Circuit board with localized stiffener for enhanced circuit component reliability
AssigneeDelphi Technologies, Inc.
InventorsSuresh K. Chengalva, David W. Ihms, Bruce A. Myers
Life of this patent
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Abstract
A circuit board assembly comprising a laminate substrate and a surface mount device having a CTE less than that of the laminate substrate and attached with at least one solder joint to a first surface of the laminate substrate. The assembly further includes a localized stiffener attached to a second surface of the laminate substrate so as to be directly opposite the circuit device. The localized stiffener is formed of a material and is shaped so that, when attached to the laminate substrate, the stiffener is capable of increasing the thermal cycle fatigue life of the one or more solder joints that attach the device to the substrate.
Claims18
A circuit board assembly comprising a laminate organic substrate having oppositely-disposed first and second surfaces, a surface-mount device attached with a plurality of solder bumps to the first surface of the laminate organic substrate, and a localized stiffener attached with a pluralitv of solder bumps to the second surface of the laminate organic substrate directly opposite the device wherein the solder bumps space the localized stiffener from the laminate organic substrate to define a gap therebetween, the device and the localized stiffener having lateral dimensions in a plane parallel to the first and second surfaces of the laminate organic substrate with at least one of the lateral dimensions of the localized stiffener being greater than the lateral dimensions of the device, the laminate organic substrate, the device, and the localized stiffener having coefficients of thermal expansion and having moduli of elasticity, the coefficients of thermal expansion of the device and the localized stiffener being less than the coefficient of thermal expansion of the laminate organic substrate, the modulus of elasticity of the localized stiffener being greater than the modulus of elasticity of the laminate organic substrate, the localized stiffener being attached to the laminate organic substrate so as to locally stiffen the laminate organic substrate beneath the device and thereby increase the fatigue life of the at least one solder bump.
A circuit board assembly comprising a laminate organic substrate having oddositely-disposed first and second surfaces, a surface-mount device attached with at least one solder joint to the first surface of the laminate organic substrate, and a localized stiffener attached to the second surface of the laminate organic substrate directly Opposite the device, the device and the localized stiffener having lateral dimensions in a plane parallel to the first and second surfaces of the laminate organic substrate with at least one of the lateral dimensions of the localized stiffener being greater than the lateral dimensions of the device, the laminate organic substrate, the device, and the localized stiffener having coefficients of thermal expansion and having moduli of elasticity, the coefficients of thermal expansion of the device and the localized stiffener being less than the coefficient of thermal expansion of the laminate organic substrate, the modulus of elasticity of the localized stiffener being greater than the modulus of elasticity of the laminate organic substrate, the localized stiffener being attached to the laminate organic substrate so as to locally stiffen the laminate organic substrate beneath the device and thereby increase the fatigue life of the at least one solder joint, wherein the laminate organic substrate has conductive vias between the first and second surfaces that thermally couple the device to the localized stiffener.
A circuit board assembly comprising a laminate organic substrate having oppositely-disposed first and second surfaces, a surface-mount integrated circuit device attached with multiple solder bumps to the first surface of the laminate organic substrate, and a non-electrically functional stiffener attached with a plurality of solder bumps to a limited region of the second surface of the laminate organic substrate directly opposite the device wherein the plurality of solder bumps space the stiffener from the laminate organic substrate to define a gap therebetween that is completely filled with an underfill material, each of the device and the stiffener having peripheral boundaries that establish a pair of transverse dimensions in a plane parallel to the first and second surfaces of the laminate organic substrate, each of the transverse dimensions of the stiffener being greater than a corresponding one of the transverse dimensions of the device, the laminate organic substrate, the device, and the stiffener having coefficients of thermal expansion and having moduli of elasticity, the coefficients of thermal expansion of the device and the stiffener being less than the coefficient of thermal expansion of the laminate organic substrate, the modulus of elasticity of the stiffener being at least about ten times greater than the modulus of elasticity of the laminate organic substrate, the stiffener being attached to the laminate organic substrate so as to locally increase the biaxial bending stiffness of the laminate organic substrate between the device and the stiffener and thereby increase the fatigue life of the solder bumps, the laminate organic substrate having conductive vias between the first and second surfaces that thermally couple the device to the stiffener.
Dependencies are inferred from the claim text.