# US 7,071,030 B2 · Method of making a flexible substrate with a filler material > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,071,030 B2 - Document ID: US7071030B2 - Status: Granted - Kind: B2 - Application number: 10/372,594 - Filed: 2003-02-24 - Published: 2003-08-14 - Granted: 2006-07-04 - Earliest claimed: 2000-08-31 - Assignees: Micron Technology, Inc. - Inventors: Tongbi Jiang; Edward Schrock - Web page: https://patentgrep.com/patent/US7071030B2 ## CPC - H10W 70/688: {Flexible insulating substrates} - H10W 40/251: {Organics} - H05K 1/0346: {containing N} - H05K 1/0373: {containing additives, e.g. fillers (H05K1/036 takes precedence)} - H05K 2201/0154: Polyimide - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS ## Abstract A method of adding a thermally conductive, electrically nonconductive filler to a flexible substrate such as a polyimide core. The substrate may be used, for example, as a part of a polyimide core for a tape or an interposer in a BGA or similar integrated circuit package. The resulting substrate has a higher thermal conductivity as compared to conventional substrates without fillers, thereby increasing the thermal dissipation through the substrate and enabling the device to cool more efficiently. The filler also reduces the coefficient of thermal expansion of the substrate to more closely match the die and reduce stresses. Furthermore, the filler increases the rigidity of the substrate, thereby enabling the device to be handled and carried more easily, for example, without a metal frame carrier. ## Claims ### Claim 1 A method of increasing the thermal conductivity of a flexible tape comprising, adding a thermally conductive filler material to a polyimide film, wherein the filler material increases the thermal conductivity of the tape by about 50% or more as compared to that of the polyimide film without the filler material. ### Claim 2 (depends on 1) The method of claim 1, wherein the filler material is added to the polyimide film prior to film formation. ### Claim 3 A method of increasing the thermal conductivity of a flexible tape comprising, adding a filler material of thermally conductive material to a polyimide film prior to film formation, wherein the filler material is added in an extrusion method. ### Claim 4 A method of increasing the thermal conductivity of a flexible tape comprising, adding a filler material of thermally conductive material to a polyimide film prior to film formation, wherein the filler material is added in a coating method. ### Claim 5 (depends on 2) The method of claim 2, wherein the filler material has an average diameter of about 75 μm or less. ### Claim 6 (depends on 1) The method of claim 1, wherein the filler material is added to the polyimide film in an amount of about 10 to 95% by weight. ### Claim 7 A method of increasing the thermal conductivity of a flexible tape comprising, adding a filler material of thermally conductive material to a polyimide film, wherein the filler material is a nitride material. ### Claim 8 (depends on 7) The method of claim 7, wherein the filler material is boron nitride. ### Claim 9 (depends on 7) The method of claim 7, wherein the filler material is silicon nitride. ### Claim 10 (depends on 2) The method of claim 2, wherein the filler material is aluminum nitride. ### Claim 11 (depends on 1) The method of claim 1, wherein the filler material is alumina. ### Claim 12 (depends on 1) The method of claim 1, wherein the filler material is silica. ### Claim 13 A method of increasing the thermal conductivity of a flexible tape comprising, adding a filler material of thermally conductive material to a polyimide film, wherein the filler material reduces the CTE of the polyimide film by about 10% or more as compared to the polyimide film without the filler material. ### Claim 14 A method of increasing the thermal conductivity of a flexible tape comprising, adding a thermally conductive filler material to a polyimide film, wherein the filler material increases the modulus of elasticity of the polyimide film as compared to the modulus of elasticity of the polyimide film without the filler material. ### Claim 15 (depends on 14) The method of claim 14, wherein the filler material increases the modulus of elasticity of the polyimide film by about 10% or more as compared to the modulus of elasticity of the polyimide film alone. ### Claim 16 A method of increasing the thermal conductivity of a flexible tape for use in an integrated circuit, comprising adding a filler of thermally conductive material to a polyimide film, wherein the filler is a nitride. ### Claim 17 (depends on 16) The method of claim 16, wherein the filler is boron nitride. ### Claim 18 (depends on 16) The method of claim 16, wherein the filler is silicon nitride. ### Claim 19 (depends on 16) The method of claim 16, wherein the filler is aluminum nitride. ### Claim 20 A method of increasing the thermal conductivity of a flexible tape for use in an integrated circuit, comprising adding a thermally conductive filler material to a polyimide film, wherein the filler material is alumina. ### Claim 21 A method of increasing the thermal conductivity of a flexible tape for use in an integrated circuit, comprising adding a thermally conductive filler material to a polyimide film, wherein the filler material is silica. ### Claim 22 (depends on 16) The method of claim 16, wherein the filler increases the thermal conductivity of the flexible tape by about 50% or more as compared to the thermal conductivity of the polyimide film alone. ### Claim 23 (depends on 16) The method of claim 16, wherein adding the filler to the polyimide film comprises blending the filler into a polyimide resin. ### Claim 24 (depends on 16) The method of claim 16, wherein adding the filler to the polyimide film comprises adding about 10 to 95% by weight filler to the polyimide film.