Stacked and redundant chip coolers

#1. Technical Field

#The present invention relates to coolers for integrated circuit chips, and more particularly to stacked and redundant coolers.

#2. Discussion of Related Art

#Preferred embodiments of the present disclosure will be described below in more detail, with reference to the accompanying drawings:

#FIG. 1 is a schematic perspective view that illustrates a stacked cooler using staggered fin layers in the heat transfer portion according to an exemplary embodiment of the present disclosure.

#FIGS. 2A-F are schematic top views of the individual layers from which the structure in FIG. 1 is built, according to an exemplary embodiment of the present disclosure.

#FIGS. 1-2 show an exemplary embodiment of a stacked cooler according to the present disclosure. A schematic sectional perspective view of a cooler 100 using staggered fin layers (see 102, FIGS. 1 and 2B) in the heat transfer portion is shown in FIG. 1. Schematic top views of the individual layers, 101-106, from which the structure in FIG. 1 is built are shown in FIGS. 2A-F, respectively. A schematic sectional perspective view of another embodiment of a stacked cooler 300 using single layer mesh structure 301 in the heat transfer portion is shown in FIG. 3. In FIGS. 1 and 3 illustrating cross-sections of the cooler, a side thereof is not shown, and no fittings or other hose attachment hardware of the top surface 106 are shown for clarity. In FIGS. 2A-F, black indicates that the sheet is not etched, white that it is fully etched through, and gray that the sheet is partially etched through from one side. The structure in FIG. 1 is built-up by stacking and joining six unique types of layers, a base (101, FIG. 2A) which is preferably 0.6 mm thick and within the range of about 0.3 to 2.0 mm thick, multiple cooling structure layers 102, where in FIGS. 1 and 2B staggered fins 102 are used, see detail in FIGS. 4A-B. In an alternate embodiment, a single layer mesh structure (301 FIGS. 3 and 5A-B) could be used. The cooling structure layers, e.g., 102 and 301, are about 0.2 to 0.4 mm thick and are etched partially from one or both sides and are etched through where etched from both sides. The number of cooling structure layers are preferably 4 or 5 and between 2 and 8 layers. With staggered fins 102, the manifold portion of the cooler 100 is formed from three unique layers 103-105, shown in FIGS. 1 & 2C-E. The three unique manifold layers 103-105, from the top to the bottom, are designated as manifold layer 105 (FIG. 2E), manifold layer 104 (FIG. 2D), and manifold layer 103 (FIG. 2C). The manifold layers 103 and 105 are preferably 0.6 mm thick and between about 0.4 and 1.0 mm thick and the manifold layer 104 is preferably 0.2 mm thick and between about 0.2 and 0.4 mm thick. It should be understood that in the completed structure, multiple instances of some of the unique manifold layers 103 and 105 may be stacked together and joined to provide the desired cross sectional area in the manifold coolant channels. A top layer 106, which seals the manifold and provides for fluid inlet and outlet, is also shown in FIGS. 1 and 2F. Fittings, such as a hose barbs, or a threaded fitting to which an elbow, or a rotatable and positionable elbow (not shown) can be attached (e.g., bonded) to the top surface of layer 106 of the cooler 100 aligned with the openings 107-108 in the top layer 106.

#In the embodiments shown in FIGS. 1 and 3, there are two inlet regions 109-110 and two outlet regions 111-112 in the cooling layers, which alternate, and which are aligned with corresponding structures in the manifold layers, resulting in three heat exchanger zones, e.g., 113a-c. When the cooling layers use staggered fins (see 102, FIG. 1), or parallel channels, slot shaped openings are formed through the cooling layers in the inlet and outlet regions to provide for coolant flow to and from the lower layers. When the cooling layers use a single layer mesh structure (see 301 FIG. 3) which allows vertical flow, in addition to the slots described above, an additional separator layer 302 is needed between the manifold layers 103-105 and the mesh layers 301 to confine the coolant flow into the mesh layers 301, as shown in FIG. 3. In a design stage, the width of the slots should be selected to balance the area available for heat transfer with the need for coolant flow.

#The preferred structures of the cooling layer include staggered fins 102 shown in FIGS. 4A-B (FIG. 4B shows a cross-section 4B-4B′ in FIG. 4A), or a single layer mesh structure, 301 shown in FIG. 5. With staggered fins, the fins (e.g., 401 in FIGS. 4A-B) at least one dimension of the fluid passages in the cooling layers may be about 100 microns or less in size. Either of these structures, FIGS. 4A-B & 5A-B (FIG. 5B shows a cross-section 5B-5B′ in FIG. 5A), can be formed by patterning and etching thin copper sheets. For the staggered fin case, different depths may be etched from each side of the sheet where the channels between the staggered fins are preferably etched between about 50 and 80 microns deep (gray regions in FIG. 4A) and enough is etched from the other side of the sheet to form the slot shaped openings through the sheet for the coolant inlets and outlets. A stacked staggered fin structure allows for flow redistribution if a channel, e.g., 402, is obstructed (e.g., fluid flow is restored to the channel at the end of one fin segment, so cooling is not lost for the whole length of the heat exchanger zone, e.g., 113a shown in FIG. 1) and the performance is improved as the boundary layer which forms along the channel sides is periodically broken up and the fluid from the center of the channel along one set of fins is brought into contact with the wall in the next set of fins. Note that with the staggered fin structure, flow is not only possible along the direction parallel to the fins, but also in the direction perpendicular to the fins. In the mesh structure, approximately equal amounts may be etched from each side of thin copper sheets such that in regions which are etched from both sides, the copper sheet is etched all the way through. In the single layer mesh structure 301 shown in FIGS. 5A-B, the height of the channel in the horizontal direction (above or below light or dark gray regions 501-502) is less than the thickness of the copper sheet used. In FIGS. 5A-B, the light gray regions 501 are etched from the top and the dark gray regions 502 are etched from the bottom. Further, the height of the horizontal channel between these regions when the sheets are stacked is more than half the thickness of the initial copper sheet. Regions 504 are preferably vertically aligned to provide a thermal conduction path up/down to regions 501 and 502; regions 501, 502 and 503 may also be vertically aligned, respectively. Also, with this arrangement, the width of the vertical gaps 503 is not strongly dependent on the alignment of adjacent sheets as after a vertical flow segment (white region 503 in FIGS. 5A-B), the next horizontal flow segment can be in the same layer if needed. With this single layer mesh structure, a single layer could be used and it would provide a continuous flow path. Further, there is no need to use an even number of cooling layers to provide a uniform horizontal flow cross section through the structure as the stacked mesh structures can be identical in structure. Note that with this mesh structure, for a stack of cooling layers, flow is possible in all three directions.