Northrop Grumman Systems Corporation

Thomas E Steelman

Robert W Koon

A structure for providing an enhanced heat transfer capability in a circuit board having electronic components and which is at least in part cooled by a gas flowing around the board. The enhanced heat transfer structure includes thermally conductive fibers attached at a first end to an exterior surface of the circuit board and jutting out generally perpendicular to the exterior surface. These fibers are used to conduct heat from the circuit board and transfer it to the gas. The fibers are attached the circuit board by electrostatic fiber flocking methods. It is preferred that these thermally conductive fibers are carbon fibers. The fibers can be attached to the exterior surface of the circuit board by a layer of adhesive. The fibers also do not necessarily have to be attached to the entire circuit board. They may be attached to only a portion of it, such as to temperature sensitive electronic board components. The enhanced heat transfer structure can be incorporated during the assembly of the board, or where the circuit board is an existing unit, the thermally conductive fibers can be attached without removing electronic components disposed thereon. Thus existing circuit boards can be retrofitted.

Enhanced heat transfer in printed circuit boards

A method and apparatus for producing a reinforced composite prepreg material comprising the steps of aligning discontinuous fibers by use of a strong electric field while simultaneously inserting the fibers through a mesh screen and into a ply or plies of fiber reinforced polymer matrix composite in an uncured state in a direction normal to the surface of the composite material. After the fibers are attached in the ply of fiber reinforced polymer matrix composite, the aligned fibers are forced through the composite material by applying a gentle pressure to the top of the conductive fibers while simultaneously being guided by the mesh screen. After the insertion process has been completed, the mesh screen is lifted vertically away from the composite material and any unaligned fibers are simultaneously removed. The newly formed reinforced prepreg composite films are then stacked on top of each other and pressurized and cured in an autoclave or press to produce an improved composite laminate.

Method for single filament transverse reinforcement in composite prepreg

A structure for providing an enhanced heat transfer capability in a circuit board having electronic components and which is at least in part cooled by a gas flowing around the board. The enhanced heat transfer structure includes thermally conductive fibers attached at a first end to at least a portion of the exterior surfaces of the circuit board and/or electronic components thereof. The fibers extend out from the aforementioned exterior surfaces in a generally perpendicular direction, and are used to conduct heat from the circuit board and/or electronic components, and transfer it to the surrounding gas. Electrostatic fiber flocking methods are employed to attached the fibers in the aforementioned perpendicular orientation. It is also preferred that these thermally conductive fibers are carbon fibers, and attached to the exterior surface of the circuit board by a layer of adhesive. The enhanced heat transfer structure can be incorporated during the assembly of the board, or where the circuit board is an existing unit, the thermally conductive fibers can be attached without removing electronic components disposed thereon. Thus existing circuit boards can be retrofitted.

Enhanced heat transfer in printed circuit boards and electronic

A method and apparatus for providing electrical conductivity between the opposing surface edges of gaps and joints in composite and metallic structures comprises fiber flocking a first and second set of conductive fibers in a direction normal to the surface edge of each side of the gap or joint. The first and second set of conductive fibers are positioned such that the conductive fibers interdigitate with respect to each other providing a compliant electrically conductive path between the opposing surface edges of the structural gaps and joints. After assembly, the defined joint or gap containing the interdigitated sets of carbon fibers may be filled with a polymer material or materials which constitute state of the art matrix materials used for conductive joints. Applications for this technology include electromagnetic shielding and low observables.

Enhanced conductive joints from fiber flocking

An isotropic resin matrix material includes resin doped with fiberballs. Fiberballs are formed from a plurality of fibers generally radiating outward from a common node. These fibers are of sufficient numbers and separation at a distal end to form a spherical shape. The fiberballs are uniformly distributed throughout the resin. Preferably, the fibers making up the fiberballs are carbon fibers. The carbon fibers impart thermal and electrical conductivity, or dielectric loss characteristics in some configurations. These conductivity and loss characteristics are isotropic in they are the same no matter where the electrical or thermal energy is applied due to the radial structure and uniform distribution of the fiberballs. The fiberballs may also be saturated with a phase change material and encapsulated in a shell so as to impart a heat dissipation capacity to the resin matrix material. Heat impinging on the resin matrix material is transferred to the phase change material via the surface of the individual fibers making up the fiberball. Here again, the radial structure and uniform distribution of the fiberballs imparts an isotropic nature to the heat dissipation capacity.

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Torrance, CA, United States of America

Thomas E Steelman