JP7694136B2 - Semiconductor Module - Google Patents

Description

The present invention relates to a semiconductor module.

Conventionally, a semiconductor module including a semiconductor chip on which a power semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) is formed is known (see, for example, Patent Document 1). Also, a technique for fixing the semiconductor chip by soldering is known (see, for example, Patent Document 2).
Patent Document 1: JP 2019-186510 A Patent Document 2: JP 2-26058 A

In semiconductor modules, it is preferable to be able to detect the deterioration state of the solder that secures the semiconductor chip.

In order to solve the above problem, one aspect of the present invention provides a semiconductor module. The semiconductor module may include a first semiconductor chip and a second semiconductor chip, each including a power semiconductor element. The semiconductor module may include a wiring portion joined to the first semiconductor chip and the second semiconductor chip. The semiconductor module may include a first solder portion joining the first semiconductor chip and the wiring portion. The semiconductor module may include a second solder portion that is more susceptible to cracking due to thermal history than the first solder portion and joins the second semiconductor chip and the wiring portion.

The second solder part may have a smaller thickness in the direction connecting the semiconductor chip and the wiring part than the first solder part.

The thickness of the second solder portion may be 20 μm or more and 100 μm or less.

The second solder portion may be formed from a material composition different from that of the first solder portion.

The indium content (wt %) in the second solder part may be less than the indium content (wt %) in the first solder part.

The semiconductor module may include a main terminal. The semiconductor module may include a main circuit section connected to the main terminal. The first semiconductor chip and the second semiconductor chip may be provided in the main circuit section.

The semiconductor module may include a cooling section disposed below the first semiconductor chip and the second semiconductor chip, which flows a coolant in a direction from the first semiconductor chip to the second semiconductor chip.

The first semiconductor chip may be provided in the main circuit section. The second semiconductor chip does not have to be provided in the main circuit section.

The first semiconductor chip and the second semiconductor chip may be fixed to the same insulating substrate.

The semiconductor module may include a plurality of first semiconductor chips. The second semiconductor chip may be sandwiched between two first semiconductor chips.

The semiconductor module may include a characteristic detection unit that detects electrical characteristics of the second solder part and the second semiconductor chip.

The semiconductor module may include an estimation unit that estimates the state of the second solder part based on the electrical characteristics detected by the characteristic detection unit.

Note that the above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions.

FIG. 2 is a top view showing an example of a semiconductor module 300. FIG. 2 is an enlarged view of the main circuit section 200-1. 3 is a diagram showing an example of a cross section taken along line AA and a cross section taken along line BB in FIG. 2 . 1 is a diagram showing the relationship between the thickness T of a solder portion and the length of a crack that occurs in the solder portion. FIG. 13 is a diagram showing the relationship between the number of temperature cycles and the crack length. 13A and 13B are diagrams showing other examples of the AA cross section and the BB cross section. 13A and 13B are diagrams showing other examples of the AA cross section and the BB cross section. 2 is a circuit diagram showing an example of a main circuit section 200-1. 11A and 11B are diagrams illustrating other examples of the arrangement of the second semiconductor chip 102. 3A to 3C are diagrams illustrating an example of the arrangement of a second semiconductor chip 102. FIG. 2 is a diagram showing an example of a configuration included in a semiconductor module 300. 11 is a diagram showing another example of a configuration included in the semiconductor module 300. FIG. FIG. 2 is a diagram illustrating an example of a cooling unit 114.

The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

In this specification and drawings, elements having substantially the same functions and configurations are designated with the same reference numerals to avoid repetitive explanations, and elements not directly related to the present invention may be omitted from illustration. In addition, in one drawing, elements having the same functions and configurations may be designated with the same reference numerals as a representative, and the reference numerals may be omitted for the others.

In this specification, one side in a direction parallel to the depth direction of a semiconductor chip is referred to as "upper" and the other side as "lower." Of the two main surfaces of a substrate, layer or other member, one surface is referred to as the upper surface and the other surface is referred to as the lower surface. The directions of "upper" and "lower" are not limited to the direction of gravity or the directions when the semiconductor module is mounted.

In this specification, technical matters may be explained using orthogonal coordinate axes of the X-axis, Y-axis, and Z-axis. The orthogonal coordinate axes merely identify the relative positions of components, and do not limit a specific direction. For example, the Z-axis does not limit the height direction relative to the ground. The +Z-axis direction and the -Z-axis direction are opposite directions. When the Z-axis direction is described without indicating positive or negative, it means a direction parallel to the +Z-axis and -Z-axis. In this specification, the orthogonal axes parallel to the upper and lower surfaces of the semiconductor chip are the X-axis and the Y-axis. Also, the axis perpendicular to the upper and lower surfaces of the semiconductor chip is the Z-axis. In this specification, the direction of the Z-axis may be referred to as the depth direction. Also, in this specification, the direction parallel to the upper and lower surfaces of the semiconductor chip, including the X-axis and the Y-axis, may be referred to as the horizontal direction.

When terms such as "same" or "equal" are used in this specification, this may include cases in which there is an error due to manufacturing variations, etc. The error is, for example, within 10%.

FIG. 1 is a top view showing an example of a semiconductor module 300. The semiconductor module 300 includes one or more first semiconductor chips 101 and one or more second semiconductor chips 102. Each semiconductor chip is a chip in which a power semiconductor element such as an IGBT is formed on a semiconductor substrate. The power semiconductor element may be a MOSFET or a diode. The power semiconductor element may be, for example, an element with a breakdown voltage of 100 V or more. The power semiconductor element may be formed on a silicon substrate, or on a compound semiconductor substrate such as GaN or SiC.

The first semiconductor chip 101 and the second semiconductor chip 102 preferably have the same structure. The area of the semiconductor substrate occupied by the power semiconductor elements such as transistors formed in the first semiconductor chip 101 may be the same as the area of the semiconductor substrate occupied by the power semiconductor elements formed in the second semiconductor chip 102. The manufacturing process of the first semiconductor chip 101 and the manufacturing process of the second semiconductor chip 102 may be at least partially the same, or may be entirely the same. The same process refers to the conditions set in the manufacturing equipment used being the same, and is not limited to processes being performed simultaneously.

The number of first semiconductor chips 101 included in the semiconductor module 300 may be greater than the number of second semiconductor chips 102 included in the semiconductor module 300. The semiconductor module 300 in this example includes one second semiconductor chip 102 and multiple first semiconductor chips 101.

The first semiconductor chip 101 and the second semiconductor chip 102 are joined to the wiring portion 170 by the solder portion. The wiring portion 170 is, for example, a thin-film wiring pattern formed on an insulating substrate. The first semiconductor chip 101 and the second semiconductor chip 102 may be joined to a plate-shaped wiring portion such as a bus bar or a lead frame by the solder portion. The wiring portion is not limited to these.

The solder portion that secures the second semiconductor chip 102 is more susceptible to cracking due to thermal history than the solder portion that secures the first semiconductor chip 101. As a result, by observing the state of the solder portion of the second semiconductor chip 102, the state of the solder portion of the first semiconductor chip 101 can be estimated. For example, if there are no cracks in the solder portion of the second semiconductor chip 102, it can be estimated that there are no cracks in the solder portion of the first semiconductor chip 101 either. Furthermore, if a crack occurs in the solder portion of the second semiconductor chip 102, it can be estimated that there is an increased possibility that a crack will occur in the solder portion of the first semiconductor chip 101.

The thermal history refers to the history of heat applied to the solder part. The thermal history may be the history of the temperature of the solder part. It is preferable that the thermal history of the solder part fixing the second semiconductor chip 102 and the solder part fixing the first semiconductor chip 101 is approximately the same, or that the thermal history of the solder part fixing the second semiconductor chip 102 is greater. A large thermal history refers to a large total amount of heat applied. The thermal history becomes large when the solder part is heated. By making the thermal history of the solder part of the second semiconductor chip 102 greater than or equal to the thermal history of the solder part of the first semiconductor chip 101, cracks are more likely to occur in the solder part of the second semiconductor chip 102. This makes it easier to detect signs of cracks occurring in the solder part of the first semiconductor chip 101.

The amount of heat generated by the first semiconductor chip 101 and the second semiconductor chip 102 is preferably equal. The second semiconductor chip 102 is preferably controlled in synchronization with any one of the first semiconductor chips 101. The second semiconductor chip 102 may be input with the same gate signal as any one of the first semiconductor chips 101. This allows the thermal history applied from each semiconductor chip to each solder part to be equal.

The semiconductor module 300 of this example includes a housing 208 and one or more main circuit sections 200. The housing 208 houses the main circuit sections 200. The main circuit sections 200 may be placed on the bottom surface 206 of the housing 208. The housing 208 is, for example, a resin case made of resin. The housing 208 of this example houses three sets of main circuit sections 200. The main circuit sections 200 of this example function as inverters, but the function of the main circuit sections 200 is not limited to this. The semiconductor module 300 of this example functions as a three-phase inverter.

Each main circuit section 200 includes one or more first semiconductor chips 101. Also, any of the main circuit sections 200 includes one or more second semiconductor chips 102. In the example of FIG. 1, one second semiconductor chip 102 is provided in the main circuit section 200-1. All other semiconductor chips are first semiconductor chips 101. In other examples, the second semiconductor chip 102 may be provided in multiple main circuit sections 200, or the second semiconductor chip 102 may be provided in all main circuit sections 200. Also, the second semiconductor chip 102 may be provided in a section other than the main circuit section 200.

The housing 208 has a plurality of main terminals 210, one or more output terminals 212, and a plurality of control terminals 214. The main terminals 210 are supplied with power from an external power source or the like. Two main terminals 210 may be provided for one main circuit section 200. One main terminal 210 may be connected to a reference potential such as a ground potential, and the other main terminal 210 may be connected to an external power source or the like.

One output terminal 212 may be provided for one main circuit section 200. The output terminal 212 is connected to a predetermined position in the main circuit section 200.

One or more control terminals 214 may be provided for one main circuit section 200. Any of the control terminals 214 may be connected to the gate terminals of the respective semiconductor chips. In this specification, the first semiconductor chip 101 and the second semiconductor chip 102 may be simply referred to as semiconductor chips. The switching operation of the semiconductor chips is controlled according to a control signal input to the control terminal 214. Any of the control terminals 214 may be connected to each sensor, such as a temperature sensor or a current sensor, provided on the semiconductor chip. The control terminal 214 may control the operation of each sensor, and may also output the detection results of each sensor to the outside.

A cooling unit for cooling the semiconductor module 300 may be disposed below the housing 208. The cooling unit is omitted in FIG. 1. The housing 208 may have a through hole 216 for fixing the semiconductor module 300 to an external device.

Figure 2 is an enlarged view of the main circuit section 200-1. In this example, the main circuit section 200-1 comprises an insulating substrate 162, wiring sections 130, 164, 166, 168, 170, a plurality of first semiconductor chips 101, and one second semiconductor chip 102. The insulating substrate 162 is a plate-shaped substrate made of an insulating material such as resin or ceramic. In Figure 2, the insulating substrate 162 is hatched with diagonal lines. However, hatching has been omitted for areas covered by the wiring sections and semiconductor chips, etc.

The upper surface of the insulating substrate 162 is provided with wiring sections 164, 166, 168, and 170. In this example, the wiring sections 164, 166, 168, and 170 are thin-film wirings provided on the upper surface of the insulating substrate 162 (the surface shown in FIG. 2). The wiring sections 164, 166, 168, and 170 are made of a conductive material such as copper. A layer made of a conductive material such as copper may also be provided on the lower surface of the insulating substrate 162 (the surface opposite to the surface shown in FIG. 2). The conductive layer provided on the lower surface of the insulating substrate 162 may be connected to a cooling section. The wiring section 130 connects the wiring section provided on the upper surface of the insulating substrate 162 and each member such as a semiconductor chip. The wiring section 130 is a wire, a lead frame, or a bus bar, etc., arranged above the upper surface of the insulating substrate 162. In FIG. 2, the wiring section 130 is indicated by a dashed line.

Each semiconductor chip has a gate pad 116 and one or more sense pads 118. The gate pad 116 is connected to the gate electrode of a transistor element formed on the semiconductor chip. The sense pad 118 is connected to a sensor section, such as a temperature sensor or a current sensor, formed on the semiconductor chip. Pads, such as emitter electrodes, are provided in areas on the top surface of the semiconductor chip where no pads are provided. Each pad of the semiconductor chip is connected to other members by wiring section 130. Pads, such as collector electrodes, are provided on the bottom surface of the semiconductor chip. The semiconductor chip in this example is a vertical device in which current flows between the top and bottom surfaces.

The wiring portion 166 is connected to the control terminal 214 shown in FIG. 1. The wiring portion 166 is connected to the gate pad 116 and the sense pad 118 of the semiconductor chip via the wiring portion 130 and the wiring portion 164. Each wiring portion 164 is connected to a plurality of wiring portions 130. The wiring portion 164 connects the two components by relaying the wiring portion 130.

The wiring section 170 is connected to the main terminal 210 shown in FIG. 1. The main circuit section 200 in this example has two wiring sections 170 corresponding to the two main terminals 210. One or more semiconductor chips are provided on each wiring section 170. A first semiconductor chip 101 and a second semiconductor chip 102 may be provided on any of the wiring sections 170. In other words, the second semiconductor chip 102 may be provided on the wiring section 170 shared with any of the first semiconductor chips 101. The wiring section 170 may be connected to other members via the wiring section 130.

The wiring section 168 is connected to the output terminal 212 shown in FIG. 1. The wiring section 168 is connected to other components by the wiring section 130.

As described above, a cooling unit may be provided below the main circuit unit 200. The cooling unit cools the main circuit unit 200 by flowing a refrigerant in a predetermined direction below the main circuit unit 200. In FIG. 2, the direction in which the refrigerant flows is indicated by an arrow. The cooling unit may flow the refrigerant in a direction from the first semiconductor chip 101 toward the second semiconductor chip 102. In other words, the second semiconductor chip 102 may be arranged downstream of the flow of the refrigerant relative to the first semiconductor chip 101. In this case, the refrigerant that reaches below the second semiconductor chip 102 has already been warmed by the heat generated by the first semiconductor chip 101. For this reason, the solder part of the second semiconductor chip 102 may have a larger thermal history than the solder part of the first semiconductor chip 101. By arranging the semiconductor chips as in this example, it is possible to easily cause cracks in the solder part of the second semiconductor chip 102, making it easier to detect signs of cracks in the solder part of the first semiconductor chip 101.

Figure 3 shows an example of the A-A cross section and the B-B cross section in Figure 2 side by side. The A-A cross section is the XZ plane that passes through the first semiconductor chip 101, and the B-B cross section is the B-B cross section that passes through the second semiconductor chip 102.

As described above, the wiring portion 170 is provided on the upper surface of the insulating substrate 162. In addition, the conductive layer 171 is provided on the lower surface of the insulating substrate 162. The wiring portion 170 and the conductive layer 171 may be formed of a metal such as copper.

The first semiconductor chip 101 and the second semiconductor chip 102 are each bonded to the wiring section 170. The first semiconductor chip 101 and the second semiconductor chip 102 may be bonded to a common wiring section 170. In other words, the wiring section 170 to which the first semiconductor chip 101 is bonded and the wiring section 170 to which the second semiconductor chip 102 is bonded may be provided continuously on the upper surface of the insulating substrate 162. In another example, the wiring section 170 to which the first semiconductor chip 101 is bonded and the wiring section 170 to which the second semiconductor chip 102 is bonded may be provided separately on the upper surface of the insulating substrate 162.

The first semiconductor chip 101 is joined to the wiring portion 170 by the first solder portion 111. The second semiconductor chip 102 is joined to the wiring portion 170 by the second solder portion 112. Each solder portion is formed of a conductive material containing solder. The solder portion may contain tin (Sn), silver (Ag), or indium (In).

The second solder portion 112 is more susceptible to cracking due to thermal history than the first solder portion 111. The second solder portion 112 may have a different resistance to thermal history from the first solder portion 111 due to a different structure such as shape and thickness. The second solder portion 112 may have a different resistance to thermal history from the first solder portion 111 due to a different material. The second solder portion 112 may have a different structure and material from the first solder portion 111.

In the example shown in FIG. 3, the thickness T2 of the second solder portion 112 is smaller than the thickness T1 of the first solder portion 111. The thickness of the solder portion refers to the thickness in the direction connecting the semiconductor chip and the wiring portion 170 (the Z-axis direction in FIG. 3). The thickness of the solder portion in this example is the thickness in the direction perpendicular to the bottom surface of the semiconductor chip. Furthermore, the thickness of the solder portion may be the average thickness of the portion that is arranged to overlap the semiconductor chip in the XY plane, or it may be the maximum thickness of that portion.

By reducing the thickness T2 of the second solder portion 112, when the semiconductor chip and the insulating substrate 162, etc. are deformed due to thermal fluctuation, the second solder portion 112 is less able to absorb the deformation, and cracks are more likely to occur in the second solder portion 112. The thickness T2 may be 75% or less of the thickness T1, half or less, or 25% or less.

Figure 4 shows the relationship between the thickness T of the solder and the length of cracks that occur in the solder. Figure 4 shows the length of the cracks when the temperature cycle of heating and cooling is repeated about 500 times. This relationship is also shown for solder parts formed from SnAg and solder parts formed from SnAgIn.

Regardless of the material used, the smaller the solder thickness, the longer the cracks in the solder. In the example of the SnAg solder, no cracks occur when the solder thickness is greater than 150 μm, but cracks occur when the thickness is 150 μm or less. In other words, the smaller the solder thickness, the more likely it is that cracks will occur in the solder. In addition, in both solder examples, the length of the cracks increases dramatically when the solder thickness is 100 μm or less.

The thickness T2 of the second solder portion 112 may be 100 μm or less. This makes it easier for cracks to occur in the second solder portion 112. The thickness T2 may be 90 μm or less, or 80 μm or less. The thickness T2 may be 20 μm or more. If the thickness T2 is too small, cracks will easily occur in the second solder portion 112, making it difficult to estimate the deterioration of the first solder portion 111. The thickness T2 may be 30 μm or more, or 40 μm or more.

The thickness T1 of the first solder portion 111 is preferably 150 μm or more. This makes it less likely for cracks to occur in the first solder portion 111. The thickness T1 may be 200 μm or less. The difference between the thickness T1 and the thickness T2 may be 10 μm or more, 50 μm or more, or 100 μm or more.

The second solder part 112 may be formed with a material composition different from that of the first solder part 111. Different material compositions include both cases where different types of materials are included and cases where the content of the materials is different. For example, the indium content (wt%) in the second solder part 112 is smaller than the indium content (wt%) in the first solder part 111. As shown in FIG. 4, the smaller the indium content, the more likely cracks will occur in the solder part. The indium content in the second solder part 112 may be half or less, ¼ or less, or 1/10 or less of the indium content in the first solder part 111. The indium content in the second solder part 112 may be 0%.

Figure 5 shows the relationship between the number of temperature cycles and the crack length. It can be seen that regardless of the number of temperature cycles, the smaller the indium content, the more likely it is that cracks will occur.

Figure 6 shows other examples of the A-A cross section and the B-B cross section. In this example, the wiring part 130 connected to the top surface of the semiconductor chip, and the first solder part 111-2 and the second solder part 112-2 that join the wiring part 130 are shown. The wiring part 130 in this example is a lead frame.

In this example, the first solder portion 111 is provided on both the top and bottom surfaces of the first semiconductor chip 101. The bottom surface of the first semiconductor chip 101 is joined to the wiring portion 170 by the first solder portion 111-1, as in the example of FIG. 3. The top surface of the first semiconductor chip 101 is joined to the wiring portion 130 by the first solder portion 111-2.

In this example, second solder portions 112 are provided on both the upper and lower surfaces of the second semiconductor chip 102. The lower surface of the second semiconductor chip 102 is joined to the wiring portion 170 by the second solder portion 112-1, as in the example of FIG. 3. The upper surface of the second semiconductor chip 102 is joined to the wiring portion 130 by the second solder portion 112-2.

The second solder section 112-2 is more susceptible to cracking due to thermal history than the first solder section 111-2. As with the first solder section 111 and the second solder section 112 described in FIG. 3 to FIG. 5, the first solder section 111-2 and the second solder section 112-2 differ in at least one of the structure and the material.

In the example of FIG. 6, the thickness T2-2 of the second solder portion 112-2 is smaller than the thickness T1-2 of the first solder portion 111-2. The thickness T2-1 of the second solder portion 112-1 arranged on the underside of the semiconductor chip may be the same as or different from the thickness of the first solder portion 111-1. According to this example, the state of the first solder portion 111-2 can be estimated by observing the state of the second solder portion 112-2.

Figure 7 is a diagram showing other examples of the A-A cross section and the B-B cross section. Each structure in this example is similar to the example in Figure 6, except that the thickness T2-1 of the second solder section 112-1 is smaller than the thickness T1-1 of the first solder section 111-1. According to this example, by observing the state of the second solder section 112-1 and the second solder section 112-2, the state of the first solder section 111-1 and the first solder section 111-2 can be estimated. In other words, if a crack occurs in either the second solder section 112-1 or the second solder section 112-2, it can be estimated that there is an increased possibility that a crack will occur in at least one of the first solder sections 111-1 and the first solder section 111-2.

Figure 8 is a circuit diagram showing an example of the main circuit section 200-1. The main circuit section 200-1 is connected to two main terminals 210. The main circuit section 200-1 in this example is a circuit electrically connected between the two main terminals 210. In this example, both the first semiconductor chip 101 and the second semiconductor chip 102 are included in the main circuit section 200-1. That is, the second semiconductor chip 102 also operates as a part of the main circuit section 200-1 (e.g., an inverter). The second semiconductor chip 102 may be connected to the same wiring section 170 (see Figure 2) as any of the first semiconductor chips 101. The second semiconductor chip 102 may be fixed to the same insulating substrate 162 as any of the first semiconductor chips 101. At least one of the voltage and the current output from the output terminal 212 changes when the second semiconductor chip 102 is switched on or off.

By using the second semiconductor chip 102 as one of the semiconductor chips included in the main circuit section 200-1, it is possible to detect deterioration of the solder section without increasing the circuit size. The second semiconductor chip 102 is preferably provided in parallel with one of the first semiconductor chips 101. In other words, the second semiconductor chip 102 is connected to the same control terminal 214 as one of the first semiconductor chips 101. This makes it possible to equalize the heat generated by the second semiconductor chip 102 and the heat generated by the first semiconductor chip 101. Furthermore, even if a crack occurs in the second solder section 112 and the resistance of the current path including the second semiconductor chip 102 increases, the increase in the resistance value of the entire circuit can be suppressed by providing the first semiconductor chip 101 in parallel.

Figure 9 is a diagram showing another example of the arrangement of the second semiconductor chip 102. In this example, the first semiconductor chip 101 is provided in the main circuit section 200, and the second semiconductor chip 102 is not provided in the main circuit section 200. The second semiconductor chip 102 in this example may receive power from a main terminal 211 different from the main terminal 210 of the main circuit section 200. However, the second semiconductor chip 102 may be connected to a control terminal 214 that is common to any of the first semiconductor chips 101. The second semiconductor chip 102 is not connected to the output terminal 212. In other words, the operating state of the second semiconductor chip 102 does not affect the voltage and current output from the output terminal 212.

The second semiconductor chip 102 is provided on a wiring section different from that of the first semiconductor chip 101. The second semiconductor chip 102 may be provided on an insulating substrate 162 different from that of the first semiconductor chip 101. According to this example, even if a crack occurs in the second solder section 112 of the second semiconductor chip 102, the operation of the main circuit section 200 is prevented from being affected.

Figure 10 is a diagram illustrating an example of the arrangement of the second semiconductor chip 102. The second semiconductor chip 102 may be arranged sandwiched between two first semiconductor chips 101 in the XY plane. As a result, the heat generated by the two first semiconductor chips 101 reaches the second solder part 112 of the second semiconductor chip 102, making it more likely to crack. For this reason, it is possible to accurately detect an increased possibility of cracks occurring in the first solder part 111. Note that the second semiconductor chip 102 being sandwiched between two first semiconductor chips 101 refers to the second semiconductor chip 102 being arranged overlapping on any of the straight lines connecting the two first semiconductor chips 101.

As shown in FIG. 10, the second semiconductor chip 102 may be disposed between two main circuit sections 200. Also, as described in FIG. 2 and the like, the second semiconductor chip 102 may be included in one of the main circuit sections 200.

Figure 11 is a diagram showing an example of the configuration included in the semiconductor module 300. The semiconductor module 300 of this example includes a characteristic detection unit 302. The characteristic detection unit 302 detects the electrical characteristics of the second solder part 112 and the second semiconductor chip 102.

When a crack occurs in the second solder portion 112, the resistance of the second solder portion 112 increases, and the electrical characteristics of the second semiconductor chip 102 change when the second solder portion 112 is used as an electrode. The characteristic detection unit 302 may detect the collector-emitter voltage _Vce of the second semiconductor chip 102 when the second solder portion 112 is used as a collector electrode or an emitter electrode. For example, the characteristic detection unit 302 may detect the voltage _Vce between the wiring portion 130 and the wiring portion 170 shown in FIG. 6. When a crack occurs in the second solder portion 112, the collector-emitter voltage _Vce rises sharply.

The characteristic detection unit 302 may output information indicating the detected electrical characteristics to an external device via the external terminal 306. The external device may control the semiconductor module 300 based on the information. For example, if the external device determines that a crack has occurred in the second solder part 112 based on the information, it may control the semiconductor chip of the semiconductor module 300 to an off state.

Figure 12 is a diagram showing another example of the configuration included in the semiconductor module 300. In addition to the configuration shown in Figure 11, the semiconductor module 300 of this example further includes an initial value generation unit 303 and an estimation unit 304.

The initial value generation unit 303 generates initial values of the electrical characteristics of the second semiconductor chip 102. For example, when the characteristic detection unit 302 detects the voltage _Vce , the initial value generation unit 303 generates an initial value of the voltage _Vce .

The estimation unit 304 compares the electrical characteristics detected by the characteristic detection unit 302 with the initial values generated by the initial value generation unit 303 to estimate whether a crack has occurred in the second solder section 112. The estimation unit 304 may estimate that a crack has occurred in the second solder section 112 when the deviation between the detected value and the initial value exceeds a predetermined threshold. The estimation unit 304 may also estimate that a crack has occurred in the second solder section 112 when the detected value exceeds a value obtained by multiplying the initial value by a predetermined coefficient. The estimation unit 304 may also estimate that a crack has occurred in the second solder section 112 when the amount of change in the detected value per unit time exceeds a predetermined threshold.

The estimation unit 304 may compare the electrical characteristics with the initial value in the form of an analog signal. In this case, the initial value generation unit 303 may have a constant voltage circuit that generates a predetermined voltage from the voltage of an internal power supply provided in the semiconductor module 300. The estimation unit 304 may compare the electrical characteristics with the initial value in the form of a digital signal. In this case, the initial value generation unit 303 may have a memory such as an EEPROM that stores the initial value. Furthermore, the characteristic detection unit 302 may have an AD converter that converts the detected electrical characteristics into a digital signal.

The estimation unit 304 outputs information indicating the estimation result. The estimation unit 304 may output the estimation result to an external device via the external terminal 306 shown in FIG. 11. In another example, the estimation unit 304 may output the estimation result to a control unit provided in the semiconductor module 300. The control unit may control each semiconductor chip based on the estimation result.

Figure 13 is a diagram showing an example of the cooling unit 114. The cooling unit 114 is provided below the main circuit unit 200. In this example, the cooling unit 114 is disposed below the bottom surface 206 of the housing 208. The cooling unit 114 may have cooling fins 95 that form a flow path through which the refrigerant flows. In this example, the cooling fins 95 form a flow path parallel to the Y-axis direction. It is preferable that the cooling fins 95 form a flow path below the first semiconductor chip 101 and the second semiconductor chip 102. As shown in Figure 2, the cooling unit 114 may flow the refrigerant in a direction from the first semiconductor chip 101 to the second semiconductor chip 102.

The present invention has been described above using an embodiment, but the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiment. It is clear from the claims that forms with such modifications or improvements can also be included in the technical scope of the present invention.

95: cooling fin, 101: first semiconductor chip, 102: second semiconductor chip, 111: first solder part, 112: second solder part, 114: cooling part, 116: gate pad, 118: sense pad, 130, 164, 166, 168, 170: wiring part, 162: insulating substrate, 200: main circuit part, 171: conductive layer, 206: bottom surface, 208: housing, 210: main terminal, 211: main terminal, 212: output terminal, 214: control terminal, 216: through hole, 300: semiconductor module, 302: characteristic detection part, 303: initial value generation part, 304: estimation part, 306: external terminal

Claims (15)

a main terminal to which power is supplied;
an output terminal for outputting a voltage and a current;
a first semiconductor chip and a second semiconductor chip each including a power semiconductor element;
a wiring portion joined to the first semiconductor chip and the second semiconductor chip;
a first solder portion that joins the first semiconductor chip and the wiring portion;
a second solder portion which is more susceptible to cracking due to thermal history than the first solder portion and which joins the second semiconductor chip and the wiring portion;
the first semiconductor chip is provided between the main terminal and the output terminal,
the second semiconductor chip is provided in parallel with the first semiconductor chip between the main terminal and the output terminal;
At least one of a voltage and a current output from the output terminal changes as the second semiconductor chip switches. The wiring portion further includes an insulating substrate having a plurality of wiring portions provided thereon,
The semiconductor module according to claim 1 , wherein the first semiconductor chip and the second semiconductor chip are provided on a common wiring portion. The wiring portion is
a first wiring portion bonded to an upper surface of the first semiconductor chip opposite to the insulating substrate;
a second wiring portion bonded to an upper surface of the second semiconductor chip opposite to the insulating substrate,
the first solder portion is provided between the top surface of the first semiconductor chip and the first wiring portion,
the second solder portion is provided between the top surface of the second semiconductor chip and the second wiring portion,
The semiconductor module according to claim 2 , wherein the second solder portion has a thickness smaller than a thickness of the first solder portion. The semiconductor module according to claim 1 , wherein the second solder section has a smaller thickness than the first solder section in a direction connecting the semiconductor chip and the wiring section. The semiconductor module according to claim 4 , wherein the second solder portion has a thickness that is 75% or less of the thickness of the first solder portion. The semiconductor module according to claim 4 , wherein the second solder portion has a thickness of not less than 20 μm and not more than 100 μm. The semiconductor module according to claim 1 , wherein the second solder portion is formed from a material having a different composition from that of the first solder portion. The semiconductor module according to claim 7 , wherein the indium content (wt %) in the second solder section is smaller than the indium content (wt %) in the first solder section. The semiconductor module according to claim 8 , wherein the indium content in the second solder section is equal to or less than half of the indium content in the first solder section. The main terminal,
and a main circuit portion connected to the main terminal,
The semiconductor module according to claim 1 , wherein the first semiconductor chip and the second semiconductor chip are provided in the main circuit portion. The semiconductor module according to claim 1 , further comprising: a cooling section arranged below the first semiconductor chip and the second semiconductor chip, the cooling section causing a coolant to flow in a direction from the first semiconductor chip to the second semiconductor chip. The semiconductor module according to claim 1 , wherein the first semiconductor chip and the second semiconductor chip are fixed to a same insulating substrate. A plurality of the first semiconductor chips are provided,
The semiconductor module according to claim 1 , wherein the second semiconductor chip is disposed between two of the first semiconductor chips. The semiconductor module according to claim 1 , further comprising a characteristic detector that detects electrical characteristics of the second solder portion and the second semiconductor chip. The semiconductor module according to claim 14 , further comprising an estimation unit that estimates a state of the second solder part based on the electrical characteristic detected by the characteristic detection unit.

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