JP2005039113A - Surface mounting method and hybrid integrated circuit using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hybrid integrated circuit which can prevent generation of an abnormality such as cracking at or in the vicinity of a joining material such as solder or conductive resin even when undergoing repetitive cycles of temperature increase and decrease. <P>SOLUTION: In a surface mounting method for mounting an electronic component on a plurality of circuits on a circuit substrate so as to straddle the circuits, the electronic component is mounted so that an insulating layer (A) is disposed in a gap between the circuits under the electronic component. A hybrid integrated circuit to which the method is applied and a circuit substrate for it are provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hybrid integrated circuit on which surface-mounted electronic components such as semiconductor elements, chip resistors, and chip capacitors are mounted, and in particular, surface mount that is mounted across a plurality of circuits, such as chip resistors and chip capacitors. The present invention relates to a mounting method for improving the durability of a conductive bonding material such as solder or conductive resin used for bonding, and a hybrid integrated circuit using the mounting method. Also, it relates to a circuit board used therefor, and is effective when applied to various circuit boards such as a printed board and a metal base board used in a hybrid integrated circuit, and particularly effective when applied to a metal base board having a large coefficient of thermal expansion. Is.

 Various circuit boards are used to realize surface mounting that enables miniaturization and labor saving during mounting, and hybrid integrated circuits with various surface mount electronic components mounted on these circuit boards are used. It has been. In particular, as a circuit board for mounting a highly heat-generating electronic component, a metal base circuit board in which an insulating layer made of an epoxy resin filled with an inorganic filler is provided on a metal plate and a circuit is provided on the insulating layer is used. ing.

  On the other hand, with respect to in-vehicle electronic devices, there is a demand for installing the electronic devices in an engine room together with downsizing and space saving. The engine room has a harsh environment such as a high temperature and a large temperature change, and a circuit board having excellent heat dissipation and high long-term reliability is required.

  Various electronic components are joined to the circuit on the circuit board via solder, conductive resin, or the like. However, if repeated temperature rise / decrease during actual use is received over a long period of time, cracks may occur in or near the bonding material such as solder or conductive resin that fixes the electronic components. As a result, there is a problem that the heat conduction path is interrupted, the function is stopped, or the electrical reliability is lowered.

  In particular, a metal base circuit board often uses an aluminum plate as a metal plate for heat dissipation and economical reasons, and sometimes uses a copper plate or the like. However, since the difference in thermal expansion coefficient between these metal plates and electronic components, particularly ceramic chip components such as chip resistors and chip capacitors, is large, similar problems occur.

  The present invention has been made in view of the above circumstances, and even when the temperature rise / fall is repeatedly received, it is difficult to cause abnormalities such as cracks in the bonding material such as solder or conductive resin or in the vicinity thereof. An object of the present invention is to provide a hybrid integrated circuit.

  In the thermoelastic-plastic analysis using the finite element method, the present inventor performs a calculation to load a thermal cycle in the range of 233K to 423K on a hybrid integrated circuit in which various electronic components are joined to various circuit boards by soldering. As a result, a circuit board structure in which the plastic strain range of the solder is not more than a specific value is preferable, and when using a circuit board by using a specific mounting method, it has high solder crack resistance and high reliability. It has been found that a hybrid integrated circuit can be obtained, and has been experimentally verified to arrive at the present invention.

  Furthermore, the present inventor has conducted various experimental studies based on the above knowledge, and has obtained the following knowledge to reach the present invention. That is, it is considered that cracks generated in the solder or in the vicinity thereof are generated by repeatedly applying heating and cooling to the hybrid integrated circuit, and by applying thermal strain generated by the thermal expansion difference between the circuit board and the electronic component to the solder. It is important to alleviate the thermal strain with the insulating layer of the circuit board. At this time, the arrangement of the insulating layer is important for sufficiently relaxing the thermal strain generated between the metal plate and the electronic component.

  Furthermore, the present inventor conducted a similar experiment when using a conductive resin as a bonding material for electronic components, and when using solder as the bonding material, the hybrid integration has high solder crack resistance and high reliability. It has been found that a circuit board having a specific structure to be a circuit is effective in suppressing the generation of cracks in the conductive resin or its vicinity even when a conductive resin is used as a bonding material for electronic components.

  That is, the present invention is a surface mounting method for mounting electronic components on a plurality of circuits on a circuit board so as to straddle the plurality of circuits, and an insulating layer (A) is formed in an inter-circuit gap below the electronic components. A surface mounting method characterized in that an electronic component is mounted.

  The present invention also provides a hybrid integrated circuit comprising electronic components mounted on a plurality of circuits on a circuit board via a conductive bonding material so as to straddle the plurality of circuits. The hybrid integrated circuit is characterized in that an insulating layer (A) is disposed in a gap between lower circuits, and preferably, the insulating layer (A) has a product of a storage elastic modulus and a thermal expansion coefficient of 1 kPa. The hybrid integrated circuit is characterized in that the hybrid integrated circuit is of / K or more and 10 MPa / K or less, more preferably the conductive bonding material is made of solder.

  Further, according to the present invention, a plurality of circuits are provided on an insulating substrate, and an insulating layer (A) is disposed up to the circuit surface height in the gaps between the circuits of the plurality of circuits on which electronic components are mounted. Preferably, the insulating substrate is a circuit board provided with an insulating layer (B) on a metal plate, and the insulating layer (B) The circuit board according to claim 1, wherein the product of the storage elastic modulus and the thermal expansion coefficient is 1 kPa / K or more and 10 MPa / K or less.

According to the surface mounting method of the present invention, there is no generation of cracks in the bonding material of the electronic component and its peripheral part even under severe temperature changes under actual use conditions, and the hybrid integration of the present invention having a highly reliable feature A circuit can be provided. In addition, since the circuit board of the present invention has a specific structure in advance so that a hybrid integrated circuit having the above characteristics can be easily obtained, the hybrid integrated circuit obtained by using the circuit board is under actual use conditions. Even with severe temperature changes, it is possible to easily achieve highly reliable characteristics without causing cracks in the bonding material such as solder and conductive resin and in the periphery thereof.

  In the mounting method of the present invention, when electronic components such as a chip resistor and a chip capacitor are fixed on a plurality of circuits on a circuit board by a bonding material such as solder or conductive resin so as to straddle the plurality of circuits, Alternatively, after fixing, it is a technical means to dispose the insulating layer (A) only in the gap between the circuits under the electronic component, and thereby, the bonding material such as solder or conductive resin used for bonding the electronic component It is possible to achieve the effect of significantly improving the durability as compared with the conventional case.

The circuit board of the present invention has a structure in which a plurality of circuits are provided on an insulating substrate, and an electronic component is mounted so as to straddle the plurality of circuits. Furthermore, electronic components such as semiconductor chips and resistor chips are fixed on the circuit of the circuit board by a bonding material such as solder or conductive resin, and in particular, a plurality of circuits such as chip resistors and chip capacitors. A hybrid integrated circuit according to the present invention includes an improved durability of a bonding material such as a solder or a conductive resin used for bonding surface-mounted electronic components used across the board.
The hybrid integrated circuit may be attached to various resin cases made of PPS (polyphenylene sulfide) or the like, or may be embedded in an epoxy resin or the like, and the electronic components are provided in one circuit. Alternatively, one electronic component may be provided across two or more circuits.
In the present invention, the circuit may be composed of a single metal foil or may be composed of a clad foil in which two or more metal layers are laminated. Further, in the present invention, the insulating layer (B) 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.

  In the present invention, the insulating layer (A) preferably contains various inorganic fillers in order to firmly fix the electronic component and maintain the durability of the solder. Further, when the insulating layer (A) has a multilayer structure, at least two or more types of units in which the type of resin, the type of inorganic filler, the type of additive to the resin, or the quantitative ratio thereof is changed It is composed of an insulating layer. For example, when the unit insulating layer is composed of three or more layers, even if any 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 does not matter.

  On the other hand, the insulating layer (B) preferably contains various inorganic fillers in order to maintain high heat dissipation of the circuit board. Further, when the insulating layer (B) has a multilayer structure, at least two or more types of units in which the type of resin, the type of inorganic filler, the type of additive to the resin, etc., or the quantitative ratio thereof are changed are used. It is composed of an insulating layer. For example, when the unit insulating layer is composed of three or more layers, even if any 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 does not matter. Although the insulating layer (B) and the insulating layer (A) do not necessarily have the same function as described above, it is possible to apply the same material, and instead, the insulating layer (B). It is preferable because the strength of the interface between the insulating layer (A) and the insulating layer (A) can be increased and the production is easy.

  In the present invention, the bonding material may be solder or conductive resin as long as it joins an electronic component and a circuit material. When the bonding material is solder, The bonding strength with the metal base circuit board is high, and therefore heat generated from the electronic component is easily dissipated, which is preferable. When the bonding material is solder, the solder may be various binary and ternary solders containing lead-tin, but various binary and ternary solders not containing lead, such as gold, silver, and copper. , Solder containing tin, zinc, bismuth, indium, antimony, or the like.

  When the bonding material is a conductive resin, even if the epoxy or acrylic resin contains one kind of conductive material such as metal such as gold, silver or copper, or graphite, conductive material such as these metal or graphite It may contain two or more types.

  In order to find a surface mounting method with excellent crack resistance at or near the joint, the present inventors have intensively studied a mounting method, a circuit board structure, and a material. When the electronic components such as chip resistors and chip capacitors are fixed with a bonding material such as solder or conductive resin so as to straddle the circuit of the circuit, in the inter-circuit gap below the electronic components, particularly between the circuits. The inventor has obtained the knowledge that when the insulating layer (A) is disposed only in the gap, a circuit board having excellent crack resistance at or near the joint portion of the electronic component can be obtained.

  That is, according to the present invention, when an electronic component is mounted on a plurality of circuits on a circuit board through a bonding material so as to straddle the plurality of circuits, a hybrid integrated circuit is obtained. In particular, by disposing the insulating layer (A) only in the inter-circuit gap, cracks are unlikely to occur in the bonding layer or in the vicinity thereof even when subjected to repeated thermal history under actual use, and excellent in crack resistance. This is based on the knowledge that a hybrid integrated circuit can be obtained.

  Hereinafter, the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a plan view showing an example of a hybrid integrated circuit according to the present invention, and FIG. 2 is a cross-sectional view taken along the line A-A 'in FIG. In the hybrid integrated circuit of the present invention, a surface mount electronic component 4 is connected to a desired portion of the circuit 2 of the circuit board on which the circuit 2 is provided on one main surface of the insulating substrate 1 through the bonding material 3. The insulating layer (A) 5 is disposed in the space between the circuits below the electronic component.

  FIG. 3 is a cross-sectional view showing another example of the hybrid integrated circuit of the present invention. The hybrid integrated circuit according to the present invention is mounted on a surface of a circuit board on a desired surface of a circuit board 2 in which a circuit 2 is provided on one main surface of a metal plate 6 with an insulating layer (B) 7 interposed therebetween. The mold electronic component 4 is mounted so as to straddle a plurality of circuits, and has a structure in which an insulating layer (A) 5 is disposed in an inter-circuit gap below the electronic component.

  In the present invention, the resin used for the insulating layer (A) and the insulating layer (B) may be any resin as long as it is excellent in heat resistance and electrical insulation. Thermosetting resins are preferred from the standpoint of stability, and among these thermosetting resins, they are easy to handle with a relatively low viscosity at room temperature or under heating, and are excellent in heat resistance, electrical insulation and adhesiveness after curing. Is preferred.

  As the epoxy resin, a flexible epoxy resin such as a non-flexible epoxy resin such as a bisphenol F type epoxy resin or a dimer acid epoxy resin can be used. An epoxy resin previously modified with acrylic rubber or the like can also be used. As the curing agent, a non-flexible curing agent such as a phenol resin or a flexible curing agent such as an aliphatic hydrocarbon diamine may be used, and these curing agents may be combined with an epoxy resin. Moreover, you may use a hardening accelerator as needed, and you may use resin components, such as a polyimide resin and a phenoxy resin, besides these hardening | curing agents.

  As the inorganic filler used in the insulating layer (A) and the insulating layer (B), those having good electrical insulation and high thermal conductivity are used, such as aluminum oxide, aluminum nitride, silicon nitride. Boron nitride and the like, and these can be used alone or in combination. 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 of its high thermal conductivity, and boron nitride has a low dielectric constant. This is preferable.

  The amount of the inorganic filler added is preferably 40 to 75% by volume in the resin composition forming the insulating layer (A) and the insulating layer (B). If it is less than 40% by volume, the effect of heat dissipation may be reduced, and the practical use may be limited. If it exceeds 75% by volume, dispersion in the resin becomes difficult, and the resistance to adhesion due to lowering of adhesiveness or remaining voids may be reduced. This is to reduce the voltage.

  Further, the insulating layer (A) and the insulating layer (B) may have the same composition or different compositions, but in the temperature range of 200K to 450K, the product of the storage elastic modulus and the thermal expansion coefficient. Is preferably from 1 kPa / K to 10 MPa / K, particularly preferably from 10 kPa / K to 1 MPa / K. This is because if this value is small, it becomes difficult to handle, and if it is large, the burden on the bonding material increases.

  In the present invention, it is sufficient that the total thickness of the insulating layer (B) is about 10 to 500 μm. However, the thickness of 20 to 150 μm is preferable because it has an advantage that the metal base 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, titanium, an alloy containing two or more of these metals, or a clad foil using the metal or alloy Etc. can be used. In addition, the manufacturing method of the said metal foil may be what was produced by the electrolytic method or the rolling method, and metal plating, such as Ni plating, Ni-Au plating, and solder plating, may be applied on the metal foil. . From the viewpoint of adhesiveness with the insulating layer (B), it is more preferable that the surface of the metal foil on the side in contact with the insulating layer (B) is roughened in advance by etching or plating.

The metal plate is made of aluminum, iron, copper and alloys thereof, or a clad material thereof. The thickness of the metal plate is not particularly specified. However, since the metal plate is rich in heat dissipation and economical, it has a thickness of 0. Aluminum of 5 to 5.0 mm is generally selected.
In addition, regarding the manufacturing method of the circuit board of this invention, several insulating materials which added additives, such as a hardening | curing agent, to the resin containing an inorganic filler suitably were prepared, and one layer or on metal plate and / or metal foil A method of forming a circuit by etching or the like from a metal foil, or preparing a sheet made of an insulating material in advance, or applying a heat treatment or the like as needed while applying a multilayer, Then, it can be obtained by a conventionally known method such as a method of forming a circuit by etching or the like after laminating metal plates or metal foils.

[Examples 1-3, Comparative Examples 1-3]
A circuit board was created by etching a circuit copper foil of a 1.0 mm thick copper foil built-in laminated printed board to form a desired circuit having a pad portion.

[Examples 4-6, Comparative Examples 4-6]
The thickness after curing is 120 μm by resin composition B made of bisphenol F type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) containing 60% by volume of aluminum oxide on an aluminum plate having a thickness of 2.0 mm. An insulating layer (B) was formed and heated at 423 K for 15 minutes to be semi-cured.

  Further, a 70 μm thick copper foil was press-laminated on the semi-cured resin composition B, and then the resin composition B 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 produce a circuit board.

  Next, two types of chip resistors each having a chip size of 2.0 mm × 1.25 mm and 3.2 mm × 2.5 mm are mounted between the copper foil pads of each circuit board obtained by the above operation. A hybrid integrated circuit as shown in FIG. When mounting the chip resistor, Examples 1 and 4 and Comparative Examples 1 and 4 were soldered by reflow at a temperature of 500 K using lead-tin eutectic solder. In Examples 2 and 5 and Comparative Examples 2 and 5, solder made of tin-copper-silver was used and soldered by reflow at a temperature of 550K. Further, Examples 3 and 6 and Comparative Examples 3 and 6 were joined by reflow using a conductive adhesive made of silver-epoxy at a temperature of 385K.

  Next, for Examples 1 to 6, the resin composition A composed of silicon oxide-epoxy was filled in the gaps between the circuits under the electronic component and cured at a temperature of 435K to form an insulating layer (A).

  In addition, about each of the said resin composition A and the resin composition B, the test piece hardened on the same conditions as the hardening conditions of the above-mentioned resin composition was prepared, and the storage elastic modulus and the thermal expansion coefficient were measured. The storage elastic modulus is a dynamic viscoelasticity measuring instrument (manufactured by Toyo Baldwin; RHEOVIBRON DDV-3-EP type), and the thermal expansion coefficient is thermomechanical under the conditions of a frequency of 11 Hz and a heating rate of 2 ° C./min. It was measured with an analyzer (Seiko Electronics Co., Ltd .; TMA120).

  The storage elastic moduli of 230K, 300K, and 420K of the resin composition A were 22 GPa, 18 GPa, and 6 GPa, respectively. Similarly, the thermal expansion coefficients were 15 ppm / K, 15 ppm / K, and 60 ppm / K, and the product of the storage elastic modulus and the thermal expansion coefficient at each temperature was 330 kPa / K, 270 kPa / K, and 360 kPa / K. .

  In addition, the storage elastic moduli of 230K, 300K, and 420K of the resin composition B were 14 GPa, 8.6 GPa, and 77 MPa, respectively. Similarly, the thermal expansion coefficients are 18 ppm / K, 18 ppm / K, and 67 ppm / K, and the product of the storage elastic modulus and the thermal expansion coefficient at each temperature is 252 kPa / K, 155 kPa / K, and 5.2 kPa / K. there were.

  With respect to each of the above hybrid integrated circuits, a heat cycle test is performed in which a predetermined number of cycles are performed in the liquid phase after holding for 233 K7 minutes and then holding for 423 K7 minutes, and after the test, each of the hybrid integrated circuits is mainly cracked in an optical microscope. The presence or absence of the occurrence of was observed. As a result, as shown in Table 1, in Comparative Examples 1 to 6, the occurrence of cracks was observed, whereas in Examples 1 to 6, it was confirmed that the occurrence of cracks was small even after 2000 heat cycles. It was done. Further, in Examples 4 to 5, it was confirmed that no crack was generated even after 3000 heat cycles and no abnormality was observed, and that the present invention was excellent in crack resistance.

  By using the surface mounting method of the present invention, it is possible to provide a highly reliable hybrid integrated circuit without causing cracks in the bonding material of the electronic component and its peripheral part even under severe temperature changes under actual use conditions. .

  Furthermore, the circuit board of the present invention provides a highly reliable hybrid integrated circuit that does not cause cracks in the bonding material such as solder and conductive resin and its peripheral part even under severe temperature changes under actual use conditions. Can do.

  In addition, the hybrid integrated circuit of the present invention has high reliability and high reliability without causing cracks in the bonding material and its peripheral part even when subjected to severe temperature changes such as repetition of 233K to 423K. Useful.

1 is a plan view of a hybrid integrated circuit according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line A-A ′ in FIG. 1. Sectional drawing which shows another example of the hybrid integrated circuit of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation board 2 Circuit 3 Bonding material 4 Surface mount electronic component 5 Insulation layer (A)
6 Metal plate 7 Insulation layer (B)

Claims (7)

A surface mounting method in which electronic components are mounted on a plurality of circuits on a circuit board so as to straddle the plurality of circuits, and an insulating layer (A) is disposed in an inter-circuit gap below the electronic components to dispose the electronic components. A surface mounting method characterized by mounting. A hybrid integrated circuit in which electronic components are mounted on a plurality of circuits on a circuit board via a conductive bonding material so as to straddle the plurality of circuits, and a gap between circuits below the electronic components An insulating layer (A) is disposed on the hybrid integrated circuit. The hybrid integrated circuit according to claim 2, wherein the insulating layer (A) has a product of a storage elastic modulus and a thermal expansion coefficient of 1 kPa / K or more and 10 MPa / K or less. 4. The hybrid integrated circuit according to claim 2, wherein the conductive bonding material is made of solder. A circuit board, wherein a plurality of circuits are provided on an insulating substrate, and an insulating layer (A) is provided up to a height of the circuit surface in a space between the circuits of the plurality of circuits on which electronic components are mounted. 6. The circuit board according to claim 5, wherein the insulating substrate is a metal plate provided with an insulating layer (B). The circuit board according to claim 6, wherein the insulating layer (B) has a product of a storage elastic modulus and a thermal expansion coefficient of 1 kPa / K or more and 10 MPa / K or less.

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