JP3418617B2 - Heat conductive substrate and semiconductor module using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board used in various electric and electronic devices and a semiconductor module using the same, and is particularly suitable for devices in which heat dissipation is strongly required, such as in the field of power electronics. The present invention relates to a heat conductive substrate.

[0002]

2. Description of the Related Art In recent years, with the demand for higher performance and smaller size of electronic equipment, higher density and higher functionality of semiconductors have been demanded. As a result, in order to mount them, it is desired that the circuit board also has a small size and high density. As a result, it has become important to design the circuit board in consideration of heat dissipation. As a technique to improve the heat dissipation of the circuit board, a metal plate such as copper or aluminum is used for the conventional glass-epoxy resin printed circuit board, and a circuit pattern is formed on one or both sides of this metal plate with an electrical insulation layer interposed. There is known a metal-based substrate that forms a substrate. Further, when higher thermal conductivity is required, a substrate in which a copper plate is directly bonded to a ceramic substrate such as alumina or aluminum nitride is used. A metal base substrate is generally used for relatively low power applications, but the electrical insulating layer must be thin in order to improve heat conduction, and is susceptible to noise between the circuit pattern and the metal plate. And the dielectric strength.

In order to solve these problems, in recent years, there has been proposed a substrate in which a resin-filled composition having a good thermal conductivity is integrated with a lead frame which is an electrode.
A substrate using such a composition is proposed in, for example, JP-A-10-173097. The manufacturing method of the heat conductive substrate is shown in FIG. According to this, a mixture slurry containing at least an inorganic filler and a thermosetting resin is formed into a film to prepare a sheet-shaped heat conduction mixture 72,
After it is dried, it is superposed on the lead frame 71 as shown in FIG. 7 (a), and then heated and pressed as shown in FIG. 7 (b) to cure the sheet-like heat conduction mixture 72 to cure the electrically insulating layer. The heat conducting substrate 74 is set to 73.

In a substrate intended to improve such heat dissipation, a semiconductor module manufactured using this substrate is brought into contact with an external heat dissipation member to quickly dissipate heat generated from the semiconductor and each component to the outside. Transmitted to the member,
It is common to use the semiconductor and each component so that the temperature does not exceed a certain value. For this purpose, a heat dissipation plate having a high thermal conductivity is often provided on the contact surface of the substrate with the external heat dissipation member.

In this case, it is important to firmly fix the heat radiating plate of the circuit board and the external heat radiating member, and to sufficiently contact them to reduce the thermal resistance between them. As a method of fixing the semiconductor module to the external heat dissipation member, screwing or the like is generally performed, and screw holes or through holes are formed at four corners or sides of the semiconductor module, that is, four corners and / or sides of the circuit board. A hole is provided and fixed to the external heat dissipation member. Further, in order to reduce the thermal resistance between the circuit board and the external heat dissipation member, it is common to apply a thin silicone compound or the like having relatively good thermal conductivity between them and then fix them.

[0006]

As described above, in order to fix the circuit board or the semiconductor module using the circuit board to the external heat dissipation member, and at the same time to improve the contact property and reduce the thermal resistance, the flatness of the circuit board is required. Becomes important. This is because when the warpage of the circuit board is large, a gap is inevitably formed between the two and the thermal resistance between them becomes high. Especially when the circuit board is warped in the concave direction when viewed from the heat dissipation plate side, if the warp is large, it does not contact at the center part even if it contacts at the four corners or sides that fix the board to the external heat dissipation member. As a result, there is a problem that the thermal resistance becomes high and the temperature of the module becomes too high, so that an operation abnormality or a component failure is likely to occur. Conversely, if the circuit board is warped in the convex direction when viewed from the heat dissipation plate side, the contact between the circuit board and the external heat dissipation member will be good, but stress will occur between them when fixing, and the insulating layer There is a problem that cracks and cracks occur, and peeling occurs between the wiring pattern or the heat sink and the insulating layer.

Further, the step of fixing the circuit board of the semiconductor module to the external heat radiation member is usually performed at room temperature, but since the circuit board is a structure in which different materials are laminated in layers,
The warpage of the substrate changes depending on the temperature. Therefore, although the contact with the external heat radiation member was almost sufficient when the circuit board was fixed, the board was warped due to the temperature rise during the operation of the semiconductor module, and the contact was lost. There was a problem that led to the thermal runaway of.

Further, in the case where the warp of the substrate changes depending on the temperature, if the change of the warp is large, the stress generated in the substrate when the substrate is fixed to the external heat dissipation member becomes large, and as a result, the substrate is cracked or cracked. However, there are problems such as poor insulation and reduced reliability.

The present invention has been made in order to solve these problems, and keeps the thermal resistance sufficiently low when the circuit board is fixed to the external heat dissipation member and used, especially when the circuit board is operated at high temperature. In this case, the contact between the module and the external heat dissipation member is strengthened to maintain a low thermal resistance, and a highly reliable heat conductive substrate and a semiconductor module using it, which does not cause the substrate to crack or crack. The purpose is to get.

[0010]

In order to achieve the above object, a heat conductive substrate of the present invention includes a wiring pattern, an electric insulating layer and a heat dissipation plate, and the electric insulating layer is an inorganic filler.
A heat-conducting substrate comprising a heat-conducting mixture containing 70 to 95% by weight and a thermosetting resin in an amount of 5 to 30% by weight, the heat-conducting substrate being used by fixing the heat-dissipating plate to an external heat-dissipating member. The size of the warp at room temperature after mounting the components of the heat conductive board is 1/500 or less with respect to the board length, and the warp of the heat conductive board increases as the temperature of the heat conductive board increases. It is characterized in that it changes in a convex direction. In the above, room temperature refers to a range of 0 ° C to 40 ° C.

Next, in the semiconductor module of the present invention, a semiconductor element and a passive component having a circuit function are mounted on the heat conducting substrate, and the heat conducting substrate is externally mounted on a portion selected from a vertex portion and a side portion. It is characterized in that a connector for fixing to the heat dissipation member is provided. The connector may be in the shape of a hole into which a screw-fastened member can be fitted, or may be another fixing means.

[0012]

According to the heat conductive substrate of the present invention, even when the semiconductor device mounted on the heat conductive substrate operates and the temperature rises, the substrate is pressed against the external heat dissipation member. As a result, not only sufficient contact between the substrate and the external heat dissipation member can be obtained, but also the thermal pressure can be lowered by the pressing pressure, and high heat dissipation and reliability can be provided. Further, depending on the surface state of the heat dissipation plate and the external heat dissipation member, it is possible to omit the heat dissipation member such as a heat dissipation compound or a resin sheet which is usually used between the substrate and the external heat dissipation member.

Further, in the heat conducting board of the present invention, the size of the warp at room temperature after the component mounting of the heat conducting board to the external heat dissipation member is 1/500 or less with respect to the board length. Within this range, when the substrate is attached to the external heat dissipation member, the gap between them becomes sufficiently small, and the heat dissipation to the outside becomes good.

Further, in the heat conductive substrate of the present invention, it is preferable that the heat dissipation plate of the heat conductive substrate has a coefficient of linear expansion larger than an average coefficient of linear expansion of the wiring pattern and the electric insulating layer.
As a result, when the temperature rises, the dimension of the heat sink becomes larger than that of the wiring pattern and the electric insulating layer, and as a result, the warp of the heat conducting substrate becomes convex toward the heat sink as the temperature rises. As a result, it becomes possible to improve heat dissipation from the substrate to the external heat dissipation member when the temperature rises.

Further, in the heat conductive substrate of the present invention, the linear expansion coefficient α1 of the heat dissipation plate of the heat conductive substrate is larger than the linear expansion coefficient α2 below the glass transition point of the electrical insulating layer, and the linear expansion coefficient α2. Is preferably larger than the linear expansion coefficient α3 of the wiring pattern. According to this, as described above, when the temperature rises, the heat dissipation plate expands more in size than the electric insulating layer and the wiring pattern, and the electric insulating layer expands more in size than the wiring pattern. As the temperature rises, the warp of the heat conducting substrate becomes convex toward the heat radiating plate, and the heat dissipation from the substrate to the external heat radiating member can be improved. Further, since α2 falls between α1 and α3, the stress due to the mismatch of the linear expansion coefficient between the respective layers becomes smaller as compared with the case where this magnitude relationship is not satisfied, and as a result, a highly reliable substrate which is not easily damaged is obtained. be able to.

In the heat conductive substrate of the present invention, it is preferable that the heat conductive mixture constituting the electric insulating layer has an elastic modulus of 50 GPa or less at room temperature. When it is fixed to the external heat dissipation member so as to suppress the warp generated in the heat conductive substrate, stress is applied to the heat conductive substrate, and cracks easily occur in the heat conductive mixture that is the electrical insulating layer. If it is not actually used, cracks do not occur and a highly reliable substrate can be obtained.

Further, in the heat conductive substrate of the present invention, it is preferable that the electric insulating layer contains a reinforcing material. Further, it is preferable that the reinforcing material is a glass nonwoven fabric. The inclusion of the reinforcing material improves the mechanical strength and workability of the electrical insulating layer, and makes it possible to greatly adjust the linear expansion coefficient. In particular, the reinforcing material is preferably a glass nonwoven fabric from the viewpoints of thermal conductivity, cost, and substrate manufacturability.

Further, in the heat conductive substrate of the present invention, it is preferable that the wiring pattern is filled up to the gap portion with the electric insulating layer so as to have a substantially flat surface. Such a board is easy to mount components, and the solder resist treatment for mounting can be performed in the same printing step as a conventional printed board, which is industrially advantageous.

Further, in the heat conductive substrate of the present invention, the thickness of the electric insulating layer is preferably 0.4 mm or more. According to this, reinforced insulation is provided between the heat sink and the wiring pattern.

Further, in the heat conductive substrate of the present invention, it is preferable that the wiring pattern is composed of a lead frame and is used as an external terminal.

Further, in the heat conductive substrate of the present invention, the heat dissipation plate is preferably made of aluminum, copper, or an alloy containing these as the main components.

The semiconductor module of the present invention is a power module, which includes a switching power supply module, D
It is preferably at least one selected from the group consisting of a C-DC converter module, an inverter module, a power factor correction module, and a rectifying / smoothing module.
These modules have a power conversion function, and generate a large amount of heat because they normally handle a large amount of power. In addition, it is often used by fixing it to an external heat dissipation member. Therefore, the effect of using the heat conductive substrate of the present invention is enhanced.

Each embodiment of the heat conductive substrate of the present invention will be specifically described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a cross-sectional view showing the structure of a heat conductive substrate according to an embodiment of the present invention. This substrate has a lead frame 11 as a wiring pattern.
And an electric insulating layer 12 and a heat dissipation plate 13. The electric insulating layer 12 is composed of a heat conduction mixture containing an inorganic filler and a thermosetting resin. Inorganic filler ratio is 7
It is preferably from 0 to 95% by weight, particularly from 85 to 95
More preferably, it is wt%. When the compounding ratio of the inorganic filler is smaller than this range, the heat dissipation of the substrate becomes poor. Furthermore, when the inorganic filler ratio is low, the linear expansion coefficient of the electric insulating layer 12 becomes large, and it becomes impossible to obtain the effect that the warp of the substrate becomes convex toward the heat dissipation plate as the temperature rises. On the other hand, when the amount is more than this range, the fluidity of the heat conductive resin composition is lowered and the wiring pattern 11 and the heat sink 1
It becomes difficult to integrate with 3.

The inorganic filler may be appropriately selected from those having excellent insulation and thermal conductivity, and particularly Al ₂ O ₃ and M
gO, BN, Si ₃ N ₄ , AlN, SiO ₂ and SiC
It is preferable to contain at least one kind of powder selected from the following as a main component. This is because these powders have excellent thermal conductivity, and it becomes possible to manufacture a substrate having a high heat dissipation property. Especially when Al ₂ O ₃ or SiO ₂ is used,
Mixing with the thermosetting resin becomes easy. Further, when AlN is used, the heat dissipation property of the heat conductive substrate is particularly high. Further, the average particle size of the inorganic filler is preferably in the range of 0.1 to 100 μm. If the particle size is out of this range, the filling property of the filler and the heat dissipation property of the substrate tend to decrease.

As the main component of the thermosetting resin in the heat conduction mixture, for example, epoxy resin, phenol resin and isocyanate resin can be used, and it is preferable to select and use at least one of these resins. This is because these resins each have excellent heat resistance, mechanical strength, and electrical insulation. As a method for producing the heat conductive mixture, the respective raw materials may be weighed and mixed. As a mixing method, for example, a ball mill, a planetary mixer or a stirrer can be used.

The elastic modulus of the electrical insulating layer at room temperature is 5
It is preferably 0 GPa or less, particularly 25 GPa
More preferably, it is 40 GPa or less. This is because if the elastic modulus is too high, the electric insulating layer becomes hard and brittle, and if the temperature of the substrate changes or stress increases during reflow soldering, cracks and the like are likely to occur. It should be noted that the room temperature in the present invention indicates a range of 0 ° C to 40 ° C.

The wiring pattern 11 may be made of a metal having a high conductivity, but copper, iron, nickel, aluminum or an alloy containing them as a main component can be used, and these are preferable because of their low resistance. The pattern forming method of the wiring pattern 11 is not particularly limited, and for example, an etching method or a punching method can be used. The surface of the wiring pattern 11 is preferably plated with at least one metal or alloy selected from nickel, tin, solder, gold and palladium. This is because the plating improves the corrosion resistance and oxidation resistance of the wiring pattern 11 and improves the adhesion with the heat conductive resin composition, thereby improving the reliability of the heat conductive substrate.

Furthermore, it is preferable that the surface of the wiring pattern 11 to be bonded to the heat conductive resin composition is roughened. This is because the adhesive strength is improved and the reliability is improved. The roughening method is not particularly limited, and blast treatment, etching treatment or the like can be used.

The heat dissipation plate 13 may be appropriately selected depending on the thermal conductivity and the coefficient of thermal expansion. For example, a metal selected from aluminum, copper, iron, nickel or an alloy plate thereof can be used, and particularly aluminum or copper. Is preferred. This is because these have a high coefficient of linear expansion, and as the temperature rises, the warp of the substrate tends to be convex toward the heat sink.

Further, at the time of heating and pressurizing as described above, it is preferable that the heat conduction mixture is filled up to the gap portion of the lead frame so that the surface becomes substantially flush. This is because the flatness facilitates post-processing such as leveling processing and solder resist processing on the substrate surface, and also improves mountability when mounting components between circuit patterns.

The thickness of the electrical insulation layer (wiring pattern-
The thickness between the heat sinks) is preferably 0.4 mm or more. This is because in this case, reinforced insulation is provided between the wiring pattern and the heat dissipation plate, which is suitable as a substrate used in the field of power electronics.

2A to 2D are cross-sectional views by step showing a method of manufacturing the heat conductive substrate according to the embodiment of the present invention shown in FIG. In FIG. 2 (a), 21 is a lead frame to be a wiring pattern, and 22 is an inorganic filler 70 to 95% by weight.
And 23 is a heat dissipation plate. When these are superposed as shown in FIG. 2 (a) and heated and pressed, as shown in FIG. 2 (b), the heat conduction mixture 22 is filled up to the gap portion of the lead frame 21 to form a substantially flush surface. At the same time, the thermosetting resin in the heat-conducting mixture 22 is cured to form the rigid electric insulating layer 24. At the same time, the electric insulating layer 22 and the heat dissipation plate 23 are adhered to each other, and the heat conductive substrate 25 is obtained. After that, solder resist printing, lead frame cutting, terminal processing, component soldering, and the like are performed as necessary. As a method of printing the solder resist, for example, a method of printing a solder resist ink by a screen printing method and curing it can be used. As the solder resist ink, for example, a commercially available thermosetting ink can be used. The frame cutting is performed to divide the connected external terminals, and a method such as cutting with a die or cutting with shirring can be used. The method using the terminal treatment includes a treatment for using the cut terminal as an external terminal,
For example, bending and plating of the terminals can be mentioned.

It is preferable to use the lead frame as the wiring pattern as in this embodiment because the wiring pattern can be thickened and the loss due to the electric resistance can be reduced. Since it can be used as a lead-out terminal, it is not necessary to separately connect an external lead-out terminal, and it is preferable in that loss due to connection resistance does not occur.

(Embodiment 2) FIGS. 3A to 3C are cross-sectional views for each step showing a method for manufacturing a heat conductive substrate according to another embodiment of the present invention. In FIG. 3 (a), 31 is a metal foil, 32 is the same heat conduction mixture as in the first embodiment,
Reference numeral 33 is a radiator plate similar to that of the first embodiment. When these are superposed on each other as shown in FIG. 3 (a) and heated and pressed, the thermosetting resin in the heat conduction mixture 32 is cured to become the electric insulating layer 34 as shown in FIG. The foil 31 and the heat dissipation plate 33 are bonded and integrated. Then Fig. 3
As shown in (c), the metal foil 31 is patterned into the wiring pattern 35, and the heat conductive substrate 36 is completed. After that, if necessary, solder resist printing, soldering of external lead terminals or parts, etc. are performed, but these can be performed by a conventionally known technique.

As the metal foil, a metal having a high conductivity may be used as in the first embodiment. For example, copper, iron, nickel, aluminum, or an alloy containing them as a main component can be used. It is preferable because of its low resistance. The patterning method is not particularly limited, and for example, a chemical etching method can be used.

(Embodiment 3) FIGS. 4A to 4C are cross-sectional views by process showing a method of manufacturing a heat conductive substrate according to another embodiment of the present invention. In FIG. 4A, the metal foil 41 is bonded onto the release film 43 via the adhesive layer 42. This metal foil 41 is patterned as shown in FIG. 4 (b) to form a wiring pattern 44, which is turned in the opposite direction,
As shown in FIG. 4C, the heat conduction mixture 45 and the heat dissipation plate 46 similar to those of the first embodiment and the wiring pattern 44 in this order.
Are in contact with the heat-conducting mixture 45.
By heating and pressurizing this, as shown in FIG. 4D, the thermosetting resin in the heat conduction mixture 45 is cured to become the electric insulating layer 47, and at the same time, the wiring pattern 44 and the heat dissipation plate 46.
Are bonded and integrated. After that, the release film 43 and the adhesive layer 42 are removed to complete the heat conductive substrate 48 as shown in FIG. In this case as well, printing of solder resist and soldering of the external lead-out terminals and components are then performed, if necessary, but these can be performed by conventionally known techniques.

The release film 41 may be one that can withstand heating and pressurization and can be removed thereafter. For example, PPS (polyphenylene sulfide),
A synthetic resin film such as PPE (polyphenylene ether) or a metal foil such as a copper foil or an aluminum foil can be used. Further, as the adhesive layer 42, it is sufficient that the metal foil 41 is not peeled off at the time of patterning shown in FIG. 4B and can be peeled and removed in the step shown in FIG. 4E. For example, a urethane adhesive, An organic adhesive such as an epoxy adhesive or a metal layer such as a nickel phosphorus layer can be used.

The patterning method is not particularly limited, and a method such as chemical etching can be used. Also,
At the time of heating and pressurization shown in FIG.
Is preferably filled to cover the end face portion of the wiring pattern 44. Further, as in the case shown in FIG. It is more preferable that they become one. This is because the flatness facilitates post-processing such as leveling processing and solder resist processing on the substrate surface, and also improves mountability when mounting components between circuit patterns. Also, the adhesion between the circuit pattern and the electrically insulating layer is improved.

(Embodiment 4) FIGS. 5A to 5C are cross-sectional views by step showing a method of manufacturing a heat conductive substrate according to another embodiment of the present invention. In FIG. 5A, metal foils 51 similar to those in the above embodiment are prepared on both sides of the heat conduction mixture 52. These are heated and pressed to cure the heat conduction mixture to form the electric insulating layer 53, and the double-sided plate with the metal foil 51 as shown in FIG. 5B is manufactured. Next, a through hole 54 as shown in FIG. 5C is provided in this double-sided plate, and as shown in FIG. 5D, the through hole 54 is plated to form a through hole 55. Thereafter, as shown in FIG. 5E, the metal foils 51 on both sides are patterned to form a wiring pattern 56, and a double-sided wiring board 57 is manufactured. Next, the double-sided wiring board 57, the heat conduction mixture 52, and the heat dissipation plate 58 similar to that of the first embodiment are installed in FIG.
When they are stacked in this order as shown in (f) and heated and pressed, the heat conduction mixture 52 is cured and the double-sided wiring board 57 and the heat dissipation plate 58 are integrated as shown in FIG. 5 (g). A heat conductive substrate 59 having two layers of wiring patterns 56 is completed. In this case as well, printing of solder resist and soldering of the external lead-out terminals and components are then performed, if necessary, but these can be performed by conventionally known techniques.

Any known plating technique may be used, and for example, electrolytic copper plating or electroless copper plating can be used. Furthermore, in the present embodiment, the plated through holes are used as the interlayer connection method for the double-sided plates, but this method is not always necessary, and methods such as via formation with conductive paste and interlayer connection with metal posts are available. Further, as the patterning method, the same method as in the third embodiment can be used.

(Embodiment 5) FIG. 6A is a sectional view showing a structure of a semiconductor module according to an embodiment of the present invention, and FIG. 6B is an external view thereof. Figure 6
In (a), the same heat conductive substrate as that shown in FIG. 1 is used, where 61 is a heat dissipation plate, 62 is a wiring pattern, and 63 is an electrical insulating layer. Wiring pattern 6
The end portion of 2 is cut, bent and used as an external extraction electrode 64. The semiconductor element 65a and the passive component 66a are mounted on the heat conductive substrate. The semiconductor element 65b and the passive component 66b are also mounted on another circuit board 67 to form a control circuit. This circuit board 67 is inserted into the external extraction electrode 64,
It is connected to the circuit on the heat conducting substrate. As shown in FIG. 6B, board fixing components 68 having through holes for fixing to an external heat dissipation member are attached to the four corners of the heat dissipation plate 61 to protect these circuits. The case 69 is attached so as to cover the circuit board and the components to form the semiconductor module 70.

The circuit board 67 is not particularly limited, and for example, a generally used printed wiring board such as a glass epoxy board or a paper phenol board can be used. The method for mounting the semiconductor element and the passive component is not particularly limited, and for example, a method by soldering or a method by wire bonding can be used.

As the case 69, the external extraction electrode 6 is used.
It suffices if the electrical insulation between the four is maintained, and a molded product such as PC (polycarbonate) or PPS (polyphenylene sulfide) can be used. If desired, the inside of the case may be sealed in order to enhance the airtightness and heat dissipation of the circuit. As the sealing material, for example, silicone or urethane can be used. However, it is not always necessary to use the case as long as the insulation between the parts and the terminals can be maintained.

The board fixing component 68 is not limited to the post-shaped component having the through hole as shown in FIG. 6, but a post-shaped component having a screw hole or the like can be used. Further, if the semiconductor module can be fixed to the external heat radiation member at the end portion or the side portion, it is not always necessary to mount the substrate fixing component, and for example, the heat radiation plate may be provided with a through hole or a notch.

In each of the above-described embodiments, in order to exert the effect of the present invention, the size of the warp at room temperature after mounting the components of the heat conductive substrate on the external heat dissipation member is 1/200 of the substrate length. It is preferably below, and particularly preferably 1/500 or below. Normal,
The contact surface of the external heat dissipation member with the substrate is often a flat surface, and in that case, the warp with respect to the flat surface can be replaced with the warp with respect to the external heat dissipation member. As means for controlling the warpage, for example, a method of controlling the shape by using a mold in a heating and pressurizing step of manufacturing a substrate, a method of cooling from a heated state to a room temperature state while applying pressure, and a method after the heating and pressurizing step Further, a method of annealing while applying pressure can be used.

In addition, in each of the above-mentioned embodiments, in order to exert the effect of the present invention, the wiring pattern, the electric insulating layer and the heat dissipation plate must be appropriately selected according to the magnitude of their linear expansion coefficient. For this selection method,
The coefficient of linear expansion of the heat sink is preferably larger than the average coefficient of linear expansion of the wiring pattern and the insulating layer. In particular, the coefficient of linear expansion α1 of the radiator is smaller than the coefficient of linear expansion α2 of the electrical insulating layer below the glass transition point. Large and the linear expansion coefficient α2
Is more preferably larger than the linear expansion coefficient α3 of the wiring pattern. When the coefficient of linear expansion of the heat sink is larger than the average coefficient of linear expansion of the wiring pattern and the insulating layer, the warp of the heat conducting board becomes convex toward the heat sink as the temperature rises due to the difference in the coefficient of linear expansion. Because it is easy to change. The average coefficient of linear expansion in this case means a weighted average of the coefficients of linear expansion of the wiring pattern and the electric insulating layer by the thickness of each layer. Further, when the linear expansion coefficient α1 of the heat sink is larger than the linear expansion coefficient α2 below the glass transition point of the electric insulation layer and the linear expansion coefficient α2 is larger than the linear expansion coefficient α3 of the wiring pattern, As the temperature rises due to the difference in temperature, the warp of the heat conductive substrate tends to change toward the heat dissipation plate side, and it also occurs in the electrical insulation layer due to the difference in the coefficient of thermal expansion between the heat dissipation plate and the wiring pattern. The stress becomes relatively small, and cracks in the electric insulating layer caused by the stress and peeling between the electric insulating layer and the wiring pattern or heat sink are prevented,
A highly reliable heat conductive substrate can be manufactured.

In making the above selection, the heat dissipation plate is preferably aluminum, copper, or an alloy containing at least one of these as the main component. These are not only excellent in mechanical strength and have high thermal conductivity, but also have a relatively large coefficient of thermal expansion, so as the temperature rises, it is easy to change the warp of the heat conductive substrate so that it becomes convex toward the heat sink,
In addition, it is easy to select the wiring pattern and the electrically insulating layer.

In each of the above-mentioned embodiments, the heat conduction mixture is preferably processed into a sheet. This is because it is easy to handle, and it is easy to heat and pressurize and integrate with the wiring pattern and the heat dissipation plate. As a method of processing into a sheet, for example, a doctor blade method, a coater method, or an extrusion method can be used.

Further, in each of the above-mentioned embodiments, the electric insulating layer may contain a reinforcing material, the strength and workability of the insulating layer are improved, and the inclusion of the reinforcing material leads to a linear expansion coefficient. It is preferable because it can be controlled. As a reinforcing material,
For example, glass woven cloth, glass non-woven cloth, ceramic non-woven cloth and aramid non-woven cloth can be used, and glass woven cloth, glass non-woven cloth and ceramic non-woven cloth are preferable because of their high thermal conductivity. Further, a glass non-woven fabric is more preferable because it is easy to bury the wiring pattern in the electrically insulating layer.

[0051]

EXAMPLES The heat conducting substrate and the method for producing the same according to the present invention will be described below in more detail with reference to specific examples.

Example 1 In order to prepare a heat-conducting mixture used for carrying out the present invention, an inorganic filler and a thermosetting resin composition were mixed and processed into a slurry. The composition of the mixed heat conduction mixture is shown below. (1) Inorganic filler: Al ₂ O ₃ (AS-40, Showa Denko KK, average particle size 12 μm) 89% by weight (2) Thermosetting resin: Brominated polyfunctional epoxy resin (NVR-1010) , Nippon Lec Co., Ltd., including curing agent) 10% by weight (3) Other additives: curing accelerator (imidazole, Nippon Lec Co., Ltd.) 0.05% by weight, carbon black (Toyo Carbon Co., Ltd.) 0.4% by weight, coupling agent (Plenact KR-46B, manufactured by Ajinomoto Co., Inc.)
0.55% by weight Methyl ethyl ketone (ME
K) was added and mixed with a stirring defoaming machine (Matsuo Sangyo Co., Ltd.). By adding MEK, the viscosity of the mixture is lowered and the mixture can be processed into a slurry, but it is not included in the composition because it is scattered in the subsequent drying step.

This slurry was used to form a film on a polyethylene terephthalate (PET) release film, the surface of which was subjected to a release treatment, by the doctor blade method. Then, it dried at 90 degreeC and the solvent was scattered and the sheet-shaped heat conduction mixture was produced. A 1 mm thick copper plate (coefficient of linear expansion 17 ppm / ° C) was prepared as a heat dissipation plate. Further, a lead frame having a pattern formed by etching a copper plate having a thickness of 0.5 mm as a wiring pattern using a commercially available etching solution was prepared.

Similar to the one shown in FIG. 2A, the lead frame, the heat conduction mixture and the heat dissipation plate were superposed in this order, and heated and pressurized at 170 ° C. and a pressure of 5 Pa for 15 minutes. As a result, the heat conductive resin composition flows to the surface of the lead frame, and the thermosetting resin contained therein hardens to become rigid and has a thickness of 2.0 mm as shown in FIG. 2 (b). Substrate (electrical insulation layer thickness 0.5
mm) was produced.

After this, further, at 6 ° C. in a nitrogen atmosphere at 175 ° C.
The heat treatment was performed for a period of time to accelerate the curing of the thermosetting resin to complete the heat conductive substrate. After that, a thermosetting solder resist ink was printed by a screen printing method, and then parts were mounted by reflow soldering. When the warpage of the board after mounting components was measured, it was 0.0 for a length of 100 mm.
The sled was 5 to 0.12 mm.

At this time, the resin heat conduction mixture was prepared by changing the ratio of the inorganic filler and the thermosetting resin in the heat conduction mixture (while keeping the ratio of the thermosetting resin and the other additives constant). Experiment number a in the same manner as above
Each substrate of ~ f was produced. Further, each of the sheet-shaped heat-conductive mixtures alone was cured at a temperature and pressure similar to the above with a flat plate having a constant thickness gap of 0.4 mm, and provided as a sample for measuring the physical properties of the electrical insulating layer.

The linear expansion coefficient and the thermal resistance of the substrate of Example 1 (Experiment Nos. A to f) and the sample for evaluation of physical properties were measured. The results are shown in Table 1. The temperature change of the substrate warp is shown in FIG.

[0058]

[Table 1]

The coefficient of linear expansion is measured by a thermomechanical analyzer (TMA; Th
ermal Mechanical Analyzer, manufactured by Seiko Instruments Inc.). In addition, the temperature change of the substrate warpage is measured by heating the substrate in a constant temperature bath and then monitoring the temperature with a thermocouple while measuring the laser surface roughness meter (Rodenstock).
Then, the length of 100 mm at the center of the substrate was measured, and the both ends were connected to each other to determine the distance of the largest portion of the warp as the size of the warp. A thermal resistance measuring device (made by Cats Electronics Design) was used for the thermal resistance measurement. As a measuring method, a semiconductor (TO-220 package) is soldered on each of the above-mentioned substrates, and a heat conduction compound (manufactured by Toray Silicone Co., Ltd.) is attached to the heat dissipation plate of the substrate.
Was applied, and the four corners of the heat sink were fixed to the heat sink with fins with screws. After that, power of 50 W is applied to the semiconductor, the voltage between B and E of the semiconductor is monitored, the temperature of the semiconductor is obtained from the temperature characteristic of the voltage, and the thermal resistance is obtained from the temperature. However, the substrate temperature immediately below the semiconductor junction was 110 ° C. for the substrate of Experiment No. c.

From the results shown in Table 1 and FIG. 8, when the ratio of the inorganic filler is changed, that is, when the linear expansion coefficient of the electric insulating layer is changed, the temperature characteristics of the warpage are changed, and the linear expansion coefficient of the heat sink (17 ppm / ° C.) is changed. It can be seen that there is a difference in the direction of the temperature change of the sled due to the relative difference between Also,
At this time, it can be seen that in the case of the substrate in which the warp changes in the concave direction when viewed from the heat dissipation plate side, the thermal resistance increases as compared to the case where it does not.

Example 2 A heat conduction mixture was prepared in the same manner as that prepared in Example 1. The composition of the mixed heat conduction mixture is shown below. (1) Inorganic filler: Al ₂ O ₃ (AS-40, Showa Denko KK, average particle size 12 μm) 88% by weight (2) Thermosetting resin: epoxy resin (XNR5002,
Nagase Ciba Co., Ltd. 11.5% by weight (3) Other additives: Silane coupling agent (A-1)
87, Nippon Unicar Co., Ltd. 0.3% by weight, carbon black (Toyo Carbon Co., Ltd.) 0.2% by weight After mixing the above materials, MEK was added to reduce the viscosity, and then carried out. A film was formed on a PET film in the same manner as in Example 1 to prepare a sheet-shaped heat conductive cured product.

Next, the above-mentioned mixture slurry was impregnated into a glass non-woven fabric (Basis weight: 50 g / m ² , thickness: 0.2 mm), followed by drying at 120 ° C. to scatter the solvent and a heat conductive cured product containing a reinforcing material. A sheet was prepared.

An aluminum plate (linear expansion coefficient: 23 ppm / ° C.) having a thickness of 1 mm was prepared as a heat dissipation plate. Further, as a wiring pattern, a copper plate having a thickness of 0.5 mm was etched by a known method to form a pattern, and a lead frame plated with nickel was prepared.

A heat radiating plate, a heat conductive mixture and a wiring pattern were superposed in the same manner as in Example 1 and heated and pressed at 170 ° C. and a pressure of 5 Pa for 60 minutes to give a thickness of 2.5 mm as shown in FIG. A substrate of (electrically insulating layer thickness 1.0 mm) was prepared. Further, similarly to Example 1, only the heat conduction mixture was cured to prepare a sample for measuring the physical properties of the electrical insulation layer.

The coefficient of linear expansion of the electrical insulating layer was measured and found to be 20 ppm / ° C. without the reinforcing material and 13 ppm / ° C. with the reinforcing material. The results of measuring the temperature change of the warp of these substrates are shown in FIG. From this figure, it can be seen that the warp of the heat conductive substrate changes to be convex toward the heat dissipation plate in accordance with the temperature increase in accordance with the linear expansion coefficient.

To evaluate the reliability, the four corners of these substrates were screwed to an aluminum heat sink having a thickness of 30 mm, and-
A temperature cycle test of 55 to 125 ° C. was performed. As a result, cracks did not occur in the substrate even after 2000 cycles in the substrate without the reinforcing material, but in the substrate with the reinforcing material, peeling occurred between the wiring pattern and the electrically insulating layer in about 1500 cycles. From this, it was found that the linear expansion coefficient of the heat dissipation plate was larger than the linear expansion coefficient of the electrical insulating layer, and the linear expansion coefficient was larger than the linear expansion coefficient α3 of the wiring pattern, the higher reliability was obtained.

Example 3 In order to prepare a heat conductive mixture used for carrying out the present invention, an inorganic filler and a thermosetting resin composition were mixed and processed into a slurry form. The composition of the mixed heat conduction mixture is shown below. (1) Inorganic filler: Al ₂ O ₃ (AL-33, manufactured by Sumitomo Chemical Co., Ltd., average particle diameter 12 μm) 89% by weight (2) Thermosetting resin: Brominated polyfunctional epoxy resin (NVR-1010) , Nippon Lec Co., Ltd., including curing agent) 10% by weight (3) Other additives: curing accelerator (imidazole, Nippon Lec Co., Ltd.) 0.05% by weight, carbon black (Toyo Carbon Co., Ltd.) 0.4% by weight, coupling agent (Plenact KR-46B, manufactured by Ajinomoto Co., Inc.)
0.55% by weight Methyl ethyl ketone (ME
K) was added and mixed with a stirring degasser (manufactured by Matsuo Sangyo Co., Ltd.), and in the same manner as in Example 1, the heat transfer mixture was formed on the release film to form a sheet-like heat transfer mixture. It was made.

Further, a part of the thermosetting resin having the above composition is used as a flexible epoxy resin (YD-171, manufactured by Tohto Kasei).
By substituting in the same manner as above to prepare sheet-like heat conduction mixtures 3a to 3d.

An aluminum plate having a thickness of 0.5 mm was prepared as a heat dissipation plate, and a copper foil having a thickness of 0.2 mm was prepared as a wiring pattern. The heat dissipation plate and the sheet-shaped heat conduction mixture and the copper foil are overlaid, and the temperature is raised from room temperature to a maximum temperature of 175 ° C. and a pressure of 5 Pa for 1 hr.
As shown in FIG. 3B, the copper foil and the heat sink were integrated. After this, an etching resist film is applied on the copper foil, covered with a circuit pattern mask, exposed to ultraviolet light, developed, etched with copper chloride, and resist stripped.
A heat conductive substrate as shown in (c) was completed. Further, in the same manner as in Embodiments 1 and 2, only the heat conduction mixture was cured and used as a sample for physical property evaluation.

The elastic modulus at 40 ° C. of each electric insulating layer was evaluated. Further, in order to confirm the reliability, each substrate was immersed in a solder bath at 260 ° C. for 1 minute, and the change in the electrical insulating layer after that was confirmed. The results are shown in Table 2. Elasticity evaluation is DM
The measurement was performed using an A device (Dynamic Mechanical Analyzer, manufactured by Seiko Instruments).

[0071]

[Table 2]

The results in Table 2 show that the elastic modulus of the heat-conducting mixture decreases as the flexible epoxy is added. Further, according to the observation after the solder dip test, cracks occurred in the electric insulating layer only on the substrate having a high elastic modulus without substituting the flexible epoxy. From this, it was found that the reliability of the substrate is high when the elastic modulus at room temperature is 50 GPa or less.

[0073]

As described above, according to the present invention, there is provided a circuit board including at least a wiring pattern, an electrical insulating layer and a heat sink, and the warp of the board is projected toward the heat sink as the temperature rises. A heat conductive substrate that changes in the direction of Due to this action, the heat dissipation from the module to the external heat dissipation member is not impaired even if the temperature rises during operation of the semiconductor module using the heat dissipation substrate, and a heat dissipation substrate with high heat dissipation can be realized. According to the invention,
It is possible to obtain a highly reliable substrate in which cracks and peeling of the substrate are unlikely to occur due to warpage at high temperatures and stress generated in the electrical insulating layer. Further, by using the heat conductive substrate of the present invention, a highly reliable semiconductor module having excellent heat dissipation can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a heat conductive substrate according to a first embodiment of the present invention.

2 (a) and 2 (b) are cross-sectional views by step showing a method for manufacturing a heat conductive substrate according to Embodiment 1 of the present invention.

3 (a) to 3 (c) are cross-sectional views by step showing a method for manufacturing a heat conductive substrate according to a second embodiment of the present invention.

4 (a) to (e) are cross-sectional views by step showing a method for manufacturing a heat conductive substrate according to a third embodiment of the present invention.

5 (a) to 5 (g) are cross-sectional views by step showing a method for manufacturing a heat conductive substrate according to a fourth embodiment of the present invention.

6A and 6B are a cross-sectional view and an external view showing a configuration of a semiconductor module according to a fifth embodiment of the present invention.

7A to 7B are cross-sectional views by step showing a method for manufacturing a heat conductive substrate of a conventional example.

FIG. 8 is a graph showing the temperature change of the warp of the heat conductive substrate in Example 1 of the present invention.

FIG. 9 is a graph showing the temperature change of the warp of the heat conductive substrate in Example 2 of the present invention.

[Explanation of symbols]

11,21,71 Lead frame 12,24,34,47,53,63,73 Electrical insulation layer 13,23,33,46,58,61 Heat sink 21,32,45,52,72 Heat conduction mixture 25,36,48,59,74 Thermal conductive board 31,41,51 Metal foil 35,44,56,62 Wiring pattern 42 Adhesive layer 43 Release film 54 through hole 55 Plating in through holes 57 Double-sided wiring board 64 External extraction electrode 65a, 65b Semiconductor element 66a, 66b Passive components 67 circuit board 68 Board fixing parts 69 cases 70 Semiconductor module

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 10-173097 (JP, A) JP 8-204071 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 23/12 H01L 23/36 H01L 25/07 H01L 25/18 H05K 1/02

Claims (12)

(57) [Claims] 1. A wiring pattern, an electrical insulating layer, and a heat sink, wherein the electrical insulating layer comprises 70 to 95% by weight of an inorganic filler.
And a heat-conducting mixture containing 5 to 30 wt% of a thermosetting resin, the heat-conducting substrate being used by fixing the heat-dissipating plate to an external heat-dissipating member, the component of the heat-conducting substrate with respect to the external heat-dissipating member. The warp size at room temperature after mounting is 1/50 of the board length.
The heat conduction substrate is 0 or less, and the warp of the heat conduction substrate changes in a direction in which it is convex toward the heat dissipation plate side as the temperature of the heat conduction substrate rises. 2. The linear expansion coefficient of the heat dissipation plate is larger than the average linear expansion coefficient of the wiring pattern and the electric insulating layer.
The heat conductive substrate according to. 3. The coefficient of linear expansion α1 of the heat sink is larger than the coefficient of linear expansion α2 of the electrical insulating layer below the glass transition point, and the coefficient of linear expansion α2 is the coefficient of linear expansion α3 of the wiring pattern.
The heat conductive substrate according to claim 1 or 2, which is larger. 4. The elastic modulus at room temperature of the heat conducting mixture constituting the electrically insulating layer is 50 GPa or less.
The heat conductive substrate according to any one of 1. 5. The heat conductive substrate according to claim 1, wherein the electrically insulating layer contains a reinforcing material. 6. The heat conductive substrate according to claim 5, wherein the reinforcing material is a glass nonwoven fabric. 7. The heat conductive substrate according to claim 1, wherein the wiring pattern is filled with an electrically insulating layer up to the gap portion to form a substantially flush surface. 8. The heat conductive substrate according to claim 1, wherein the electrically insulating layer has a thickness of 0.4 mm or more. 9. The heat conductive substrate according to claim 1, wherein the wiring pattern is a lead frame and is used as an external terminal. 10. The heat conductive substrate according to claim 1, wherein the heat dissipation plate is made of aluminum, copper, or an alloy containing at least one of these as a main component. 11. A semiconductor element and a passive component having a circuit function are mounted on the heat conductive substrate according to claim 1, and a portion selected from a vertex portion and a side portion of the heat conductive substrate. A semiconductor module comprising a connector for fixing to the external heat dissipation member. 12. The semiconductor module is a switching power supply module, a DC-DC converter module,
The semiconductor module according to claim 11, which is at least one power module selected from an inverter module, a power factor correction module, and a rectifying / smoothing module.