Electroplated Cu/SnAg double bumps (a) tilted view and (b) side view of Cu column/SnAg bumps.
(a) Cross-sectional image of Cu/SnAg double-bump flip chip assembly and (b) magnified image of (a).
PCB Cu line design for bumps contact resistance measurement: (1) chip center, (2) chip edge, and (3) chip corner.
Mesh design for FEA.
T/C test results of Cu/SnAg double-bump flip chip assembly (a) cumulative distribution and (b) the ratio of contact resistance of bumps over at various bump positions.
SAM -scan images of Cu/SnAg double-bump flip chip assembly after (a) reliability tests RH, 1000 h and (b) T/C test, 1002 cycles.
T/C failure of Cu/SnAg double-bump flip chip assembly: (a) SAM image, (b) cross-sectional image of A position (center bumps), and (c) cross-sectional image of B position (corner bumps).
FEA results: (a) the deformation of a flip chip assembly at and (b) Von-Mises stress distribution during T/C.
EPMA mapping results of Cu/SnAg double joints after T/C. (a) Schematic illustration of Cu/SnAg double bump, (b) SEM image of Si chip/Al pad/Cu column interface of corner bumps after 1002 thermal cycles, (c) Al mapping, (d) Ti mapping, (e) Cu mapping, and (f) Si mapping.
FEA results: (a) the equivalent plastic strain, PEEQ and (b) the dissipated plastic energy density.
Strain components on Cu column bumps. (a) —plastic normal strain in the -direction (transverse direction of a Si chip), (b) —plastic normal strain in the -direction (perpendicular direction of a Si chip), and (c) —plastic shear strain.
Maximum normal plastic strain on Cu column bumps in the -direction in low temperature region ,
Material properties used in 2D FEA.
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