte

#13761

Re: Package tilting during assemly | 20 October, 1998

All SM machines pick components with a vacuum nozzle. Most likely the component is picked in the geometric center, which may not be the center of gravity ( SOT 23, SO 89 ). Any other pick position than the center may be taught upon requirement, but your optical inspection system ( you'll have to use for your type of component ) will expect your component in the nozzle center or as a max. of 20-30% off the center. If you use a large nozzle, which fits the size of your component and the nozzle surface is parallel to your board surface coplanarity should not be an issue.

| Hello : | Some of the recent FBGA (a Chip Scale Package) packages that I am looking into have body sizes having aspect ratio's 2:1. In particular, body sizes of 14x8mm, 15x8 mm etc. The ball count for this particular package is around 40-68 I/Os. My question is how are packages with these aspect ratio's picked up during assembly? Some kind of a vacuum pick up? If so does it pick it up in the center ? The reason I am asking this is because the location of the solder balls plays a critical role in the board reliability of the package. If the ball matrix is concentrated around the center of the package, will the package be tilted during assembly, giving rise to non - uniform solder joints ? | | Any thoughts would be greatly appreciated. | | Thanks and regards | | Vis Valluri |

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Dave f

#13762

Re: Package tilting during assemly | 23 October, 1998

| Hello : | Some of the recent FBGA (a Chip Scale Package) packages that I am looking into have body sizes having aspect ratio's 2:1. In particular, body sizes of 14x8mm, 15x8 mm etc. The ball count for this particular package is around 40-68 I/Os. My question is how are packages with these aspect ratio's picked up during assembly? Some kind of a vacuum pick up? If so does it pick it up in the center ? The reason I am asking this is because the location of the solder balls plays a critical role in the board reliability of the package. If the ball matrix is concentrated around the center of the package, will the package be tilted during assembly, giving rise to non - uniform solder joints ? | | Any thoughts would be greatly appreciated. | | Thanks and regards | | Vis Valluri | Vis: Adding to and not disagreeing with Stephan, many bumped packages need to be placed by a machine that can image on the bumps, rather than the package outline, to do a good job in place parts. Dave F

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