Patent Application
20110048795
This invention is directed to a problem in uniformly applying a thermally conductive interface material (TIM) between an electronic device and an enclosing metal lid or cover. Additionally, the method of application of the thermal material taught here creates a low stress bond between the device and lid, reducing potential of damage to the device.
Known solutions include attaching and bonding a TIM between a lid and an electronic device, typically in a limited coverage area. The TIM is applied either to the inside of the lid or to the surface of the device, and then the lid and electronic device substrate are mated together at the edges of the lid sides. Force is applied typically to the top of the lid to make contact between the lid, the substrate, the TIM and the electronic device simultaneously.
This creates a challenge to manage all surface contacts due to non-planarity on any given surface (lid, TIM, substrate, electronic device), resulting in non-attached areas either between the lid sides and the substrate, the inner side of the lid and TIM, or between the TIM and the electronic device surface. An inadequate attachment can create either environmental or structural damage to the device(s) being packaged, or functional damage to the device due to poor thermal conductivity between the heat source (electronic device) and the lid.
One purpose of this invention is to provide a metallic cover designed and constructed with four sides and a top or lid and a pattern of aperture openings (holes) in the cover located in the lid surface and/or sides of the cover.
An other purpose is to provide a method of manufacturing an electronic package that consists of mounting a cover or lid onto a substrate, and subsequently inserting a liquid thermal interface material (through dispensing, injection molding or printing through apertures in the cover or lid) between the surface of the electronic device and the cover, and curing the TIM to a solid state.
The advantage of using this invention instead of known solutions is that this invention provides a way to create a uniform, low stress, thermal interface between a heat source (electronic device) and dispersion source (cover or lid) with no loss of thermal conduction caused by air gaps in the TIM or between interfaces and/or non-uniform TIM coverage of the electronic device.
Some of the purposes of the invention having been stated, others will appear as the description proceeds, when taken in connection with the accompanying drawings, in which:
While the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which a preferred embodiment of the present invention is shown, it is to be understood at the outset of the description which follows that persons of skill in the appropriate arts may modify the invention here described while still achieving the favorable results of the invention. Accordingly, the description which follows is to be understood as being a broad, teaching disclosure directed to persons of skill in the appropriate arts, and not as limiting upon the present invention.
As briefly mentioned above, the invention has two aspects. The first addressed here is the mechanical structure involved.
Referring now to
As an alternative, the device cover (here, indicated at 20 in
The second aspect is the process of assembly using the covers 10, 20 disclosed (
The package (module) is then sent through a normal curing process to solidify the thermal interface material. As part of this process, the module may be in a fixture that applies pressure between the lid and the package substrate, causing a uniform cure and forcing any air that might be trapped in the liquid material to outgas. Alternatively, the module may go through a curing process without need for a fixture. Any excess material can be cleaned from surface of the cover if necessary. This can be done either chemically or mechanically.
By attaching the lid to the substrate and curing first, any warpage between surfaces of the inside of the lid and the electronic device will determined. Subsequently inserting the thermal interface material between the device (heat source) and the lid will provide maximum material uniformity and improved thermal conductivity between source and lid can be established. See
In the drawings and specifications there has been set forth a preferred embodiment of the invention and, although specific terms are used, the description thus given uses terminology in a generic and descriptive sense only and not for purposes of limitation.
