JP2008248782A - Igniter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an igniter having an ion current detection function which is capable of suppressing generation of migration and miniaturized, and having an ion current detection function with superior engine mountability. <P>SOLUTION: In a ceramic substrate in which a low-voltage signal wire and a high-voltage power supply wire are not physically separated from each other on the same substrate with both sides being wired, one side of the substrate is fixed onto a heat sink with an adhesive, a terminal of the heat sink is fixed with an adhesive to the inside of an insert-molded container-shaped connector, and the terminal and a substrate input-output pattern are subjected to bonding connection by an aluminum wire. The substrate, the heat sink, the aluminum wire, and the terminal are molded with an epoxy resin filled inside the connector, and further molded with an ignition coil filling resin inside an ignition coil. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a structure for fixing a substrate built in an igniter, and more particularly to a structure for fixing a ceramic substrate to a heat sink.

  In the ignition device for an internal combustion engine having an ion current detection function shown in FIG. 1, 1 is a primary coil, 2 is a central iron core, 3 is a secondary coil, 4 is an ignition coil case, and 5 is an igniter. The igniter 5 is installed on the upper part of the primary coil 1, the central iron core 2 and the secondary coil 3, and is assembled together with the primary coil 1, the central iron core 2 and the secondary coil 3 in the ignition coil case 4, and then ignited. Molded with coil filling resin.

  The igniter 5 has a structure as shown in FIG. 2. 51 is a primary current interrupting element, 52 is a heat sink, 53 is a control circuit, 54 is a ceramic substrate, 55 is an aluminum wire, 56 is a collector terminal, and 57 is a battery supply terminal. , 58 are secondary coil low voltage connection terminals. Further, in order to generate an ion current that can be detected by applying a voltage between the plug gaps during combustion of the internal combustion engine, the igniter 5 has a built-in ion current detection power source 59 of 70V to 300V.

  A circuit for the ion current detection power supply 59 is formed on the power supply board 59, 59a is an ion current detection voltage creation ZD, 59b is an ion current detection power supply capacitor, and is mounted on the glass epoxy board 59c. The high voltage wiring of the ion current detection power source on 59c and the low voltage signal voltage wiring on the ceramic substrate 54 are physically separated.

The igniter 5 and the primary coil 1 in FIG. 1 are connected by a collector terminal 56, and both the collector terminal 56 and the heat sink 52 are electrically connected by aluminum wire bonding. The collector of the IGBT 51 as a primary current interrupting element is die-bonded on the heat sink 52 using a high melting point solder, and the gate and emitter of the IGBT 51 are a copper or 42 alloy bonding pad mounted on the ceramic substrate 54 and the IGBT. The gate and emitter are each electrically connected by aluminum wire bonding.
The pattern wiring on the ceramic substrate 54 is electrically connected to the control circuit 53, and at the same time, is electrically connected to the substrate input / output pattern for power supply input, GND, ignition signal input, and ion current detection signal output. Finally, aluminum wire bonding is performed and electrically connected to both the bonding pads mounted on the ceramic substrate 54 and the input / output terminals insert-molded in the connector. The power supply board 59 is electrically and mechanically connected by solder bonding after crimping with the secondary coil low-voltage connection terminal 58 and the power supply board connection terminal connected to the GND.

  FIG. 3 shows a method for fixing the ceramic substrate 53 and the heat sink 52. In the ceramic substrate 53, the conductor 21 containing silver is formed on one side of the ceramic substrate 20, and the protective glass 22 is formed on the ceramic substrate 53 so as to be in direct contact with the conductor 21. One side of the ceramic substrate 20 on which no wiring pattern is formed is fixed to a heat sink 52 by an epoxy resin 24 having a high heat resistance and a low linear expansion coefficient. The heat sink fixed inside the connector molded in a container shape is sealed with an epoxy resin 25 having a high heat resistance and a low linear expansion coefficient.

The required characteristics of the epoxy resin 24 for fixing the ceramic 53 to the heat sink 52 are that only a low voltage of a signal level is applied on the ceramic substrate 53 and a heat sink to which a high voltage is applied due to the counter electromotive force when the primary coil current is cut off. Since there is no circuit pattern on the side, only mechanical characteristics such as high heat resistance and low linear expansion coefficient and DC withstand voltage characteristics are required.
On the other hand, the required characteristic of the epoxy resin 25 filled in the igniter 5 is that it directly adheres to the primary current blocking element 51 and the control circuit 53 which are bare chips. In order to prevent migration of copper and aluminum used in the minute pattern, it is required to be a resin in which the concentration of ionic impurities such as chlorine ions and sodium ions is controlled to a low level.

  Conventionally proposed ceramic substrates are shown in FIGS. Note that 21a, 22a, 7a, 8a, 6 in FIG. 4 and 2a, 3a, 5a, 6 in FIG. 5 are circuit patterns wired on both sides of the ceramic substrate, respectively, and the circuit pattern is formed only on one side. The formed substrate is not formed.

  In the ceramic substrate shown in FIG. 4, 20 is a ceramic substrate, 21 and 21a are conductors, 7 and 7a are resistors, 22 and 22a are protective glasses, 8 and 8a are trimming portions, and 9 is a protective epoxy layer. . The ceramic base 20 is mainly composed of alumina, and after firing the base, the conductors 21 and 21a are conductor pastes containing silver, the resistors 7 and 7a are resistor pastes having arbitrary resistance values, and the protective glass 8 And 8a are formed by printing and baking paste-like glass, respectively. After the glass baking is finished, the resistance values of the resistors 7 and 7a, which are called trimming, are adjusted by laser from the protective glasses 8 and 8a as necessary. At this time, a minute groove extending from the surface of the protective glasses 8 and 8a through the resistors 7 and 7a to the ceramic substrate 20 is formed. Further, it is necessary to bias the resistor near the both ends of the resistors 7 and 7a to be trimmed, or to measure the resistance value at the positions corresponding to both ends of the equivalent circuit. The glass opening 10 is necessary. That is, the conductors 21 and 21a are completely exposed in the protective glass opening 10 and the trimming portions 8 and 8a.

  As shown in FIG. 6, when the above ceramic substrate is used for an igniter, the exposed conductor and the resistor are protected from the thermal stress of the epoxy resin 24 used for fixing the ceramic substrate to the heat sink 52. A protective epoxy layer 9 is formed by coating a resin.

  In the ceramic substrate shown in FIG. 7, 20 is a ceramic substrate, 21 and 21a are conductors, 7 and 7a are resistors, 22 is protective glass, 8 and 8a are trimming portions, and 9 is a protective epoxy layer. The ceramic base 20 is mainly composed of alumina, and after firing the base, the conductors 21 and 21a are conductor pastes containing silver, the resistors 7 and 7a are resistor pastes having arbitrary resistance values, and the protective glass 8 Is formed by printing and baking paste-like glass. The conductor 21a and the resistor 7a formed on one side of the substrate are completely exposed. In this state, trimming is performed by laser from the protective glass 8 on one side and directly on the resistor 7a on the other side. . When the resistance value is adjusted to an arbitrary value by trimming, an epoxy resin is completely coated on one side of the substrate where the conductor 21a and the resistor 7a are exposed to form the protective epoxy layer 9.

As shown in FIG. 8, when the above-described ceramic substrate is used for an igniter, the epoxy resin 24 that directly contacts the protective epoxy layer 9 fixes the ceramic substrate to the heat sink 52.
Japanese Patent Laid-Open No. 2006-009687 JP 2006-012599 A

  In the conventional ignition coil igniter shown in FIGS. 1 and 2, the low voltage portion of the signal processing circuit on the ceramic substrate 54 and the high voltage portion 59 for ion current detection are physically provided. In order to suppress the occurrence of migration on the ceramic substrate 54, it is considered that there is no part having a large potential difference, and the high voltage power supply unit 59 is created as a separate substrate, and the potential difference varies from several tens to 300V. A sufficient inter-pattern distance is set in the part. Here, the occurrence of migration within the igniter means that the silver contained in the circuit pattern formed on the ceramic substrate precipitates between patterns where a potential difference occurs under specific conditions, and finally short-circuits between patterns. It is a phenomenon that leads to. That is, migration occurs in various metals, and metals used in electronic circuits, such as silver, copper, tin, lead, nickel, and gold, are known as metals that are prone to migration, and silver is the metal that is most easily migrated. Are known. The occurrence of migration is accelerated under specific conditions, that is, high electric field strength, high temperature, halogen / alkali ionic impurities, and the presence of moisture. Regarding moisture, migration may occur due to moisture absorption before sealing and penetration of moisture absorbed by the sealing resin even when sealed with the sealing resin.

The following reactions are considered for the silver migration described above.
(1) When a potential difference occurs between opposing wiring patterns, the silver in the high-potential side wiring pattern and the water present in the periphery are ionized, and the ionized water and ionized silver react to produce silver hydroxide. .
Ag → Ag + + e−
2H2O → H3O + + OH-
Ag + + OH- → AgOH
(2) Silver hydroxide is decomposed to become silver oxide and is deposited on the wiring pattern on the high potential side.
2AgOH → Ag2O + H2O
(3) The precipitated silver oxide becomes silver ions and hydroxide ions by the hydration reaction, and the silver ions move to the low potential side pattern to precipitate silver.
2Ag2O + H2O->2AgOH-> 2Ag ++ 2OH-
Ag + + e- → Ag
The occurrence of silver migration is caused by the presence of moisture and electric field. The acceleration of chemical reaction by ambient temperature and the acceleration of silver ionization by halogen / alkali ionic impurities cannot be ignored as acceleration factors.

  In recent years, there has been a movement to further reduce fuel consumption of internal combustion engines in response to demands for environmental performance. However, high efficiency combustion and weight reduction have been studied as specific projects. In particular, with respect to weight reduction, the engine is in the direction of miniaturization, and the ignition coil is required to have improved engine mountability by further miniaturization. In the conventional ignition coil igniter shown in FIG. 1 and FIG. 2, the low voltage portion of the signal processing circuit and the high voltage portion for detecting the ionic current have a large potential difference on a single substrate. Although it is difficult to ensure the distance between patterns in different wiring pattern parts, migration can be suppressed by physically separating the wiring by using the ceramic substrate with wiring on both sides shown in FIG. 4 or FIG. It becomes. However, in order to fix the ceramic substrate on the heat sink 52 serving as a battery voltage, it is necessary to electrically insulate between the pattern wiring on the back side of the substrate and the heat sink 52.

  In the conventional double-sided wired ceramic substrate shown in FIG. 4, a protective epoxy layer 9 for electrically and mechanically protecting the conductor opening of the glass protective layer 22a is formed on the back side of the substrate. In the conventional method shown in FIG. 1, there is a protective epoxy layer 9 for protecting the conductor 21a and the resistor 7a. However, in the conventional igniter having the ion current detection function shown in FIGS. 1 and 2, the potential difference in the wiring pattern on the ceramic substrate 54 is only about 14 V, which is a potential difference between the battery voltage and GND. Therefore, the epoxy resin used for the protective epoxy layer 9 is not particularly controlled as a characteristic value for the ionic impurities described above, and has an ionic impurity concentration of several tens to several hundred ppm. Therefore, when a voltage of several tens to 300 V of the ion current detection power supply voltage is applied to the wiring on the substrate, the risk of occurrence of migration increases.

  The present invention has been made in view of the above-described problems, and enables the miniaturization of an igniter having an ion current detection function by suppressing the occurrence of migration, and an igniter having an ion current detection function excellent in engine mountability. The purpose is to provide.

  With respect to claim 1, a ceramic substrate in which a low-voltage signal wiring and a high-voltage power supply wiring are not physically separated on the same substrate that is wired on both sides, and one side of the substrate is fixed on a heat sink with an adhesive, The heat sink is fixed to the inside of a connector with insert-molded terminals by an adhesive, the terminals and the board I / O pattern are bonded and connected with aluminum wires, and the board, heat sink, aluminum wires, and terminals are filled with resin inside the connector. An igniter molded with epoxy resin and molded with ignition coil filling resin inside the ignition coil.

  According to claim 2, in the structure in which the circuit pattern is composed of a silver-containing conductor on both sides of the ceramic base and is fixed on the heat sink by an adhesive that directly contacts the circuit pattern on one side of the substrate, the ionic impurities are low. An igniter characterized in that an epoxy resin for semiconductor encapsulation, which is suppressed in concentration, is used as an adhesive for the adhesive structure.

  The circuit pattern is formed of a conductor containing silver on both sides of the ceramic base material, glass is formed on both sides of the substrate as a substrate protective material, and an epoxy protective layer is formed on the substrate protective material on one side of the substrate. An igniter including an electronic circuit board in which an epoxy resin for semiconductor encapsulation, in which ionic impurities are suppressed to a low concentration, is used as the substrate protective material in a substrate having a structure in which is formed.

  The circuit pattern is composed of a silver-containing conductor on both sides of the ceramic base material, the glass substrate is directly adhered to the circuit pattern as a substrate protective material, and the epoxy resin is applied to the substrate protective material after trimming the resistor on one side of the substrate. An igniter having a built-in electronic circuit board in which a semiconductor sealing epoxy resin in which ionic impurities are suppressed to a low concentration is used as the epoxy resin in a substrate having a structure in direct contact with the circuit pattern.

  The igniter according to claim 1, which has an ion current detection function.

  In the present invention, the low voltage part of the processing circuit and the high voltage part for detecting the ionic current are wired by fixing the ceramic substrate on the heat sink with the double-sided wiring that achieves both suppression of migration and insulation. Can be realized on the same ceramic substrate.

  The embodiment of the present invention has a structure in which a ceramic substrate 54 is fixed to a heat sink 52 shown in FIG. 11 in an igniter built in the ignition coil shown in FIGS. In FIG. 9, 1 is a primary coil, 2 is a central iron core, 3 is a secondary coil, 4 is an ignition coil case, and 5 is an igniter. The igniter 5 has a structure as shown in FIG. 2. 51 is a primary current interrupting element, 52 is a heat sink, 53 is a control circuit, 54 is a ceramic substrate, 55 is an aluminum wire, 56 is a collector terminal, and 57 is a battery supply terminal. , 58 are secondary coil low voltage connection terminals. On the ceramic substrate 54, a circuit pattern of a low voltage portion of the signal processing circuit and a high voltage portion for ion current detection is formed.

  In FIG. 11, 20 is a ceramic substrate, 21 is a conductor, 22 is protective glass, 52 is a heat sink, 24 is an epoxy resin for semiconductor encapsulation in which halogen and alkali ionic impurities are suppressed to a low concentration, and 25 is high. It is an epoxy resin for semiconductor encapsulation, which has heat resistance, a low linear expansion coefficient, and a low concentration of ionic impurities. Various types of epoxy resins used for sealing electronic and electric parts have been proposed with the required properties of weather resistance, low expansion, heat resistance and insulation. Particularly in an epoxy resin for sealing a semiconductor, in addition to the above-mentioned required characteristics, a low required concentration of ionic impurities is required for semiconductor sealing. Since the wiring pattern of the semiconductor that constitutes the integrated circuit is fine, it is more likely to be affected by the migration described above and has been regarded as a problem from before, and an epoxy resin in which ionic impurities are suppressed to a low concentration than before, Widely used as a semiconductor sealing material, it is used to suppress migration in a fine wiring pattern of an integrated circuit.

  On the ceramic substrate 54 of the igniter shown in FIG. 10, a control circuit 53 for the primary current interrupting element 51 and a ZD 59a and a capacitor 59b constituting a high-voltage power supply circuit for detecting ion current are mounted. As shown in FIG. 11, the wiring 25 of the high-voltage power supply circuit is a substrate having a via connection 28 except for the mounting land of the ZD 59a and the capacitor 59b and the pad portion connected to the secondary coil low-voltage connection terminal by aluminum wire bonding. The low-voltage signal wiring 21 and the ceramic substrate 20 are separated as an insulator.

  With respect to the ZD 59a and capacitor 59b mounting land used for the high-voltage power supply circuit, the component electrodes, and the aluminum wire bonding pad portion for connection, physical separation is performed by securing a distance from the signal wiring or the GND wiring.

  On the component mounting surface side, after the ceramic substrate 54 shown in FIG. 10 is fixed to the heat sink 52 with the epoxy resin 24 as shown in FIG. 11, aluminum wire bonding is connected to both the pads on the substrate and the terminals insert-molded to the connector. Molded with epoxy resin 25, and finally the high-voltage portion of the high-voltage power supply circuit on the component mounting surface side is migrated by epoxy resin 25 for semiconductor encapsulation in which the distance between patterns on the substrate and ionic impurities are suppressed to a low concentration It is kept in a state that suppresses the occurrence of.

  On the other hand, only the high-voltage wiring is provided on the substrate surface opposite to the component mounting surface to make the potential difference between the patterns substantially equal, and the ceramic substrate 54 that directly contacts the high-voltage wiring is ionized as an adhesive that adheres to the heat sink 52. Occurrence of migration is suppressed by using an epoxy resin for semiconductor encapsulation in which a low concentration of conductive impurities is suppressed.

  The thickness of the epoxy resin layer 24 is about 100 μm, and the heat sink 52 biased by the battery voltage and the high voltage wiring are electrically insulated. As for the thickness of the epoxy resin layer 24, the distance between the ceramic substrate 54 and the heat sink 52, that is, the thickness of the epoxy resin layer 24 can be made uniform by making the filler particle size spherical with a particle size of about 100 μm. Further, in order to insulate from the heat sink 52 while suppressing the occurrence of migration of the high voltage wiring portion wired on the component mounting surface side, the double-sided ceramic substrate shown in FIGS. 12 and 13 may be used. .

  In the ceramic substrate shown in FIG. 12, 20 is a ceramic substrate, 21 and 21a are conductors, 7 and 7a are resistors, 22 and 22a are protective glasses, 8 and 8a are trimming portions, and 9 is a protective epoxy layer. .

  In the ceramic substrate shown in FIG. 13, 20 is a ceramic substrate, 21 and 21a are conductors, 7 and 7a are resistors, 22 is protective glass, 8 and 8a are trimming portions, and 9 is a protective epoxy layer.

  That is, if the protective epoxy layer 6 shown in FIGS. 12 and 13 is coated on the glass protective layer using the above-described semiconductor sealing epoxy resin with controlled ionic impurities, the protective epoxy layer 6 is used. The occurrence of migration can be suppressed, and the ceramic substrate 54 can be fixed to the heat sink 52 by an inexpensive conventional epoxy resin.

  Wiring between the low-voltage part of the processing circuit and the high-voltage part for detecting the ionic current is achieved by fixing the ceramic substrate on the heat sink with double-sided wiring that achieves both suppression of migration and insulation as described above. Can be realized on the same ceramic substrate.

  As mentioned above, although embodiment of this invention was described, embodiment is not specifically limited to the said form. It can be used for any engine that requires the ignition device.

  Various modifications and improvements that can be made by those skilled in the art based on the spirit of the present invention are also possible.

The figure which shows the structure of the ignition coil for internal combustion engines which concerns on a prior art example The figure which shows the structure of the igniter which concerns on a prior art example The figure which shows the heat sink fixing method of the ceramic substrate which concerns on a prior art example The figure which shows the structure of the double-sided wiring ceramic substrate concerning the conventional example The figure which shows the resistor glass opening part concerning a prior art example The figure which shows the heat sink fixing method of the double-sided wiring ceramic substrate which concerns on a prior art example The figure which shows the structure of the double-sided wiring ceramic substrate concerning the conventional example The figure which shows the heat sink fixing method of the double-sided wiring ceramic substrate which concerns on a prior art example The figure which shows the structure of the ignition coil for internal combustion engines which concerns on an Example The figure which shows the structure of the igniter which concerns on an Example The figure which shows the heat sink fixing method of the ceramic substrate based on an Example The figure which shows the structure of the double-sided wiring ceramic substrate of the igniter which concerns on an Example The figure which shows the structure of the double-sided wiring ceramic substrate of the igniter which concerns on an Example

Explanation of symbols

5 Igniter 20 Ceramic substrate 25 Epoxy resin 52 Heat sink 55 Aluminum wire 56 Connector

Claims (5)

  A low-voltage signal line and a high-voltage power line are not physically separated on the same substrate that is wired on both sides, and one side of the substrate is fixed on the heat sink with an adhesive. It is fixed with an adhesive inside the insert-shaped connector, the terminal and board I / O pattern are bonded and connected with aluminum wire, and the board, heat sink, aluminum wire and terminal are molded with epoxy resin filled inside the connector. And an igniter molded with an ignition coil filling resin inside the ignition coil.   In a structure in which the circuit pattern is composed of a silver-containing conductor on both sides of the ceramic substrate and fixed on the heat sink by an adhesive that directly contacts the circuit pattern on one side of the substrate, ionic impurities are suppressed to a low concentration An igniter characterized in that an epoxy resin for sealing a semiconductor is used as an adhesive for the adhesive structure.   The circuit pattern is composed of silver-containing conductors on both sides of the ceramic substrate, glass is formed on both sides of the substrate as a substrate protection material, and a protective layer of epoxy material is formed on the substrate protection material on one side of the substrate. An igniter having a built-in electronic circuit board in which an epoxy resin for semiconductor encapsulation, in which ionic impurities are suppressed to a low concentration, is used as the substrate protective material.   The circuit pattern on both sides of the ceramic substrate is composed of a conductor containing silver, and the glass is used as a substrate protective material to directly adhere to the circuit pattern. On one side of the substrate, the epoxy resin is used as a substrate protective material to directly adhere to the circuit pattern. An igniter having a built-in electronic circuit board in which an epoxy resin for semiconductor encapsulation, in which ionic impurities are suppressed to a low concentration, is used as the epoxy resin.   3. The igniter according to claim 1, having an ion current detection function having the above structure.

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