Manufacturing And Reliability Challenges With QFN - SMTA

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Manufacturability (Rework)• Can be difficult to replace a package and getadequate soldering of thermal / internal pads.Mini-stencils or rebump techniques can be used to getsufficient solder volume• Not directly accessible with soldering iron and wirePortable preheaters used in conjunction with soldering ironcan simplify small scale repair processes• Close proximity with capacitors often requiresadjacent components to be resoldered / replaced aswell© 2004 - 200935
Manufacturability (Stencil Design)• Stencil thickness and aperture design can be crucial formanufacturabilityExcessive amount of paste can inducefloat, lifting the <strong>QFN</strong> off the boardExcessive voiding can also be inducedthrough inappropriate stencil design• Follow manufacturer’s guidelinesGoal is 2-3 mils of solder thickness• Rules of thumb (thermal pad) Ratio of aperture/pad ~0.5:1 Consider multiple, smaller apertures(avoid large bricks of solder paste) Reduces propensity for solder balling© 2004 - 200936
Page 4 and 5: Who Uses DfR?Military / Avionics /
Page 6 and 7: Knowledge and Education(Website)•
Page 8 and 9: Introduction (cont.)• Why is know
Page 10 and 11: Component Packaging• Most of us h
Page 12 and 13: 2 nd Level Interconnect Reliability
Page 14 and 15: Solder Wearout (cont.)• Eliminati
Page 17 and 18: Industry Response to SJ Wearout?•
Page 19 and 20: Quad Flat Pack No-Lead (QFN)© 2004
Page 21 and 22: QFN (cont.)• Availability 1 x 2 m
Page 24 and 25: Advantages: Thermal Performance•
Page 26 and 27: QFN: Why Not?• QFN is a ‘next g
Page 28 and 29: Bond Pads (cont.)• Extend bond pa
Page 30 and 31: Singulated operationTitle: Reliabil
Page 32 and 33: Title: Reliability study of surface
Page 36 and 37: Manufacturability (cont.)• QFN so
Page 38 and 39: Reliability (Thermal Cycling)• Or
Page 40 and 41: Reliability (Bend Cycling)• Low d
Page 42 and 43: Dendritic Growth (cont.)• The ele
Page 44: QFN: Risk Mitigation• Assess manu

Manufacturing And Reliability Challenges With QFN - SMTA

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