Fujitsu Corporation

Albert Wong Chan

Michael G Lee

Solomon I Beilin

Mark Thomas McCormack

Hunt Hang Jiang

Yasuhito Takahashi

Theresa M Larson

A method for joining large area semiconductor substrates, a liquid thermoset polymer. Two large area substrates, such as wafers or circuit boards (e.g., rigid or flexible), can be joined together by dispensing a liquid polymer inwardly from the edges of the semiconductor substrates. The substrates can then be pressed together so that the liquid thermoset flows in an outwardly direction ward the edges of the semiconductor substrates. Conducting surfaces on the first and second substrates may contact each other after pressing the liquid thermoset polymer. The liquid thermoset polymer in the formed structure may then be cured to a hardened state. The liquid thermoset polymer preferable has a low viscosity, low levels of ionic contaminants, good adhesion to the substrates, low moisture absorbing properties and favorable thermal expansion properties.

Method for joining large substrates

A method of depositing solder on a conductive region of a substrate comprising providing a substrate having a substrate aperture and a coefficient of thermal expansion. A polymeric stencil is also provided such as to have a stencil aperture and a coefficient of thermal expansion which is approximately equal to the coefficient of thermal expansion of the substrate. The method also includes disposing the polymeric stencil on the substrate such that the stencil aperture is aligned with a conductive region; and reflowing the solder paste while the polymeric stencil remains disposed on the substrate. The polymeric stencil is then removed from the substrate essentially without any solder-paste being removed with the polymeric stencil. A method of forming a polymeric stencil for solder-paste printing comprising forming in a polymeric sheet of plurality of apertures having wrinkles in the polymeric sheet in proximity to the plurality of apertures, and compressing opposing surfaces of the apertured polymeric sheet toward each other. The compressed apertured polymeric sheet is then heated and rapidly cooled to remove wrinkles in proximity to the apertures. A stencil for use in a fine pitch bumping process comprising a releasable polymeric sheet having a coefficient of thermal expansion of less than about 4.0 ppm/&deg;C. and a structure defining a pair of apertures spaced from each other at a distance less than about 0.20 mm.

Stencil and method for depositing solder

A conductive composition, and articles and methods using the conductive composition are disclosed.

Conductive composition

An interconnect assembly and a fluxless method for forming the interconnect assembly. The fluxless method includes providing a first semiconductor substrate having a first pad connected thereto. A post is connected to the first pad and includes a length greater than a thickness of the first pad, and a metallic solder disposed on an associated end of the post. A second semiconductor substrate is provided as having a second pad connected thereto. The fluxless method further includes depositing an unfilled polymeric liquid on the second pad, aligning and contacting the metallic solder with the unfilled polymeric liquid, and forcing by pressure the first and second semiconductor substrate toward each while simultaneously heating the metallic solder and the unfilled polymeric liquid to form a metallurgical joint between the second pad and the metallic solder.

Interconnect assembly and Z-connection method for fine pitch substrates

Methods for making circuit substrates and electrical assemblies are disclosed. A conductive composition is disposed between confronting conductive regions and can be cured to form a via structure. The conductive composition includes conductive particles and a carrier. The carrier can include a fluxing agent and an epoxy-functional resin having a viscosity of less than about 1000 centipoise at 25&deg; C.

Methods for making circuit substrates and electrical assemblies

Printed circuit substrates and electrical assemblies including a conductive composition are disclosed. The printed circuit substrate and the electrical assembly embodiments comprise a first conducting region and a second conducting region. A dielectric layer is disposed between the first and second conducting regions. An aperture is disposed in the dielectric layer and a via structure including the conductive composition is disposed in the aperture. The conductive composition is preferably in a cured state and electrically communicates with the first and second conducting regions. In preferred embodiments, the conductive composition comprises conductive particles in an amount of at least about 75 wt. % based on the weight of the composition. At least 50% by weight of the conductive particles have melting points of less than about 400.degree. C. The composition further includes a carrier including an epoxy-functional resin in an amount of at least about 50 wt. % based on the weight of the carrier, and a fluxing agent in an amount of at least about 0.1 wt % based on the weight of the carrier. The epoxy functional resin can have a viscosity of less than about 1000 centipoise at 25.degree. C.

Multi-layer circuit substrates and electrical assemblies having

A method for depositing a solder paste or other conductive or non-conductive material on a contact pad or other designated region of a substrate. A layer of resist is applied over the boundary of a region in which a bump of a deposited material is to be formed. The resist layer is applied by a screen printing process in which the portion of the screen overlying the region is blocked so that no resist is deposited where the bump is to be formed. The screen is open in the areas surrounding the blocked portion, permitting resist to be deposited over any non-planar surfaces surrounding the intended bump location. This provides a substantially planar surface which may be used as a mask for direct paste deposition into the region where the bump is to be formed, or the planar surface may be used as a flat surface upon which a stencil may be supported. After formation of the bump of conductive or non-conductive paste, the sacrificial resist layer is removed.

Growing community of inventors

Cupertino, CA, United States of America

Albert Wong Chan