A method for measuring the thermal resistance of a gallium nitride device

Abstract

The present invention provides a method for measuring the thermal resistance of a gallium nitride device, aiming to solve the problems of unstable results and errors in the thermal resistance measurement method of gallium nitride power devices. A method for measuring the thermal resistance of a gallium nitride device includes the following steps: 1) Using the on-resistance of the gallium nitride power device as a temperature-sensitive parameter, measure the K coefficient of the device; 2) Weld the gallium nitride power device to two different test adapter PCBs respectively, and use the double-interface method to measure two transient cooling curves; 3) Perform numerical operations on the data of the two transient cooling curves using the structure function algorithm to convert them into two structure functions, and the separation point of the two function curves is the junction-case thermal resistance. The present invention uses the on-resistance of the gallium nitride power device as a temperature-sensitive parameter. Since the on-resistance of the device is small, the on-resistance is measured through a four-pin Kelvin connection to improve the measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of power device thermal resistance testing, and particularly to a thermal resistance testing method for gallium nitride devices. Background Art

[0002] Junction-to-case thermal resistance is an important thermal characteristic parameter of power devices, which characterizes the thermal conduction ability from the working part of the chip inside the package to the package shell. Existing power device thermal resistance testing usually adopts the electro-optical method, selects the diode conduction voltage drop of the device as the temperature-sensitive parameter (TSP) to characterize the device junction temperature, and adopts the double-interface testing method to obtain the junction-to-case thermal resistance. For example, the Chinese invention patent application number is 2014100222168, and the patent name is: Thermal Resistance Testing Method for Semiconductor Devices. The test object of this patent is a semiconductor integrated circuit, the temperature-sensitive parameter is the forward conduction voltage Vf of the PN junction of the semiconductor device, and the voltage of the diode is collected. The diode has only two electrodes; if the shell of the device under test is in direct contact with the constant temperature platform, using the application and non-application of thermal silicone grease as the double interface, the directly tested is the junction-to-case thermal resistance; if the device under test is soldered on the PCB, using the application of thermal grease and non-application of thermal silicone grease as the double interface, the directly tested is the junction-to-PCB thermal resistance, and the junction-to-case thermal resistance is deduced and analyzed through the structure function. Gallium nitride power devices do not have a PN junction, and gallium nitride power devices adopt DFN packaging and have no pins, so it is impossible to directly connect the thermal resistance test line and impossible to adopt the test method provided by this patent. Summary of the Invention

[0003] In order to solve the above problems, the present invention proposes a thermal resistance testing method for gallium nitride devices, aiming to solve the problems that the results of the thermal resistance testing method for gallium nitride power devices are unstable and there are errors.

[0004] The technical solution of the present invention is realized as follows: A thermal resistance testing method for gallium nitride devices includes the following steps:

[0005] 1) Taking the on-resistance of the gallium nitride power device as the temperature-sensitive parameter, placing the device in a constant temperature device. The gallium nitride power device is provided with a source electrode, a gate electrode, and a source electrode. A voltage Vgs is applied between the gate electrode and the source electrode to make the channel conduct, a test current Isense is applied between the drain electrode and the source electrode, the voltage Vds between the drain electrode and the source electrode is collected, the temperature of the constant temperature device is adjusted, the voltage Vds between the drain electrode and the source electrode at different temperatures is tested, a Vds-T curve is obtained, and the K coefficient is obtained by linear fitting;

[0006] 2) Welding the gallium nitride power device to two different PCBs for testing respectively, and measuring two transient cooling curves by the double-interface method;

[0007] 3) The data of the two transient cooling curves are numerically calculated using the structure function algorithm and converted into two structure function curves. The separation point of the two function curves is the junction-to-case thermal resistance.

[0008] Preferably, the specific method of step 2) is as follows:

[0009] 2.1 Solder the back of the gallium nitride power device onto a PCB board with a heat sink pad for testing, then place it on a cold plate. Apply a voltage Vgs between the gate and the source, and a large heating current Iheat between the drain and the source to heat the device. When it reaches a steady state, quickly switch to a small test current Isense, and test the curve of the voltage Vds between the drain and the source changing with time. Convert the voltage Vds between the drain and the source into the junction temperature through the K coefficient, and measure a transient cooling curve.

[0010] 2.2 Solder the back of the gallium nitride power device onto a PCB board without a heat sink pad for testing, repeat step 2.1, and measure another transient cooling curve.

[0011] Preferably, one side of the back of the gallium nitride power device is provided with a drain, and the other side is respectively provided with a gate, a Kelvin source, and a source. A heat sink is provided on the device near the source side.

[0012] Advantages of the present invention:

[0013] The present invention uses the on-resistance of the gallium nitride power device as the temperature-sensitive parameter. Since the on-resistance of the device is small, the on-resistance test is carried out through a four-pin Kelvin connection to improve the test accuracy. And this thermal resistance test method can directly obtain the junction-to-case thermal resistance by soldering the gallium nitride power device to the test adapter PCBs with and without heat sink pads. Description of the drawings

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0015] Figure 1 It is a schematic diagram of the back structure of the DFN package gallium nitride power device of the present invention;

[0016] Figure 2 It is a schematic diagram of the PCB board with a heat sink pad of the present invention;

[0017] Figure 3 It is a schematic diagram of the PCB board without a heat sink pad of the present invention;

[0018] Figure 4 This is the Vds-T curve diagram of the present invention;

[0019] Figure 5 This is the curve of Vds changing with time of the present invention. Curve A is the test curve of the PCB board without a heat sink pad, and curve B is the test curve of the PCB board with a heat sink pad;

[0020] Figure 6 These are two transient cooling curves of the present invention. Curve A is the test curve of the PCB board without a heat sink pad, and curve B is the test curve of the PCB board with a heat sink pad;

[0021] Figure 7 This is the flow chart of the thermal resistance test method of the present invention.

[0022] In the figure: 1 - drain; 2 - source; 3 - Kelvin source; 4 - gate; 5 - heat sink; 11 - drain pad; 12 - source pad; 13 - Kelvin source pad; 14 - gate pad; 15 - heat sink pad; 21-1 drain pin; 21-2 drain pin; 22-1 source pin; 22-2 source pin; 24 - gate pin. Detailed implementation manners

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. 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 those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0024] There is no PN junction inside the gallium nitride power device. This device has three electrodes, namely the gate, drain, and source. The on-resistance of the gallium nitride power device is selected as the temperature-sensitive parameter (TSP) to characterize the device junction temperature. Test method of on-resistance: Apply a voltage Vgs between the gate and the source to make the channel fully conductive, apply a test current Isense between the drain and the source, and measure the voltage Vds between the drain and the source. On-resistance = voltage Vds between the drain and the source / current Isense between the drain and the source.

[0025] As Figure 1 shown, on the back side of the DFN-packaged gallium nitride power device, there is a drain on one side, and a gate, a Kelvin source, and a source are respectively arranged on the other side. There is a heat sink on the side of the device close to the source.

[0026] Since the DFN-packaged gallium nitride power device has no pins and cannot be directly welded to the electrical test wire, and the outer surface of the device under test cannot be directly contacted with the constant temperature platform, the device must be welded to the PCB. During the thermal resistance test, the back of the PCB is directly contacted with the constant temperature platform.

[0027] Moreover, the traditional test method uses applying thermal conductive adhesive and not applying thermal conductive adhesive as the double interface, and the separation point of the double interface is the junction-PCB thermal resistance. In the present invention, the packaged gallium nitride power device is respectively welded to a PCB with a heat sink pad and a PCB without a heat sink pad as the double interface, as shown in Figure 2 and Figure 3 respectively.

[0028] The sizes of the gate pad, Kelvin source pad, source pad, drain pad, and heat sink pad on the PCB are respectively the same as the sizes of the gate, Kelvin source, source, drain, and heat sink on the back of the packaged gallium nitride power device. And in the PCB with a heat sink pad, the Kelvin source, source, and heat sink are connected to lead out the source pin, and in the PCB without a heat sink pad, the Kelvin source and source are connected to lead out the source pin. In order to perform the on-resistance test with 4-wire Kelvin connection, the PCB leads out 2 source pins and 2 drain pins.

[0029] On-resistance test connection method: Apply voltage Vgs between the gate pin 24 and the source pin 22-1, apply current between the drain pin 21-1 and the source pin 22-1, and test the voltage Vds between the drain pin 21-2 and the source pin 22-2.

[0030] As shown in Figures 4 - 7 , a thermal resistance test method for a gallium nitride device includes the following steps:

[0031] 1) Taking the on-resistance of the gallium nitride power device as the temperature-sensitive parameter, placing the device in a constant temperature device. The gallium nitride power device is provided with a source, a gate, and a source. Apply voltage Vgs between the gate and the source to make the channel conduct, apply test current Isense between the drain and the source, collect the voltage Vds between the drain and the source, adjust the temperature of the constant temperature device, test the voltage Vds between the drain and the source at different temperatures, obtain the Vds-T curve, and obtain the K coefficient through linear fitting; Figure 4 The slope of the curve fitting in is the K coefficient, and the unit is mV / ℃;

[0032] 2) Weld the gallium nitride power device to two different PCBs for testing respectively, and measure two transient cooling curves by the double interface method;

[0033] Specific method: 2.1 Weld the back of the gallium nitride power device on a PCB board with a heat sink pad for testing, then place it on a cold plate. Apply a voltage Vgs between the gate and the source, and apply a large heating current Iheat between the drain and the source to heat the device. When it reaches a steady state, quickly switch to a small test current Isense, and test the variation curve of the voltage Vds between the drain and the source over time. Convert the voltage Vds between the drain and the source to the junction temperature through the K coefficient, and measure a transient cooling curve;

[0034] 2.2 Weld the back of the gallium nitride power device on a PCB board without a heat sink pad for testing, repeat step 2.1, and measure another transient cooling curve;

[0035] 3) Perform numerical operations on the data of the two transient cooling curves using the structure function algorithm to convert them into two structure functions. The separation point of the two function curves is the junction-case thermal resistance.

[0036] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for testing the thermal resistance of a gallium nitride device, characterized in that, The steps include: 1) Taking the on-resistance of the gallium nitride power device as the temperature-sensitive parameter, since there is no PN junction inside the gallium nitride power device, place the device in a constant-temperature device. The gallium nitride power device is provided with a source electrode, a gate electrode, and a drain electrode. Apply a voltage Vgs between the gate electrode and the source electrode to turn on the channel, apply a test current Isense between the drain electrode and the source electrode, collect the voltage Vds between the drain electrode and the source electrode, adjust the temperature of the constant-temperature device, test the voltage Vds between the drain electrode and the source electrode at different temperatures, obtain the Vds-T curve, and obtain the K coefficient through linear fitting; 2) Weld the gallium nitride power device to two different PCBs for testing respectively, and measure two transient cooling curves by using the double-interface method; Specific method: 2.1 Weld the back of the gallium nitride power device to the PCB with a heat sink pad for testing, then place it on a cold plate. Apply a voltage Vgs between the gate electrode and the source electrode, and apply a large heating current Iheat between the drain electrode and the source electrode to heat the device. When it reaches a steady state, quickly switch to a small test current Isense, and test the change curve of the voltage Vds between the drain electrode and the source electrode with time. Convert the voltage Vds between the drain electrode and the source electrode to the junction temperature through the K coefficient, and measure a transient cooling curve; 2.2 Weld the back of the gallium nitride power device to the PCB without a heat sink pad for testing, repeat step 2.1, and measure another transient cooling curve; 3) Numerically operate on the data of the two transient cooling curves by using the structure function algorithm to convert them into two structure functions. The separation point of the two function curves is the junction-case thermal resistance.

2. The thermal resistance testing method of a gallium nitride device according to claim 1, characterized in that, One side of the back of the gallium nitride power device is provided with a drain electrode, and the other side is respectively provided with a gate electrode, a Kelvin source electrode, and a source electrode. A heat sink is provided on the device near the source electrode side.

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