The present invention is directed to thermal dissipation structures and methods for removing heat from electronic components. More particularly, the present invention is directed to a thermal dissipation structure and method with enhanced bonding between a heat sink of the thermal dissipation structure and an electronic component, wherein the bonding surfaces of the heat sink and electronic component comprise dissimilar materials with different coefficients of thermal expansion.
As an electronic component operates, heat is generated which must be removed or dissipated. Typically, heat is dissipated by a cooling structure, such as an aluminum (Al) or copper (Cu) heat sink coupled to the electronic component. The heat sink absorbs heat from the electronic component, and dissipates the heat via direct air convection. Heat sinks are well known in the electronics industry and are used extensively to dissipate heat generated by electronic components used in computers and various other electronic equipment.
Improvements in integrated circuit (IC) design and fabrication allow IC manufacturers to produce ever smaller and lighter weight IC devices and other electronic components which require cooling.
For lighter weight electronic components, graphite composite (e.g., graphite/epoxy) heat sinks offer advantage over conventional aluminum or copper heat sinks in that their thermal performance is nearly that of aluminum and copper heat sinks, but at a fraction of the weight and cost. One example of a graphite composite heat sink is described in commonly assigned, U.S. Pat. No. 6,684,501, entitled “Foil Heat Sink and A Method for Fabricating Same”, which is hereby incorporated herein by reference in its entirety.
Applicants have discovered that problems arise when attempts are made to attach a graphite composite heat sink to, for example, a module cap or thermal spreader of an electronic component comprising a dissimilar material (e.g., a metal cap or spreader). Because of an inherent coefficient of thermal expansion (CTE) mismatch between, for example, a graphite composite heat sink and a typical module cap or thermal spreader of an electronic component, and because of a relatively large distance to neutral point (DNP) of today's heat sinks, use of solder or an epoxy bonding attach material can be difficult (e.g., when DNP becomes greater than 40 mm). This is because too much strain would be put on the bonded interface due to the CTE mismatch and the relatively large DNP, resulting in interface fracturing.
Therefore, a need exists for an enhanced thermal dissipation structure and method which allow a heat sink and electronic component of dissimilar materials with different coefficients of thermal expansion to be bonded together using an epoxy based or solder based attach material by reducing shear stresses within the bond.
The needs of the art are addressed, and additional advantages are provided, by the present invention which in one aspect is a thermal dissipation structure which includes a heat sink having a first surface configured to couple to a second surface of an electronic component for facilitating removal of heat from the electronic component. The first surface of the heat sink and the second surface of the electronic component are assumed to comprise dissimilar materials with different coefficients of thermal expansion. In accordance with an aspect of the invention, the first surface of the heat sink has a pattern of channels therein. The pattern of channels define multiple heat sink substructures. Each heat sink substructure includes a portion of the first surface of the heat sink, with the portions of the first surface of the heat sink substructures being coplanar and providing a reduced distance to neutral point across the first surface of the heat sink so that when the portions of the first surface of the heat sink are bonded to the second surface of the electronic component, shear stress within the bond is reduced.
In another aspect, an electronic assembly is provided comprising an electronic component and a thermal dissipation structure. The thermal dissipation structure includes a heat sink having a first surface configured to couple to a second surface of the electronic component for facilitating removal of heat from the electronic component. The first surface of the heat sink and the second surface of the electronic component comprise dissimilar materials with different coefficients of thermal expansion. The first surface of the heat sink includes a pattern of channels therein. The pattern of channels define multiple heat sink substructures, with each heat sink substructure including a portion of the first surface of the heat sink. The portions of the first surface of the heat sink substructures are coplanar and provide a reduced distance to neutral point across the first surface of the heat sink. The electronic assembly further includes a bonding material disposed between the portions of the first surface of the heat sink substructures and the second surface of the electronic component, wherein the bonding material comprises a thermal interface between the portions of the first surface of the heat sink of the multiple heat sink substructures and the second surface of the electronic component.
In another aspect, a thermal dissipation method for an electronic component is provided. The method included: providing a heat sink having a first surface configured to couple to a second surface of the electronic component for facilitating removal of heat from the electronic component, wherein the first surface of the heat sink and the second surface of the electronic component comprise dissimilar materials with different coefficients of thermal expansion, and wherein the first surface of the heat sink has a pattern of channels therein, the pattern of channels defining multiple heat sink substructures, each heat sink substructure including a portion of the first surface of the heat sink, the portions of the first surface of the heat sink substructures being coplanar, and providing a reduced distance to neutral point across the first surface of the heat sink; bonding the portions of the first surface of the heat sink substructures to the second surface of the electronic component, wherein the portions of the first surface of the heat sink of the multiple heat sink substructures with the reduced distance to neutral point result in shear stress within the bond between the first surface of the heat sink and the second surface of the electronic component being reduced.
Further, additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
As used herein, “electronic component” comprises any heat generating component of, for example, a computer system or other electronics system requiring cooling. The term includes one or more integrated circuit devices, electronic devices, or electronic modules, either with or without a thermal cap or thermal spreader.
As noted, certain advantages can be realized by transitioning the heat sink material to, for example, a graphite composite material. The disadvantage of this transition, however, is that a coefficient of thermal expansion mismatch results between the heat sink and the electronic component to which the heat sink is to be coupled.
Where:
As shown in
For example, with a pattern of grooves as shown in
Those skilled in the art will note from the above discussion that other heat sink embodiments are possible without departing from the present invention. For example, in an alternate embodiment, the heat sink substructures could be separately manufactured and then assembled onto a heat sink base, or even bonded directly to a thermal cap or thermal spreader of an electronic component such that the resultant structure would resemble that of a monolithic heat sink. Machining the base as shown in
Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.