Peter Biocca, Senior Market Development Engineer, Kester
Edward Zamborsky, Regional Sales Manager, OK International Inc.
Doug Dixon, Global Marketing Director, Henkel Electronics
Mike Scimeca, President, FCT Assembly
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There is no standard that supports the percentage of voids in thermal pads of QFN or LGA packages. The customer and the manufacturer have to come to an agreement on the percentage of the voids acceptable. Some customers demand that the voids in the thermal pad be less for RF supporting QFNs.
However masking the via holes, providing the via holes of correct dimension and type and at equal spacing, will reduce the percentage of voids. Proper stencil designing for the thermal pads will also reduce the voids in thermal pads. Increasing the metal load or reducing the flux content in the solder paste will give some good results. Thermal pad design plays the major role in voiding, so discuss with the customer and come to an agreement on the thermal pad voids.
S.S
Is it acceptable if a void, or total voids, are less than 25% of an BGA ball? I was told that this criteria is also applicable for QFN and LGA packages. However, I find it hard to accept. A 0.1mm size void in a BGA of 1mm ball size is difference from a 0.1mm size void in a LGA pad which is rectangular in shape. The ratio of the void to ball in term of area for BGA is definitely much smaller compare to that of LGA or QFN.
To me, taking all parameters constant, the solder joint reliability for QFN or LGA pad would be much lower compared to the BGA ball. As I am not involved in process, I could be totally wrong. I would like to learn from anyone of you in this aspect.
Sunstone Circuits, has released the newest version of their design software, PCB123. Bottom line, the design process just got easier. Sunstone Circuits
There's simply no reason to scrap circuit boards when they have contacts contaminated with solder. Restore them using the Gold Contact Plating Kit. CircuitMedic
Multicore TFN700B is a no-clean, halide-free tacky flux formulated to address the challenging requirements of package-on-package applications. Henkel Corporation
Once you have made the decision to package your electronics with rigid flex, it makes sense to pick a production partner who can build it right. Printed Circuits, Inc.
Once you have made the decision to package your electronics with rigid flex, it makes sense to pick a production partner who can build it right. Printed Circuits, Inc.
Components encapsulated in plastic or organic compounds are susceptible to moisture damage. So are PCBs, all can cause early field failures. Control MSDs per IPC J-Std-033b.1 and 1601. Super Dry®
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However masking the via holes, providing the via holes of correct dimension and type and at equal spacing, will reduce the percentage of voids. Proper stencil designing for the thermal pads will also reduce the voids in thermal pads. Increasing the metal load or reducing the flux content in the solder paste will give some good results. Thermal pad design plays the major role in voiding, so discuss with the customer and come to an agreement on the thermal pad voids.
S.S
To me, taking all parameters constant, the solder joint reliability for QFN or LGA pad would be much lower compared to the BGA ball. As I am not involved in process, I could be totally wrong. I would like to learn from anyone of you in this aspect.
Wee Mei, DSO National Laboratories, Singapore