International Business Machines Corporation

Thomas M Culnane

Michael A Gaynes

Mark Vincent Pierson

Ramesh R Kodnani

Hussain Shaukatullah

Ping Kwong Seto

Charles Gerard Woychik

Miguel Angel Jimarez

Li Li

Lisa Jeanine Jimarez

Donald I Mead

David N Cokely

Mixtures for attaching a semiconductor chip to a substrate. The semiconductor chip has an array of joining material bumps, such as C4 solder balls. The substrate has an array of conductive pads corresponding to the array of joining material bumps. In a first embodiment the fixture has a body having a first cavity containing the semiconductor chip and a second cavity for containing the substrate. The substrate is placed over the semiconductor chip with the conductive pads opposing and in contact with the joining material bumps, such that during reflow of the joining material bumps, the weight of the substrate acts against the joining material bumps and aids in the attachment of the semiconductor chip to the substrate to form electrical connections therebetween.

Method of attaching a conformal chip carrier to a flip chip

A semiconductor chip carrier assembly which includes a flexible substrate having a metallicized path on one of its surfaces in electrical communication with a semiconductor chip. A stiffener is disposed adjacent to said flexible substrate and is bonded thereto by an adhesive composition. The adhesive composition which comprises a microporous film laden with a curable adhesive is disposed between the flexible substrate and the stiffener. A cover plate is adhesively bonded to the semiconductor chip and to the stiffener. A process of making the assembly involving disposition of the flexible substrate in a vacuum fixture upon which the adhesive composition and stiffener is placed followed by the application of heat and pressure to cure the curable adhesive is also described.

Process for making semiconductor chip assembly

Fixtures for attaching a semiconductor chip to a substrate. The semiconductor chip has an array of joining material bumps, such as C solder balls. The substrate has an array of conductive pads corresponding to the array of joining material bumps. In a first embodiment the fixture has a body having a first cavity for containing the semiconductor chip and a second cavity in communication with the first cavity for containing the substrate. Whereby the substrate is placed over the semiconductor chip with the conductive pads opposing and in contact with the joining material bumps, such that during reflow of the joining material bumps, the weight of the substrate acts against the joining material bumps and aids in the attachment of the semiconductor chip to the substrate to form electrical connections therebetween. In a second embodiment the fixture has a first plate having a first opening for disposal of the semiconductor chip therein, a second plate stacked below the first plate and having a thickness substantially equal to the thickness of the substrate, the second plate further having a second opening opposing the first opening for disposal of the substrate therein, and a third plate stacked below the second plate such that the substrate is flattened in the second opening under the weight of the first plate thereby aiding in the attachment of the joining material bumps to their corresponding conductive pads during solder reflow to form electrical connections therebetween. Methods for use of the fixtures is also provided.

Fixture for attaching a conformal chip carrier to a flip chip

Semiconductor chip carrier assembly

A stiffener (34 or 52 or 72) includes a pathway which allows gases and fluids, such as air, to be vented from the interface between surface bonding regions (35 or 60 or 74) of the stiffener and an adhesive (38 or 56 or 80) on a flexible substrate (36 or 54 or 78). The pathway may take the form of a porous material used for the stiffener or one or more bore holes (58 or 59 or 70) formed in the stiffener. The stiffener may also include an internal cavity (76) for promoting venting of fluids and gases. By venting fluid and gases from the adhesive/stiffener interface, better adhesion between the stiffener and flexible substrate is achieved.

Stiffeners with improved adhesion to flexible substrates

An aluminum or copper heat sink is attached to a ceramic cap or exposed semiconductor chip using flexible-epoxy to provide improved thermal performance. The aluminum may be coated by anodizing or chromate conversion or the copper may be coated with nickel. Such structures are especially useful for CQFP, CBGA, CCGA, CPGA, TBGA, PBGA, DCAM, MCM-L, single layer ceramic, and other chip carrier packages as well as for flip chip attachment to flexible or rigid organic circuit boards. These adhesive materials withstand thermal cycle tests of 0.degree. to 100.degree. C. for 1,500 cycles, -25.degree. to 125.degree. C. for 400 cycles, and -40.degree. to 140.degree. C. for 300 cycles; and withstand continuous exposure at 130.degree. C. for 1000 hours without loss of strength. Flexible-epoxies have a modulus of elasticity below 100,000 psi and a glass transition temperature below 250.degree. C., are much stronger than typical silicone adhesives, and do not contaminate the module or circuit board with silicone. The flexible epoxy may contain a material having a low coefficient of thermal expansion (CTE) in order to provide a CTE between that of the silicon die and the metal of the heat sink.

Apparatus for attaching heat sinks directly to chip carrier modules

An aluminum or copper heat sink is attached to a ceramic cap or exposed semiconductor chip using flexible-epoxy to provide improved thermal performance. The aluminum may be coated by anodizing or chromate conversion or the copper may be coated with nickel. Such structures are especilly useful for CQFP, CBGA, CCGA, CPGA, TBGA, PBGA, DCAM, MCM-L, single layer ceramic, and other chip carrier packages as well as for flip chip attachment to flexible or rigid organic circuit boards. These adhesive materials withstand thermal cycle tests of 0.degree. to 100.degree. C. for 1,500 cycles, -25.degree. to 125.degree. C. for 400 cycles, and -40.degree. to 140.degree. C. for 300 cycles; and withstand continuous exposure at 130.degree. C. for 1000 hours without loss of strength. Flexible-epoxies have a modulus of elasticity below 100,000 psi and a glass transition temperature below 25.degree. C., are much stronger than typical silicone adhesives, and do not contaminate the module or circuit board with silicone. The flexible epoxy may contain a material having a low coefficient of thermal expansion (CTE) in order to provide a CTE between that of the silicon die and the metal of the heat sink.

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Lanesboro, PA, United States of America

Thomas M Culnane