JP5343901B2 - Power cycle life prediction method, life prediction device, and semiconductor device including the life prediction device - Google Patents

Description

  The present invention relates to power cycle life prediction of a power semiconductor used for power conversion, for example, a power semiconductor module (hereinafter also simply referred to as a module) made of IGBT (Insulated Gate Bipolar Transistor).

  Conventionally, a power cycle test (intermittent energization test) has been applied to estimate (predict) the operating life of a power semiconductor module such as an IGBT module. In the power cycle test (intermittent energization test), for example, with the IGBT module fixed to the heat radiating fin, an electrical load of energization / interruption as shown in FIG. 5 is given to increase the junction temperature (Tj) of the IGBT chip. The heat stress is generated by lowering and is performed until it is destroyed. Further, it is known that there are a ΔTj power cycle and a ΔTc power cycle (thermal fatigue life test) in the power cycle test (see Non-Patent Document 1). The ΔTj power cycle is a test that raises and lowers the bonding temperature in a relatively short period as shown in FIG. 5, and mainly evaluates the life of the aluminum wire joint and the solder joint under the silicon chip. In addition, the ΔTc power cycle (not shown) is energized until the case temperature (Tc) reaches an arbitrary temperature. When the case temperature reaches the arbitrary temperature, the energization is stopped. This is a test that repeats the period until returning to the state as one cycle, and mainly evaluates the life of the solder joint between the insulating substrate and the copper base and the solder joint under the silicon chip.

  Conventionally, in a semiconductor device (power semiconductor module) using a power semiconductor, for example, IGBT, for power conversion, a life estimation device (hereinafter referred to as a first conventional technology) for estimating the life of the power semiconductor module is known. . For example, as shown in FIG. 6, the lifetime estimation apparatus includes a temperature detector 90, a ripple temperature detector 93, a counter 94, and a cumulative damage rate calculation unit 95 in order to estimate the lifetime of the IGBT module 82 constituting the inverter. The lifetime detector 96 includes a temperature detector 90 that measures the copper base temperature of the IGBT module 82 that constitutes the inverter, and a ripple temperature detector 93 that detects the copper base temperature detected value during the unit measurement period of operation / stop. The ripple temperature is measured for each temperature range, the counter 94 counts the number of occurrences for each ripple temperature for each unit measurement period, the cumulative damage rate calculation unit 95 calculates the cumulative damage rate CD using the Miner's law, The life calculation unit 96 estimates the life L (= 1 / CD) from the cumulative damage rate CD (see Patent Document 1).

  Conventionally, a failure prediction method for a semiconductor device (power semiconductor module) using a power semiconductor, for example, an IGBT, a power transistor, a MOS-FET, or the like for power conversion (hereinafter referred to as a second prior art) is known (Patent Literature). 2). The second prior art estimates the life of the power semiconductor module from the temperature change, the number of cycles of the temperature change, and the power cycle life characteristics. In this case, if the temperature difference generated in the power semiconductor element is different, the operable cycle at each temperature difference is different, so that the failure determination cannot be performed using the number of cycles in each operation mode as it is. In view of this, on the basis of one operable cycle number N, the other cycle number n is weighted to determine a failure.

JP 2002-101668 A Japanese Patent Laid-Open No. 10-38960 (paragraph 0040, FIG. 7)

Ryosuke Ryokaku 2 "Reliability Design Technology in Power Semiconductor Modules" Fuji Time Report, Vol. 74, No. 2, PP. 45-48, 2001

  When the first conventional technology is actually mounted on a microcomputer / DSP (Digital Signal Processor), etc., if the life is calculated using the detected ripple temperature as it is, the life information for every temperature difference or the calculation based on the minor rule An expression is required. In addition, since the detected temperature difference value is infinite, the circuit scale and the required memory size are increased. Therefore, a certain temperature range must be set, and all temperature differences within that temperature range must be rounded to a representative temperature difference set within that temperature range. At this time, since an error due to rounding occurs, there is a problem that it is impossible to perform accurate life calculation.

  The power semiconductor device failure prediction method shown in the second prior art is based on a conversion formula based on the assumption that the power cycle life curve is a straight line over the entire operating temperature range as shown in FIG. I'm calculating. However, the actual power cycle life curve is not represented by a single straight line but by a plurality of straight lines having different slopes depending on the temperature range. Therefore, an error occurs in the life calculation based on the conversion formula based on one straight line. Therefore, the second prior art has a problem that it is impossible to perform accurate life calculation like the first prior art.

  Accordingly, an object of the present invention is to provide a power cycle life prediction method, a life prediction device, and a semiconductor device including the life prediction device that can eliminate a cause of error due to rounding and perform highly accurate life prediction.

  In order to solve the above-described problem, the power cycle life prediction method of the present invention divides the entire operating temperature range of a semiconductor device composed of power semiconductor elements into a plurality of temperature ranges, and sets a reference temperature difference set in each temperature range. Calculating the number of cycles using a value weighted to the number of power cycles in, and predicting the lifetime by calculating the cumulative damage using the minor rule based on the calculated number of cycles between the divided temperature regions It is characterized by.

  Further, the power cycle life prediction method of the present invention is a temperature difference at a point (inflection point) where a plurality of straight lines intersect from a power cycle life curve approximated by a plurality of straight lines analyzed in advance through a power cycle test. And a step of setting a reference temperature difference in each of the plurality of straight lines and holding the slope of the straight line as a calculation parameter, and in actual operation, detecting a copper base temperature of the power semiconductor element with a temperature sensor, A process of A / D converting the temperature sensor output at a constant sampling period, and detecting a temperature difference from the A / D conversion output, and detecting the detected temperature difference and an inflection point temperature difference held in advance. Whether the detected temperature difference from the comparison result is on which side of a plurality of straight lines approximating a power cycle life curve analyzed through a power cycle test in advance Flip characterized in that it comprises a process of outputting the service life calculated life information by receiving the operation parameters held for a predetermined reference temperature difference in the slope and the straight line of a straight line is approximated.

The power cycle life prediction apparatus of the present invention includes a temperature sensor that detects a copper base temperature of a power semiconductor element, an A / D converter that A / D converts the temperature sensor output at a constant sampling period, and the A / D converter. The temperature difference is detected from the D converter output, the detected temperature difference is compared with the inflection point temperature difference held in advance, and the detected temperature difference is analyzed in advance through a power cycle test from the comparison result. Receives the slope of the straight line to be approximated according to which side of the plurality of straight lines approximating the power cycle life curve and the operation parameter held in the life data register for the reference temperature difference preset in the straight line A life calculation circuit that calculates life and outputs life information, and a life data register that stores operation parameters for performing life calculation in the life calculation circuit. To.

  Further, a semiconductor device provided with the power cycle life prediction apparatus of the present invention is characterized in that the power cycle life prediction apparatus described above is mounted and integrated in a case of a semiconductor module.

  According to the present invention, when an actual power cycle life curve is approximated by a straight line and a life calculation is performed using the slope of the straight line, an error occurring in a plurality of regions within the operating temperature range (straight line of the power cycle life curve). By dividing each of these areas into different ranges), setting the reference temperature in each area, and calculating the service life, the rounding error that occurs when calculating the service life using the slope of the straight line that approximates the entire operating temperature range is eliminated. Therefore, it is possible to predict the life with high accuracy.

It is a figure which shows the structure outline | summary of the power cycle life prediction apparatus which concerns on embodiment of this invention. It is a figure which shows the detail of the lifetime calculating circuit and lifetime data register which were shown in FIG. It is a figure (the 1) which shows the example of the power cycle life curve used by this invention. It is a figure (the 2) which shows the example of the power cycle life curve used by this invention. It is a figure which shows the mode of a power cycle test. It is a figure which shows the structure outline | summary of the conventional power cycle life estimation apparatus. It is a figure which shows the example of the power cycle life curve used by the prior art example.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a diagram showing a schematic configuration of a power cycle life prediction apparatus according to an embodiment of the present invention. A power cycle life prediction apparatus according to an embodiment of the present invention predicts the life of a power semiconductor module incorporating a power semiconductor device. In the following, an example in which the lifetime of an IGBT module incorporating an IGBT (Insulated Gate Bipolar Transistor) is predicted will be described. In general, an inverter is well known to those skilled in the art as a circuit block that converts direct current into alternating current, and the above-described IGBT module is used as its component. The power semiconductor element is not limited to an IGBT, and a power transistor, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), or the like is used.

  As shown in FIG. 1, a power cycle life prediction apparatus according to an embodiment of the present invention includes a temperature sensor 10 that measures the temperature of an IGBT module 2 that is a component of an inverter, and outputs the temperature sensor 10 at a constant sampling period. The A / D converter 20 that performs A / D conversion (analog / digital conversion), the life calculation circuit 30, and the life data register 40 are configured.

Here, the temperature sensor 10 measures the temperature in the IGBT module. There are a number of joints in the IGBT module. Specifically, a circuit pattern was formed between the electrode on the back surface of the IGBT as the power semiconductor device and the circuit pattern on which the IGBT was mounted, and between the electrode on the front surface of the IGBT and the external lead-out terminal. For example, between the copper foil and the copper base formed on the opposite side of the circuit pattern of the insulating substrate. The IGBT back surface electrode-circuit pattern, and the copper foil-copper base are joined by, for example, solder. Since the front electrode of the IGBT and the external lead-out terminal are connected by, for example, wire bonding, the front electrode of the IGBT and the bonding wire and the external lead-out terminal and the bonding wire are ultrasonically bonded, for example. .

  Each joint location in the IGBT module as described above affects the life of the IGBT module, and in particular, a joint location near the power semiconductor element (IGBT) serving as a heat source is easily affected by the power cycle.

Therefore, it is desirable for the temperature sensor 10 to measure the temperature at the junction near the power semiconductor element (IGBT).
For example, in the process of manufacturing a power semiconductor element (IGBT), a temperature detecting diode is manufactured in the chip. The temperature of the chip surface may be detected using the thermal characteristics of the temperature detecting diode. By incorporating a temperature detection diode in the IGBT, it is possible to detect the temperature at a location very close to the heat source. In addition, the limited space in the IGBT module can be effectively used, and the package size of the IGBT module can be reduced.

  The temperature sensor 10 is not limited to the temperature detection diode. For example, the temperature detection diode may be formed as a separate component from the IGBT chip and disposed on the insulating substrate. Further, as a temperature detection element, for example, a thermistor may be used and disposed on an insulating substrate. Thus, by configuring the temperature detection element as a separate component from the IGBT, the degree of freedom in designing the IGBT chip is increased, and the accuracy of temperature detection can be freely set by selecting another component. Moreover, if it installs in the place close | similar to the IGBT chip | tip on an insulated substrate, the temperature of the part near a heat-generation source can be measured.

  The life calculation circuit 30 detects a temperature difference (ΔT) from the output of the A / D converter 20, and determines the IGBT from the power cycle life curve derived through the power cycle test in advance for the IGBT to be the life prediction target of the present invention. Is approximated by a straight line having two different slopes at the inflection point temperature difference (ΔTx), and compares the detected temperature difference (ΔT) with the inflection point (ΔTx) held in advance, The life is calculated by receiving calculation parameters from the life data register 40 for the slope of the straight line and the reference temperature difference to be approximated according to which side of the two straight lines the temperature difference (ΔT) detected from the comparison result is. Outputs life information. The life data register 40 receives the comparison result between the temperature difference (ΔT) and the temperature difference (ΔTx) at the inflection point from the life calculation circuit 30, and outputs a calculation parameter corresponding thereto.

The lifetime calculation in the lifetime calculation circuit 30 and the calculation parameters held in the lifetime data register 40 will be described in detail later.
Although not the subject of the present invention, as is widely known to those skilled in the art, the inverter is composed of the IGBT module 2 and supplies the AC power to the load by switching the IGBT module 2 by the control device 4. Is to do. The DC power supplied to the inverter is obtained, for example, by rectifying AC power from a commercial power source with the rectifier 1.

  Specifically, the control device 4 switches the IGBT by applying a control signal to the gate of each IGBT in the IGBT module via the driver 5. As an inverter control method, switching power is controlled by PWM (Pulse Width Modulation) or PAM (Pulse Amplitude Modulation) to supply AC power to the load. In the example of FIG. 1, a motor 3 is connected as a load.

Here, the temperature difference (ΔTx) at the inflection point will be described. Conventionally, the life is calculated by a conversion formula on the assumption that the power cycle life curve as shown in FIG. 7 is a straight line. On the other hand, in the present invention, the power cycle life of an actual IGBT module is measured and analyzed, and is acquired and held in the pre-stage of actual product life prediction. For example, the power cycle life curve of the IGBT module to which the present invention is applied is represented by two straight lines having different slopes depending on the temperature range, as shown in FIG. This is because the slope is a1 and the reference temperature difference is ΔTs1 in the power cycle life curve represented by the straight line on the low temperature side across the point where two straight lines intersect, that is, the inflection point (temperature difference ΔTx). In the power cycle life curve represented by a straight line on the high temperature side, the slope is a2 and the reference temperature difference is ΔTs2. The reference temperature differences ΔTs1, ΔTs2 are set in advance based on the power cycle life curve of the IGBT as shown in FIG.

  Then, the temperature difference ΔTx at the inflection point is used as a calculation parameter used in the life calculation by the ΔTx holding unit 32 (see FIG. 2) in the life calculation circuit 30, and the slopes a1 and a2 and the reference temperature differences ΔTs1 and ΔTs2 are used as calculation parameters. Each is held in the data register 40 (see FIG. 2). Using the stored calculation parameters, damage conversion is performed by a damage conversion formula, and cumulative damage calculation (minor rule calculation) is performed to calculate the life. These will be described later.

FIG. 2 is a diagram showing details of the life calculation circuit and the life data register shown in FIG. In FIG. 2, a life data register 40 holds operation parameters for calculating cumulative damage in an n-bit digital data format. In other words, as an operation parameter to hold,
Reference temperature difference parameter ΔTs: ΔTs1, ΔTs2 (in the case of FIG. 4, also ΔTs3)
Life cycle parameters at ΔTs Ns: Ns1, Ns2 (In the case of Fig.4, Ns3 is also included)
Inclination parameter in cycle life curve a: a1, a2 (In the case of Fig.4, a3 is also included)
In addition, the life data register 40 selects the optimum parameter from the calculation parameters held in advance based on the comparison result of the magnitude relationship between ΔT and ΔTx that is the output of the ΔTx holding unit / ΔT and the ΔTx comparison unit 32. To the damage conversion unit 33 and the cumulative damage calculation unit 34. The ΔT detection unit 31 outputs the detected ΔT to the ΔTx holding unit / ΔT and the ΔTx comparison unit 32, and outputs the calculation command 1 to the damage conversion unit 33 to instruct the calculation process.

  In the damage conversion unit 33, the ΔT temperature cycle number detected by the ΔT detection unit 31 (corresponding to the damage received by the IGBT chip 2 ′, for example, A / D conversion is performed on the peak amplitude value that appears in each cycle of the illustrated temperature cycle. The value obtained by analog-to-digital conversion in the device 20) is converted into the number of cycles at the set reference temperature difference ΔTs.

  If the detected temperature difference ΔT is in the range of ΔT <ΔTx, that is, if ΔT is on the cycle life curve side where the slope of FIG. .DELTA.Ts1, Ns1, and a1 are selected from the stored calculation parameters and are output to the damage conversion unit 33 and the cumulative damage calculation unit. The damage conversion unit 33 in FIG. 2 calculates the converted damage N1 by the following equation (1) using the detected ΔT value and ΔTs1, Ns1, a1 selected and output from the life data register 40.

If the detected temperature difference ΔT is in the range of ΔT> ΔTx, that is, if ΔT is on the cycle life curve side where the slope in FIG. 2 are selected as the stored calculation parameters and output to the damage conversion unit 33 and the cumulative damage calculation unit 34. The damage conversion unit 33 in FIG. The converted damage N2 is calculated by the following equation (2) using the data selected from the parameters held in the above, that is, ΔTs2, Ns2, and a2.

2 outputs the calculated converted damage N1 or N2 and the calculation command 2 to the cumulative damage calculator 34. The cumulative damage calculation unit 34 calculates the damage in the entire temperature range from the calculated damage (N1 or N2) in each temperature range (temperature range lower than the inflection point ΔTx and higher temperature range) calculated by the damage conversion unit 33 and the minor rule. Calculate cumulative damage. Explaining this in detail, the cumulative damage calculation unit 34 executes the following calculations (A) and (B).
(A) When N1 or N2 is updated based on the detected ΔT and a calculation instruction 2 is input, the following calculation is executed. That is,
1) If ΔT <ΔTx,
ND1 = N1_old + N1
2) If ΔT> ΔTx,
ND2 = N2_old + N2
(B) Next, the value of cumulative damage D is obtained using the above ND1, ND2 and the following equation (3), and the value of D is output to the remaining life calculation / life judgment unit 50.

In the above formula (3), it is determined that the life span is reached when the value of cumulative damage D is D = 1. In FIG. 2, a remaining life calculation / life determination unit 50 not shown in FIG. 1 is added to the life calculation circuit 30, but this is an option when it is necessary to provide the remaining life calculation / life determination result. Thus, the configuration of the life calculation circuit 30 is not essential.

  Incidentally, damage conversion in the case of the power cycle life curve used in the conventional example shown in FIG. 7 is performed as follows. That is, similarly to the case of the present invention described above, the damage conversion unit converts the detected temperature cycle number of ΔT (corresponding to damage) into the cycle number at the set reference temperature difference ΔTs. After that, the cumulative damage N is calculated by the following equation (4) using the detected ΔT value and the data held in the life data register equivalent.

The process by which this equation (4) is derived will be further explained. In the power cycle life curve shown in FIG. 7, the life cycle number at the reference temperature difference ΔTs is Ns, and the life cycle number at the detected ΔT is N When the slope of the straight line is a, the following equation (5) is established.

Here, when the two expressions are integrated and the logarithmic notation is canceled to change the expression format of the expression, it can be expressed as the following expression (6).

By further modifying this equation (6), the above equation (4) can be obtained. Thus, the damage conversion formula according to the above formula (4) is calculated based on the power cycle life curve shown in FIG. 7, and utilizes the fact that the power cycle life curve is a single straight line (slope a).

  On the other hand, the power cycle life curve of the present invention shown in FIG. 3 uses the characteristic that the slope of the straight line varies depending on the temperature region that can be divided by the inflection point temperature difference ΔTx by detailed analysis of the IGBT module power cycle test. To do. Accordingly, rounding errors occur when the damage conversion equation according to the above equation (4) is applied to the one having such characteristics and approximated by one straight line having the inclination a as shown in FIG.

  FIG. 3 is a diagram (part 1) illustrating an example of a power cycle life curve used in the power cycle life prediction apparatus according to the embodiment of the present invention. As shown in FIG. 3, the power cycle life curve (part 1) used in the power cycle life prediction apparatus of the present invention is divided into a plurality of (= 2) operating temperature ranges (power) according to the actual power cycle life curve. The range in which the inclination of the straight line of the cycle life curve is different) is divided individually, and the reference temperatures ΔTs1, ΔTs2 are set in each region, and the life is calculated from damage conversion and calculation of cumulative damage. By doing so, it is possible to eliminate the prediction error that occurs when performing life calculation from damage conversion and cumulative damage calculation using one straight line slope a as in the prior art.

Here, the basic concept of power cycle life prediction according to the present invention will be described again based on the power cycle life curve shown in FIG. 3. A range that can be represented by a straight line in the power cycle life curve is defined as one temperature range. For example, the example shown in FIG. 3 is a case where the power cycle life curve is approximated by two straight lines as a temperature range, and is approximated by a straight line having a slope a1 in a low temperature region and a straight line having a slope a2 in a high temperature region, It is assumed that the temperature difference at the inflection point where both straight lines intersect is ΔTx. Further, it is assumed that the reference temperature difference in the low temperature region is ΔTs1, the power cycle life number in the reference temperature difference ΔTs1 is Ns1, the reference temperature difference in the high temperature region is ΔTs2, and the power cycle life number in the reference temperature difference ΔTs2 is Ns2. In that case, the temperature difference ΔT detected by detecting the peak amplitude value in each temperature cycle through the A / D sampling period obtained by operating the semiconductor device to be predicted, for example, the IGBT chip 2 ′ shown in FIG.
(B) In the range of ΔT <ΔTx (low temperature range), the following conversion formula
N1 = (ΔTs1 / ΔT) a1 × Ns1
Is obtained by converting (weighting) the cycle life number N1 at ΔT to the cycle life number Ns1 at the reference temperature difference ΔTs1. Here, a1 is the slope of the approximate straight line, but is also the weighting coefficient in the above equation.

Similarly, the temperature difference ΔT detected through the A / D sampling period for the peak amplitude value in each temperature cycle obtained by operating the IGBT chip 2 ′ is
(B) In the range of ΔT> ΔTx (high temperature range), the following conversion formula
N2 = (ΔTs2 / ΔT) a2 × Ns2
Is obtained by converting (weighting) the cycle life number N2 at ΔT to the cycle life number Ns2 at the reference temperature difference ΔTs2. Here, a2 is the slope of the approximate straight line, but is also the weighting coefficient in the above equation.

Based on the detected ΔT, N1 or N2 is updated and the calculation command 2 is input.
1) If ΔT <ΔTx,
ND1 = N1_old + N1
2) If ΔT> ΔTx,
ND2 = N2_old + N2
The cycle life times ND1 and ND2 updated in each temperature range are obtained by the above, and cumulative damage (damage rate) D is calculated by using a minor rule for the cycle life times ND1 and ND2.
D = (ND1 / Ns1) + (ND2 / Ns2)
The cumulative damage (damage rate) D is predicted to reach the end of life when D = 1. The calculation formula of D is the above-described formula (3) itself, and the value of the cumulative damage D is obtained by this, and the value of D is output to the remaining life calculation / life determination unit 50. In FIG. 2, a remaining life calculation / life determination unit 50 not shown in FIG. 1 is added to the life calculation circuit 30, but as described above, this needs to be provided up to the result of remaining life calculation / life determination. This is an option in the case where there is, and is not essential as a configuration of the life calculation circuit 30.

  FIG. 4 is a diagram (part 2) illustrating an example of a power cycle life curve used in the power cycle life prediction apparatus according to the embodiment of the present invention. As shown in FIG. 4, the power cycle life curve (part 2) used in the power cycle life prediction apparatus of the present invention is divided into a plurality of (= 3) operating temperature ranges (power) according to the actual power cycle life curve. The range in which the inclination of the straight line of the cycle life curve is different) is individually divided, and the reference temperatures ΔTs1, ΔTs2, ΔTs3 are set in each region, and the life is calculated from the damage conversion and cumulative damage calculation. By doing so, it is possible to eliminate the prediction error that occurs when performing life calculation from damage conversion and cumulative damage calculation using one straight line slope a as in the prior art.

Next, the basic concept of power cycle life prediction according to the present invention will be described based on the power cycle life curve shown in FIG. 4. FIG. 4 shows the case where the power cycle life curve is approximated by a straight line as a temperature range. The temperature difference at the inflection point where the straight line with the slope as described above intersects each other is approximated by the straight line with the slope a1 in the low temperature region, the straight line with the slope a2 in the medium temperature region, and the straight line with the slope a3 in the high temperature region. To ΔTx1 and ΔTx2. The reference temperature difference in the low temperature region (ΔT <ΔTx1) is ΔTs1, the power cycle life count in the reference temperature difference ΔTs1 is Ns1, the reference temperature difference in the medium temperature region (ΔTx1 <ΔT <ΔTx2) is ΔTs2, and the reference temperature difference ΔTs2 Assume that the power cycle life number is Ns2, the reference temperature difference in the high temperature region (ΔT> ΔTx2) is ΔTs3, and the power cycle life number in the reference temperature difference ΔTs3 is Ns3. In that case, the temperature difference ΔT detected by detecting the peak amplitude value in each temperature cycle through the A / D sampling period obtained by operating the semiconductor device to be predicted, for example, the IGBT chip 2 ′ shown in FIG.
(B) In the range of ΔT <ΔTx (low temperature range), the conversion formula shown by the following formula (7)

Is obtained by converting (weighting) the cycle life number N1 at ΔT to the cycle life number Ns1 at the reference temperature difference ΔTs1. Here, a1 is the slope of the approximated straight line, but is also the weighting coefficient in the above equation (7).

Similarly, the temperature difference ΔT detected through the A / D sampling period for the peak amplitude value in each temperature cycle obtained by operating the IGBT chip 2 ′ is
(B) In the range of ΔTx1 <ΔT <ΔTx2 (medium temperature range), the conversion formula shown by the following formula (8)

Is obtained by converting (weighting) the cycle life number N2 at ΔT to the cycle life number Ns2 at the reference temperature difference ΔTs2. Here, a2 is the slope of the approximate straight line, but is also the weighting coefficient in the above equation (8).

Furthermore, the temperature difference ΔT detected through the A / D sampling period for the peak amplitude value in each temperature cycle, which is also obtained by operating the IGBT chip 2 ′,
(C) In the range of ΔT> ΔTx2 (high temperature range), the conversion formula shown by the following formula (9)

Is obtained by converting (weighting) the cycle life number N3 at ΔT to the cycle life number Ns2 at the reference temperature difference ΔTs2. Here, a2 is the slope of the approximated straight line, but is also the weighting coefficient in the above equation (9).

  Then, based on the detected ΔT, N1, N2 or N3 is updated, and the calculation command 2 is input, so that the damage calculation unit 34 calculates the following equation (10)

As shown in Fig. 3, the cycle life times ND1, ND2, and ND3 updated in each temperature range are obtained, and the cumulative damage (damage rate) D is calculated using the minor rule for the cycle life times ND1, ND2, and ND3 as follows: Equation (11)

The cumulative damage (damage rate) D is predicted to reach the end of life when D = 1. The calculation formula of D shown in the above formula (11) is obtained by adding the third term to the calculation formula of the above formula (3). Output to calculation / life determination unit 50. In FIG. 2, a remaining life calculation / life determination unit 50 not shown in FIG. 1 is added to the life calculation circuit 30, but as described above, this needs to be provided up to the result of remaining life calculation / life determination. This is an option in the case where there is, and is not essential as a configuration of the life calculation circuit 30.

The present invention is not limited to the example of the power semiconductor module having the above-described power cycle life prediction device, but also for products for which a product life warning accompanying other thermal stress is desired.
(Power Module: Intelligent power module)

1 Rectifier
2 IGBT module
2 'IGBT chip
3 Motor
4 Control unit
5 Driver
10 Temperature sensor
20 A / D (analog / digital converter)
30 Life calculation circuit
31 ΔT detector
32 ΔTx holder / ΔT and ΔTx comparator
33 Damage conversion section
34 Cumulative damage calculator
40 Life data register
50 Remaining life calculation / life judgment part

Claims (5)

  Dividing the entire operating temperature range of the semiconductor device composed of power semiconductor elements into a plurality of temperature ranges, and calculating the number of cycles using a value weighted to the number of power cycles at the set reference temperature difference in each temperature range, A power cycle life prediction method characterized by calculating a cumulative damage using a minor rule based on each calculated number of cycles between the divided temperature regions to predict a life.   From the power cycle life curve that is analyzed in advance through a power cycle test and approximated by a plurality of straight lines, a temperature difference at a point (inflection point) where the plurality of straight lines intersect is obtained and a reference for each of the plurality of straight lines Including a process of setting a temperature difference and holding the slope of the straight line as a calculation parameter. In the actual operation, the process of detecting the copper base temperature of the power semiconductor element by the temperature sensor, and the temperature sensor output at a constant sampling period The temperature difference is detected from the A / D conversion process, the detected temperature difference is compared with the inflection point temperature difference held in advance, and the detected temperature difference is compared with the comparison result. The slope of the straight line approximated according to which side of the plurality of straight lines approximating the power cycle life curve analyzed in advance through the power cycle test and Power cycle longevity estimation method, which comprises a process of outputting the service life calculated life information by receiving the operation parameters held for predetermined reference temperature difference.   A temperature sensor for detecting the copper base temperature of the power semiconductor element, an A / D converter for A / D converting the temperature sensor output at a constant sampling period, and detecting a temperature difference from the A / D converter output; A plurality of straight lines approximating a power cycle life curve in which the detected temperature difference is compared with a previously held inflection point temperature difference, and the detected temperature difference is analyzed in advance through a power cycle test. The life calculation that receives the calculation parameters held in the life data register for the slope of the straight line to be approximated according to which side of the line and the reference temperature difference preset in the straight line, calculates the life and outputs the life information A power cycle life prediction apparatus comprising: a circuit; and a life data register for holding a calculation parameter for performing life calculation in the life calculation circuit. The life calculation circuit includes a temperature difference detection unit that detects a temperature difference from the output of the A / D converter, a temperature difference output from the temperature difference detection unit, and a temperature difference output from the temperature difference detection unit. The inflection point temperature difference holding unit for comparing the inflection point temperature difference / temperature difference and inflection point temperature difference comparison unit, and the life data register according to the comparison result of the temperature difference and inflection point temperature difference comparison unit And the reference temperature difference preset in the straight line and the life cycle value at the reference temperature difference are received as calculation parameters and the inflection point temperature difference holding unit / temperature difference and variable A damage conversion unit that receives the detected temperature difference from the inflection point temperature difference comparison unit and converts the detected temperature difference into a life cycle based on the reference temperature difference, and the temperature difference and the inflection point temperature difference. According to the comparison result of the comparison part In addition, the straight line to be approximated output from the life data register, the reference temperature difference preset in the straight line, and the life cycle value at the reference temperature difference are received as operation parameters and output from the damage conversion unit. It has a cumulative damage calculator that receives the converted life cycle value, calculates the cumulative damage according to the minor rule, and outputs it.
The life data register includes a reference temperature difference ΔTs and a reference temperature difference ΔTs for a plurality of straight lines approximating a power cycle life curve analyzed in advance through a power cycle test as calculation parameters for calculating cumulative damage. Holds digital data about the life cycle and slope of the cycle life curve,
The power cycle life prediction apparatus according to claim 3. 5. A semiconductor device comprising a power cycle life prediction apparatus according to claim 3, wherein the power cycle life prediction apparatus according to claim 3 is mounted and integrated in a case of a semiconductor module.