TWI858695B - Fixing element for heat dissipation device and method of mounting the same - Google Patents

Abstract

A method of mounting a heat dissipation device to a bare die heat source using fixing elements is disclosed. The fixing elements respectively include a screw, which has a spring fitted thereon and is disposed in a sleeve. Limiting units are provided on the sleeve for holding the spring in the sleeve in a compressed state. To mount the heat dissipation device to the bare die heat source, first use the fixing elements to preliminarily screw the heat dissipation device to a top of the heat source. Then, the springs compressed in the sleeves of all the fixing elements are elastically released synchronously to apply evenly distributed downward forces that push the heat dissipation device toward the bare die heat source stably.

Description

Fixing element of heat dissipation device and installation method thereof

The present invention relates to a heat sink fixing element and its installation method, and in particular to a heat sink fixing element and its installation method that can provide synchronous and uniform downward pressure to avoid damage or thermal resistance caused by uneven contact force and asynchronism between a bare die type heat source and a heat sink.

In order to provide electronic devices with high-performance computing capabilities, high-performance and high-power chips are currently used. When the chip is operating, it generates a considerable amount of heat. Traditional computing chips have a packaging shell on the outside, and the packaging shell encapsulates the chip inside to protect the chip from damage. As the computing performance of the chip increases, the chip will generate a higher temperature than the traditional one when performing computing work. In addition, the packaging shell encapsulated on the outside of the chip has seriously affected the heat dissipation of the chip and the efficiency of heat conduction to the outside; therefore, most of the chips on the market are packaged in a packaged shell. The chip has been changed to a bare chip for installation. However, since the bare chip surface is not flat but has an outward convex arc shape, and there is no protective shell, its heat exchange contact surface is small and has low strength. Therefore, it is easy to be damaged and cracked when combined with a heat sink. In addition, when the traditional heat sink is fixed on the heat source (bare chip), a single locking point is used to lock in sequence, resulting in the time points of each locking being asynchronous and prone to contact tilt. The bare chip cannot withstand such uneven pressure, which can easily cause problems such as chip cracking and damage.

Refer to Figures 1 and 2, which are schematic diagrams of the heat sink and bare crystal combination. The heat source A (bare crystal type) is set on a substrate D. Copper pillars B with internal threads are set at the four corners of the substrate D corresponding to the outer side of the heat source A. The heat sink C is also provided with four holes C3 at the positions corresponding to the copper pillars B and is penetrated by screw units C1. The screw units C1 are covered with a spring C2. When the heat sink C and the heat source A are locked together, the screwing operation is usually performed by manual or mechanical arm operating an electric screwdriver to directly perform the screwing operation in sequence. In order to speed up the assembly time and Completed within the limited assembly time, usually each fixing screw is fastened directly and once in place. When the screw unit C1 is locked to the fixed point one by one, the spring C2 sleeved on the screw unit C1 also supports in the direction of the heat source A. The lack of uneven force caused by the single-point locking immediately causes the heat source to collide. As mentioned above, the heat source A (bare crystal) is brittle. However, the single-point screw unit C1 locking and the spring C2 pressure cannot provide complete and comprehensive (four corners of the bare crystal) synchronous and uniform downward pressure on the heat source A (bare crystal). The bare crystal is easily damaged due to uneven force.

Furthermore, the bare die is quite fragile. As mentioned above, the four corners of the bare die must be simultaneously and synchronously provided with uniform downward pressure to provide bonding force for assembly. If the four corners of the bare die cannot be simultaneously provided with downward pressure in an evenly applied manner, it is easy to cause the heat sink or heat dissipation device to warp and not fully bond or cause damage to the heat source (bare die), and it is also easy to form thermal impedance, which will cause uneven heating or thermal conduction failure.

Therefore, how to improve the heat dissipation device to fully and comprehensively provide uniform pressure to fit tightly with the heat source, and how to maintain the appropriate bonding force between the bare die and the heat dissipation device and enable repeated installation or adjustment are the primary issues that the industry needs to solve.

Therefore, in order to effectively solve the above-mentioned problems, the main purpose of the present invention is to provide a fixing element of a heat sink and its installation method, which can provide a synchronous and uniform downward pressure on the heat sink and the bare die type heat source, effectively avoiding the problem of a single locking point being locked first, resulting in the bare die computing unit cracking or breaking due to uneven and asynchronous force.

To achieve the above-mentioned purpose, the present invention provides a fixing element for a heat dissipation device, which comprises: a screw, a spring, and a sleeve; the spring is passed through the screw, and a retaining ring is provided at one end of the screw to provide abutment against one end of the spring so that the retaining ring provides a limit for the spring to prevent the spring from detaching from the screw.

The sleeve is a tubular structure with two open ends, and has a containing space inside. The two open ends of the sleeve are respectively connected to the containing space. The containing space of the sleeve is sleeved with the screw with the spring, and the sleeve can limit one end of the spring by means of clamping or interference through a limiting unit, so that the spring is restricted in the containing space of the sleeve and presents a compressed state.

To achieve the above purpose, the present invention provides a method for installing a heat sink and a bare die heat source using the above fixing elements, so as to achieve a uniform force effect when the two are attached, which includes the following steps: Step A: prepare a heat sink, and install the fixing elements at the four corners of the heat sink; Step B: place the heat sink on top of a bare die heat source, and first use the fixing elements to temporarily pre-lock and position the bare die heat source in a screw-locked manner; Step C: Finally, release all the springs on the heat sink that are restricted in the sleeve at the same time, so that the springs provide a synchronous and uniform downward pressure on the heat sink to the bare die heat source.

3:Fixed components

31: Screws

311: Screw head

312: External thread

313: Annular groove

314: Buckle

32: Sleeve

321: Top

322: Lower end

323: Storage space

324: Window

3241: Upper Edge

3242: Lower Edge

325: Limiting unit

3251: First page

3252: Second side

33: Spring

331: Top

332: bottom

4: Press-in fixture

5: Copper column

Figure 1 is a schematic diagram of a conventional heat sink and bare die combination.

Figure 2 is a schematic diagram of a conventional heat sink and bare die combination.

Figure 3 is a three-dimensional exploded view of the fixing components of the heat dissipation device of the present invention.

Figure 4 is a three-dimensional assembly diagram of the fixing components of the heat dissipation device of the present invention.

Figure 5 is a three-dimensional exploded view of the fixing components of the heat dissipation device of the present invention.

Figure 6 is a cross-sectional view of the fixed element assembly of the heat dissipation device of the present invention.

Figure 7 is a flow chart of the steps of the installation method of the heat dissipation device and the bare die heat source of the present invention.

Figure 8 is a schematic diagram of the steps of the installation method of the heat dissipation device and the bare die heat source of the present invention.

Figure 9 is a schematic diagram of the steps of the installation method of the heat dissipation device and the bare die heat source of the present invention.

Figure 10 is a schematic diagram of the steps of the installation method of the heat dissipation device and the bare die heat source of the present invention.

The above-mentioned purpose of the present invention and its structural and functional characteristics will be explained according to the preferred embodiments of the attached drawings.

Please refer to Figures 3, 4, 5, and 6, which are three-dimensional exploded and assembled cross-sectional views of the heat sink fixing element of the present invention applied to a bare crystal type heat source. As shown in the figure, the heat sink fixing element 3 applied to the bare crystal type heat source has: a screw 31 and a sleeve 32; the upper and lower ends of the screw 31 respectively have a screw head 311 and a plurality of external threads 312, the screw 31 is provided with an annular groove 313 above the external threads 312, and the annular groove 313 is clamped with a retaining ring 314. A spring 33 is sleeved on the outside of the screw 31 and is located between the screw head 311 and the retaining ring 314. The spring 33 has a top end 331 and a bottom end 332. The bottom end 332 of the spring 33 abuts against one side of the retaining ring 314, and the retaining ring 314 provides axial limitation for the bottom end 332 of the spring 33 to prevent the spring from being separated from the lower end of the screw 31.

The sleeve 32 is a tubular structure having an upper and lower open end 321, 322 and a receiving space 323. The receiving space 323 is located between the upper and lower ends 321, 322 and is interconnected. The receiving space of the sleeve 32 is provided with the screw 31 having the spring 33 inserted therethrough. A pair of windows 324 are provided near the upper end of the sleeve 32. The windows 324 are arranged on the sleeve 32 at 180 degrees from the outer side of the sleeve 32 to the receiving space 323 of the sleeve 32 and are connected to the receiving space 323.

The sleeve 32 can be used or through a limit unit 325 to press one end of the spring 33. The limit unit 325 can be directly formed on the sleeve 32 and integrated with the sleeve 32, or used in conjunction with the sleeve 32 in the form of an additional preset element. Through the application of the limit unit 325, the spring 33 can be directly compressed and limited in the accommodation space 323 of the sleeve 32 by means of clamping or interference.

In this embodiment, the limiting unit 325 is selected to be arranged on the wall of the sleeve 32 and is directly integrated with the sleeve 32. The window 324 of the sleeve 32 has an upper edge 3241 and a lower edge 3242. The two ends of the limiting unit 325 are connected to the upper and lower edges 3241 and 3242 of the window 324. The limiting unit 325 of this embodiment is a movable or flexible convex body, and the limiting unit 32 5 has a first surface 3251 and a second surface 3252, the first surface 3251 and the second surface 3252 are respectively arranged on the inner and outer surfaces of the limiting unit 325, at least one of the first surface 3251 and the second surface 3252 is convex, the first surface 3251 convexes toward the accommodating space 323, so that the top end 331 of the spring 33 is pressed by the surface of the first surface 3251 and is limited. If the limiting unit 325 is squeezed and deformed by external force, the first surface 3251 will be deformed from convex to concave, and retracted into the window 324 in the opposite direction, so that the second surface 3252, which was originally concave, is deformed to convex and protrudes out of the window 324 toward the outer side of the sleeve 32.

In addition, the limiting unit 325 can be an external component type and can be matched with the sleeve 32 to achieve the purpose of limiting and buckling the spring 33. The limiting unit 325 is extended or embedded or inserted or clamped into the accommodating space 323 of the sleeve 32 through one of the windows 324, and generates interference compression on the top end 331 of the spring 33, so that the spring 33 is limited in the accommodating space 323 of the sleeve 32. The limiting unit 325 has a variety of styles and can be a sheet or plate or rod or ring or other geometric structure. The limiting unit 325 of this embodiment is illustrated by two horizontal rods but is not limited thereto. The unit 325 has an upper surface 3251A and a lower surface 3251B, and extends from the window 324 into the accommodating space 323 in the radial direction of the sleeve 32 to limit and compress the top end 331 of the spring 33. The upper surface 3251A of the limiting unit 325 is limited by the upper edge 3241 of the window 324, so that the lower surface 3251B of the crossbars can buckle the top end 331 of the spring 33, so that the spring is compressed in the sleeve 32. Then, by removing the limiting unit 325 from the window 324, the limit on the spring 33 is removed, thereby releasing the originally compressed spring 33.

Please refer to Figures 7, 8, 9, and 10, which are the step flow chart and schematic diagram of the installation method of the heat sink and the bare die type heat source of the present invention. As shown in the figure, the installation method of the heat sink and the bare die type heat source of the present invention uses the aforementioned fixing components of the heat sink applied to the bare die type heat source for assembly, and includes the following steps;

Step A: Prepare a heat sink and install the fixing elements at the four corners of the heat sink respectively; the present invention intends to provide a method for installing a heat sink that can be directly combined with a bare die type heat source and provide heat exchange. However, since the bare die type heat source has no protective structure on its surface, when combined with the heat sink for heat conduction, a synchronous and uniform downward bonding force must be provided to prevent the bare die from being damaged due to uneven downward pressure. In order for the heat sink 1 to provide a uniform downward pressure (bonding force) to the bare die type heat source 2, the fixing element 3 of the present invention is different from the general traditional fixing element. Please refer to Figures 3 and 4 and the aforementioned description implementation and illustrations, which will not be elaborated here.

Referring to FIG. 8 , the heat sink 1 has a heat contact area 11, which directly corresponds to the bare die heat source 2 for bonding. A fixing element 3 is respectively provided at the four corners of the outer side of the heat contact area 11. When the heat sink 1 is combined with the bare die heat source 2, the fixing elements 3 provided at the four corners of the heat sink 1 provide an average pressure at the four corners. Therefore, in order to provide an average downward pressure, the fixing elements 3 provided at the four corners must simultaneously and synchronously press the heat sink 1 downward, so that the heat sink 1 and the bare die heat source 2 can be closely bonded without generating thermal resistance and preventing the bare die from being damaged.

After the screw 31 passes through the heat sink 1 through one end with an external thread 312, a retaining ring 314 is provided at the annular groove 313. The retaining ring 314 is attached to the lower surface of the heat sink 1. The spring 33 and the lower end 322 of the sleeve 32 abut against the upper surface of the heat sink 1, so that the fixing element 3 is temporarily fixed to the heat sink 1.

Step B: The heat sink is placed on a bare die heat source and is pre-locked with the bare die heat source by the fixing elements in a preliminary screw lock manner; the bare die heat source 2 is a heat source on a substrate (circuit board), and in order to facilitate the installation and fixation of the bare die heat source 2 and the heat sink 1, the substrate is adjacent to the bare die heat source. A plurality of copper pillars 5 with internal threads are usually provided at the four outer corners of the bare die heat source 2 for the external threads 312 of the fixing elements 3 to perform preliminary pre-locking and positioning. At this time, the heat sink 1 is only lightly placed on the bare die heat source 2 and the two are not yet tightly locked together, that is, the heat sink 1 does not apply any downward pressure to the bare die heat source 2.

Step C: Finally, all the springs on the heat sink that are restricted in the sleeve are released at the same time, so that the springs are released and simultaneously provide a uniform downward pressure to the heat sink against the bare die heat source.

The last step is to release the compression restriction of all the springs 33 installed on the heat sink 1 synchronously and consistently, and the springs 33 release their spring force, so that the springs 33 provide synchronous and uniform downward pressure on the four corners of the heat sink 1, thereby making the heat sink 1 and the bare die type heat source 2 fit tightly.

First, refer to Figures 3, 4, 5, and 6 again. As mentioned above, the springs 33 are directly interfered by the limiting unit 325 inside the sleeve 32 and are compressed and restricted in the sleeve 32. Therefore, the spring force of the spring 33 must be released by releasing the interference or restriction of the limiting unit 325 on the spring 33, so that the top end 331 of the spring 33 pushes the screw head 311 upward, and the bottom end 332 of the spring 33 presses the upper surface of the heat sink 1 downward to press the heat sink 1 toward the bare die type heat source 2, so that the heat sink 1 is tightly attached to the bare die type heat source 2 downward.

Please refer to Figures 9 and 10. In order to synchronously remove the interference or limitation of the limit unit 325 of each sleeve 32 on the top 331 of the spring 33, the purpose of synchronous operation can be achieved by applying external force through manual or automatic mechanical equipment (not shown in the figure), or the mechanical equipment can be matched with a fixture. This embodiment is used as an illustrative embodiment to remove the limitation of the limit unit 325 on the spring 33 by the corresponding design of the press-fit fixture 4, but it is not limited to this. The limit unit 325 can also be directly actuated by the mechanical equipment.

The press-in jig 4 corresponds to the limiter unit 325 of each sleeve 32 of the fixing element 3. When the mechanical device provides downward pressure to the press-in jig 4, the press-in jig 4 also simultaneously applies pressure to the first surface 3251 of the limiter unit 325, forcing the limiter unit 325 to be pressed into the window 324, thereby removing the interference limit on the upper end of the springs 33 and simultaneously releasing the compression of each spring 33 to release the elastic force.

The design of another structure provided by the present invention and how to remove the restriction on the spring 33 are described as follows. Since the limit unit 325 extends into the window 324 in the form of an external component, the limit unit 325 only needs to be moved radially and horizontally out of the window 324 to remove the restriction on the spring 33 and achieve the purpose of releasing the spring.

Referring to Figures 5 and 10, the limiter unit 325 disclosed in this embodiment is an external component. The external component is illustrated in the form of two cross bars. The cross bars radially penetrate the sleeve 32 from the window 324, and the two cross bars are arranged horizontally and correspondingly, with a distance between them. The top end 331 of the spring 33 abuts against the lower side of the two cross bars. When the restriction of the spring 33 being compressed is to be released, the restriction of the two cross bars on the spring must be removed, that is, the distance between the two cross bars is increased to allow the spring 33 to be freed from the pressure of the cross bars and return to its original state.

This embodiment uses a press-in fixture 4 to move vertically downward relative to the two cross bars, and as the press-in fixture 4 moves downward, the gap between the two cross bars will continue to increase (that is, the two cross bars move outward respectively). When the distance between the two cross bars continues to increase until the two cross bars completely remove the pressure on the top end 331 of the spring 33, the top end 331 of the spring 33 can be separated from the pressure of the cross bar and freely release its spring force upward, and press against the bottom of the screw head 311 of the screw 31, thereby achieving the purpose of releasing the spring 33.

The heat sink fixing method proposed in this case is applicable to a bare die type heat source. The main technical means is to provide the heat sink with a uniform downward bonding force, and to release the springs at the same time, so that the heat sink and the bare die type heat source are evenly stressed and do not warp when they are bonded, thereby preventing the bare die from cracking.

There are many ways and structures for temporarily compressing and fixing the springs, and releasing the spring force when the heat sink is attached to the bare die heat source. There are also many ways for the various limit units 325 to be matched with the springs. The springs can be fixed and removed by axial sliding, radial twisting, or horizontal outward stripping. The present invention only lists two of these ways as examples, but they are not limited to them.

The main technical means of the present invention is to achieve the effect of uniform force fitting by simultaneously releasing the spring force of each spring provided on the heat sink, thereby improving the defects of the existing conventional heat sink and bare chip combination.

Claims (7)

A fixing element of a heat sink comprises: a screw having a screw head at one end and a plurality of external threads at the other end, the screw having an annular groove above the section of the external threads for clamping a retaining ring, a spring passing between the screw head and the external threads, the spring having a top end and a bottom end, the bottom end of the spring abutting against the retaining ring; a sleeve having a tubular structure with both ends open, the interior of the sleeve having a containing space, the containing space A screw with a spring is provided, and the sleeve can limit the upper end of the spring through a limiting unit, so that the spring is compressed in the accommodating space of the sleeve. The limiting unit can be directly formed on the sleeve and integrated with the sleeve, or used in conjunction with the sleeve in the form of an additional preset element. By removing the interference or limitation of the limiting unit on the spring, the spring force of the spring is released, so that the top end of the spring pushes the screw head upward. As for the fixing element of the heat dissipation device of claim 1, the sleeve has an upper end and a lower end in an open state, the accommodation space is between the upper and lower ends, and a pair of windows are opened near the upper end of the sleeve, the window has an upper edge and a lower edge, and the windows penetrate from the outer side of the sleeve toward the accommodation space of the sleeve and connect to the accommodation space. As for the fixing element of the heat dissipation device of claim 2, the two ends of the limiting unit are connected to the upper and lower edges of the window, the limiting unit is a movable or flexible convex body, and the limiting unit has a first surface and a second surface, the first surface and the second surface are respectively arranged on the inner and outer surfaces of the limiting unit, at least one of the first surface and the second surface is convex, and the first surface convexes toward the accommodating space. As in claim 2, the fixing element of the heat dissipation device, wherein the limiting unit is an external element and is correspondingly arranged through the window into the accommodation space for the upper end of the spring to abut against, so that the spring is compressed and limited within the accommodation space of the sleeve. As for the fixing element of the heat dissipation device of claim 4, the limiting unit is any one of a sheet, a crossbar or a ring, which radially penetrates or is embedded into the accommodation space of the sleeve through the two windows to interfere with the spring and limit it in the accommodation space of the sleeve. A method for installing a heat sink comprises the following steps: providing a fixing element of a heat sink as in any one of claim items 1 to 4; step A: preparing a heat sink and installing the fixing elements at the four corners of the heat sink; step B: placing the heat sink on a corresponding position above a bare die heat source and pre-locking the bare die heat source with the fixing elements by screws; step C: finally releasing all springs on the heat sink that are restricted in the sleeve at the same time, so that the springs are released to provide the heat sink with a synchronous and uniform downward pressing force to the bare die heat source. The method for installing a heat sink as described in claim 6, wherein the sleeve of the fixing element and the lower end of the spring abut against the upper surface of the heat sink, the buckle abuts against the lower surface of the heat sink, and the fixing element is fixed to the heat sink.

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