JP2001210758A - Semiconductor power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems that the substrate cracks or warps by the stresses due to thermal expansion of a primary sealing resin in the conventional semiconductor power module having a first substrate, second substrate disposed above it, primary sealing resin layer disposed on the first substrate and secondary sealing resin disposed thereon so as to bury the second substrate. SOLUTION: The power module is constituted such that a member having opening only at the downside is formed in a case supporting the first and second substrates, and the downside of the member contacts the primary sealing resin to form closed spaces inside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor module formed by arranging electronic components.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view of a conventional semiconductor module used as a high power electronic component module such as a power transistor module or a switching power supply module. 7, 100 is a case, 10
Reference numeral 1 denotes a base substrate disposed below the case 100 and having a connection surface with a heat sink, 102 denotes an electronic component mounted on the base substrate 101, 103 denotes a terminal mounted on the base substrate 101, and 104 denotes a terminal of the base substrate 101. Case 10 upward
Reference numeral 105 denotes a control board disposed so as to be supported by the control board 104, reference numeral 105 denotes an electronic component mounted on the control board 104, and reference numeral 106 denotes a terminal mounted on the control board 104. The base substrate 10
As 1, a ceramic substrate is often used, and as the control substrate 104, a glass epoxy substrate is often used. The case is made of PPS (polyphenylene sulfide), which is one of engineering plastics having excellent heat resistance.

Reference numeral 107 denotes a primary sealing resin layer formed by filling a primary sealing resin so that the base substrate 101 and the electronic component 102 are buried and do not contact the control substrate 104. Reference numeral 108 denotes a secondary sealing resin layer, which is formed by filling the secondary sealing resin on the primary sealing resin layer 107 so as to bury the control substrate 104 and curing the resin. Here, a gel silicon resin is used as the primary sealing resin, and an epoxy resin is used as the secondary sealing resin.

Since there are portions on the base substrate 101 connected by wire bonding, it is necessary to dispose the primary sealing resin layer 107 in a gel state on the base substrate so as not to be disconnected by a heat cycle. Since the primary sealing resin layer 107 easily absorbs moisture, it is necessary to dispose the secondary sealing resin layer 108 on the primary sealing resin layer 107 in order to prevent this. Since the price of the primary sealing resin is higher than that of the secondary sealing resin, it is preferable that the amount of the primary sealing resin used in the primary sealing resin layer 107 be kept to the minimum necessary.

In general, a gel silicone resin as a primary sealing resin has a larger coefficient of thermal expansion than an epoxy resin as a secondary sealing resin. Therefore, the primary sealing resin layer 107 accompanying the temperature rise due to a heat cycle or the like of the entire apparatus.
Due to the expansion of the base plate 101, stress acts on the base substrate 101, cracks are generated in the base substrate 101, and the reliability of the base substrate 101 is impaired. However, there is a problem that the heat radiation characteristics of the heat radiation element are deteriorated.

[0006] Conversely, the primary sealing resin layer 107 shrinks as the temperature decreases, but if it does not shrink completely in the closed housing, there is a problem that voids are generated and the insulation characteristics are impaired.

A method for solving the problem caused by the difference in thermal expansion between the primary sealing resin and the secondary sealing resin has been studied. FIG. 8 is a sectional view of a semiconductor device described in Japanese Patent Application Laid-Open No. 4-321259. In FIG. 8, 20
1 is a metal base also serving as a heat sink, 202 is a metal base 2
Reference numeral 203 denotes an electronic component mounted on the insulating plate 202, 204 denotes an external lead terminal, 205 denotes an insulating case, 206 denotes an upper cover of the insulating case 205, and 207 denotes a gel. A resin filler 208, a sealing resin layer made of excibo resin or the like filled and cured on the gel resin filler 207, a first partition 209 provided inside the side wall of the insulator case, 210 is a second partition provided on the upper lid 206, 211 is a first partition 209
And an internal pressure absorption chamber defined as a pocket-shaped closed space defined between the first partition wall 210 and the second partition 210.

[0008] In such a configuration, the gel-like resin filler 2 is formed by the temperature rise accompanying the heat cycle of the semiconductor device.
Even if 07 expands, the expanded volume enters the internal pressure absorbing chamber 211 and is absorbed. Conversely, when the temperature decreases, the space of the internal pressure absorbing chamber 211 increases due to shrinkage of the gel-like resin filler, but it is possible to prevent voids from being generated inside the gel-like resin filler 207.

[0009]

However, in the method of forming the internal pressure absorbing chamber with the upper lid as described above, when using two substrates, a base substrate and a control substrate, the upper lid is formed, and the upper lid and the gel are formed. Since it is necessary to create a space between the resin and the resin, it is necessary to increase the size of the case, or to reduce the size of the control board or change the design. There was a problem that occurred.

Further, in the method of forming a hollow layer described in Japanese Patent Application Laid-Open No. 5-90448, the operation is complicated because it is necessary to install a sealing member for each electronic component and inject silicon resin in two or more steps. It will be.

[0011] In addition, the use of a stress buffer coating film in which air bubbles are dispersed in a rubber base material described in JP-A-10-294404 absorbs the contraction and expansion of the primary sealing resin to prevent the generation of stress. In the method, a new rubber is required as a tertiary sealing agent in addition to the primary sealing resin and the secondary sealing resin, and a step of mixing a filler into the rubber is required as a pre-process of the tertiary sealing agent. Since a step of applying a tertiary sealing agent to the surface of the primary sealing resin is required,
The manufacturing process becomes complicated, resulting in an increase in manufacturing man-hours and material costs.

The present invention has been made to solve such a problem. By providing an internal pressure absorbing space between a base substrate and a control substrate, it is possible to prevent the occurrence of stress and to prevent the occurrence of cracks and warpage. It is an object of the present invention to provide a semiconductor module which can prevent a decrease in strength and has excellent reliability and manufacturability without changing the size of a conventional case or a substrate circuit.

[0013]

In the semiconductor module according to the present invention, the case has a member having an opening only on the lower surface, and the member is thermally expanded while the opening is in contact with the primary sealing resin layer. It was arranged under the second substrate so as to have a space in which the primary sealing resin could be housed.

Further, the upper end of the member is in contact with the second substrate.

Further, the member is arranged so that its opening is located above the first electronic component.

Further, in the semiconductor power module according to the present invention, at least one hollow member that can be deformed in response to stress from the primary sealing resin is disposed in the primary sealing resin layer.

Further, the hollow member is made of silicon.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a sectional view showing a semiconductor module according to Embodiment 1 of the present invention.

In FIG. 1, reference numeral 1 denotes a case. Reference numeral 2 denotes a base substrate arranged under the case 1. Reference numeral 3 denotes an electronic component mounted on the base substrate 2, and is electrically connected to a circuit (not shown) on the base substrate 2 by a bonding wire. Reference numeral 4 denotes a terminal connected to a circuit on the base substrate 2 by a bonding wire. Reference numeral 5 denotes a control board arranged above the base board 2 so as to be supported by the case 1. Reference numeral 6 denotes an electronic component mounted on the control board 5. Reference numeral 7 denotes a terminal mounted on the control board 5.

Reference numeral 8 denotes a primary sealing resin layer formed by filling the primary sealing resin so that the base substrate 2 and the electronic component 3 are buried and do not contact the control substrate 5. As the primary sealing resin, a thermosetting silicone resin is used. Reference numeral 9 denotes a secondary sealing resin layer, which fills the primary sealing resin layer 8 with the secondary sealing resin so as to bury the control substrate 5,
It is cured. Epoxy resin is used as the secondary sealing resin.

FIG. 2 is a partial perspective view of the case 1. The case 1 is formed by combining four horizontal wall members 1a in a frame shape. The horizontal wall member 1a has a first step 1b toward the inside and a second step 1c located above the first step 1b. I have. A member 1d having an open portion only on the lower surface is formed from the first step 1b of one of the four horizontal wall members 1a toward the inside of the frame. Further, the lower surface of the lateral wall member 1a has a notch 1e, and the case 1 and the base substrate 2 are positioned so that the base substrate 2 fits into the notch 1e. Also,
By arranging the primary sealing resin layer 8 so as to be in contact with the lower opening of the member 1d having an opening only on this lower surface, the internal pressure absorbing space 10 in FIG. 1 is formed.

Incidentally, such a semiconductor module is produced in the following flow. First, electronic components such as the electronic components 3 and the terminals 4 are mounted on the base substrate 2 to form a circuit.
The base substrate 2 is placed under the case 1. Next, the base substrate 2 and the electronic component 3 mounted on the base substrate 2
Is filled with the primary sealing resin until it comes into contact with the lower opening of the member 1b having an opening only on the lower surface. At the time of filling, since the primary sealing resin is in a liquid state, it is accumulated horizontally in the case 1, and the internal pressure absorbing space 10 is formed in the member 1b having an opening only on the lower surface while leaving the gas.

Next, with the case 1 kept at a predetermined temperature, the primary sealing resin is thermoset to be in a gel state. Thereby, the air in the internal pressure absorption space 10 is sealed. afterwards,
The control substrate 5 is disposed above the base substrate 2 so as not to be in contact with the primary sealing resin layer 8, and is electrically connected to the base substrate 2 through terminals (not shown) wired in the case 1. Next, the secondary sealing resin is filled from the upper surface until the electronic component 6 on which the control board 5 is mounted is buried, and is thermally cured.
Since the secondary sealing resin is liquid at the time of filling, a hole of about 3 to 5φ is made in the control substrate 5 in advance, so that the lower side of the control substrate 5 is also filled.

Next, the size of the internal pressure absorbing space 10 will be described. The volume of the internal pressure absorbing space 10 needs to be at least equal to the volume expansion and contraction of the primary sealing resin layer 8 under a predetermined heat cycle temperature condition. Here, the volume of the primary sealing resin layer 8 is about 32 × 10 ^ 3 [mm ^ 2], the thermal expansion coefficient of the primary sealing resin is 1.00 × -10 ^ 3 [1 / k], and the heat cycle is −40. ° C
From 125 ° C to ΔT = 165 ° C, the internal pressure absorption space 1
The volume of 0 is 32 x 10 ^ 3 x 165 x 1.00 x -10 ^ 3 = 5.28
× 10 ^ 3 [mm ^ 2] or more is required.

As described above, the inner pressure absorbing space 10 has an opening surface in contact with the primary sealing resin layer 8 to form a closed space.
Gas is sealed in the manufacturing process. Here, when the primary sealing resin layer 8 of the case 1 expands with the occurrence of a temperature change due to a heat cycle during operation, the increased volume enters the internal pressure absorbing space 10 to absorb the increased pressure. .

In this case, the gas in the internal pressure absorbing space 10 is compressed. When the pressure applied to the gas by the volume expansion of the primary sealing resin layer 8 is compared with the reaction force generated by the compression of the gas, the reaction force is Is sufficiently small, the expansion of the primary sealing resin layer 8 due to the temperature rise can be absorbed in the internal pressure absorbing space 10.
Similarly, the volume shrinkage of the primary sealing resin layer 8 due to the temperature drop can be offset by the internal pressure absorbing space 10. Therefore, the pressure generated by the expansion and contraction of the primary sealing resin layer 8 due to the heat cycle can be reduced, and the stress can be reduced, so that the occurrence of cracks and warpage of the base substrate 2 can be prevented.

A member 1d having an opening only on the lower surface
If the case 1 is formed integrally and the primary sealing resin is filled up to the opening, the internal pressure absorbing space 10 can be easily formed, so that there is no need to change the size of the conventional case or the substrate circuit. The internal pressure absorbing space 10 can be arbitrarily arranged as long as the open portion is in contact with the primary sealing resin layer 8.
Further, the structure may be such that the upper surface of the member 1d having an open portion only on the lower surface is in contact with the control board 5 and used as a support section of the control board 5. Further, by controlling the volume of the internal pressure absorbing chamber 10, the pressure of contraction and expansion of the primary sealing resin layer 8 can be controlled.

Embodiment 2 FIG. 3 is a cross-sectional view of a semiconductor module according to Embodiment 2 of the present invention.
, The arrangement of the internal pressure absorbing space can be arbitrarily changed. FIG. 4 is a partial perspective view of a case according to Embodiment 2 of the present invention.

In FIG. 3, reference numeral 1f denotes a member having an opening only on the lower surface, and is disposed above the electronic component 3 mounted on the base substrate 2. Further, in the case 1, as shown in FIG. 4, the first step 1b of the horizontal wall member 1a and the first step 1b of the horizontal wall member 1a arranged at opposite positions have an opening only on the lower surface. The member 1f is bridged with the opening facing downward. The member 1f having an opening only on the lower surface can be installed at an arbitrary position. Therefore, the internal pressure absorbing space 10 is formed by arranging the primary sealing resin so as to be in contact with the lower opening of the member 1f having the opening only on this lower surface.

In such a configuration, the base substrate 2 is installed on the lower surface of the case 1 and then, among the electronic components 3 mounted on the base substrate 2, those having a particularly large calorific value are opened only on the lower surface. The internal pressure absorbing space 11 can be formed in the upper part of the electronic component 3 generating a large amount of heat by installing the member 1f having. By disposing the internal pressure absorbing space 11 directly above the electronic component 3 generating a large amount of heat, the gas in the internal pressure absorbing space 11 can be used as a heat insulating material, and the local heat transfer on the control board can be diffused and reduced. Yes, it is efficient. This is effective when the electronic component 6 mounted on the control board 5 directly above the electronic component 3 having a large heat generation amount on the base substrate 2 is an electronic component that is particularly vulnerable to heat.

FIG. 5A shows the direction of heat conduction when the internal pressure absorption space is not arranged above the electronic component, and FIG. 5A shows the heat conduction direction when the internal pressure absorption space is arranged above the electronic component. This is shown in FIG. Here, the heat transfer coefficient of the primary sealing resin is about 0.2 W / mK, while the heat transfer coefficient of the gas is 0.03 W / mK.
The effect is great because it is about mk and about 1/10. When a plurality of components generate heat, a plurality of internal pressure absorbing spaces 11 may be provided.

Embodiment 3 FIG. FIG. 6 is a sectional view of a semiconductor module according to Embodiment 3 of the present invention.
In, instead of forming the internal pressure absorption space by a member having an open portion only on the lower surface integrally molded with the case,
A plurality of hollow silicon balls are arranged.

In FIG. 6, reference numeral 12 denotes a hollow silicon ball, and a plurality of hollow silicon balls are arranged on a boundary surface between the primary sealing resin layer 8 and the secondary sealing resin layer 9. The number is such that the total volume of the inner space of all the hollow silicon balls 12 is at least equal to the expansion and contraction amount of the primary sealing resin layer. When the volume of the primary sealing resin 8 is about 32 × 10 3 [mm ^ 2], 300 or more silicon balls having a diameter of about 3 mm may be used.

The hollow silicon balls 12 may be placed in such a manner that the primary sealing resin is filled and thermally cured to form the primary sealing resin layer, and then the gel-like primary sealing resin layer is formed on the upper surface of the gelled primary sealing resin layer. The hollow silicon ball 12 is disposed so as to be buried, and then the control board 5 is mounted on the second step 1c of the case 1, filled with a secondary sealing resin, and thermally cured.

As described above, by using a member having a closed space such as a hollow silicon ball, a closed space can be easily formed on the semiconductor module.

[0036]

As described above, according to the present invention, a change in internal pressure due to expansion and contraction of the primary sealing resin layer caused by a heat cycle can be absorbed in the absorption space, so that the occurrence of cracks and warpage is reduced. A semiconductor power module having high reliability can be provided.

Further, since a member having an open portion only on the lower surface is integrally formed with the case, the number of steps for forming the absorption space can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor module according to Embodiment 1 of the present invention.

FIG. 2 is a perspective view of a case according to Embodiment 1 of the present invention.

FIG. 3 is a sectional view of a semiconductor module according to Embodiment 2 of the present invention;

FIG. 4 is a perspective view of a case according to Embodiment 2 of the present invention.

FIG. 5 is a diagram showing a heat conduction direction in Embodiment 2 of the present invention.

FIG. 6 is a sectional view of a semiconductor module according to Embodiment 3 of the present invention.

FIG. 7 is a sectional view of a conventional semiconductor module.

FIG. 8 is a cross-sectional view of a conventional semiconductor device.

[Explanation of symbols]

1 case, 1a side wall member, 1b first step,
1c 2nd stage, 1d a member having an opening only on the lower surface, 1e notch, 1f a member having an opening only on the lower surface, 2 base substrate, 3 electronic components, 4 terminals, 5 control substrate, 6 electronic components, 7 terminals, 8
Primary sealing resin layer, 9 Secondary sealing resin layer, 10 Internal pressure absorption space, 11 Internal pressure absorption space, 12 hollow silicon ball

Claims (5)

[Claims] 1. A case, a first substrate disposed on a bottom surface of the case, a first electronic component disposed on the first substrate, and a second substrate supported by the case. A first sealing resin layer formed by filling a gel-like primary sealing resin so as to bury the first electronic component on the first substrate, and a first sealing resin layer formed on the first sealing resin layer. In a semiconductor power module having a secondary sealing resin layer formed by filling a secondary sealing resin, the case has a member having an open portion only on a lower surface, and the member has a primary sealed The second sealing member is in contact with the sealing resin layer and has a space in which the thermally expanded primary sealing resin can be housed.
A semiconductor power module, wherein the semiconductor power module is disposed below a substrate. 2. The semiconductor power module according to claim 1, wherein an upper end of the member is in contact with the second substrate. 3. The semiconductor power module according to claim 1, wherein the member is arranged such that an opening thereof is located above the first electronic component. 4. A case, a first substrate disposed on a bottom surface of the case, a first electronic component disposed on the first substrate, and a second substrate supported by the case. A first sealing resin layer formed by filling a gel-like primary sealing resin so as to bury the first electronic component on the first substrate; and In a semiconductor power module having a secondary sealing resin layer formed by filling a secondary sealing resin, at least a hollow member deformable in response to stress from the primary sealing resin in the primary sealing resin layer. A semiconductor power module, wherein one is arranged. 5. The semiconductor power module according to claim 4, wherein the hollow member is made of silicon.