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Defect reduction on RF design

Views: 929


CL

#36702

Defect reduction on RF design | 19 September, 2005

Good Morning Everyone,

We have a customer that produces RF based assemblies. We are building several board types for them, all of which have an "RF" area of the PCB. This RF area does not have any mask to define pads. There are also several issues with components sharing pads, unequal thermal mass between pads and via's on some of the common pads that "thieve" the solder. The net result is an unacceptable amount of tombstones and shifted components. We have worked extensively to develop a profile that minimizes thermal delta but it seems that design is more the root cause than profile. Any suggestions would be appreciated.

Thanks In Advance

Chris

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#36737

Defect reduction on RF design | 20 September, 2005

2251 - Design Guide for the Packaging of High Speed Electronic Circuits 2252 - Design Guide for RF/Microwave Circuit Boards

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#36739

Defect reduction on RF design | 20 September, 2005

Several suggestions. Your hands may be tied but here goes. 1. Doctor your stencil so that pads are not shared etc and reduce the apertures more that what you would normally. This may stop one pad wetting into another etc. 2. The use of a Pb-free solder MAY also help. 3. Change to an NC flux if you are using water based. 4. Dispense adhesive after paste print. The adhesive will set before relow takes place, holding the components in position. Many SMD adhesives will withstand a reflow profile without giving up.

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Slaine

#36750

Defect reduction on RF design | 21 September, 2005

go beat the designer over the head until he separates the pads or uses solder mask.

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