CN216413059U

CN216413059U - Current-limiting protector

Info

Publication number: CN216413059U
Application number: CN202123136582.0U
Authority: CN
Inventors: 徐胜; 王剑国; 王峰
Original assignee: Changshu Switchgear Manufacturing Co Ltd
Current assignee: Changshu Switchgear Manufacturing Co Ltd
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2022-04-29
Anticipated expiration: 2031-12-14

Abstract

The utility model discloses a current-limiting protector, which comprises a circuit board, a radiator and a group of power semiconductor devices attached to the circuit board, wherein each power semiconductor device comprises a shell, pins and a copper substrate, wherein the pins and the copper substrate extend out of the shell from the inside of the shell; each power semiconductor device is provided with at least one heat conducting block, each heat conducting block is respectively attached to a copper foil of a circuit board where a copper substrate of the power semiconductor device is located, and the radiator is in compression joint with the shell of the power semiconductor device and the upper portion of the heat conducting block through an insulating heat conducting gasket. Compared with the prior art, the utility model has the advantages of higher heat dissipation efficiency, higher current-carrying capacity, higher production efficiency and lower production cost.

Description

Current-limiting protector

Technical Field

The utility model relates to a current-limiting protector.

Background

The current-limiting protector for electric fire prevention (or short for current-limiting protector) is a device which uses solid electronic switch as breaking main loop fault current, when short-circuit fault occurs, it can quickly limit short-circuit current at microsecond level and implement non-arc breaking so as to obviously reduce electric fire accident and ensure safety of personnel and property in use place. In a current-limiting protector product, a power semiconductor device is required to bear current, a surface-mounted MOSFET is usually selected and directly mounted on a circuit board, and a Tab pin is welded on a copper foil of the circuit board.

Because the power semiconductor device in the current-limiting protector needs to bear large current, a good heat dissipation structure becomes the core performance of the current-limiting protector. The existing current-limiting protector heat dissipation measures and disadvantages are analyzed as follows: the copper foil laying area of the Tab pins on the circuit board is increased, the area of the circuit board is synchronously increased, the cost of the circuit board is increased, and the miniaturization design of products is not facilitated; tin stacking is carried out on the copper foil, so that the heat dissipation area is enlarged, the tin stacking height is not controllable, the process steps are increased, and the automation production is not facilitated; punching is carried out on the copper foil, so that the heat dissipation area is enlarged, and the device arrangement on the reverse side of the circuit board is influenced;

meanwhile, the three measures have limited effect of improving the heat dissipation effect, and are suitable for application environments with small loss and small heat emission. Solid-state electronic switch in current-limiting protector product needs to bear the electric current of little to several ampere times, big to several ten ampere times, and the loss is big, and it is big to generate heat, as shown in fig. 1, can enlarge heat radiating area through the crimping radiator and promote the radiating effect, fills heat conduction gap filler between radiator and circuit board, forms following heat dissipation route: silicon chip-copper substrate-circuit board copper foil-heat conducting gap filler-radiator-air. However, in the above-mentioned heat dissipation structure, because the coefficient of heat conductivity of heat conduction gap filler is little a lot with metals such as copper foil, in the product production link, can uncontrollable formation bubble, cavity during the packing, influence the radiating effect, under the condition that adopts a plurality of MOSFET, cause the heat dissipation inhomogeneous easily, and then cause MOSFET current uneven flow, influence product reliability, heat conduction gap filler belongs to special macromolecular material simultaneously, and is with high costs, has increased the manufacturing cost of product.

SUMMERY OF THE UTILITY MODEL

The utility model aims to overcome the defects of the prior art and provides a current-limiting protector adopting a special heat dissipation structure, which has better heat dissipation performance and lower realization cost.

A current-limiting protector comprises a circuit board, a radiator and a group of power semiconductor devices attached to the circuit board, wherein each power semiconductor device comprises a shell, pins and a copper substrate, the pins and the copper substrate extend out of the shell from the inside of the shell, and the copper substrate of each power semiconductor device is attached and fixed to a copper foil of the circuit board; each power semiconductor device is provided with at least one heat conducting block, each heat conducting block is respectively attached to a copper foil of a circuit board where a copper substrate of the power semiconductor device is located, and the radiator is in compression joint with the shell of the power semiconductor device and the upper portion of the heat conducting block through an insulating heat conducting gasket.

Preferably, the side surface of the heat conduction block is tightly attached to the copper substrate of the power semiconductor device to which the heat conduction block belongs.

Further preferably, a gap between the heat conduction block and the power semiconductor device to which the heat conduction block belongs is filled with solder.

Preferably, the heat conduction block is made of metal.

Preferably, the power semiconductor devices are MOSFETs, the MOSFETs are grouped in pairs, two MOSFETs in each group are electrically connected in anti-series, and the MOSFETs in each group are electrically connected in parallel.

Preferably, the width and thickness of the heat conducting block are the same as those of the power semiconductor device to which the heat conducting block belongs.

Compared with the prior art, the utility model has the following beneficial effects:

the heat conduction area is increased through the heat conduction block, the thermal resistance between the power semiconductor device and the radiator is reduced, the heat dissipation efficiency is higher, and the current-carrying capacity is larger; because the heat conduction block adopts the surface mounting mode like a power semiconductor device, the existing surface mounting automatic production line can be adopted for mounting at the same time, the production efficiency is higher, and the heat conduction gap filler of high polymer materials is not needed, so that the production cost is lower.

Drawings

Fig. 1 is a schematic view of a heat dissipation structure of a current-limiting protector;

FIG. 2 is a schematic view of a heat dissipation structure of the current-limiting protector of the present invention;

FIG. 3 is a schematic circuit diagram of a current limiting protector employing MOSFETs;

FIGS. 4 and 5 are a top view and a front view, respectively, of an embodiment of the present invention;

FIG. 6 is a top view of another embodiment of the present invention.

The following reference numerals are included in the figures:

1. the circuit board comprises 11-14 parts of circuit board, copper foil, 2 parts of MOSFET, 21 parts of shell, 22 parts of pin, 23 parts of copper substrate, 24 parts of silicon chip, 3 parts of radiator, 4 parts of heat conducting gasket, 5 parts of heat conducting block, 6 parts of other elements.

Detailed Description

Aiming at the problems of the existing heat dissipation structure, the utility model adopts the solution that the heat conduction block is utilized to increase the heat conduction area and reduce the thermal resistance between the power semiconductor device and the radiator so as to improve the heat dissipation efficiency and reduce the cost.

Specifically, the current-limiting protector comprises a circuit board, a radiator and a group of power semiconductor devices attached to the circuit board, wherein each power semiconductor device comprises a shell, pins and a copper substrate, the pins and the copper substrate extend out of the shell from the inside of the shell, and the copper substrate of each power semiconductor device is attached and fixed to a copper foil of the circuit board; each power semiconductor device is provided with at least one heat conducting block, each heat conducting block is respectively attached to a copper foil of a circuit board where a copper substrate of the power semiconductor device is located, and the radiator is in compression joint with the shell of the power semiconductor device and the upper portion of the heat conducting block through an insulating heat conducting gasket.

Preferably, the heat conduction block is made of metal.

For the public understanding, the technical scheme of the utility model is explained in detail by a plurality of specific embodiments and the accompanying drawings:

taking the most commonly used current-limiting protector based on the MOSFET as an example, the heat dissipation structure proposed by the present invention is shown in fig. 2, the current-limiting protector includes a circuit board 1, a heat sink 3 and a set of MOSFETs 2 attached to the circuit board, the MOSFET2 includes a housing 21 and pins 22 and a copper substrate 23 extending from the inside of the housing 21 to the outside of the housing 21, the copper substrate 23 of the MOSFET2 is attached and fixed on the copper foil 11 of the circuit board; each MOSFET2 is provided with at least one heat conducting block 5, each heat conducting block 5 is respectively attached to the copper foil 11 of the circuit board on which the copper substrate 23 of the MOSFET belongs to the MOSFET, and the radiator 3 is pressed and connected above the shell 21 of the MOSFET2 and the heat conducting block 5 through an insulating heat conducting gasket 4; the remaining elements 6 that make up the current limiting protector are mounted on the opposite side of the circuit board 1.

When the power semiconductor device of the current-limiting protector is selected from the MOSFETs, the single MOSFETs do not have the capability of cutting off alternating current, and the MOSFETs are connected in series and then used in an anti-series mode, wherein the mode is drain-source-drain (D-S-S-D). The rated current of the current-limiting protector is expanded by increasing the number of parallel anti-series groups. Defining a near-incoming line L-side MOSFET as an upper bridge and a near-load side MOSFET as a lower bridge, wherein the circuit connection is as shown in FIG. 3;

fig. 4 and 5 show a specific heat dissipation structure of the current-limiting protector shown in fig. 3. The upper bridge MOSFET2 is attached on the circuit board 1, the Tab pin is welded on the copper foil 12, the S pin is welded on the copper foil 13, the upper bridge corresponding to the heat conducting block 5 is attached closely to the Tab pin of the upper bridge MOSFET and is also welded on the copper foil 12 of the circuit board; the lower bridge MOSFET is attached to the circuit board 1, Tab pins of the lower bridge MOSFET are welded on the copper foil 14, S pins of the lower bridge MOSFET are welded on the copper foil 13, the lower bridge corresponding heat conduction block 5 is attached to the Tab pins of the lower bridge MOSFET and is also welded on the copper foil 14 of the circuit board, the attaching positions of the MOSFET2 and the heat conduction block 5 are shown in figure 4, and the side surface of the heat conduction block 5 is tightly attached to the copper substrate 23 of the MOSFET 2.

The heat conducting block is made of copper, aluminum and other metals, and the size width and the thickness of the heat conducting block are equivalent to those of the MOSFET, so that the subsequent installation of the radiator is facilitated; the gap between the heat conducting block and the MOSFET can be filled with tin to fill the gap between the heat conducting block and the MOSFET, so that the heat dissipation effect is further improved.

After applying ointment or plaster heat conduction gasket on the radiator, with the radiator crimping in circuit board top, both guarantee appropriate clearance height through the space post, the difference of the height in clearance and MOSFET thickness will be less than heat conduction gasket's thickness, heat conduction gasket extension deformation is complete with heat conduction piece surface contact during the crimping, heat conduction gasket need be insulating material.

In the above embodiment: the heat dissipation path of the MOSFET is silicon chip-copper substrate (Tab) -heat conduction block-heat conduction gasket-radiator-air, wherein the copper substrate and the heat conduction block pass through the copper foil and tin supplement of the same circuit board, the heat conduction block can be considered as the extension of the copper substrate, and the heat resistance between the copper substrate and the heat conduction block is extremely small and negligible.

Since the MOSFETs of the upper and lower bridges are mounted side by side, respectively, it is also possible, as shown in fig. 6, for the MOSFETs 2 of the upper and lower bridges to share a heat conducting block 5, for example, an elongated copper strip.

From the above specific embodiments, it can be seen that: the heat conducting block is tightly attached to the Tab pin of the MOSFET for welding (gap can be used for supplementing soldering tin), the thermal resistance between the heat conducting block and the Tab pin is very small, the heat conducting block is regarded as the extension of the Tab pin, the thermal capacity is enlarged, and the short-time overcurrent capacity of a device is enhanced; the heat-conducting block increases the heat-radiating area of the device, reduces the thermal resistance between the MOSFET and the radiator, and has higher heat-radiating efficiency and higher current-carrying capacity; other elements can be pasted on the reverse side of the circuit board, so that the area utilization rate of the circuit board is improved, and the area of the circuit board is reduced; the heat-conducting block and the MOSFET can be simultaneously mounted on the circuit board in a mounting link, so that the production steps are reduced, the production automation degree is improved, and the labor cost is saved; the heat-conducting gasket can be directly applied to the pressure-connecting surface of the radiator, so that a cavity between the heat-conducting block and the radiator is avoided, the heat-radiating uniformity of the MOSFETs is improved, and the reliability of the product is improved; the heat dissipation form of the utility model can fully use the current carrying capacity of the MOSFET, reduce the parallel connection quantity, reduce the area of the circuit board and the volume of the radiator, greatly reduce the cost of the product device and improve the reliability of the product.

Claims

1. A current-limiting protector comprises a circuit board, a radiator and a group of power semiconductor devices attached to the circuit board, wherein each power semiconductor device comprises a shell, pins and a copper substrate, the pins and the copper substrate extend out of the shell from the inside of the shell, and the copper substrate of each power semiconductor device is attached and fixed to a copper foil of the circuit board; the power semiconductor device heat radiator is characterized in that each power semiconductor device is provided with at least one heat conduction block, each heat conduction block is respectively attached to a circuit board copper foil where a copper substrate of the power semiconductor device to which the heat radiator belongs is located, and the heat radiator is pressed and connected above a power semiconductor device shell and the heat conduction block through an insulating heat conduction gasket.

2. The current-limiting protector of claim 1 wherein the sides of the thermally conductive block are closely adjacent to the copper substrate of the power semiconductor device to which it belongs.

3. The current limiting protector as claimed in claim 2, wherein a gap between the heat conducting block and the power semiconductor device is filled with solder.

4. The current-limiting protector of claim 1 wherein the thermally conductive mass is metal.

5. A current limiting protector according to claim 1 wherein the power semiconductor devices are MOSFETs, the MOSFETs being grouped in pairs, the two MOSFETs of each group being electrically connected in anti-series, the MOSFETs of each group being electrically connected in parallel.

6. The current limiting protector of claim 1 wherein the thermally conductive mass has the same width and thickness as the power semiconductor device to which it belongs.