Microelectronic assemblies having low profile connections

Abstract

A microelectronic assembly includes a first microelectronic element having a first face and contacts accessible at the first face, and a layer of a dielectric material having a bottom surface contacting the first microelectronic element, a top surface facing away from the first microelectronic element and holes extending between the top and bottom faces in alignment with the contacts on the first microelectronic element. The assembly includes conductive protrusions extending through the holes to the contacts, the conductive protrusions projecting beyond the top surface of the dielectric layer. The assembly also has a second microelectronic element having a first surface with conductive elements being accessible at the first surface thereof, the second microelectronic element being assembled with the first microelectronic element so that the contacts of the second microelectronic element are connected with the conductive protrusions and the top surface of the dielectric layer is spaced from the first surface of the second microelectronic element.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application is a continuation of U.S. patent application Ser. No. 10 / 699,328, filed Oct. 31, 2003, which claims the benefit of U.S. Provisional Application Ser. No. 60 / 426,478 filed Nov. 13, 2002, the disclosures of which are hereby incorporated by reference herein.FIELD OF THE INVENTION [0002] The present invention relates to methods of making microelectronic assemblies and to microelectronic assemblies. BACKGROUND OF THE INVENTION [0003] Microelectronic elements are typically packaged and assembled with a microelectronic component to facilitate connection to external circuitry. Heat is generated in use, as well as during manufacturing operations such as, for example, bonding. When heat is generated within the assembly, the various parts of the assembly expand and contract according to the coefficient of thermal expansion for the particular part. Incorporating various materials having different coefficients of thermal expan...

AI Technical Summary

Benefits of technology

[0007] In one aspect of the present invention, a method of making a microelectronic assembly comprises providing a microelectronic element having a first major surface with protrusions projecting from the first major surface, covering the first major surface and the protrusions with a material, removing a portion of the material so that portions of the protrusions are accessible, and assembling the microelectronic element with a microelectronic component. The material applied to the first major surface reduces the height of the projections. In certain embodiments, the protrusions comprise bumps and the material allows the assembly to behave, in certain respects, as if bumps having a lower height were provided on the first major surface. The protrusions desirably comprise a solder, such as high lead solder, C4 solder or eutectic solder.

[0008] In certain preferred embodiments, the protrusions of the microelectronic element are interconnected with conductive elements of the microelectronic component. In certain preferred embodiments, a dielectric layer is formed so as to extend between the microelectronic component and the microelectronic element and so that the leads are embedded in the dielectric layer. The material applied to the first major surface reduces the height of the projections so that the dielectric layer incorporates less of the projections and interferes less with the ability of the dielectric layer to adapt to dimensional changes within the assembly.

[0026] In a further aspect of the present invention, a semiconductor chip assembly has a semiconductor chip with a first major surface and protrusions projecting from the first major surface a distance of less than about 50 μm, and a dielectric layer overlying the first major surface and having conductive elements extending through the dielectric layer and being connected to the protrusions. The dielectric layer may comprise a compliant material and the conductive elements may comprise leads. Assemblies according to this aspect subject the leads to lower stresses due to dimensional changes within the assembly.

[0031] The dielectric layer desirably has a thickness of between about 100 μm and about 200 μm. The projections desirably project from the first major surface a distance between about 10 μm and about 50 μm. The particular dimensions are not essential to the invention. In preferred embodiments, an assembly has a dielectric layer with a thickness in the aforementioned range, projections which project from the first major surface in the aforementioned range, and conductive elements extending through the dielectric layer, so that the stress on the conductive elements is low.

Problems solved by technology

However, the larger the dielectric layer, the more stress the leads experience.

This is compounded by the presence of bonding material between the contacts and the leads, which interferes with the flexibility of the dielectric layer.

However, some connections incorporate a significant amount of bonding material, which adds to the height of the connection between the leads and contacts, and impacts the reliability of the assembly.

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