JP2003142809A - Metal base circuit board and module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal base circuit board and a module which hardly cause abnormality such as cracking in or nearby a joining material such as solder and conductive resin even when the temperature is repeatedly raised and dropped. SOLUTION: The metal base circuit board which has a circuit provided on a metal plate 1 across an insulating layer 2 and is provided with a projection part 6 which can control the thickness of the joining material when a heat- generating electronic component 5 is joined with the circuit surface by using the joining material 4 is provided on the surface of the circuit where the heat- generating electronic component 5 is provided. Further, the metal base circuit board is characterized that the projection part 6 is provided at a part other than the circumferential part of the part where the heat-generating electronic component 5 is mounted and the difference between the highest part and lowest part of the surface of the circuit mounted with the heat-generating electronic component 5 is 0.005 to 0.2 mm, and a module uses it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a module having a heat-generating electronic component such as a semiconductor element mounted thereon, and more particularly to improving durability of a bonding material such as solder or conductive resin used for bonding the heat-generating electronic component. Module and a metal-based circuit board suitable therefor.

[0002]

2. Description of the Related Art Conventionally, as a circuit board for mounting a highly heat-generating electronic component, a metal plate is provided with an insulating layer made of epoxy resin or the like filled with an inorganic filler, and a circuit is provided on the insulating layer. A base circuit board is used.

On the other hand, with regard to in-vehicle electronic equipment, it is desired to install the electronic equipment in the engine room as well as to reduce its size and space. The engine room is in a harsh environment with high temperature and large temperature changes.
A circuit board having excellent heat dissipation is required. For such applications, attention has been paid to the metal-based circuit board having excellent heat dissipation.

Various electronic parts are joined to the circuit of the metal base circuit board through solder or conductive resin. Further, for the metal base circuit board, an aluminum plate is often used as a metal plate for heat dissipation and economical reasons, and a copper plate or the like may be used. However, since there is a large difference in the coefficient of thermal expansion between these metal plates and electronic parts, especially ceramic chip parts, the solder or the conductive material that fixes the electronic parts undergoes repeated temperature rises / falls in actual use. Cracks may occur at or near the bonding material such as resin, resulting in interruption of the heat conduction path,
There is a problem in that the heat of the high heat generating electronic component is not sufficiently dissipated, the temperature of the electronic component rises, thermal degradation occurs, the function stops, or the electrical reliability decreases.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and cracks are generated in a bonding material such as solder or conductive resin or in the vicinity thereof even if temperature rise / fall is repeatedly received. It is an object of the present invention to provide a metal-based circuit board and a module in which abnormalities such as the above are unlikely to occur.

[0006]

SUMMARY OF THE INVENTION The present inventor has conducted a thermal elasto-plastic analysis using the finite element method to find a module of 233K to 398K for a module in which various electronic components are soldered to various metal base circuit boards. Perform a calculation to load the thermal cycle of the range, as a result, the plastic strain range of the solder is preferably a metal base circuit board structure such that it is a specific value or less, when using a metal base circuit board having a specific structure, The present invention has been completed by finding that a module having a high solder crack resistance and a high reliability can be obtained.

Further, the present inventor has based on the above findings.
The present invention has been achieved through various experimental studies and the following findings. That is, cracks generated in the solder or in the vicinity thereof are generated by the thermal strain generated by the difference in thermal expansion between the metal plate of the metal base circuit board and the electronic component being applied to the solder by repeatedly heating and cooling the module. Therefore, it is important to relax the thermal strain in the insulating layer of the metal-based circuit board. At this time, in order to sufficiently reduce the thermal strain generated between the metal plate and the electronic component, it is important to control the shape of the circuit portion on which the electronic component is mounted.

Further, the present inventor has conducted similar experiments when a conductive resin is used as a bonding material for electronic parts, and when solder is used as the bonding material, the solder crack resistance is high and the reliability is high. It has been found that the metal base circuit board having a specific structure to be a module has an effect of generating cracks in the conductive resin or the vicinity thereof even when the conductive resin is used as a bonding material for electronic components.

That is, the present invention is a metal base circuit board in which a circuit is provided on a metal plate via an insulating layer, and the heat-generating electronic component is provided on the surface of the portion of the circuit on which the heat-generating electronic component is mounted. A metal base circuit board characterized in that a convex portion capable of controlling the thickness of the bonding material is provided on the surface of the circuit when the bonding material is used for bonding. The metal base circuit board is characterized in that it is provided in a portion other than the peripheral portion of the mounting portion.

Further, according to the present invention, the difference between the highest portion and the lowest portion of the surface of the circuit on which the heat-generating electronic component is mounted is 0.005.
It is the said metal base circuit board characterized by being -0.2 mm.

Further, the present invention is characterized in that the heat-generating electronic component is mounted on the portion of the metal base circuit board on which the heat-generating electronic component having the convex portion of the circuit is mounted via a bonding material. In the above module, the joining material is made of solder.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The metal base circuit board of the present invention is
An insulating layer is provided on a metal plate, and a circuit is provided on the insulating layer. Further, the module of the present invention is one in which a heat-generating electronic component such as a semiconductor chip or a resistance chip is fixed on the circuit of the metal base circuit board with a bonding material such as solder or conductive resin. May be attached to various resin cases made of PPS (polyphenylene sulfide) or the like, or may be embedded in epoxy resin or the like. The electronic component may be provided in one circuit, or one electronic component may be provided over two or more circuits. Further, in the present invention, the circuit may be formed of a single metal foil or a clad foil in which two or more metal layers are laminated. Further, in the present invention, the insulating layer is composed of one or more unit insulating layers, and the unit insulating layer may be a single layer or a plurality of unit insulating layers.

The insulating layer preferably contains various inorganic fillers in order to keep the heat dissipation of the metal base circuit board high. In addition, when the insulating layer has a multi-layer structure, at least two or more unit insulating layers having different kinds of resins, kinds of inorganic fillers, kinds of additives to the resin, or their quantitative ratios are used. It is configured. For example, when the unit insulating layers are composed of three or more layers, no matter which unit insulating layer has a different composition, adjacent unit insulating layers have different compositions, and non-adjacent unit insulating layers have the same composition. It doesn't matter.

In the present invention, the joining material may be solder or conductive resin as long as it joins the electronic component and the circuit material, but when the joining material is solder, High bonding strength between parts and metal base circuit board,
Therefore, the heat generated from the electronic component is easily dissipated, which is preferable. When the bonding material is solder, the solder is lead-
Even various binary and ternary solders containing tin, various binary and ternary solders not containing lead, such as gold, silver, copper, tin,
A solder containing zinc, bismuth, indium, antimony or the like may be used.

When the bonding material is a conductive resin, even if the resin such as epoxy or acrylic contains one kind of conductive material such as metal such as gold, silver and copper, or graphite, it is possible to use such metal or graphite. It may contain two or more kinds of conductive materials.

The inventors of the present invention conducted extensive studies on the metal base circuit board structure in order to find a metal base circuit board having excellent crack resistance at or near the joint, and as a result, identified the structure of the circuit part on which electronic parts are mounted. When controlling to the structure of, the knowledge that a metal base circuit board excellent in crack resistance of the joint portion or its vicinity is obtained,
Especially on the surface of the circuit where heat-generating electronic components are mounted,
By providing a convex part that can control the thickness of the bonding material when bonding the heat-generating electronic component to the circuit surface, it is difficult for cracks to form at or near the bonding part, that is, a module with excellent crack resistance is obtained. The present invention has been achieved based on the knowledge that the above can be achieved. That is, according to the present invention, when an electronic component is mounted on a circuit of a metal-based circuit board via a bonding material to obtain a module, the thickness of the bonding material is not uniform. By configuring the outer peripheral thickness of the layer to be thicker than the central portion thickness of the bonding layer, cracks are unlikely to occur in the bonding layer or in the vicinity thereof even when subjected to repeated thermal history under actual use. This is based on the finding that a module having excellent cracking properties can be obtained.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view showing an example of a module of the present invention, and FIG. 2 is a sectional view taken along the line AA ′ in FIG. The module of the present invention has a heat generating electronic component 5 via a bonding material 4 to a desired portion of the circuit 3 of a metal base circuit board in which the circuit 3 is provided on one main surface of the metal plate 1 via the insulating layer 2. Has a structure in which is mounted.

In the present invention, as illustrated in FIG. 2, on the circuit surface of the portion where the heat-generating electronic component 5 is mounted,
When the bonding material is used for bonding, the convex portion 6 capable of controlling the thickness of the bonding material is provided. At this time, this convex portion 6
It is even more important that is provided in a portion other than the peripheral portion of the portion on which the heat-generating electronic component 5 is mounted, that is, an inner portion hidden by the heat-generating electronic component 5 when viewed from above. As a result, the thickness of the bonding material 4 around the heat-generating electronic component 5 is increased, and the crack resistance of the bonding material and its vicinity is further secured. Further, the thin portion of the bonding material 4 can be provided in the vicinity of the heat-generating electronic component 5, so that sufficient heat dissipation can be ensured.

Further, dt in FIG. 2 is the heat-generating electronic component 5.
Shows the difference in height between the highest part and the lowest part of the circuit surface on which is mounted, and it is preferable that dt is 0.005 or more and 0.2 mm or less. This is because if dt is less than 0.005 mm, the effect of relaxing thermal strain may not be sufficiently exerted, and if it exceeds 0.2 mm, it may be difficult to form a circuit.

FIG. 3 is a sectional view taken along the line BB 'in FIG. The shape of the convex portion 6 on the circuit surface of the portion of the circuit 3 where the heat-generating electronic component 5 is mounted has a gentle slope.

FIG. 4 is a sectional view taken along the line CC 'in FIG. The heat-generating electronic component 5 is bonded to the bonding material 4 across the two circuits 3.
In the case of mounting by using, the convex portion 6 is provided for each mounting portion using the bonding material 4 of the heat-generating electronic component 5.

As illustrated in FIGS. 2 and 3, in the present invention, the convex shape is, for example, a cone, a cylinder, or a triangular pyramid.
Any polygonal pyramid such as a quadrangular pyramid, a polygonal prism, or the like may be used as long as it forms a convex portion. Further, as illustrated in FIG. 5, when the heat-generating electronic component 5 is mounted using the bonding material 4 across the two circuits 3, the circuit surface of the heat-generating electronic component 5 mounting portion of the two circuits 3 is Convex part 6
May have different shapes.

Further, in the case of a module in which a plurality of heat-generating electronic components are mounted, a part of the heat-generating electronic components to be mounted, particularly one having a large heat-generating property, may satisfy the above condition, but it is more reliable. In order to obtain a metal-based circuit board or module with high heat resistance, it is preferable that all the heat-generating electronic components satisfy the above conditions. Furthermore, when a plurality of heat-generating electronic components are mounted, the directions between the heat-generating electronic components may not be the same, but for each heat-generating electronic component, dt is 0.005 mm or more and 0.
It is preferably bonded on the circuit surface of 2 mm or less. Note that a plurality of electronic components may be mounted on one circuit.

In the present invention, the resin used for the insulating layer may be any resin as long as it has excellent heat resistance and electrical insulation. A curable resin is preferable, and among thermosetting resins, it has a relatively low viscosity at room temperature or under heating and is easy to handle,
An epoxy resin having excellent heat resistance, electric insulation, adhesiveness and the like after curing is preferable.

As the epoxy resin, a non-flexible epoxy resin such as bisphenol F type epoxy resin or a flexible epoxy resin such as dimer acid epoxy resin can be used. Also, an epoxy resin previously modified with acrylic rubber or the like can be used.

As the curing agent, a curing agent having no flexibility such as phenol resin or a curing agent having flexibility such as diamine of aliphatic hydrocarbon can be used. By combining these curing agents and epoxy resin, Good. Further, a curing accelerator may be used if necessary, and a resin component such as a polyimide resin or a phenoxy resin may be used in addition to these curing agents.

As the inorganic filler used for the insulating layer,
A material having a good electrical insulation property and a high thermal conductivity is used, and examples thereof include aluminum oxide, aluminum nitride, silicon nitride, boron nitride, etc. These may be used alone or in combination of two or more. it can.
In particular, aluminum oxide is preferable because it has a spherical particle shape and can be highly filled because it is inexpensive and easily available, aluminum nitride is preferable because it has high thermal conductivity, and boron nitride has a low dielectric constant. Therefore, it is preferable.

The addition amount of the inorganic filler is preferably 40 to 75% by volume in the resin composition forming the insulating layer. If it is less than 40%, the heat dissipation effect may be reduced, and practical use may be limited. If it exceeds 75%, it may be difficult to disperse it in the resin, and the adhesiveness may be decreased or the withstand voltage due to the remaining voids This is because it causes a decrease.

In the present invention, the total thickness of the insulating layer is 10
Approximately 500 μm is sufficient, but 20 to 150 μm
A value of m is preferable because it also has an advantage that a metal-based circuit board can be manufactured with high productivity.

As the metal foil constituting the circuit, any one of copper, aluminum, nickel, iron, tin, gold, silver, molybdenum, and titanium, an alloy containing two or more kinds of these metals, or the above metal or alloy is used. A clad foil or the like can be used. The metal foil may be produced by an electrolytic method or a rolling method, and the metal foil may be plated with a metal such as Ni plating, Ni-Au plating, and solder plating. . From the viewpoint of adhesiveness to the insulating layer, it is more preferable that the surface of the metal foil that is in contact with the insulating layer be roughened in advance by etching, plating, or the like.

The metal plate used in the present invention is made of aluminum, iron, copper and their alloys, or clad materials thereof, and the thickness thereof is not particularly specified, but it is rich in heat dissipation and economical. Therefore, aluminum having a thickness of 0.5 to 5.0 mm is generally selected.

Regarding the method for manufacturing a metal base circuit board of the present invention, a plurality of insulating materials prepared by appropriately adding additives such as a curing agent to a resin containing an inorganic filler are prepared, and a metal plate and / or a metal foil are prepared. While applying one layer or multiple layers on top, if necessary, heat treatment etc. is applied and cured, and then a circuit is formed from a metal foil by etching or the like, or a sheet made of an insulating material is prepared in advance. It can be obtained by a conventionally known method such as a method of laminating a metal plate or a metal foil via the sheet and then forming a circuit by etching or the like.

In order to provide the convex portion 6 on the heat-generating electronic component 5 mounting portion of the circuit 3, a metal foil having the convex portion can be formed in advance by a method such as etching.
The convex portion 6 can be formed by plating or etching during or after the production of the metal base circuit board.

[0034]

[Examples] [Examples 1 to 6, Comparative Examples 1 to 3] 2.0 mm
Aluminum oxide on the aluminum plate of
A resin composition comprising a bisphenol F type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) containing vol%
An insulating layer with a thickness of 120 μm after curing is formed, 423K
It was semi-cured by heating for 15 minutes.

Further, a copper foil having a thickness of 70 μm was press-laminated on the semi-cured resin composition, the resin composition was further cured at 423 K for 5 hours, and then the copper foil was etched. A desired circuit having a pad portion was formed to form nine types of metal base circuit boards. The difference between the highest part and the lowest part of the surface of the circuit of each circuit board is as shown in Table 1. The convex portion on the surface of the circuit on which the heat-generating electronic component is mounted was formed into a desired shape by performing the etching operation a plurality of times.

[0036]

[Table 1]

Next, a chip size of 2.0 mm × 1..mm was provided between the copper foil pads of each metal base circuit board obtained in the above operation.
Five types of chip resistors of 25 mm each, 3.2 mm × 2.5 mm, and five types each were mounted to form a module. When mounting the chip resistors, for Examples 1 and 2 and Comparative Example 1, lead-tin eutectic solder was used and soldering was performed by reflow at a temperature of 500K. For Examples 3 to 4 and Comparative Example 2, tin-copper-silver solder was used.
Soldering was performed by reflow at a temperature of 50K. Further, in Examples 5 to 6 and Comparative Example 3, a conductive adhesive made of silver-epoxy was used and joined by reflow at a temperature of 385K.

For each of the above modules, a heat cycle test was conducted in which a cycle of holding 233 K7 minutes in the liquid phase and then holding 398 K7 minutes was treated a predetermined number of times,
After the test, each module was observed with an optical microscope mainly for the presence of cracks in the joint portion. The results are shown in Table 2.
As shown in FIG. 5, in Comparative Examples 1 to 3, the occurrence of cracks was observed, whereas in Examples 1 to 6, it was confirmed that the occurrence of cracks was small even after 500 heat cycles. Furthermore, in Examples 1 to 3, it was confirmed that no crack was generated even after 700 heat cycles, and it was clear that the present invention had excellent crack resistance.

[0039]

[Table 2]

[0040]

The metal-based circuit board of the present invention is used for joining a heat-generating electronic component on the surface of a portion on which a heat-generating electronic component is mounted by using a bonding material such as solder or conductive resin on the circuit surface. It has a specific structure that can control the thickness of the bonding material. Therefore, it is a highly reliable module that does not crack the bonding material and its surroundings due to severe temperature changes under actual use conditions. Can be provided.

Further, the metal base circuit board of the present invention is
The difference between the highest part and the lowest part of the surface of the circuit that mounts the heat-generating electronic components is a specific value, and therefore, even when the temperature changes under actual use conditions, the bonding material such as solder or conductive resin and its It is possible to provide a highly reliable module without causing cracks in the peripheral portion.

The module of the present invention is, for example, 233K.
Even when subjected to a severe temperature change such as repetition of up to 398 K, the bonding material and its peripheral portion are not cracked, which is highly reliable and industrially useful.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a module of the present invention.

FIG. 2 is a sectional view taken along the line A-A ′ in FIG.

FIG. 3 is a sectional view taken along the line B-B ′ in FIG.

FIG. 4 is a cross-sectional view taken along the line C-C ′ in FIG.

FIG. 5 is a sectional view showing another example of the module of the present invention.

[Explanation of symbols]

1 metal plate 2 insulating layers 3 circuits 4 Bonding material 5 Exothermic electronic components 6 convex

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5E315 AA05 BB03 BB11 BB15 CC01                       DD16 DD25 GG11 GG16 GG20                 5E319 AA03 AB05 AC06 AC11 AC15                       AC16 BB05 CC33 CD04 CD26                       CD29 GG03 GG20                 5E336 AA04 AA16 BB19 BC34 CC32                       CC33 CC51 CC55 EE01 GG05                       GG16

Claims (5)

[Claims] 1. A metal base circuit board having a circuit provided on a metal plate via an insulating layer, wherein a heat-generating electronic component is provided on a surface of a portion of the circuit where the heat-generating electronic component is mounted. A metal base circuit board comprising a convex portion capable of controlling the thickness of the bonding material when bonding with the bonding material. 2. The metal base circuit board according to claim 1, wherein the convex portion is provided on a portion other than a peripheral portion of a portion on which the heat-generating electronic component is mounted. 3. The metal base according to claim 1, wherein the difference between the highest portion and the lowest portion of the surface of the circuit on which the heat-generating electronic component is mounted is 0.005 to 0.2 mm. Circuit board. 4. A heat-generating electronic component is mounted on a portion of the metal base circuit board according to claim 1, 2 or 3 on which a heat-generating electronic component having a convex portion of the circuit is mounted via a bonding material. A module characterized by 5. The module according to claim 4, wherein the bonding material is solder.