Press-fit structure for press-fit MOSFET

Abstract

A press-fit structure for press-fit MOSFET, comprising a first copper block, an elastic structure, a press-fit MOSFET, a circuit board and a second copper block. A plurality of press-fit MOSFETs can form a parallel array, arranged in a ring or matrix. The press-fit structure has a simple and compact structure, and has enhanced current flow capacity and heat dissipation capacity, thus broadening the scope of application.

Description

Technical Field

[0001] The invention relates to a press-fit structure of a MOSFET, in particular to a press-fit structure applied to a press-fit type MOSFET or a press-fit type MOSFET array, and belongs to the technical field of electrical engineering. Background Art

[0002] Metal-oxide-semiconductor field-effect transistor, abbreviated as MOSFET, is a widely used field-effect transistor. It can be used in digital signal processing occasions such as microprocessors and microcontrollers, and more and more integrated circuits for analog signal processing are implemented using MOSFET.

[0003] The traditional MOSFET is a lateral current-passing structure, and its gate, drain, and source are usually soldered on the circuit board. The heat generated by the device during operation is mainly dissipated through the circuit board. Affected by the package type, the heat dissipation capacity is poor, which limits its current capacity. Press-fit MOSFET, such as Figure 1 As shown, it is a longitudinal flow structure, the drain is the top metal shell. During use, the bottom source and gate can be welded to the circuit board respectively, the left and right drains are welded to the circuit board, and the top drain is crimped to the metal connection structure to increase the heat dissipation capacity.

[0004] In high-power applications, a large number of MOSFETs are usually connected in parallel to form an array to achieve the function of large current conduction and shutdown. For example, the turn-off module of the gate drive circuit of the integrated gate-commutated thyristor (IGCT), as shown in Figure 2(a), uses a large number of parallel MOSFET arrays Q G and pre-charged parallel capacitor group C off In series, during the IGCT off period, by triggering the MOSFET array Q G The IGCT is turned on, so that the cathode current of the IGCT is commutated to the gate, thereby turning off the IGCT. For example, in the drive circuit of the emitter turn-off thyristor (ETO) based on the GCT or GTO element, as shown in Figure 2(b), two sets of parallel MOSFET arrays Q G and Q E During ETO conduction period, Q G Shutdown, Q E When ETO is turned off, Q E Shutdown, Q G The current commutates from the cathode of the GCT or GTO element to the gate, turning it off.

[0005] Most existing MOSFET arrays use traditional MOSFETs welded on circuit boards. Due to the limited current-carrying capacity of a single MOSFET, a large number of parallel connections are required in high-power applications. If a press-fit MOSFET is used, the number of parallel connections can be greatly reduced, but its heat dissipation method is special, and there is currently no heat dissipation structure for press-fit MOSFET arrays. In addition, in some applications, in order to increase the commutation speed of the turn-off device current from the cathode to the gate using IGCT and ETO drive circuits, the stray inductance of the loop should be reduced as much as possible. For this reason, the MOSFET should be integrated into the device shell package. Since molybdenum sheets need to be crimped on both sides of GCT or GTO and a pressure of more than tens of kN is applied, and a single press-fit MOSFET can only withstand a pressure of 50-100N, if the MOSFET is integrated into the shell, there are pressure differences and matching problems between different components. Summary of the invention

[0006] In order to overcome the defects of the prior art, the present invention proposes a press-fit structure applied to a press-fit type MOSFET array.

[0007] The technical solution is as follows:

[0008] A press-fit structure, applied to a press-fit type MOSFET, characterized by comprising a first copper block, an elastic structure, a press-fit type MOSFET, a circuit board, and a second copper block;

[0009] Wherein, a groove is provided at the bottom of the first copper block, and the elastic structure and the crimp-type MOSFET are placed in the groove;

[0010] The top of the elastic structure is electrically connected to the first copper block; the bottom of the elastic structure is coupled to the drain top of the press-fit MOSFET;

[0011] In the absence of external pressure, the first copper block is not in contact with the circuit board, and the first copper block is electrically connected to the drain of the compression-type MOSFET only through the elastic structure;

[0012] The press-fit MOSFET is arranged on the circuit board, and the source and gate at the bottom of the press-fit MOSFET are electrically connected to the circuit board;

[0013] A second copper block is rigidly connected underneath the circuit board.

[0014] Furthermore, the elastic structure includes a main spring, two auxiliary spring sheets and a metal base; wherein the metal base has a groove structure, one end of the main spring is coupled to the groove of the metal base, and one end of the auxiliary spring sheet is coupled to the metal base; the other end of the main spring is coupled to the bottom groove of the first copper block, and when there is no external pressure, the other end of the auxiliary spring sheet is in slight contact or no contact with the bottom groove of the first copper block.

[0015] Furthermore, the bottom of the metal base of the elastic structure is electrically coupled to the top of the drain of the compression-contact MOSFET.

[0016] Furthermore, the circuit board adopts a FR4 substrate, an aluminum substrate or a copper substrate.

[0017] Furthermore, the circuit board includes a top circuit layer, a first insulating heat-conducting layer, an intermediate circuit layer, a second insulating heat-conducting layer and a substrate.

[0018] Furthermore, when the pressure applied between the first copper block and the second copper block is small, the elastic structure deforms less, the first copper block does not contact the circuit board, and the first copper block is electrically connected to the drain of the crimped MOSFET only through the elastic structure.

[0019] Furthermore, when a large pressure is applied between the first copper block and the second copper block, the deformation of the elastic structure increases, and the first copper block contacts the circuit board. The first copper block is electrically connected to the drain of the crimped MOSFET through the elastic structure, and is also electrically connected to the drain of the crimped MOSFET3 through the contact surface between the first copper block and the circuit board and the copper-clad area of ​​the top circuit layer of the circuit board.

[0020] Furthermore, the edge of the drain metal shell of the press-fit MOSFET is coupled to the top circuit layer of the circuit board, the gate of the press-fit MOSFET is coupled to the middle circuit layer of the circuit board through a via, and the source of the press-fit MOSFET is coupled to the substrate of the circuit board through a conductive and thermally conductive medium.

[0021] Furthermore, a plurality of press-fit MOSFETs are included to form a press-fit MOSFET array, and the press-fit MOSFET array is arranged in a ring or matrix shape.

[0022] Furthermore, the first copper block, the second copper block and the elastic structure are arranged accordingly according to the arrangement of the crimped MOSFET array.

[0023] Furthermore, when the drains of the plurality of crimp-type MOSFETs are at different potentials, a plurality of first copper blocks are provided, and insulating ring spacers are added between different first copper blocks;

[0024] When the sources of the plurality of press-fit MOSFETs are at different potentials, a plurality of second copper blocks are provided, and insulating ring spacers are added between different second copper blocks.

[0025] Compared with the prior art, the press-fit structure applied to the press-fit type MOSFET array of the present invention has the following beneficial effects:

[0026] (1) Suitable for press-fit MOSFET parallel arrays, with a simple and compact structure.

[0027] (2) The elastic structure provides pressure to the contact surface, reduces the contact resistance, and uses auxiliary springs to increase the flow area, thereby increasing the flow capacity of the overall structure.

[0028] (3) Elastic structure provides pressure to the contact surface and reduces the thermal resistance of the contact surface. At the same time, copper-based circuit boards and auxiliary springs are used to enhance the heat dissipation capacity of the overall structure.

[0029] (4) The elastic structure can limit the upper limit of the pressure on the surface of the MOSFET, thereby increasing the range of pressure applied between the first copper block and the second copper block and making it more applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 : The press-fit MOSFET structure of the prior art;

[0031] Figure 2a : A shut-off module of a gate drive circuit of an integrated gate-commutated thyristor IGCT in the prior art;

[0032] Figure 2b : A driving circuit of an emitter-turned-off thyristor (ETO) based on a GCT or GTO element in the prior art;

[0033] Figure 3 : An embodiment structure of the press-fit structure of the present invention applied to a press-fit type MOSFET array;

[0034] Figure 4 : An embodiment structure of the spring structure of the press-fit structure applied to a press-fit type MOSFET array of the present invention;

[0035] Figure 5 : An embodiment structure of a circuit board of the present invention applied to a press-fit structure of a press-fit type MOSFET array;

[0036] Figure 6 : The ring-shaped arrangement structure diagram of the crimping type MOSFET array of the present invention;

[0037] Figure 7 : A multi-ring arrangement structure diagram of the crimping type MOSFET array of the present invention;

[0038] Figure 8 : Another multi-ring arrangement structure diagram of the crimped MOSFET array of the present invention (top view and side view). DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments, but is not intended to limit the present invention.

[0040] In one embodiment, the press-fit structure applied to the press-fit type MOSFET array is as follows: Figure 3 As shown, from top to bottom, it includes: a first copper block 1, an elastic structure 2, a press-fit MOSFET 3, a circuit board 4, and a second copper block 5. A groove is provided at the bottom of the first copper block 1, and the elastic structure 2 and the press-fit MOSFET 3 are placed in the groove. The press-fit structure includes one or more elastic structures 2 and press-fit MOSFET 3, and the elastic structure 2 corresponds to the press-fit MOSFET 3 one by one. One or more grooves are provided at the bottom of the first copper block 1, and each group of elastic structures 2 and press-fit MOSFET 3 is provided in the corresponding groove, forming an array in the press-fit structure.

[0041] Spring structure 2, such as Figure 4 As shown, it includes a main spring 6, two auxiliary springs 7, and a metal base 8. The metal base 8 has a groove structure, and one end of the main spring 6 is coupled to the groove of the metal base 8. One end of the auxiliary spring 7 is coupled to the metal base 8; the other end of the main spring 6 is coupled to the groove at the bottom of the first copper block 1, and when there is no external pressure, the other ends of the two auxiliary springs 7 are slightly in contact with or not in contact with the groove at the bottom of the first copper block 1.

[0042] The circuit board 4 can be a common FR4 substrate circuit board, or an aluminum substrate or a copper substrate. Figure 5 As shown, the circuit board 4 includes a top circuit layer, a first insulating heat-conducting layer, a middle circuit layer, a second insulating heat-conducting layer and a copper substrate.

[0043] like Figure 3 As shown, the elastic structure 2 and the press-fit MOSFET 3 are arranged in the groove at the bottom of the first copper block 1, and the top of the elastic structure 2 is electrically connected to the inner surface of the groove. When no pressure is applied, the first copper block 1 does not contact the circuit board 4, and the first copper block 1 is electrically connected to the drain of the press-fit MOSFET 3 only through the elastic structure 2. The metal base 8 at the bottom of the elastic structure 2 is coupled to the top of the drain of the press-fit MOSFET 3, and the source and gate at the bottom of the press-fit MOSFET 3 are electrically connected to the circuit board 4; the press-fit MOSFET 3 is arranged on the circuit board 4; the second copper block 5 is rigidly connected to the bottom of the circuit board 4.

[0044] In one embodiment, the press-fit structure applied to the crimp-type MOSFET array has the following properties in terms of electrical characteristics: when the pressure applied between the first copper block 1 and the second copper block 5 is small, the elastic structure 2 is deformed slightly, the first copper block 1 is not in contact with the circuit board 4, and the first copper block 1 is electrically connected to the drain of the crimp-type MOSFET 3 only through the elastic structure 2. The auxiliary spring piece 7 in the elastic structure 2 is used to increase the flow area and contact area, and reduce the flow resistance and thermal resistance.

[0045] When a large pressure is applied between the first copper block 1 and the second copper block 5, the elastic structure 2 is deformed greatly, the first copper block 1 contacts the circuit board 4, and the first copper block 1 can be electrically connected to the drain of the crimped MOSFET 3 through the elastic structure 2, and can also be electrically connected to the drain of the crimped MOSFET 3 through the contact surface between the first copper block 1 and the circuit board 4 and the copper-clad area of ​​the top circuit layer of the circuit board 4, thereby increasing the flow area between the first copper block 1 and the drain of the crimped MOSFET 3 and reducing the flow resistance. Similarly, the auxiliary spring 7 in the elastic structure 2 is used to increase the flow area and contact area and reduce the flow resistance and thermal resistance.

[0046] The bottom of the metal base 8 of the elastic structure 2 is coupled to the top of the drain of the press-fit MOSFET 3 , and the main spring 6 is used to provide pressure on the contact surface to reduce contact resistance and thermal resistance.

[0047] like Figure 5 As shown, the edge of the drain D metal shell of the crimped MOSFET 3 is coupled to the top circuit layer of the circuit board 4, the gate G of the crimped MOSFET 3 is coupled to the middle circuit layer of the circuit board 4 through a via and is connected to the gate trigger signal receiving terminal of the circuit board, and the source S of the crimped MOSFET 3 is coupled to the copper substrate of the circuit board 4 through a conductive and heat-conducting medium (such as solder paste).

[0048] The second copper block 5 is electrically connected to the source of the compression-type MOSFET 3 through the circuit board 4 .

[0049] In one embodiment, the press-fit structure applied to the crimp-type MOSFET array has the following properties in terms of mechanical characteristics: This press-fit structure can apply the pressure required by different applications between the top of the first copper block 1 and the bottom of the second copper block 5, which can be as high as tens of kN.

[0050] When the pressure applied between the first copper block 1 and the second copper block 5 is small, the deformation of the elastic structure 2 is small, the first copper block 1 is not in contact with the circuit board 4, and the second copper block 5 is in rigid contact with the circuit board. The pressure applied between the first copper block 1 and the second copper block 5 is the sum of the pressures of the crimped MOSFET 3 array and the metal base 8.

[0051] When the pressure applied between the first copper block 1 and the second copper block 5 increases, the first copper block 1 is in rigid contact with the circuit board 4, and the second copper block 5 is in rigid contact with the circuit board 4. At this time, the spring deformation no longer increases. Therefore, the parameters of the main spring 6 can be designed according to the pressure requirements (50-100N) of the metal base 8 of the elastic structure 2 and the crimping type MOSFET 3, so that the main spring 6 provides the required pressure value at the maximum deformation. If the pressure continues to increase, the excess pressure will be applied to the contact surface between the first copper block 1 and the circuit board 4, avoiding mechanical stress damage to the crimping type MOSFET 3 due to excessive pressure.

[0052] In one embodiment, the press-fit structure applied to the press-fit MOSFET array has the following properties in terms of thermal characteristics: the heat generated by the press-fit MOSFET 3 during the on-current period can be dissipated through the upper and lower surfaces. On the upper surface, heat is dissipated through the metal base 8, the auxiliary spring 7, the first copper block 1, and the heat sink connected to the first copper block 1. Heat can also be dissipated through the two ends of the metal shell of the drain D, the top circuit layer of the circuit board 4, the first copper block 1, and the heat sink connected to the first copper block 1. On the lower surface, heat is dissipated through the solder paste, the copper substrate, the second copper block 5, and the heat sink connected to the second copper block 5. Thus, the effect of double-sided heat dissipation is achieved.

[0053] The pressure applied between the first copper block 1 and the second copper block 5 is beneficial to reducing the thermal resistance of each contact surface, thereby enhancing the thermal conductivity.

[0054] In one embodiment, the crimped MOSFET array may be arranged in a ring to form a ring, such as Figure 6 As shown; or form multiple rings, such as Figure 7 The three rings shown in FIG. 1 can also be arranged in a matrix. The first copper block, the second copper block and the elastic structure should be designed accordingly according to the arrangement of the crimped MOSFET array. Figure 7 According to the distribution shown in FIG. 1 , if the drains of the crimp-type MOSFETs in different rings have different potentials, multiple first copper blocks should be designed, and insulating rings should be added between different first copper blocks. Figure 8 If the sources of the crimp-type MOSFETs in different rings have different potentials, then multiple second copper blocks should be designed for the same reason.

[0055] The press-fit structure applied to the press-fit type MOSFET array of the present invention has the following beneficial effects:

[0056] (1) Suitable for press-fit MOSFET parallel arrays, with a simple and compact structure.

[0057] (2) The elastic structure provides pressure to the contact surface, reduces the contact resistance, and uses auxiliary springs to increase the flow area, thereby increasing the flow capacity of the overall structure.

[0058] (3) Elastic structure provides pressure to the contact surface and reduces the thermal resistance of the contact surface. At the same time, copper-based circuit boards and auxiliary springs are used to enhance the heat dissipation capacity of the overall structure.

[0059] (4) The elastic structure can limit the upper limit of the pressure on the surface of the MOSFET, thereby increasing the range of pressure applied between the first copper block and the second copper block and making it more applicable.

[0060] The above description is only a preferred embodiment of the present invention and should not be understood as limiting the scope of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A press-fit structure, applied to a press-fit type MOSFET, characterized in that: It includes a first copper block, an elastic structure, a press-fit MOSFET, a circuit board, and a second copper block; Wherein, a groove is provided at the bottom of the first copper block, and the elastic structure and the crimp-type MOSFET are placed in the groove; The top of the elastic structure is electrically connected to the first copper block; the bottom of the elastic structure is coupled to the drain top of the press-fit MOSFET; In the absence of external pressure, the first copper block is not in contact with the circuit board, and the first copper block is electrically connected to the drain of the compression-type MOSFET only through the elastic structure; The press-fit MOSFET is arranged on the circuit board, and the source and gate at the bottom of the press-fit MOSFET are electrically connected to the circuit board; A second copper block is rigidly connected underneath the circuit board.

2. The press-fit structure according to claim 1, characterized in that: The elastic structure includes a main spring, two auxiliary spring sheets and a metal base; wherein the metal base has a groove structure, one end of the main spring is coupled to the groove of the metal base, and one end of the auxiliary spring sheet is coupled to the metal base; the other end of the main spring is coupled to the bottom groove of the first copper block, and when there is no external pressure, the other end of the auxiliary spring sheet is in slight contact or no contact with the bottom groove of the first copper block.

3. The press-fit structure according to claim 2, characterized in that: The bottom of the metal base of the elastic structure is electrically coupled to the top of the drain of the compression-type MOSFET.

4. The press-fit structure according to claim 1, characterized in that: The circuit board adopts a FR4 substrate, an aluminum substrate or a copper substrate.

5. The press-fit structure according to claim 1, characterized in that: The circuit board comprises a top circuit layer, a first insulating heat-conducting layer, an intermediate circuit layer, a second insulating heat-conducting layer and a substrate.

6. The press-fit structure according to claim 1, characterized in that: When the pressure applied between the first copper block and the second copper block is small, the elastic structure deforms less, the first copper block does not contact the circuit board, and the first copper block is electrically connected to the drain of the crimped MOSFET only through the elastic structure.

7. The press-fit structure according to claim 1, characterized in that: When a large pressure is applied between the first copper block and the second copper block, the deformation of the elastic structure increases, the first copper block contacts the circuit board, and the first copper block is electrically connected to the drain of the press-fit MOSFET through the elastic structure, and is also electrically connected to the drain of the press-fit MOSFET through the contact surface between the first copper block and the circuit board and through the copper-clad area of ​​the top circuit layer of the circuit board.

8. The press-fit structure according to claim 1, characterized in that: The edge of the drain metal shell of the press-fit MOSFET is coupled to the top circuit layer of the circuit board, the gate of the press-fit MOSFET is coupled to the middle circuit layer of the circuit board through a via, and the source of the press-fit MOSFET is coupled to the substrate of the circuit board through a conductive and thermally conductive medium.

9. The press-fit structure according to claim 1, characterized in that: The invention comprises a plurality of press-fit MOSFETs to form a press-fit MOSFET array, wherein the press-fit MOSFET array is arranged in a ring shape or a matrix shape.

10. The press-fit structure according to claim 9, characterized in that: The first copper block, the second copper block and the elastic structure are arranged accordingly according to the arrangement of the press-fit MOSFET array.

11. The press-fit structure according to claim 10, characterized in that: When the drains of the plurality of crimp-type MOSFETs are at different potentials, a plurality of first copper blocks are provided, and insulating ring spacers are added between different first copper blocks; When the sources of the plurality of press-fit MOSFETs are at different potentials, a plurality of second copper blocks are provided, and insulating ring spacers are added between different second copper blocks.

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