JP2009277699A - Heat sink, heat sink assembly, semiconductor module, and semiconductor device with cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat sink that is used for a heat generating semiconductor element to keep its temperature low, and makes a cooling means small in volume and inexpensive, to keep the reliability high. <P>SOLUTION: The heat sink 1 has may heat radiating fins 1B constituted on a base 1A to a thin thickness and a narrow pitch of sub-millimeter order, and is set to 60 mm or shorter, in a direction along a flow of air of a fan, the heat radiating fins is set to 40 mm or shorter. A plurality of heat sinks 1 similar to this may be arranged and thermally connected to one another by a heat transport device 4 to constitute a heat sink assembly. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat sink, a heat sink assembly, a semiconductor module, and a semiconductor device with a cooling device.

  In general, as shown in FIG. 10 and FIG. 11, the power semiconductor element cooling device 100 bolts a heat sink 104 to a power semiconductor module 101 via an insulating material 102 and a thermal interface material 103 such as grease or heat conductive adhesive. It is the structure made to press-contact by tightening. And the fan 105 is installed so that it may blow in the direction along the fin of the heat sink 104 for forced air cooling.

  During operation of the power conversion device, heat generated in the power semiconductor element passes from the power semiconductor module 101 through the thermal interface material 103 at the contact boundary to the base 104A of the heat sink 104 and the heat radiation fin 104B to the surrounding environment (atmosphere). Dissipate heat.

However, in the case of a conventional forced air cooling type power semiconductor element cooling device, the heat transfer coefficient (several tens W / m ² ) of the heat sink 104 as a heat radiating part with respect to the heat generation density (several tens W / cm ² ) of the power semiconductor element. In order to keep K) low and within an acceptable temperature difference (several tens of degrees Celsius), it was necessary to expand the heat radiation area to several hundred times the heat generation area.

  In this expansion process, heat conduction resistance (heat resistance due to solid heat conduction), contact heat resistance (heat resistance due to contact between solid and solid), spread heat resistance (heat sink 104 while heat from the heat generating component spreads at an angle of 45 °. Factors that hinder heat dissipation, such as heat resistance (heat resistance), fin efficiency (correction that the temperature of the entire fin 104B is not uniform), heat sink efficiency (correction that the inlet and outlet temperatures are not uniform) For this reason, the volume of the heat sink 104 is much larger than the volume of the power semiconductor module 101.

As an example of the prior art, a power conversion device constituted by the large IGBT module and the cooling device shown in FIG. 10 will be described. If the heat loss of the power semiconductor element is 2000 W and the allowable junction temperature is 125 ° C. (ambient temperature 40 ° C.), the large caulking heat sink 104 (W330 mm × L300 mm × H110 mm) equipped with the forced air cooling fan 105 is applied. One of the valid solutions. At this time, the thermal resistance of the heat sink 104 is 0.028K / W, volume because 10890Cm ^3, volumetric thermal resistance is 305cm ³ K / W (performance index of the heat sink).

  In order to reduce the volume of the heat sink 104, cooling means for efficiently radiating heat is necessary. One of the means is a cooler that transports heat using latent heat and movement caused by evaporation and condensation of refrigerant such as heat pipe type and boiling type, and the heat sink volume can be reduced to about 1/2 to 1/3. (Non-Patent Document 1). This heat sink is also widely used as a cooling device for electric vehicles (Patent Document 1).

  Another means is a cooler that forcibly circulates a refrigerant by a water-cooled pump or the like to perform heat transport. A microchannel is formed in the immediate vicinity of the heat generating component to reduce the heat conduction resistance, increase the heat radiation area and reduce the heat transfer resistance to the refrigerant, increase the heat flow rate that can be cooled, and Some of them enable cooling (Patent Documents 2 to 5). In addition, there is also one that uses a collision jet to reduce heat transfer resistance and obtain a similar effect (Patent Documents 6 and 7).

  However, although the heat receiving block can be reduced in size, a separate gas-liquid heat exchanger is required for heat dissipation to the surrounding environment (atmosphere). If peripheral components (drive pump and tube) are included, the volume of the water-cooled cooling device can be reduced. Is equivalent to or better than a heat pipe type or boiling cooling type cooling device.

As described above, since the conventional power semiconductor element cooling apparatus requires a heat transport mechanism by circulating the refrigerant, the cost of the entire heat sink including the heat receiving block, the heat transport mechanism, and the heat radiation fins has increased. In addition, since the heat receiving block and the heat radiating fin can be separated, the degree of freedom of layout is high, but the volume of the entire cooling device including the heat receiving block, the heat transport mechanism, and the heat radiating fin is about 1/2 to 1/3. Don't get smaller. In addition, there is a problem that countermeasures are required because the problem of freezing of refrigerant and liquid leakage may occur.
JP 2000-60106 A JP-A-6-326226 JP-A-7-66338 JP 2002-151640 A JP 2006-19730 A JP-A-5-3274 Japanese Patent Laid-Open No. 10-22428 Denso Technical Review Vol7, No. 1. “Development of boiling cooler using natural refrigerant circulation technology”, 2002

  The present invention has been made to solve the above-described problems of the prior art, and can be used for a heat-generating semiconductor element to keep the temperature low, and to reduce the volume of the cooling means. An object of the present invention is to provide a heat sink that can be manufactured at low cost and can maintain high reliability, and a heat sink assembly using the heat sink, a semiconductor module, and a semiconductor device with a cooling device.

  One feature of the present invention is a heat sink for use with a forced air cooling fan, in which a large number of heat dissipating fins are formed on a base in a thin and narrow pitch on the order of submillimeter, and the length of the fan in the direction along the wind flow. The heat sink has a thickness of 60 mm or less and a height of the radiation fins of 40 mm or less.

  Another feature of the present invention is a heat sink assembly in which a plurality of the heat sinks are arranged, and the heat sinks are thermally connected by a heat transport device.

  Another feature of the present invention is that a heat receiving block is disposed on the heat receiving surface of the base opposite to the heat radiating fin with respect to the heat sink in a state where heat can be conducted, and the heat receiving block has a heat generating semiconductor element. Is a semiconductor module installed.

  According to still another aspect of the present invention, a heat receiving block is disposed on a heat receiving surface opposite to a heat radiating fin on a base of any heat sink with respect to the heat sink assembly in a state where heat can be conducted, and the heat receiving block generates heat. This is a semiconductor module in which a conductive semiconductor element is installed.

  Another feature of the present invention is a semiconductor device with a cooling device in which the semiconductor module is housed in a housing, and a fan that blows outside air to the radiating fins of the semiconductor module is attached to the housing.

  According to the heat sink or heat sink assembly of the present invention, the temperature can be kept low by using it together with a forced air cooling fan as a cooling device for forcibly cooling a heat-generating semiconductor element, and the volume of the cooling device can be reduced. In addition, it is inexpensive and can maintain high reliability.

  Further, according to the semiconductor module and the semiconductor device with a cooling device of the present invention, a small, inexpensive, and reliable heat sink or heat sink assembly is used as the cooling means. Further, the semiconductor device can be reduced in size.

  First, the principle of the present invention will be described. If the heat sink outer shape (width W, height H, length L) and the cooling fan capability are determined, the fin shape with the best heat dissipation capability can be obtained by the following equation. From this calculation result, it is understood that the heat sink length L does not need to be longer than a certain length when taking the fin shape with the best heat dissipation capability. That is, conventional air-cooled heat sinks for power semiconductor elements are mainly those with a heat sink length of 200 mm to 300 mm, but the same heat dissipation capability can be realized with a heat sink length of 20 mm to 30 mm, resulting in smaller size and lower cost. It is superior in both aspects.

1) Flow analysis The hydraulic equivalent diameter D [m] of a rectangular duct having a heat sink length L [m], a fin height H _fin [m], and a gap g [m] is as follows.

The Reynolds number is as follows from the fluid density ρ [kg / m ³ ], the fluid viscosity μ [kg / ms], and the fin average flow velocity U _ar [m / s].

Although the turbulent transition starts from Re≈2300, the heat sink with a narrow fin pitch is mostly a laminar flow. The hydraulic distance x ⁺ is as follows from the representative length x (heat sink length L).

The friction coefficient f of a fully developed laminar flow is as follows:

Here, the channel aspect ratio G is

And the friction coefficient f _app of the laminar flow being developed is

It is. The run-up distance X until fully developed is

In this approach section, an extra pressure loss occurs.

A reduction coefficient Kc and an enlargement coefficient Ke are obtained. Fin density σ is

And the reduction factor Kc is

And the enlargement factor Ke is

The pressure loss ΔP _hs [Pa] of the heat sink is

It is.

Here, _Har is a fin hydraulic head.

The volume flow rate V [m ³ / s] is calculated from the heat sink width W [m],

It is.

Since fan power P [W] is equal to volume flow rate x pressure loss,

It is.

2) Heat transfer analysis Nusselt number Nu of the fully developed laminar flow of the rectangular duct is

The thermal channel length x ^* is

It is.

The average Nusselt number Nu _m is

And the average heat transfer coefficient h _m [W / m ² K] is calculated from the thermal conductivity k _f [W / mK] of air,

And the convective thermal resistance θ _con [K / W] of the heat sink is obtained from the heat sink surface area A _w [m ² ],

It is.

The capacity heat resistance θ _cap [K / W] of the heat sink is obtained from the specific heat c _p [J / KgK] of air,

The number of transfer units NTU of the concept used in the heat exchanger is

It is.

Heat sink efficiency ε, which is the actual ratio to ideal heat transfer, is

It is.

Correction by fin efficiency η is added.

Here, b is from the thermal conductivity k _s [W / mK] of the fin,

The heat resistance θ _hs [K / W] of the heat sink is

It is.

  As an example, when fan power PQ = 0.05 [W], heat sink width W = 40 [mm], and heat sink height H = 10 (base thickness 1) [mm], heat sink length L [mm] The calculation results obtained by optimizing the fin thickness Tf [mm] and the fin gap Gf [mm] so that the heat dissipation capability is the best are as described in the following description of the embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
1 to 3 show a configuration of a high-density fin heat sink 1 for a power semiconductor according to a first embodiment of the present invention. As shown in FIG. 1, the shape of the heat sink 1 is changed to a width W, a height H, a length L, a thickness Tb of the cooling surface base 1A, a thickness Tf of the radiating fin 1B, a gap Gf, a height corresponding to the outer shape. Is defined by Hf. The width W of the heat sink 1 is the length in the direction in which the heat dissipating fins 1B are arranged, and the length L of the heat sink 1 is the length of the heat dissipating fins 1B in the direction along the wind flow of the fan.

  As shown in FIG. 2 and FIG. 3, three effects can be obtained by configuring the heat dissipating fins 1 </ b> B with a submillimeter-scale thin wall and a narrow pitch and reducing the length L and height H of the heat sink 1.

  The first is that the heat radiation fin 1B is constructed with a thin and narrow pitch of submillimeter scale, so that although the pressure loss of the heat sink 1 increases, the area of the heat radiation fin can be increased and the effect equivalent to the increase of the heat sink length L is obtained. Thus, the length L of the heat sink 1 can be significantly shortened compared to the conventional one, and the size can be reduced.

  Secondly, since the length L of the heat sink 1 is shortened, the utilization rate of the boundary run-up section (undeveloped area) is increased, and a heat dissipation capability superior to the conventional one can be obtained.

  Third, since the heat sink 1 becomes smaller, it is possible to eliminate almost all the factors that hinder heat dissipation such as heat conduction resistance, spreading resistance, fin efficiency, and heat sink efficiency.

When the cooling device for forced air cooling parameter semiconductor module is configured using the fan 105 shown in FIGS. 10 and 11, the fan power per unit area is PQ = 125 (W / m ² ), the width is 40 mm, and the height is 10 mm. FIG. 7 shows the calculation results of the thermal resistance, the volume thermal resistance, and the optimum fin shape as a function of the heat sink length L.

  From this calculation result, when the optimum fin shape on the submillimeter scale is always adopted, as shown in the graph of FIG. 7A, the heat resistance of the heat resistance can be increased even if it is further increased when the heat sink length L is 60 mm or more. It can be seen that it hardly contributes to the decrease, and that the volume heat resistance indicating the cooling performance per volume increases, that is, gets worse as the heat sink length L shown in FIG. From the above, it can be seen that in the case of a forced air cooling type cooling device that uses air as a fluid with a general fan or blower, improvement in cooling performance can hardly be expected when the length L of the heat sink 1 is 60 mm or more.

  Similarly, in the heat sink 1 having a width of 40 mm and a length of 10 mm, the calculation results of thermal resistance, volume thermal resistance, and optimum fin shape as a function of the heat sink height H are shown in FIG. From this result, it can be seen that when the heat sink height H is 40 mm or more, even if the heat sink height H is increased further, it hardly contributes to the decrease in thermal resistance, and the volume thermal resistance increases, that is, continues to deteriorate. Under general conditions, it can be seen that almost no improvement in cooling performance can be expected when the heat sink height is 40 mm or more.

  For reference, the calculation result regarding the heat sink width W is shown in FIG. It shows that the width W of the general heat sink 1 and the thermal resistance are in an inversely proportional relationship.

In the case of the heat sink 1 of the present embodiment, a high-density fin heat sink (W330 × L15 × H15 × 3P) can be used to achieve the same performance as the conventional power semiconductor module cooling device shown in FIGS. is there. At this time, since the heat resistance of the heat sink 1 is 0.028 K / W and the volume is 223 cm ³ , the volume heat resistance is 6.2 cm ³ K / W. The size can be reduced by about 1/50 compared with the conventional case.

  As described above, in the case of the heat sink 1 of the present embodiment, the heat radiation fin 1B is configured with a submillimeter-scale thin wall and a narrow pitch, and the length L and the height H of the heat sink 1 are reduced, thereby reducing the volume of the heat sink 1. In addition to being able to greatly reduce, there is an advantage that an inexpensive and highly reliable semiconductor cooling device can be configured because there is no heat transport mechanism by circulating refrigerant.

  Conventionally, heat radiation fins could not be constructed inexpensively with submillimeter-scale thin-walled and narrow pitches, but with the recent progress in manufacturing technology, this technology has been improved by applying technologies such as precision machining presses. The density fin heat sink 1 can be manufactured. At present, the material cost of the conventional caulking type heat sink and the mass production cost of the high-density fin heat sink of the present embodiment are almost equal. As a result, the heat sink having the same thermal resistance is equivalent to several tenths of the same cost. Can be offered in sizes. In the future, if the material cost increases, the cost will be superior.

  The high-density fin heat sink 1 of the present embodiment is assumed to be used for a cooling device for power semiconductor elements such as IGBTs and MOSFETs, but is applicable to any exothermic semiconductor element such as a CPU or a resistor. Is possible.

  The high-density fin heat sink 1 constituting the thin and narrow pitch radiating fins is thin and narrow pitch, so there is anxiety about the strength and dirt of the radiating fins. In such an environment, it is desirable to provide an air filter to prevent fouling. For this purpose, if the fan 105 is a suction fan, an air filter can be provided at the suction port. If the fan 105 is an exhaust fan, an air filter can be provided at the suction port on the side opposite to the fan installation side of the housing that houses the cooling device.

[Second Embodiment]
Next, a heat sink assembly 5 according to a second embodiment of the present invention will be described with reference to FIG. In the heat sink assembly 5 of the present embodiment, a plurality of high-density fin heat sinks 1 of the first embodiment are connected in the height direction by a heat transport device 2 such as a heat pipe or a heat lane, and the heat receiving surface receives heat. This is a structure in which a block 3 is installed.

  In the case of the high-density fin heat sink 1, the cooling capacity is not improved even if the heat sink height H is increased to a certain level or more. However, by using the heat transport device 2 as in the present embodiment, the heat sink due to the increase in height. The thermal resistance of one unit can be reduced, and the cooling capacity can be improved.

  Similarly to the heat sink 1 of the first embodiment, the heat sink assembly 5 of the present embodiment is also used as a cooling device for forced air cooling semiconductor elements and a cooling device for forced air cooling semiconductor modules.

[Third Embodiment]
Next, a semiconductor device 8 with a cooling device according to a third embodiment of the present invention will be described with reference to FIG. In the semiconductor device 8 with the cooling device of the present embodiment, the heat receiving block 3 is arranged on the heat receiving surface of the base 1A of the high-density fin heat sink 1 of the first embodiment, and the power semiconductor element 6 is placed on the heat receiving block 3. The power semiconductor module 9 is configured by fixing, and the entire power semiconductor module 9 is built in the housing 7, and the air cooling fan 105 is attached to the housing 7 in the same manner as shown in FIGS. 10 and 11. Structure.

  Also in the semiconductor device 8 with the cooling device of the present embodiment, the power semiconductor element 6 and the heat sink 1 are electrically connected, and the heat sink 1 is used as a part of the electrode terminal.

[Fourth Embodiment]
Next, a semiconductor device 10 with a cooling device according to a fourth embodiment of the present invention will be described with reference to FIG. The semiconductor device with a cooling device 10 of the present embodiment incorporates a plurality of high-density fin heat sinks 1 of the first embodiment in a housing 7 and receives heat from the heat receiving block 3 of each high-density fin heat sink 1. The power semiconductor element 6 is fixed to the surface to form a power semiconductor module 9, and the power semiconductor module 9 is built in a multi-stage housing 7. The housing 7 is similar to that shown in FIGS. 10 and 11. In this structure, an air cooling fan 105 is attached.

  Also in the semiconductor device 10 with the cooling device of the present embodiment, each power semiconductor element 6 and the heat sink 1 are electrically connected, and the heat sink 1 is used as a part of the electrode terminal.

  In the third and fourth embodiments, the high-density fin heat sink 1 is disposed on both surfaces of the power semiconductor element 6, and each heat sink 1 receives the heat of the power semiconductor element 6 by solder joint or pressure contact. It is also possible to make the structure to be.

The perspective view of the heat sink of the 1st Embodiment of this invention. The front view and side view of the heat sink of the 1st Embodiment of this invention. The enlarged view of the C section in FIG. The front view of the heat sink assembly of the 2nd Embodiment of this invention. The perspective view which can partly fracture | rupture the semiconductor device with a cooling device of the 3rd Embodiment of this invention. The perspective view which can partly fracture | rupture the semiconductor device with a cooling device of the 4th Embodiment of this invention. The graph which shows the characteristic of the thermal resistance regarding the length of the heat sink of the 1st Embodiment of this invention, volume thermal resistance, and optimal fin shape. The graph which shows the characteristic of the thermal resistance regarding the height of the heat sink of the 1st Embodiment of this invention, volume thermal resistance, and optimal fin shape. The graph which shows the characteristic of the thermal resistance regarding the width | variety of the heat sink of 1st Embodiment of this invention, volume thermal resistance, and optimal fin shape. The perspective view of the cooling device of the conventional power semiconductor element. Sectional drawing of the cooling device of the conventional power semiconductor element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High density fin heat sink 1A Base 1B Radiation fin 3 Heat receiving block 4 Heat transport device 5 Heat sink assembly 6 Power semiconductor element 7 Case 8 Semiconductor device with cooling device 9 Power semiconductor module 10 Semiconductor device with cooling device 105 Fan

Claims (10)

A heat sink for use with a forced air cooling fan,
A heat sink in which a large number of radiating fins are formed on a base with a thin thickness on the order of sub-millimeters and with a narrow pitch, the length in the direction along the fan flow is 60 mm or less, and the height of the radiating fins is 40 mm or less.   2. The heat sink according to claim 1, wherein a thickness of the radiation fin is 0.1 to 0.6 mm, and a gap between the radiation fins is 0.4 to 1.3 mm.   A heat sink assembly, wherein a plurality of heat sinks according to claim 1 or 2 are arranged, and the heat sinks are thermally connected by a heat transport device. With respect to the heat sink according to claim 1 or 2, a heat receiving block is disposed on a heat receiving surface of the base opposite to the heat radiating fin in a state where heat can be conducted,
A semiconductor module comprising an exothermic semiconductor element installed in the heat receiving block. With respect to the heat sink assembly according to claim 3, a heat receiving block is disposed on a heat receiving surface opposite to the heat radiating fin on the base of any one of the heat sinks in a state capable of conducting heat,
A semiconductor module comprising an exothermic semiconductor element installed in the heat receiving block.   The semiconductor module according to claim 4, wherein the semiconductor element is a power semiconductor element.   The semiconductor module according to claim 5, wherein the heat sink is an electrode terminal. Housing the semiconductor module according to claim 4 in a housing;
A semiconductor device with a cooling device, wherein a fan for blowing outside air to the heat radiating fins of the semiconductor module is attached to the housing.   The semiconductor device with a cooling device according to claim 8, wherein an air filter is provided in an outside air inlet formed in the housing.   The semiconductor device with a cooling device according to claim 8, wherein the semiconductor element constitutes a power conversion circuit.

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