CN111725163A - A kind of electronic switch installation method to reduce thermal impedance - Google Patents

Abstract

The invention discloses an electronic switch installation method for reducing thermal resistance, which includes a chip. There are mainly two heat dissipation paths for the heat generated by the chip, wherein the first path is from the junction of the chip to the top plastic package of the chip (R. ), through the convection/radiation (R.) to the surrounding air, through the method of the chip, install the heat sink on the top of the chip, which can further reduce the thermal resistance of the electronic switch, so that the electronic switch can effectively reduce the thermal resistance during installation , easy to use, and then blowing by the low-power fan inside, the airflow generated inside can drive the internal heat to dissipate, so that the internal heat can be dissipated better, which can reduce its thermal resistance, easy to use Finally, the thermal conductive silicone grease is injected into the sealed mold, so that the internal power system components are emitted to the outside world through the thermal conductive silicone grease, thereby further reducing the thermal impedance of the electronic switch, which is convenient to use.

Description

A kind of electronic switch installation method to reduce thermal impedance

Technical field:

The invention relates to the technical field of electronic switch installation, in particular to an electronic switch installation method for reducing thermal impedance.

Background technique:

The DC-DC power supplies we design generally include capacitors, inductors, Schottky, resistors, chips and other components; power

The conversion efficiency of the product cannot be 100%, and there must be losses. These losses will be presented in front of us in the form of temperature rise. The power system will accelerate the decay of life due to poor thermal design, so thermal design is the system reliability. It is particularly important in the design process, but thermal design is also very difficult. There are too many factors involved, such as the size of the circuit board and whether there is air flow. When we look at IC product specifications, we often see RjA, T, Tsro, TLEAD and other terms, first of all R]a refers to the thermal resistance of the chip, that is, the corresponding chip junction temperature rise per 1W loss, Tr refers to the junction temperature of the chip, Tsrco refers to the storage temperature range of the chip, TLEAD is It refers to the processing temperature of the chip, so it can be known that the existing technology cannot reduce the thermal resistance of the electronic switch well.

Invention content:

The purpose of the present invention is to provide a method for installing an electronic switch with reduced thermal impedance in view of the defects of the prior art.

The present invention is achieved through the following technical solutions:

A method of mounting an electronic switch with reduced thermal impedance, including a chip, for the heat generated by the chip, there are mainly two heat dissipation paths, the first path is from the junction of the chip to the top plastic package (R.) of the chip, through convection / Radiation (R.) to ambient air, for chips without thermal pads, Rrc refers to the thermal resistance from the junction to the top of the plastic body; because Rre represents the lowest thermal resistance path from the junction inside the chip to the outside, where copper Lateral thermal resistance length of copper plane L=1cm, width=1cm, foil thickness=0.0035cm, thermal conductivity of copper (λa)=4W/(cm°C), typical 12mil via thermal resistance, via length L= 0.165cm, hole wall copper thickness=0.00175cm, aperture=0.01524cm, copper thermal conductivity (λa)=4W/ (cm°C); the second path is from the junction of the chip to the back pad (R2 ), conducted to the surface of the PCB board and the surrounding air by convection/radiation (R.), the thermal resistance from the surface of a square with a side length of 1cm on the PCB board to the surrounding air caused by natural convection.

Wherein, the described DC step-down scheme is to output 5V, the current is 1A, the conversion efficiency η is 90%, and the ambient temperature TA is 50°C. The rated temperature of the capacitor used is 100°C, and it is very close to the chip. The temperature of the chip TJ is required to be controlled at 90C°.

Wherein, the thermal resistance of the described selection chip should be lower than 71.4 "C/W, and wherein the model of the chip can be selected as SOP8-EP chip.

Wherein, the product space range is relatively large, and it is not in a sealed environment, and a low-power fan can be placed inside the product space, so that the low-power fan can generate airflow, thereby reducing the overall thermal resistance of the system.

Wherein, the waterproof, dustproof and anti-vibration products need to be put into the inside of the sealed mold, and the method is to pour thermal conductive silicone grease into the sealed mold, so that the components of the power system can dissipate heat through the thermal conductive silicone grease. transferred to the housing, which in turn dissipates the heat.

The beneficial effects of the electronic switch installation method for reducing thermal impedance of the present invention are:

By reducing the DC voltage drop, the thermal resistance of the electronic switch can be reduced first, and then a heat sink is installed on the top of the chip through the chip method, which can further reduce the thermal resistance of the electronic switch, so that the electronic switch can be installed during installation. Effectively reduce the thermal resistance, easy to use, and then blowing through the internal low-power fan, the internal air flow can drive the internal heat to dissipate, so that the internal heat can be dissipated better, and then can reduce its heat. The thermal resistance is easy to use. Finally, the thermal conductive silicone grease is injected into the sealed mold, so that the internal power system components are dissipated to the outside through the thermal conductive silicone grease, thereby further reducing the thermal resistance of the electronic switch and easy to use.

Detailed ways:

The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by the technical personnel without creative work fall within the protection scope of the present invention;

The present invention provides a technical solution:

An electronic switch mounting method for reducing thermal impedance, comprising: including a chip, and for the heat generated by the chip, there are mainly two heat dissipation paths, wherein the first path is from the junction of the chip to the top plastic package (R.) of the chip, By convection/radiation (R.) to the surrounding air, for chips without thermal pads, Rrc refers to the thermal resistance from the junction to the top of the plastic body; since Rre represents the lowest thermal resistance path from the junction inside the chip to the outside world, Among them, the lateral thermal resistance length of copper-copper plane L=1cm, width=1cm, foil thickness=0.0035cm, thermal conductivity of copper (λa)=4W/(cm°C), typical 12mil via thermal resistance, via length L=0.165cm, hole wall copper thickness=0.00175cm, aperture=0.01524cm, copper thermal conductivity (λa)=4W/ (cm°C); the second path is from the junction of the chip to the back pad (R2), conducted to the surface of the PCB board and the surrounding air by convection/radiation (R.), the thermal resistance from the surface of a square with a side length of 1cm on the PCB board to the surrounding air caused by natural convection;

The DC step-down solution is that the output is 5V, the current is 1A, the conversion efficiency η is 90%, and the ambient temperature TA is 50°C. The rated temperature of the capacitor used is 100°C, and it is very close to the chip. The temperature of the chip TJ is required to be controlled at 90C°. By reducing the internal power output, the internal electrical impedance can be reduced, which is convenient to use;

The thermal resistance of the described selection chip will be lower than 71.4 "C/W, wherein the model of the chip can be selected as the SOP8-EP chip, and the signal of the chip can reduce the thermal impedance, and then further reduce the thermal impedance when the electronic switch is installed, using Convenient, the heat sink can effectively reduce the temperature of the chip. For SMD components, the position of the heat sink is located on the top of the chip plastic package, which can further reduce the thermal resistance of the electronic switch, so that the electronic switch can be installed effectively. reduce thermal resistance;

The product space range is relatively large, and it is not in a sealed environment. A low-power fan can be placed inside the product space, so that the low-power fan can generate airflow, thereby reducing the overall thermal resistance of the system. Blowing can make the internal air flow to drive the internal heat to dissipate, so that the internal heat can be dissipated better, and then its thermal resistance can be reduced;

The waterproof, dust-proof and anti-vibration products need to be put into the inside of the sealed mold. The method is that the heat-conducting silicone grease can be poured into the sealed mold, so that the components of the power system can transfer heat to the mold through the heat-conducting silicone grease. The shell is then dissipated, and finally the thermal grease is injected into the sealed mold, so that the internal power system components are dissipated to the outside through the thermal grease, thereby further reducing the thermal impedance of the electronic switch.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are more specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention.

Claims (7)

1. An electronic switch installation method for reducing thermal impedance, characterized in that it comprises a chip, and for the heat generated by the chip, there are mainly two heat dissipation paths, wherein the first path is from the junction of the chip to the plastic package on the top of the chip ( R.), through convection/radiation (R.) to the surrounding air, for chips without thermal pads, Rrc refers to the thermal resistance from the junction to the top of the plastic package; because Rre represents the lowest point from the junction inside the chip to the outside world Thermal resistance path, where the lateral thermal resistance length L=1cm, width=1cm, foil thickness=0.0035cm, copper thermal conductivity (λa)=4W/(cm°C), typical 12mil via thermal resistance , via length L=0.165cm, hole wall copper thickness=0.00175cm, aperture=0.01524cm, copper thermal conductivity (λa)=4W/ (cm°C); the second path is from the junction of the chip To the back pad (R2), it is conducted to the surface of the PCB board and the surrounding air by convection/radiation (R.), the thermal resistance from the surface of the 1cm square on the side of the PCB board to the surrounding air caused by natural convection. 2. a kind of electronic switch installation method that reduces thermal impedance as claimed in claim 1, it is characterized in that, described DC step-down scheme is to output 5V, electric current 1A, conversion efficiency η is 90%, and ambient temperature TA is 50C ° . 3. The rated temperature of the capacitor used is 100°C, and it is very close to the chip. The temperature of the chip TJ is required to be controlled at 90°C. 4. a kind of electronic switch installation method that reduces thermal impedance as claimed in claim 1, it is characterized in that, the thermal resistance of described selection chip will be lower than 71.4 "C/W, and wherein the model of chip can be selected as SOP8 -EP chip. 5. The electronic switch installation method for reducing thermal impedance according to claim 1, wherein the heat sink can effectively reduce the temperature of the chip, and for the SMD components, the heat sink is located in the chip plastic package. top. 6. The electronic switch installation method for reducing thermal impedance according to claim 1, characterized in that, the product space range is relatively large, and it is not in a sealed environment, and a low-power fan can be put into the product space Inside, the low-power fan can generate airflow, thereby reducing the overall thermal resistance of the system. 7. A kind of electronic switch installation method for reducing thermal impedance as claimed in claim 1, it is characterized in that, described need to put waterproof, dustproof, anti-vibration products into the inside of the sealed mold, the method is to pass The thermal grease is poured into the sealed mold, so that the power system components transfer heat to the housing through the thermal grease, and then dissipate the heat.