JP3390661B2 - Power module - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a power module, for example, a technology for downsizing a power module such as an inverter, reducing the cost, and simplifying the manufacturing process.

[0002]

2. Description of the Related Art Since a power semiconductor device operates under a large current and a high voltage, in such a power module for power, a high insulation property is ensured and heat generated by the operation is external to the semiconductor device. Efficient escape is essential.

FIG. 4 shows a power transistor chip (hereinafter, referred to as an example of such a power semiconductor device).
FIG. 3 is a vertical cross-sectional view showing the structure of a power module including a “power chip”) and a logic chip that controls the power chip.

As shown in FIG. 4A, one main surface of the ceramic substrate 31P is formed by using an etching technique.
A wiring pattern made of copper foil 13P is formed, and a power chip 1P and a logic chip 2P are mounted on a predetermined wiring pattern. Then, each mounting component and the wiring pattern are connected by the bonding wires 3P and 4P, and a desired electric circuit is formed. At this time, a thick aluminum wire 3P is used for connecting the power chip 1P that handles a large current and its wiring pattern, and a thin aluminum wire 4P is used for other connections. Further, the ceramic substrate 31P and one main surface of the metal base plate 32P are soldered to each other via the copper foil 13P entirely formed on the other main surface of the ceramic substrate 31P.

Further, as shown in FIG. 4B, the composite substrate structure shown in FIG. 4A is connected to the external leads 22P and then sealed. That is, the metal base plate 3
A terminal connected to the external lead 22P of the insert mold case 33P arranged so as to surround the end portion of the 2P and the wiring pattern are connected by the thick aluminum wire 3P and the thin aluminum wire 4P. Then, each component is sealed by the mold resin 5P in the insert mold case 33P.

In the structure of the power module shown in FIG. 4 (b), the heat generated by the power chip 1P is radiated to the outside of the package via the molding resin 5P, and
Heat is radiated to the outside of the package through the ceramic substrate 31P and the metal base plate 32P.

However, if the structure shown in FIG. 4B is adopted even in the case of a module which generates a small amount of heat, there is a problem that the expensive ceramic substrate 31P makes the module expensive. Also, the ceramic substrate 31P
In addition, since the solder must be soldered to the metal base plate 32P, the manufacturing process becomes complicated and, as a result, the cost of the module increases from the viewpoint of the manufacturing cost of the module.

Therefore, in order to solve the above-mentioned problems, in a small-capacity module that generates a small amount of heat, a high thermal conductive insulating layer in which silica particles or the like for enhancing thermal conductivity is mixed with an epoxy resin is used. A substrate formed on one main surface of a metal plate such as aluminum or aluminum and further having a wiring pattern formed by a copper foil on the surface of the high thermal conductive insulating layer (hereinafter,
A "metal substrate" is used. This allows
The ceramic substrate 31P of FIG. 4 is replaced with a high thermal conductive insulating layer, and the conventional process of soldering the ceramic substrate 31P and the metal base plate 32P of FIG. 4 is unnecessary. Therefore, by adopting this metal substrate, the effects of reducing the forest material cost and simplifying the manufacturing process were obtained.

However, in order to further reduce the cost, another power module structure has been proposed in which encapsulation can be performed easily and at low cost. For example, Japanese Patent Laid-Open No. 9-22970 discloses another structure of such a transfer mold type power module. Therefore, such a module structure will be illustrated in FIG. 5, and another structure of the transfer mold type power module will be described below with reference to the longitudinal sectional view of FIG.

As shown in FIG. 5, a high thermal conductive insulating layer 12P is formed on one main surface of an aluminum plate 11P which also serves as a heat radiating plate and a circuit wiring board, and the surface of the high thermal conductive insulating layer 12P is further formed. The wiring pattern 13P is formed on the copper foil by applying an etching technique or the like to the copper foil. These members 11P, 12P and 13P form a metal substrate 10P. Then, this wiring pattern 13
Component parts such as the power chip 1P and a logic chip (not shown) are mounted on each part of the P except the part where the external lead 22P is provided, and the power chip 1P and a predetermined part of the copper foil wiring pattern 13P are bonded to each other. It is connected by a wire 3P. Also, aluminum plate 1
The other main surface of 1P is exposed from the package of the power module without being covered with the molding resin 5P.

Thus, in FIG. 5, the metal substrate 1
Since 0P has both the function as a conductor wiring board corresponding to the ceramic substrate 31P of FIG. 4B and the function of a heat dissipation plate corresponding to the metal base plate 32P of FIG. 4B, the power of FIG. Compared with the module, it is possible to reduce the number of members and the number of manufacturing processes.

[0012]

In the power module shown in FIG. 5, the number of members and the number of manufacturing steps are certainly reduced as compared with the module shown in FIG. However, it is considered that the conventional technique of FIG. 5 does not make any practical proposal for an effective technique for further downsizing the power module shown in FIG.
That is, the conventional technique of FIG. 5 does not provide any incentive for the main purpose of the present application to further reduce the cost by realizing the further downsizing of the power module.

Below, the problems that occur when the power module shown in FIG. 4 is further miniaturized will be verified, but the discussion on this point shows that the structure of the module shown in FIG. 5 is used to solve this problem. It will be clear that the means cannot be anything. In addition, the problems described below are as shown in FIG.
Also, since it is common to both power modules shown in FIG. 5, the structure shown in FIG. 5 will be described in detail as an example.

In the power module structure as shown in FIG. 5, the wiring pattern through which a large current flows is formed by using the copper foil 13P on the surface of the metal substrate 10P. The copper foil wiring pattern 13P is formed by forming a high thermal conductive insulating layer 12P on one main surface of the aluminum plate 11P and then etching the copper foil entirely formed on the surface of the high thermal conductive insulating layer 12P. It is formed by removing unnecessary portions of the copper foil. However, in the case of isotropic etching, etching of the copper foil also proceeds in the lateral direction at the mask edge, that is, in the direction parallel to the mask surface. Therefore, in the isotropic etching, when the copper foil 13P is etched only from the surface side like the metal substrate 10P, the etching width needs to be at least 2t with respect to the thickness t of the copper foil. Therefore, in order to form a fine wiring pattern on the copper foil while completely separating the wiring patterns, there arises a problem that the thickness of the copper foil is limited. In other words, in the power module having the structure shown in FIG. 5, the formation of the copper foil wiring pattern by etching is nothing but preventing the miniaturization of the power module.

In addition, in a power module through which a large current flows, a wiring having a larger cross-sectional area is required from the viewpoint of reducing electric resistance and thermal resistance. However, when the wiring pattern is formed by etching as in the power module of FIG. 5, the thickness of the copper foil is limited as described above. Therefore, in order to secure a larger cross-sectional area, the wiring width must be increased. There is no choice but to expose the problem of enlarging the entire module.

As described above, in the power module having the structure shown in FIG. 5, the thickness of the copper foil wiring pattern 13P is
This limits the miniaturization of power modules. And this problem also becomes a factor that prevents further cost reduction of the power module.

One solution to this problem is as follows:
A method of forming a wiring pattern having a desired copper foil thickness in advance and adhering it with an adhesive or the like is also conceivable. However, since the adhesive is squeezed out at the time of bonding, this method cannot be put to practical use.

The present invention has been made in order to solve the above-mentioned problems, and promotes the further miniaturization of the power module and realizes the further cost reduction, and the transfer mold sealing having a novel structure. A first object is to provide a static power module.

Further, a second object of the present invention is to improve the versatility of the manufacturing member and the manufacturing process, promote the simplification of the manufacturing process of the power module, and realize a further cost reduction. To provide a module.

[0020]

According to a first aspect of the present invention, there is provided a power module of a transfer mold encapsulation type, wherein a first main surface and a second main surface facing the first main surface are provided. The first main surface and the second
A lead frame on which a wiring pattern of a predetermined electric circuit is formed, which includes a plurality of power chip mounting portions, a logic chip mounting portion, a lead portion, and a tie bar portion by punching between main surfaces. The duplicate of the wiring pattern
Mounted on the first main surface of a number of power chip mounting portions
A plurality of power transistor chips, a logic chip for controlling the power transistor chips mounted on the first main surface of the logic chip mounting portion of the wiring pattern, and an arrangement for the plurality of power chip mounting portions.
A high thermal conductive metal substrate,
The metal substrate is mounted on the second main surface of each power chip mounting part.
Solder and copper foil arranged in the order of
Commonly arranged for copper foil and solder on the chip mounting area
Are placed on the copper foil in this order,
And a conductive insulating layer and a metal plate .

A power module according to the second aspect of the invention.
Le is in the power module according to claim 1, wherein
The high thermal conductive layer and the metal plate are the plurality of power chips.
It is characterized in that it is provided locally on the mounting portion .

[0022]

[0023]

[0024]

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, in the module structure shown in FIG. 4, the conductor wiring board is composed of the ceramic substrate 31P and the copper foil wiring 13P, and the heat dissipation plate is composed of the metal base plate 32P. It is formed of a member. For this reason, the module structure of FIG. 4 cannot fully respond to the downsizing and cost reduction.
It can be said that these problems have been alleviated by the proposal of the module of FIG. 5, which adopts the structure in which the conductor wiring board and the heat dissipation plate are integrated. However, the present invention
In order to meet the demand for further miniaturization and cost reduction of the power module, the technical idea in the above structure, which seems to recede from the power module of FIG. 5, that is, the conductor wiring board and the heat sink, Is based on the idea of actively utilizing the idea of being composed of separate members. From the description of the embodiments described below, the module structure according to the present embodiment is smaller in size and lower in cost than the module shown in FIG.
Moreover, there is an effect that good heat dissipation can be exhibited.

(Embodiment 1) An example of the structure of the transfer mold type power module according to Embodiment 1 of the present invention will be described in detail below with reference to FIGS. 1 is a vertical cross-sectional view schematically illustrating the structure of the power module according to the first embodiment, and the positional relationship between various mounting parts and the wiring relationship between various aluminum wires, which will be described later, are schematically shown. I'm just there. 2 is a top view showing an example of the lead frame according to the first embodiment, and FIG. 1 is a vertical cross-sectional view of the structure taken along the line II 'shown in FIG. It corresponds to what you saw. Further, in FIG. 3, FIG. 3A is a top view showing the module immediately after being sealed with the mold resin and before the cutting step,
The module is completed as a form shown in FIG. 2B by separating and cutting unnecessary parts of the lead frame 21.

The structure of the power module shown in FIGS. 1 to 3 will be described below through the description of its manufacturing process.

First, the first of the 0.7 mm thick copper frame
By punching between the main surface 21S1 and the second main surface 21S2, a wiring pattern as shown in FIG. 2 is formed on the lead frame 21. That is, as shown in FIG. 2, the lead frame 21 includes the mounting portion 6 of the power transistor chip (hereinafter referred to as “power chip”) 1.
And a logic chip 2 for controlling the power chip 1
The mounting part 7 of is included. Here, in the case of having a plurality of power chip mounting portions 6 _i (1 ≦ i ≦ n) and a plurality of logic chip mounting portions 7 _k (1 ≦ k ≦ m) as shown in FIG. Is an arbitrary power chip mounting portion 6 _i , and the logic chip mounting portion 7 is a mounting portion 7 _k of the logic chip 2 that controls the power chip 1 mounted on the power chip mounting portion 6 _i. . Furthermore, FIG.
As shown in FIG.
3, the inner lead portion 24 connected to the mounting portion 6 of the power chip 1 and the like, and the adjacent outer lead portions 23 are bridged,
Moreover, the outer leads 23 at both ends and the frame portion 2 facing the outer leads 23
The tie bar portion 25 that also bridges 8a and the frame portion 28
a or tie bar portion 25, and includes holding portions 26a and 26b which are separated from the frame portion 28a or tie bar portion 25 in a cutting step described later. Here, the holding unit 2
6a and 26b are collectively referred to as a holding portion 26, and a frame portion 28a in which the tie bar portion 25 is bridged and an external lead portion 23 are provided.
The frame portion 28b connected to the above will be collectively referred to as a frame portion 28. As described above, the structure of the lead frame 21 as described above is generically called a wiring pattern.

Further, in a cutting step described later, after sealing in the lead frame 21, unnecessary parts are separated and cut, and as shown in FIG. 3B, the external lead portion of FIG. Thus, the lead portion 27 including only the inner lead portion 23 and the inner lead portion 24 is formed.

In addition, as shown in FIG. 2, the wiring pattern of the lead frame 21 has a plurality of power chip mounting portions 6 _i.
(1 ≦ i ≦ n) and a plurality of logic chip mounting parts 7 _k (1
.Ltoreq.k.ltoreq.m), the power is not provided between any power chip mounting portion 6 _i and another power chip mounting portion 6 _{i + 1} without interposing any logic chip mounting portion 7 _k. By forming another power chip mounting portion 6 _{i + 1} as a wiring pattern so that the chip mounting portion 6 _i and another power chip mounting portion 6 _{i + 1} are adjacent to each other, the lead frame 21 shown in FIG. As in an example of the wiring pattern, the power chip mounting portions 6 _i can be collectively formed at desired positions without being scattered in the lead frame 21.

Next, the first main surface 2 of the power chip mounting portion 6
The power chip 1 is mounted on 1S1, and the logic chip 2 is mounted on the first main surface 21S1 of the logic chip mounting portion 7.
After being mounted on top, the hydrogen furnace (hydrogen concentration 20%, temperature 36
At 0 ° C.), the chips 1 and 2 and the chip mounting portions 6 and 7 are soldered to each other.

Next, ultrasonic wire bonding is performed on a desired portion to make electrical connection. At this time, a thick aluminum wire 3 having a diameter of 300 μm is used in a portion through which a large current flows, for example, a connecting portion between the power chip 1 and the internal lead portion 24 in FIG. 2, and other portions,
For example, a thin aluminum wire 4 having a diameter of 35 μm is used at the connecting portion between the logic chip 2 and the internal lead portion 24.

Here, the high thermal conductive metal substrate 10 functioning as a heat dissipation plate is a metal plate, for example, 2 mm as shown in FIG.
On one main surface of the thick aluminum plate 11, a high thermal conductive insulating layer 12 in which an insulating material such as silica particles having good thermal conductivity is mixed with an epoxy resin or a polyimide resin is formed with a thickness of 100 μm. It has a laminated structure in which a copper foil 13 is formed on the surface of the high thermal conductive insulating layer 12. The copper foil 13 is formed on the surface of the high thermal conductive insulating layer 12 and later on the metal substrate 1.
0 and the second main surface 21S2 of the power chip mounting portion 6 are formed only at the positions necessary for bonding. Also,
In the first embodiment, the aluminum plate 11 is used as the metal plate.
However, it goes without saying that other metal such as copper may be used as the base portion of the metal substrate 10 instead.

Then, by the steps described below, the second main surface 21 of the mounting portion 6 is so positioned that the metal substrate 10 is located only above the second main surface 21S2 of the power chip mounting portion 6.
Solder 14 is interposed on S2, and they are joined as shown in FIG. First, the solder 14 is preliminarily supplied onto the second main surface 21S2 of the power chip mounting portion 6 while vibrating the molten solder with an ultrasonic (20 kHz) horn. Thereafter, while heating the metal substrate 10, the metal substrate 10 is brought into contact with the previously-supplied solder 14 to perform solder joining. It should be noted that there is no problem even if the preliminary supply process of the solder 14 and the solder joining process of the metal substrate 10 are performed at the same time. Further, since ultrasonic waves are applied during the preliminary supply of the solder 14, the oxide film on the second main surface 21S2 of the power chip mounting portion 6 is destroyed by the cavitation effect. Preliminary supply is possible. Furthermore, by performing Au plating on the surface of the copper foil 13 forming the uppermost layer of the metal substrate 10, more stable fluxless soldering becomes possible.

An ultrasonic horn may not be used in the solder joining.

Here, in the first embodiment, as shown in FIG. 1, the area of the surface of the copper foil 13, that is, the surface of the surface facing the second main surface 21S2 of the power chip mounting portion 6 and being soldered thereto. Is almost the same as the area of the surface forming the second main surface 21S2 of the power chip mounting portion 6, and the aluminum plate 1
1, the area of the aluminum plate 11 facing the second main surface 21S2 of the power chip mounting portion 6 is as shown in FIG.
As shown in, the second main surface 21S of the power chip mounting portion 6
The area of the surface forming 2 is about the same. The area of the aluminum plate 11 facing the second main surface 21S2 of the power chip mounting portion 6 may be formed to be slightly larger, but within a range that does not reach the upper side of the second main surface 21S2 of the logic chip mounting portion 7. Need to be limited to.

Next, by using a well-known transfer mold sealing method, a portion within a range surrounded by a dotted line indicated by reference numeral 29 in FIG. 2 is covered with the mold resin 5, and the power module of FIG. The transfer mold is sealed as shown in FIG. At this time, as shown in FIG. 1, the present module is sealed such that the other main surface of the aluminum plate 11 is exposed from the mold package.

After that, in the wiring pattern of the lead frame 21 protruding or exposed to the outside from the surface of the mold package, unnecessary portions corresponding to the frame portion 28, the tie bar portion 25, and the holding portion 26 are separated and cut in the cutting step. As a result, the power module having the form as shown in FIG. 3B is completed.

As described above, in the structure of the power module according to the first embodiment, the ceramic substrate 31P and the copper foil wiring 13P in the conventional module structure shown in FIG. 4 are used.
That is, the conductor wiring board made of is formed by the wiring pattern of the lead frame 21, and the heat dissipation plate made of the metal base plate 32P is formed by the locally arranged high thermal conductive metal board 10. From the above and above viewpoints, the unique effects produced by the power module structure of the first embodiment will be described below.

First, according to the structure of the power module of the first embodiment, since the wiring pattern of the predetermined electric circuit of the lead frame 21 is formed by press punching, an expensive ceramic substrate 31P (see FIG. 4). Therefore, cost reduction can be achieved as compared with the module shown in FIG. At the same time, a great simplification of the manufacturing process is realized as compared with the etching technique which requires a plurality of processes as in the case of the conventional copper foil wiring. Further, since the external lead portion 23 is formed as the wiring pattern of the lead frame 21, the external lead portion 22P (see FIGS. 4 and 5) and the copper foil wiring 13P (see FIGS. 4 and 5) are formed like the conventional power module. Also, the step of making an electrical connection with (see) can be omitted. This brings about an effect that the cost can be further reduced as compared with the conventional power module illustrated in FIGS. 4 and 5.

In addition, since a predetermined wiring pattern is formed on the lead frame 21 itself, a wiring having a sufficiently large cross-sectional area as compared with the conventional copper foil wiring 13P (see FIGS. 4 and 5) is used. It can be easily formed. As a result, the electrical resistance and thermal resistance of the wiring through which a large current flows can be significantly reduced, and it is possible to promote the densification of the wiring pattern. That is, the conventional copper foil wiring 13P
Then, when the film thickness is 0.07 mm, the steady-state current value is 15 A
A copper foil wiring width of 10.0 mm is required to pass an (effective value) current, but if the wiring pattern is formed on the lead frame 21 having a thickness of 0.7 mm in the first embodiment, Even if the same amount of current is handled in the same cross-sectional area as the copper foil wiring, the minimum wiring width can be reduced to 1 mm, so that the wiring pattern can be made denser. As a result, it is possible to further reduce the size of the power module as compared with the conventional technology shown in FIGS. 4 and 5, and at the same time, it is possible to further reduce the cost. Be done.

Further, according to the first embodiment, it is possible to obtain an effect that the size reduction of the metal substrate 10 as the heat dissipation plate can be promoted. That is, since it has a larger cross-sectional area than the conventional copper foil wiring 13P (see FIGS. 4 and 5), the thermal resistance of the wiring is significantly reduced, and the heat radiation characteristics of the wiring are improved. Therefore, it is possible to reduce the amount of heat radiation from the power chip 1 which is a heat source through the mold sealing material. Furthermore, if this point is utilized, the mounting portion 6 of the power chip 1 is locally provided with a high thermal conductive metal substrate. Even if only 10 is provided, sufficient heat dissipation characteristics can be obtained. As a result, the volume of the metal substrate 10 can be further reduced as compared with the conventional power module in which the heat dissipation plate is provided on the entire surface of the wiring pattern, so that the cost of the metal substrate 10 can be reduced. It is possible to further promote the power consumption, and also from this point, it is possible to further reduce the size of the power module itself.

Further, the second main surface 2 of the power chip mounting portion 6
The fact that the fluxless solder bonding on the 1S2 is possible does not require the cleaning step in the conventional solder bonding technique, and the metal substrate 10 can be locally provided. It is possible to increase the degree of freedom in the step 10 of solder joining. For example, each chip can be mounted, and after the wire bonding process is completed, the solder bonding process of the metal substrate 10 can be performed.

Further, according to the power module having the lead frame 21 shown in FIG. 2, since the power chip mounting portions 6 _i (1 ≦ i ≦ n) are collectively formed at a desired location, n power chip mounting portions 6 _i are formed. Power chip mounting portion 6 _i , that is, n
Therefore, it is not necessary to dispose n high thermal conductive metal substrates 10 for each power chip 1. That is, in FIG. 2, since the n power chip mounting portions 6 _i are formed in alignment with one side of the lead frame 21, one power chip mounting portion 6 ₁ to 6 _n has one area. The metal substrate 10 may be provided. Of course, this does not impair the heat dissipation characteristics of the high thermal conductive metal substrate 10. Thus, according to the first embodiment,
Since the number of high thermal conductive metal substrates 10 is reduced as compared with the case where a plurality of high thermal conductive metal substrates are individually arranged, the material cost of the high thermal conductive metal substrates 10 can be further reduced, and at the same time, Since the number of installation steps is reduced, the manufacturing cost can be reduced. Therefore, due to the above, there is an effect that the cost reduction of the power module can be further promoted.

(Modification 1) This modification 1 provides a high thermal conductive metal substrate having a structure that can be arranged on the second main surface of the power chip mounting portion by another method without using solder joining. It is about technology.

First, as an example, instead of the high thermal conductive metal substrate 10 of FIG. 1, a high thermal conductive metal having a structure in which a high thermal conductive insulating layer 12 is laminated on one main surface of an aluminum plate 11 of FIG. It is conceivable that the substrate is brought into direct contact and the high thermal conductive metal substrate is fixed via the molding resin sealing. As a result, the same effect as that of the first embodiment is expected. However, since the high thermal conductive insulating layer 12 itself in FIG. 1 is formed by sintering the epoxy resin or the like applied on the surface of the aluminum plate 11, the flatness of the surface of the high thermal conductive insulating layer 12 after sintering. Is not always enough. Therefore, if the high thermal conductive insulating layer 12 is brought into direct contact with the second main surface 21S2 of the power chip mounting portion 6, a sufficient contact area may not be obtained depending on the above flatness, and in this case, There is also a problem that sufficient heat conduction cannot be obtained. In this respect, the high-thermal-conductivity metal substrate 10 shown in FIG. 1, which further has the copper foil 13 and is soldered, does not cause such a fear, and thus can be said to be the most preferable embodiment.

Therefore, as another method which does not cause such a problem and does not rely on solder joining, the following modified example can be proposed. That is, (i) a high thermal conductive metal substrate composed of the aluminum plate 11 and the high thermal conductive insulating layer 12 is arranged on the second main surface 21S2 of the power chip mounting portion 6 with the high thermal conductive sheet interposed, and the mold resin 5 This is a method of arranging the metal substrate by holding the shape of the metal substrate. In addition, (ii) a high thermal conductive adhesive is used instead of the high thermal conductive sheet, as shown in FIG.
A structure in which the high thermal conductive insulating layer 12 on the aluminum substrate 11 and the second main surface 21S2 of the power chip mounting portion 6 shown in FIG. In addition, (iii) it is also possible to use an insulating high heat conductive sheet or a high heat conductive adhesive to contact or bond only the aluminum substrate 11 of FIG. 1 to the second main surface of the power chip mounting portion. In some cases, there is also an advantage that the high thermal conductive insulating layer may be unnecessary. Of course, in any of such modified examples (i) to (iii),
It goes without saying that the same action and effect as those obtained in the first embodiment can be obtained.

(Modification 2) The first embodiment is a case in which n power chip mounting portions 6 _i are formed in alignment with one side of the lead frame 21, as shown in FIG. However, due to the design of the wiring pattern, there may be a case where the power chip mounting portion 6 _i cannot be integrated at a desired position on the lead frame 21. Even in such a case, the power chip mounting section and the other power chip mounting section can be connected to each other without interposing the arbitrary logic chip mounting section between the arbitrary power chip mounting section and the other power chip mounting section. Wiring patterns are designed to be adjacent to each other, and one common high thermal conductive metal substrate (for example, corresponds to the high thermal conductive metal substrate 10 of FIG. 1) on the second main surface of the adjacent power chip mounting portions. Structure) is disposed with a common high thermal conductive layer or separate high thermal conductive layers (for example, solder) interposed, the number of high thermal conductive substrates is equal to the total number of power chip mounting parts.
That is, the number can be reduced to less than n, and the power module can be further downsized and the cost can be flexibly changed according to various wiring patterns.

(Modification 3) In Embodiment 1, Modification 1 and Modification 2, as shown in FIG. 1, the other surface of the aluminum plate 11 constituting the high thermal conductive metal substrate is exposed from the surface of the mold package. However, when the power chip 1 having a relatively small heat generation amount is mounted, the mold resin 5 covers the entire metal substrate 10 so that the other surface of the aluminum plate 11 is not exposed. Is also good. In this case, there is an effect that package cracking due to heat generation of the power chip can be effectively prevented.

According to the first embodiment and the first to third modifications,
The power module according to the present invention has the following unique effects in addition to the above effects.

First, since the wiring pattern is formed as the lead frame 21 which is stamped and punched, the thickness and density of the wiring pattern can be set arbitrarily, which means that the electric resistance and thermal resistance of the wiring can be set arbitrarily. Means

The large degree of freedom in the design of the wiring pattern means that the thickness and density of the wiring pattern are appropriately designed when manufacturing various power modules having different standards such as current capacity. It is possible to flexibly cope with the situation by changing only the thickness of the lead frame material according to each standard without changing the structure or the structure of the power module itself.

Further, even in the case where a power transistor chip that generates a large amount of heat is mounted, the thermal resistance on the wiring side can be reduced by increasing the thickness of the wiring pattern. Even if the area of the power module is not changed, sufficient heat dissipation characteristics of the power module can be realized. As a result, the versatility of the high thermal conductive metal substrate having a predetermined area and the manufacturing process is improved.

In this way, it is possible to realize a power module which can meet the demand for further cost reduction from the viewpoint of manufacturing cost reduction in manufacturing power modules of various standards. Of.

When the description of the technical idea according to the first embodiment and the first to third modifications thereof is summarized, it can be recognized as the following relationship. That is, the high heat conductive metal substrate is a metal plate such as aluminum, or a high heat conductive insulating layer in which an insulating material such as silica particles having good heat conductivity is mixed with epoxy resin or the like on one main surface of the metal plate. And a substrate having a three-layer laminated structure in which a copper foil is formed on the surface of a high thermal conductive insulating layer formed on one main surface of a metal substrate.

Furthermore, the arrangement of the high thermal conductive metal substrate means
(I) A form in which the high heat conductive metal substrate and the second main surface of the power chip mounting portion are in contact with each other via an insulating high heat conductive sheet, (ii) high heat conductive sheet (in this case, insulating property) (Not limited to the above), the high heat conductive metal substrate and the second main surface of the power chip mounting portion are in contact with each other, and (iii) the high heat conductive adhesive has an insulating property. The conductive metal substrate and the second main surface of the power chip mounting portion are bonded to each other, and (iv) the high heat conductive adhesive (in this case, not limited to the insulating property), the high heat conductive metal substrate and the power. A mode in which the second main surface of the chip mounting portion is bonded, and further, (v) the high thermal conductive metal substrate is bonded to the second main surface of the power chip mounting portion via solder. The forms are collectively referred to.

In addition, the insulating high thermal conductive sheet in (i) above, the high thermal conductive sheet in (ii) above, the insulating high thermal conductive adhesive in (iii) above, and the high thermal conductive adhesive in (iv) above. The agent and the solder in the above (v) are collectively referred to as a high thermal conductive layer.

(Embodiment 2) The basic structure of the transfer mold type power module according to Embodiment 2 is the same as the structure of the module according to Embodiment 1 or Modifications 1 to 3 thereof. However, this module
It is characterized by a heat dissipation structure suitable for mounting a power chip having a relatively small heat generation capacity, particularly a structure of a high thermal conductive metal substrate functioning as a heat dissipation plate. Therefore, in the following description, the structure of the high thermal conductive metal substrate will be mainly described.

FIG. 6 is a vertical cross-sectional view schematically showing the structure of the module 51 in the same manner as in FIG. 1, and the same components as those of the module according to the first embodiment or the modifications 1 to 3 thereof. Are denoted by the same reference numerals, and description thereof will be omitted.
The same applies to FIGS. 7 and 8 described later.

As shown in FIG. 6, the high thermal conductive metal substrate 101, which is a feature of the module 51, is transferred on a whole surface of a metal plate, for example, an aluminum plate (aluminum heat sink) 111 having a thickness of 3 mm in a separate process. It is formed by using a mold sealing method, for example, by coating with a resin layer (thickness is, for example, 0.3 mm) made of, for example, epoxy mixed with silica filler, which is an insulating high thermal conductive material. Hereinafter, the resin layer will be referred to as a "high thermal conductive epoxy resin layer 121". The area of the high thermal conductive metal substrate 103 or the aluminum plate 111 is the same as that of the high thermal conductive metal substrate according to the first embodiment or the modified examples 1 to 3 described above.

Then, on the one main surface of the above-mentioned high thermal conductive metal substrate 101, and on the first main surface, components necessary for the configuration of the module such as the power chip 1 and the logic chip 4 are mounted, and predetermined wiring is provided. This module 51 is completed by mounting the lead frame 21 in a mold with the second main surface 21S2 of the power chip mounting portion 6 in contact therewith, and transfer-mold sealing with the semiconductor sealing mold resin 5. To do. At this time, the main surface of the high thermal conductive metal substrate 101 opposite to the one main surface (hereinafter referred to as “the other main surface”) is sealed so as to be exposed to the outside of the mold package.

As described above, the high thermal conductive epoxy resin layer 1
Since 21 contains a silica filler, good heat dissipation characteristics can be obtained. The same effect can be obtained by using a ceramic filler instead of the silica filler.

Further, since the high heat conductive epoxy resin layer 121 is formed by using the transfer molding method which is simple and low in cost, the high heat conductive metal substrate 101 can be manufactured with high productivity.

In addition, according to the high thermal conductive metal substrate 101, various heat dissipation characteristics can be realized only by changing the kind of resin or the content of filler such as silica.
There is no need to replace the molding die when manufacturing 01. Therefore, according to the method for manufacturing the high thermal conductive metal substrate 101 described above, it is possible to flexibly deal with power modules of various standards having different heat generation amounts.

The high heat conductive epoxy resin layer 121 on one main surface side of the high heat conductive metal substrate 101 has a function of insulating the lead frame 21 and the aluminum plate 111 from each other. In consideration of the heat dissipation characteristics of 101, it may be advantageous to expose the surface of the aluminum plate 111 to the outside of the mold package on the other main surface side of the high thermal conductive metal substrate 101.

Therefore, in such a case, instead of the high thermal conductive metal substrate 101, the high thermal conductive epoxy resin layer 121 is provided on the other main surface of the high thermal conductive metal substrate 101 as in the module 52 shown in FIG. If the high thermal conductive metal substrate 102 having no form is used, the heat dissipation through the exposed portion 133 can further improve the heat dissipation of the power module.

(Modification 1 of Embodiment 2) The module 53 according to the modification 1 shown in FIG.
Instead of the high heat conductive epoxy resin layer 121 of the high heat conductive metal substrates 101 and 102 in 1, 52, the high heat conductive metal substrate 103 having the ceramic layer 123 formed by an inexpensive manufacturing method is characterized.

As shown in FIG. 8, the high thermal conductive metal substrate 10 is used.
3 is an aluminum plate (aluminum heat sink) 1
A ceramic layer 123 (having a thickness of 0.1 mm, for example) made of alumina, for example, is formed on the entire surface of 11.
This alumina ceramic layer 123 is formed in a separate step by plasma spraying method using arc plasma as a heat source on the entire surface of the aluminum plate 111.

Further, like the modules 51 and 52 (see FIGS. 6 and 7, respectively), one main surface of the high thermal conductive metal substrate 103 and the power chip mounting portion 6 of the lead frame 21.
Is disposed in contact with the second main surface 21S2, and the main surface opposite to the one main surface (hereinafter referred to as "the other main surface") is exposed to the outside of the mold package. It is sealed as a form. Moreover, like the above-mentioned high thermal conductive metal substrate 102, a high thermal conductive metal substrate having no alumina ceramic layer 123 on the other main surface of the high thermal conductive metal substrate 103 may be used.

The process of forming the alumina ceramic layer 123 by the plasma spraying method described above does not require large-scale equipment and can be performed in the atmosphere, and therefore the process itself is a low cost process. I can say. Further, according to the manufacturing method, since it is possible to form the dense alumina ceramic layer 123 having high adhesion,
It is possible to obtain a high thermal conductive layer having good thermal conductivity,
Therefore, high heat dissipation characteristics can be exhibited.

If a high heat conduction characteristic is not required, a ceramic thin plate is used as the alumina ceramic layer 123 and is interposed between the lead frame 21 and the aluminum plate 111. A high thermal conductive metal substrate bonded to the main surface side (a main surface on the side corresponding to one main surface of the high thermal conductive metal substrate 103) may be used.

As described above, in the above-mentioned high heat conductive metal substrates 101, 102, 103 according to the second embodiment, the surface of the aluminum plate (heat sink) 111 is made of a high heat conductive epoxy resin layer 121 made of an insulating high heat conductive material. Alternatively, since the structure is covered with the alumina ceramic layer 123, the amount of the material used can be small. That is, the conventional metal substrate required an expensive ceramic plate material,
Highly thermally conductive metal substrates 101, 102, 1 according to the second embodiment
In No. 03, since the high thermal conductive layer is formed on the entire surface of the inexpensive aluminum plate or at least on one of the main surfaces by a low-cost manufacturing method using a small amount of the insulating high thermal conductive material, the expensive high thermal It is possible to reduce the amount of conductive material used, or not to use it at all. Therefore, the high thermal conductive metal substrates 101, 102, 10
Since 3 can reduce the material cost of the high heat conductive metal substrate as compared with the conventional metal substrate, it can be said that it is a heat dissipation plate that can contribute to the cost reduction of the power module.

Further, the high thermal conductive metal substrates 101, 102,
Since 103 is provided only on the second main surface 21S2 of the power chip mounting portion 6, a low heat conductive material such as the mold resin 5 can be used in other portions that do not require high heat dissipation characteristics. Therefore, the material cost of the entire module can be significantly reduced, and the cost of the power module can be reduced.

Further, the high thermal conductive metal substrates 101, 102,
According to 103, by appropriately selecting an insulating high heat conductive material suitable for the heat generation capacity of the power module or power chip, a wide range of power modules can be obtained without changing the shape and structure of the module and the high heat conductive metal substrate. Since it can be applied, the cost of the power module can be reduced from this point of view.

Now, the above-mentioned modules 51, 52, 53
In the above, the other main surface of the high thermal conductive metal substrates 101, 102, 103 is exposed to the outside of the mold package. However, the power chip 1 having a small heat generation amount as in the second embodiment and its modification 1 is used. When the module is mounted, like the module according to the third modification of the first embodiment described above,
High heat conductive metal substrates 101, 102, 1 with molding resin 5
It is good also as a structure which covers the whole 03. In this case, there is an effect that package cracks due to heat generation of the power chip 1 can be effectively prevented.

The power modules 51, 52, 5
3 has been described as a specific example of a structure suitable for mounting a power chip having a relatively small amount of heat generation due to the surface state of the high thermal conductive metal substrates 101, 102, 103. It goes without saying that if 101, 102, and 103 are arranged via the high thermal conductive layer according to the first embodiment or the first modified example thereof, it can be applied to a power module having a relatively large heat generation amount.

Further, also in the power module according to the first modification of the first embodiment, when the power chip 1 having a relatively small heat generation amount is mounted, the high thermal conductive sheet according to the first modification of the first embodiment. The high thermal conductive metal substrate according to the first modification of the first embodiment may be arranged on the second main surface 21S2 of the power chip mounting portion 6 without interposing the above or the like.

Further, the power modules 51, 52, 5
It goes without saying that the third embodiment can also obtain the effect of further downsizing and cost reduction of the power module due to the lead frame 21 as in the first embodiment and the second modification thereof.

The characteristic part of the present invention clarified in the above-described second embodiment and its first modification can be grasped bilaterally as follows.

(A) First, the high thermal conductive metal substrates 101, 1
02 and 103 are provided on at least one of the main surfaces in the upward direction so as to have a high thermal conductive epoxy resin layer 121 or an alumina ceramic layer 123.
When considered as an integrated structure made of a metal plate (aluminum plate 111) having an insulating high heat conductive layer, the high heat conductive metal substrates 101, 102 and 103 are the second main parts of the wiring pattern excluding the logic chip mounting portion 7. Surface 21S
2 has a shape that can be arranged in the upper direction, and "directly contacts" the second main surface 21S2 of the power chip mounting portion 6
Can be said to be doing.

Therefore, a metal plate having an insulating high thermal conductive layer on at least one main surface is further added to the concept of the “high thermal conductive metal substrate” according to the first embodiment and the modifications 1 to 3 thereof. Then, similarly, the "arrangement of the high thermal conductive metal substrate" may include a mode in which the high thermal conductive metal substrate and the second main surface of the power chip mounting portion are in "direct contact".

On the contrary, the above-described first embodiment and its modification 1
When the “high heat conductive layer” and the metal plate according to 3 to 3 are regarded as a “high heat conductive metal substrate” as an integrated structure, the high heat conductive metal substrate is the second main surface of the wiring pattern excluding the logic chip mounting portion. The second main surface 21S2 of the power chip mounting portion 6 has a shape that can be arranged in the upward direction.
It is also possible to describe the above as being in "direct contact".

(B) On the other hand, high thermal conductive metal substrates 101, 1
Regarding Nos. 02 and 103, the insulating high thermal conductive layer such as the high thermal conductive epoxy resin layer 121 or the alumina ceramic layer 123 formed on at least one main surface of the aluminum plate 111 is formed according to the above-described first embodiment and its modification. When newly added as one form of the “high thermal conductivity layer” according to Examples 1 to 3, in the power module according to the second embodiment and its modification 1, a metal plate such as an aluminum plate is newly added as the “high thermal conductivity metal”. The high thermal conductive metal substrate is referred to as a “substrate”, and the high thermal conductive metal substrate is connected to the second substrate of the power chip mounting portion via the high thermal conductive layer.
The form in which the main surface is in contact can be regarded as one form of the “arrangement of the high thermal conductive metal substrate” according to the above-described Embodiment 1 and Modifications 1 to 3 thereof.

[0084]

(1) According to the invention of claim 1,
Since the lead frame is press-punched in a mode involving a wiring pattern of a predetermined electric circuit, a wiring pattern for flowing a large current can be easily formed, as compared with the case of a conventional copper foil wiring. As a result, there is an advantage that a power module structure capable of simplifying the manufacturing process can be provided.

In addition, according to the first aspect of the invention, since the lead frame itself is provided with the wiring pattern of the predetermined electric circuit in which the region for mounting the power transistor chip and the like is formed, Wiring having a sufficiently large cross-sectional area can be formed as compared with the case of foil wiring. As a result, the electrical resistance and thermal resistance of the wiring through which a large current flows is significantly reduced, so that it is possible to promote the densification of the wiring pattern and further promote the miniaturization of the power module. Become.

Moreover, according to the first aspect of the present invention, the thickness or cross-sectional area of the wiring pattern can be arbitrarily set by changing the thickness of the lead frame material, so that the electrical resistance and thermal resistance of the wiring can be arbitrarily set. Can be set. This is
It is possible to properly design the thickness and density of the wiring pattern according to the standard such as the current capacity required for each power module, which can promote the miniaturization of power modules of various standards. Bring about the effect.

Further, according to the first aspect of the present invention, the thickness of the wiring pattern, and thus the electrical resistance and thermal resistance of the wiring can be arbitrarily set by changing the thickness of the lead frame material. The action effect also produces the following effect. That is, the above-mentioned arbitrary design does not require the manufacturing process, the wiring structure, or the structure of the power module itself to be changed when manufacturing various power modules with different standards, and the thickness of the lead frame material is changed according to each standard. The effect of being able to respond flexibly by changing only the height is achieved. As a result, the versatility of the manufacturing process and the power module structure can be ensured for the manufacture of power modules of various standards, and the effect that a power module that can sufficiently satisfy the demand for reduction in manufacturing cost can be achieved is obtained. To be

Moreover, according to the first aspect of the invention, the fact that the thermal resistance of the wiring can be arbitrarily designed can reduce the heat radiation amount from the transfer mold encapsulant as compared with the conventional power module. It also has an effect.
That is, since the heat radiation characteristics of the wiring itself can be improved by realizing the wiring with low thermal resistance, the heat radiation amount through the transfer mold sealing material can be reduced.

Further, according to the invention of claim 1, a plurality of
Power chip mounting part, that is, multiple power chips
Since multiple high heat conductive metal substrates are not installed,
Compared to the case where heat conductive metal substrates are individually arranged,
(I) High thermal conductivity High thermal conductivity because the number of metal substrates is reduced
The material cost of the metal substrate can be reduced, and (ii) gold
Manufacturing cost is reduced because the number of metal substrate installation steps is reduced
it can. Due to the effects of (i) and (ii), power is increased.
The cost reduction of the module can be promoted.

(2) According to the invention of claim 2,
A power module that has a heating plate over the wiring pattern.
Reduce the volume of high thermal conductive metal substrate compared to
It is possible to reduce the cost of the high thermal conductive metal substrate.
And the compactness of the power module itself
The effect that can be realized is also brought about.

[0091]

[0092]

[0093]

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a power module according to a first embodiment of the present invention.

FIG. 2 is a top view showing a lead frame according to the first embodiment of the present invention.

FIG. 3 is a top view showing the power module according to the first embodiment of the present invention.

FIG. 4 is a vertical sectional view showing a manufacturing process of a power module according to a conventional technique.

FIG. 5 is a vertical sectional view showing a power module according to another conventional technique.

FIG. 6 is a vertical sectional view showing a power module according to a second embodiment of the present invention.

FIG. 7 is a vertical sectional view showing a power module according to the second embodiment of the present invention.

FIG. 8 is a vertical sectional view showing a power module according to a second embodiment of the present invention.

[Explanation of symbols]

1 power transistor chip, 2 logic chip,
3 thick aluminum wire, 4 thin aluminum wire, 5 mold resin, 6 power transistor chip mounting part, 7 logic chip mounting part, 10 high thermal conductive metal substrate, 11 aluminum plate, 12 high thermal conductive insulating layer, 13 copper foil, 14 solder, 21 lead frame,
21S1 Lead frame first main surface, 21S2 Lead frame second main surface, 51, 52, 53 Power module, 101, 102, 103 High thermal conductive metal substrate, 111
Aluminum plate, 121 high thermal conductive epoxy resin layer,
123 Alumina ceramic layer.

Front page continuation (72) Inventor Hisashi Kawafuji 2-3-3 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Co., Ltd. (56) Reference JP-A-9-153572 (JP, A) JP-A-8-116012 ( JP, A) Actual Kaihei 5-15449 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 25/00-25/18

Claims (2)

(57) [Claims] 1. A transfer mold-sealed power module, comprising: a first main surface and a second main surface facing the first main surface;
By punching between the first main surface and the second main surface, a wiring pattern of a predetermined electric circuit including a plurality of power chip mounting portions, logic chip mounting portions, lead portions, and tie bar portions is formed. A lead frame, a plurality of power transistor chips mounted on the first main surface of the plurality of power chip mounting portions of the wiring pattern, and a first main surface of the logic chip mounting portion of the wiring pattern onboard, the logic chip that controls the power transistor chip, are disposed to the plurality of power chip mounting portion hyperthermia
And a conductive metal substrate, wherein the high thermal conductive metal substrate is arranged on the second main surface of each power chip mounting portion in this order.
Placed solder and copper foil, and the copper foil and solder on each power chip mounting part
Commonly arranged and arranged in this order on the copper foil.
And a high heat conductive insulating layer and a metal plate . 2. The power module according to claim 1, wherein the high thermal conductive layer and the metal plate are the plurality of power chucks.
Power module, which is provided locally on the mounting part .