CN115863279A

CN115863279A - High overload capacity power module based on chip top metal block design

Info

Publication number: CN115863279A
Application number: CN202211730406.6A
Authority: CN
Inventors: 蒋华平; 魏镜枫; 冉立; 廖瑞金
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 2022-12-30
Filing date: 2022-12-30
Publication date: 2023-03-28

Abstract

The invention relates to a high overload capacity power module designed based on a metal block at the top of a chip, which comprises a substrate, a second solder layer, a lower copper layer of a ceramic copper-clad plate, a ceramic layer of the ceramic copper-clad plate, an upper copper layer of the ceramic copper-clad plate, a first solder layer and the chip which are sequentially arranged from bottom to top; the welding of third solder layer has the metal block that promotes the heat capacity and can strengthen power module overload capacity in the top of chip, and the metal block welds on the copper layer on the ceramic copper-clad plate through first solder layer simultaneously, is provided with the space that is used for filling insulating material in the both sides of chip, and the metal material that has high specific heat capacity is filled to the metal block, through the produced heat of metal material short-term overload of chip of quick absorption, strengthen power module's overload capacity. The invention improves the overload capacity of the power module, the realization method is simple and only needs vacuum welding, and the temperature response speed is higher and no additional thermal resistance is added to the power module because the added structure is close to the upper part of the chip.

Description

High overload capacity power module based on chip top metal block design

Technical Field

The invention relates to the technical field of semiconductor devices, in particular to a high overload capacity power module designed based on a metal block on the top of a chip.

Background

In power electronic systems, there is a short time overload condition. For example, the inrush current in the black start mode of the power grid system is 3 times of the rated current and lasts for 4.4s; the motor controller can be directly in a short-time overload state which lasts for 10s or even longer by 1.5 times in order to ensure the dynamic performance of the motor; when the power system is in relay protection action, the duration of the fault current which is 2 times of the rated current is 0.12s.

The total loss of the power device mainly comprises two parts of switching loss and conduction loss: p _tot ＝P _sw +P _dc ＝(E _on +E _off )*f _sw + D V I, wherein P _tot The total loss of the power chip; p _sw Is a switching loss; p _dc Is a conduction loss; e _on Loss for turn-on; e _off To turn off losses; f. of _sw Is the switching frequency; d is the duty cycle; v is the conduction voltage drop; i is the on current. On one hand, the larger the conduction current is, the larger the conduction voltage drop is, and the larger the conduction loss is; on the other hand, the larger the on-current, the larger the on-loss and off-loss, and the larger the switching loss. When a power electronic system is in an overload state, the current borne by a device is several times of the rated current, the loss is rapidly increased, the junction temperature is rapidly increased, and great challenges are brought to the reliability of a power device. Therefore, the improvement of the short-time overload capacity of the power device has important significance on the safe and reliable operation of the power electronic system.

The short-time overload capability of the power device is related to the chip structure, the packaging structure and the grid driving state. According to the Cauer thermal network model of the power module, as shown in fig. 1, in the operation process of the power module, the junction temperature is determined by the product of power loss and incrustation thermal resistance, and the incrustation thermal resistance of the power module is formed by the RC thermal network model of each layer of material:

wherein Z _thjc For power module crustResisting; r _i Is the ith layer thermal resistance; c _i Is the ith layer heat capacity. Therefore, at the package level, there are two basic approaches to improve the short-time overload capability of power devices: firstly, the thermal resistance of the packaging structure is reduced; and secondly, the heat capacity of the packaging structure is increased.

The university of Chongqing proposes that the short-time overload capacity of the power module is improved by filling a phase-change material in the traditional power module, as shown in figure 2, the power module comprises a substrate, a ceramic copper-clad plate, a phase-change module and a power terminal; the upper surface of the substrate is rectangular, the ceramic copper-clad plates are respectively arranged on the substrate and are connected through copper bars; the phase change module is arranged on the ceramic copper-clad plate, and the plurality of power terminals are arranged on the power terminal mounting end; the phase change module comprises a heat transfer enhancement frame and a sealing cover, and phase change materials are filled in the heat transfer enhancement frame; the outer surface of the sealing cover is welded with a power semiconductor chip. The technology suppresses the junction temperature of the power module under an overload condition by increasing the instantaneous heat capacity of the power module. However, the conventional power module has low equivalent heat capacity, large equivalent transient heat resistance and insufficient short-time overload capacity, is difficult to meet the actual application requirements of a power electronic system, and is easy to generate safety problems such as system operation breakdown caused by thermal failure. And the phase-change material is filled between the chip and the ceramic copper clad plate by the phase-change power module, so that the thermal resistance of the power module in normal work is increased, thermal stress is generated between the chip and the heat transfer enhancement frame when the temperature of the heat transfer enhancement frame is increased, the chip can be damaged, the process difficulty is high, the cost of the required phase-change material is high, and the manufacturing and implementation cost is high.

It is noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure and therefore may include information that does not constitute prior art that is already known to a person of ordinary skill in the art.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a high overload capacity power module designed based on a metal block on the top of a chip, and solves the problems of the traditional power module.

The purpose of the invention is realized by the following technical scheme: a high overload capacity power module designed based on a metal block at the top of a chip comprises a substrate, a second solder layer, a lower copper layer of a ceramic copper-clad plate, a ceramic layer of the ceramic copper-clad plate, an upper copper layer of the ceramic copper-clad plate, a first solder layer and the chip which are sequentially arranged from bottom to top;

the top of chip has the metal block that promotes the heat capacity in order to strengthen power module overload capacity through the welding of third solder layer, and the metal block welds on the copper layer on the pottery copper-clad plate through first solder layer simultaneously, is provided with the space that is used for filling insulating material in the both sides of chip, prevents that power module from being punctured by high electric field, and the metal material that is filled with high specific heat capacity in the metal block, through the produced heat when the metal material short-term overload of metal material quick absorption chip, strengthen power module's overload capacity.

The metal block comprises a middle bulge, the metal block is welded on the chip through a third solder layer by a vacuum reflow soldering technology, the middle bulge extends upwards to the left side and the right side of the chip respectively by arcs with the radius of r, then extends transversely for a distance d, and then extends vertically downwards for a distance h to obtain a left bulge and a right bulge, gaps for filling insulating materials are formed between the left bulge and the middle bulge as well as between the right bulge and the middle bulge, the power module is prevented from being broken down by a high electric field, and the middle bulge is filled with a metal material with high specific heat capacity;

and the left convex part and the right convex part are welded on the copper layer on the ceramic copper-clad plate through a first solder layer.

The middle protruding part is welded in an active area in the middle of the chip through a third welding flux layer, the area of the bottom surface of the middle protruding part is smaller than that of the active area, the middle protruding part is not in contact with a terminal area on the periphery of the chip, a space is reserved for a bonding wire, and the chip is guaranteed to be electrically connected with the outside.

The distance between the middle bulge and the left bulge and the distance between the middle bulge and the right bulge are 5mm to 20mm, the radius r is 1mm to 5mm, so that insulation is ensured, and enough metal materials are filled in the middle bulge; d is 1mm to 5mm, and the height of h is greater than the height of one chip with the radius r.

The above-mentionedThe metal block comprises a middle bulge part which is welded on the chip through a third solder layer by a vacuum reflow soldering technology, and the radius of the middle bulge part is r towards the left side and the right side of the chip respectively ₁ Extend upwards, then extend transversely a distance d, and then with a radius r ₂ The arc of the power module extends downwards to obtain a left convex part and a right convex part, and gaps for filling insulating materials are formed between the left convex part and a middle convex part as well as between the right convex part and the middle convex part to prevent the power module from being broken down by a high electric field, and a metal material with high specific heat capacity is filled in the middle convex part;

The support extends from two sides of the metal block, a round hole is formed in the center of the support and connected with other chips or terminals in a bolt mode, and electrical connection is achieved.

Radius r ₂ Is 1mm to 5mm to ensure insulation and sufficient metal material is filled in the middle convex part; radius r ₂ Radius of (d) to radius r ₁ Is longer by the length of one chip, and d is 1mm to 5mm.

The edge of the metal block is uniformly coated with single-layer graphene so as to increase the thermal conductivity and achieve the purposes of temperature equalization and heat conduction; the insulating material comprises silica gel, and the metal material comprises molybdenum or copper or silver material.

The invention has the following advantages: the high overload capacity power module based on the chip top metal block design improves the overload capacity of the power module, the adopted materials are low in cost, the implementation method is simple, only vacuum welding is needed, and due to the fact that the added structure is close to the upper portion of the chip, the temperature response speed is high, and extra thermal resistance is not added to the power module.

Drawings

FIG. 1 is a schematic diagram of a Cauer model of a conventional power module;

FIG. 2 is a schematic structural diagram of a conventional phase change power module;

fig. 3 is a schematic structural view of embodiment 1 of the present invention;

FIG. 4 is a schematic view showing the structure of a void in embodiment 1 of the present invention;

FIG. 5 is a schematic structural view of embodiment 2 of the present invention;

FIG. 6 is a schematic view showing the structure of voids in embodiment 2 of the present invention;

fig. 7 is a top view of embodiment 2 of the present invention;

in the figure: 1-substrate, 2-second solder layer, 3-copper layer under ceramic copper clad plate, 4-ceramic copper clad plate ceramic layer, 5-copper layer on ceramic copper clad plate, 6-first solder layer, 7-chip, 8-third solder layer, 9-metal block, 91-left protrusion, 92-right protrusion, 93-middle protrusion, 10-bracket, 11-round hole.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the detailed description of the embodiments of the present application provided below in connection with the appended drawings is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application. The invention is further described below with reference to the accompanying drawings.

As shown in fig. 3, the invention specifically relates to a high overload power module designed based on a metal block on the top of a chip, wherein one real-time mode comprises a substrate 1, a second solder layer 2, a lower copper layer 3 of a ceramic copper-clad plate, a ceramic layer 4 of the ceramic copper-clad plate, an upper copper layer 5 of the ceramic copper-clad plate, a first solder layer 6 and a chip 7. In order to effectively enhance the overload capacity of the power module and avoid adding additional thermal resistance to the power module, a third solder layer 8 and a metal block 9 are added above the chip 7, wherein the connecting part of the metal block and the chip is called a middle bulge 93 of the metal block 9, and the connecting parts of the two sides of the metal block 9 and the copper layer 5 on the ceramic copper-clad plate are respectively called a left bulge 91 of the metal block 9 and a right bulge 92 of the metal block 9.

Furthermore, the middle protrusion 93 of the metal block 9 is soldered on the chip 7 through the third solder layer 8 by the vacuum reflow soldering technique, and in consideration of the thermal adaptation problem of the power module, the solder material above the chip is a material with a thermal expansion coefficient that is not much different from that of the chip material, such as molybdenum, and if the cost and other factors are considered, other metal materials such as copper and aluminum can be selected. The bottom surface area of the middle protruding part 9 of the metal block 9 is smaller than that of the chip 7, the metal block 9 is welded in an active area of the chip 7 and is not contacted with a terminal area of the chip 7, a certain allowance needs to be reserved, a space is reserved for a bonding wire, and the chip is guaranteed to be electrically connected with the outside.

A certain radian is left when the middle protrusion 93 of the metal block 9 extends upwards to fill more metal materials, then the left protrusion 91 and the right protrusion 92 which extend out of the metal block 9 transversely are welded on the copper layer 5 on the ceramic copper-clad plate through the first solder layer 6, the transverse extension length is 5mm to 20mm, namely, the distance between the middle protrusion 92 of the metal block 9 and the left protrusion 91 or the right protrusion 93 of the metal block 9 is 5mm to 20mm, so as to ensure the electrical connection between the chip 7 and the outside. When the power module normally works, an electric field exists between the gaps of the metal block 9, and therefore, insulating substances, such as silica gel and other materials, need to be filled between the gaps to ensure that the device is not broken down by the high electric field, as shown in fig. 4. Since the breakdown voltage of the silica gel material is 20-25kV/mm, the radius of the arc of the middle protruding portion 93 of the metal block 9, i.e., r in fig. 4, needs to be greater than 1mm to ensure insulation, and needs to be less than 5mm to fill enough metal material, the length h of the protruding portions on both sides is higher than the middle protruding portion 93 by the height of one chip, the length of the height h is usually 0.1 mm to 2 mm, and the distance d between the arc and the protruding portions on both sides is 1mm to 5mm. In addition, the gap can be a reserved space for volume expansion after the temperature of the metal block 9 rises, and the edge of the metal block 9 can be uniformly coated with single-layer graphene to increase the thermal conductivity, so that the effects of temperature equalization and heat conduction are achieved.

As shown in fig. 5, another embodiment of the invention includes a substrate 1, a second solder layer 2, a lower copper layer 3 of a ceramic copper clad laminate, a ceramic layer 4 of the ceramic copper clad laminate, an upper copper layer 5 of the ceramic copper clad laminate, a first solder layer 6 and a chip 7. In order to effectively enhance the overload capacity of the power module and avoid adding additional thermal resistance to the power module, a third solder layer 8 and a metal block 9 are added above the chip 7, wherein the connecting part of the metal block and the chip is called a middle bulge 93 of the metal block 9, and the connecting parts of the two sides of the metal block 9 and the copper layer 5 on the ceramic copper-clad plate are respectively called a left bulge 91 of the metal block 9 and a right bulge 92 of the metal block 9.

Further, as shown in fig. 6, a certain radian is set at the corner of the metal block 9 added to the high overload power module to increase the metal material added thereto, and the gap of the metal block 9 is filled with insulating substances such as silica gel, and since the breakdown voltage of the silica gel material is 20-25kV/mm, the arc radius of the middle protrusion 93 of the metal block 9 needs to be greater than 1mm to ensure insulation, and needs to be less than 5mm to be filled with enough metal material, i.e., r in fig. 6 ₁ Shown, the radius r of the arc of the convex portion on both sides ₂ Ratio r ₁ The height of the chip 7 is usually 0.1 mm to 2 mm, and the distance d between the arc of the central protrusion 93 and the arc of the two side protrusions is 1mm to 5mm. As shown in fig. 7, the power chip with high overload capacity does not adopt a bonding wire mode to realize electrical connection, the metal block 9 can extend out of the support 10, the center of the support 10 is provided with a round hole 11, and the round hole 11 can be connected with other chips 7 or terminals with round holes 11 in a bolt mode, so that electrical connection is realized, the use of a bonding wire can be avoided, and the power module can be prevented from failing due to aging and failure of the bonding wire.

The foregoing is illustrative of the preferred embodiments of the present invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and is not to be construed as limited to the exclusion of other embodiments, and that various other combinations, modifications, and environments may be used and modifications may be made within the scope of the concepts described herein, either by the above teachings or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A high overload capacity power module based on chip top metal block design which characterized in that: the soldering flux comprises a substrate (1), a second soldering flux layer (2), a lower copper layer (3) of a ceramic copper-clad plate, a ceramic layer (4) of the ceramic copper-clad plate, an upper copper layer (5) of the ceramic copper-clad plate, a first soldering flux layer (6) and a chip (7) which are arranged in sequence from bottom to top;

the top of chip (7) has metal block (9) of promotion heat capacity in order to strengthen power module overload capacity through third solder layer (8) welding, metal block (9) weld on copper layer (5) on the ceramic copper-clad plate through first solder layer (6) simultaneously, both sides in chip (7) are provided with the space that is used for filling insulating material, prevent that power module from being punctured by high electric field, metal material that is filled with high specific heat capacity in metal block (9), produced heat when transshipping in the short-term through metal material quick absorption chip (7), strengthen power module's overload capacity.

2. The high overload capacity power module based on the design of the metal block on the top of the chip as claimed in claim 1, wherein: the metal block (9) comprises a middle bulge (93) which is formed by welding the metal block (9) on the chip (7) through a third solder layer (8) by a vacuum reflow soldering technology, the middle bulge (93) extends upwards to the left side and the right side of the chip (7) by an arc with the radius of r respectively, then extends for a distance d transversely, and then extends for a distance h vertically downwards to obtain a left bulge (91) and a right bulge (92), gaps for filling insulating materials are formed between the left bulge (91) and the middle bulge (93) and between the right bulge (92) and the middle bulge (93), the power module is prevented from being broken through by a high electric field, and the middle bulge (93) is filled with a metal material with high specific heat capacity;

the left convex part (91) and the right convex part (2) are welded on the copper layer (5) on the ceramic copper-clad plate through a first solder layer (6).

3. The high overload capacity power module based on the design of the metal block on the top of the chip as claimed in claim 2, wherein: the middle protruding portion (93) is welded in an active area located in the middle of the chip (7) through a third solder layer (8), the area of the bottom face of the middle protruding portion (93) is smaller than that of the active area, the middle protruding portion does not contact with a terminal area located on the periphery of the chip (7), a space is reserved for a bonding wire, and the chip (7) is guaranteed to be electrically connected with the outside.

4. The high overload capacity power module based on the design of the metal block on the top of the chip as claimed in claim 2, wherein: the distance between the middle convex part (93) and the left convex part (91) and the distance between the middle convex part (93) and the right convex part (92) are 5mm to 20mm, the radius r is 1mm to 5mm, so that insulation is ensured, and enough metal material is filled in the middle convex part (93); d is 1mm to 5mm, and the height of h is greater than the height of one chip (7) with radius r.

5. The high overload capacity power module based on the design of the metal block on the top of the chip as claimed in claim 1, wherein: the metal block (9) comprises a middle bulge part (93) which is welded on the chip (7) through a third solder layer (8) by a vacuum reflow soldering technology, and the middle bulge part (93) respectively uses the radius r to the left side and the right side of the chip (7) ₁ Extend upwards, then extend transversely a distance d, and then with a radius r ₂ The arc of the power module extends downwards to obtain a left convex part (91) and a right convex part (92), gaps for filling insulating materials are formed between the left convex part (91) and a middle convex part (93) and between the right convex part (92) and the middle convex part (93), the power module is prevented from being broken down by a high electric field, and the middle convex part (93) is filled with a metal material with high specific heat capacity;

6. The high overload capacity power module based on the design of the metal block on the top of the chip as claimed in claim 5, wherein: the support (10) extends out of two sides of the metal block (9), a round hole (11) is formed in the center of the support (10), and the round hole (11) is connected with other chips or terminals in a bolt mode to achieve electrical connection.

7. The high overload capacity power module based on the design of the metal block on the top of the chip as claimed in claim 4, wherein: radius r ₂ Is 1mm to 5mm to ensure insulation and sufficient metal material is filled in the middle protruding part (93); radius r ₂ Radius of (d) to radius r ₁ Is longer by the length of one chip (7), and d is 1mm to 5mm.

8. The high overload capability power module based on the design of the metal block on the top of the chip according to any one of the claims 1 to 7, wherein: the edge of the metal block (9) is uniformly coated with single-layer graphene so as to increase the heat conductivity and achieve the purposes of uniform temperature and heat conduction; the insulating material comprises silica gel, and the metal material comprises molybdenum or copper or silver material.