JP4737116B2 - Joining method - Google Patents

Description

  The present invention relates to a bonding method between electrodes or between an electrode and a lead member when an electronic component such as a semiconductor device is mounted on a mounting substrate.

  Bare chip mounting assembly technology for supporting and fixing a semiconductor integrated circuit element on a multilayer wiring board and forming an electrical connection between the wiring board and the semiconductor element includes a chip carrier method, a film carrier method, a chip and wire method, and a flip chip method. The beam lead method is known. Of these, the flip chip method is a method in which solder bumps are formed on the inner lead bonding pads of the bare chip and soldered down on the multilayer wiring board, and is widely used because of its excellent mounting density. Has been used. However, there is a problem in terms of heat dissipation, and a special heat dissipation design is required. For this purpose, for example, a circuit component having heat generation is stored in a recess of a circuit board, solder bumps of the circuit component are soldered to land electrodes of the circuit board, and the circuit board thus obtained is used as a parent circuit board. By mounting the terminal electrode on the side of the circuit board and soldering to the land electrode on the parent circuit board, the heat generated from the circuit components is transmitted to the parent circuit board. A heat dissipating module is shown.

  On the other hand, in a non-insulated semiconductor device which is one of power semiconductor devices used for an inverter or the like, a member for fixing a semiconductor element is also one of electrodes of the semiconductor device. For example, in a semiconductor device in which a power transistor is mounted on a fixing member (for example, a copper-cuprous oxide composite material) using a Sn-Pb brazing material, the fixing member (base material) serves as a collector electrode of the power transistor. In the collector electrode portion, a current of several amperes or more flows when the semiconductor device is in operation, and the transistor chip generates heat. In order to avoid destabilization of characteristics and a decrease in service life due to this heat generation, the base material must be excellent in heat dissipation and ensure the reliability of the brazed part.

  Even in an insulated semiconductor device, in order to operate a semiconductor element safely and stably, heat generated during operation of the semiconductor device is efficiently dissipated out of the package, and connection reliability of the brazed portion is further ensured. There is a need.

  As a connection material having high heat dissipation and connection reliability, a conductive adhesive using a conductive composition containing a particulate silver compound is known (for example, Patent Document 1). However, since this conductive adhesive is a method using a binder as the bonding mechanism at the interface, the conductive adhesive is inferior in terms of heat dissipation and bonding reliability as compared with bonding where the interface is metal-bonded.

  On the other hand, when the particle size of the metal particle is reduced to a size of 100 nm or less and the number of constituent atoms is reduced, the surface area ratio with respect to the volume of the particle increases rapidly, and the melting point and the sintering temperature are greatly reduced compared to the bulk state. It is known. Using this low-temperature firing function, metal particles having an average particle size of 100 nm or less whose surface is coated with an organic material are used as a bonding material, and the organic particles are decomposed by heating to perform bonding by sintering the metal particles. Known (for example, Patent Document 2). In this bonding method, the metal particles after bonding change into a bulk metal and at the same time are bonded by metal bonding at the bonding interface, so that they have very high heat resistance, reliability, and high heat dissipation. In addition, there is an urgent need for lead-free soldering, but there is no substitute material for high-temperature solder. Since the use of hierarchical solder is indispensable for mounting, the appearance of a material that replaces this high-temperature solder is desired. Therefore, this joining technique is also expected as a material to replace this high temperature solder.

JP 2003-309352 A JP 2004-107728 A

  In the joining method using metal particles having an average particle diameter of 100 nm or less as described in Patent Document 2 and the like, as described above, joining by metal bonding is performed at the joining interface, so that high heat resistance and reliability are high. Has heat dissipation. On the other hand, very fine metal particles having an average particle diameter of 100 nm or less are likely to agglomerate, and it is necessary to form an organic protective film in order to stabilize such metal particles. This organic protective film needs to be removed at the time of bonding, but it is difficult to completely remove the protective film by heating at a low temperature, and it becomes difficult to obtain sufficient bonding strength. On the other hand, when the molecular design is performed so that the protective film of the organic substance of the metal particles is decomposed at a low temperature, when such metal particles are produced at a room temperature of 20 ° C. to 30 ° C., the metal particles immediately Since aggregation occurs, it is difficult to produce metal particles that can be sintered at a low temperature. In addition, since metal particles having an average particle size of 100 nm or less are troublesome operations such as removal of impurities after the metal particles are produced, it is difficult to reduce the cost of the bonding material.

  The problem with these impurities is the N and S components. If they are present, they remain in the sintered metal, adversely affecting the conductivity. On the other hand, as disclosed in Patent Document 2, composite-type metal nanostructures in which a core composed of metal particles having an average particle size of 100 nm or less is bound and covered with an organic substance mainly composed of C, H, and O. Although there is a method of using particles as a bonding agent, there is a great concern that due to the presence of C, it exists as a carbon residue at the bonding interface during sintering and adversely affects the thermal conductivity. As described above, in the bonding method using metal particles having an average particle diameter of 100 nm or less, problems in practical use such as metal particle production, removal of impurities after the production, storage, and handling remain.

  An object of the present invention is to provide a joining process that can achieve a reduction in joining temperature in the joining process during the mounting process and that has less organic residue after joining.

  By adding a reducing agent made of an organic substance to metal compound particles having an average particle diameter of 1 nm to 50 μm, the metal compound particles are reduced at a lower temperature than when the metal compound particles are decomposed by heating. It has been found that metal particles having a particle size of 100 nm or less are produced. At this time, after forming an oxide layer on the joint surface in advance before bonding, the layer is oxidized to generate an oxide layer with a thickness greater than the natural oxide thickness. The organic matter can be efficiently discharged, and the shear strength of the joint surface can be greatly increased.

  That is, the present invention provides a bonding material in which an oxide layer containing oxygen is formed at a bonding interface of a member to be bonded, and a metal compound particle having an average particle size of 1 nm or more and 50 μm or less and a reducing agent made of an organic substance at the bonding interface Then, the members to be joined are joined by heating and pressurizing the members to be joined.

  According to the present invention, the bonding temperature can be lowered in the bonding process during the mounting process, and a bonding process with less organic residue after bonding can be provided.

  Hereinafter, embodiments of the present invention will be specifically described.

  In the bonding method of the present invention, a bonding material including a reducing agent composed of a metal compound having an average particle diameter of 1 nm to 50 μm and an organic substance is disposed between bonded members, and the bonded members are bonded by heating and pressing. . At this time, bonding is performed using a phenomenon in which metal particles having a particle size of 100 nm or less are produced during heating and pressing during bonding, and then agglomerate and change into a bulk metal. In this joining method, it is necessary to efficiently discharge organic substances in the joining layer at the time of joining. Usually, organic substances are discharged at the time of bonding by pressurization, but in the present invention, an oxide layer is formed on the bonding surface in advance before bonding as shown in FIG. An oxide layer having a thickness greater than that of the natural oxide film is generated. By performing this surface treatment, it becomes possible to burn organic substances with oxygen present in the surface layer and to discharge organic substances more efficiently.

  The organic matter is considered to be present at the joining interface as a carbon residue, which reduces the shear strength of the joining surface. However, the organic treatment can be efficiently removed by applying the surface treatment of the present invention. It is possible to greatly increase the shear strength of the surface. Moreover, since the organic substance removal effect by oxygen existing on the bonding surface is promoted, it is possible to reduce the pressure applied during bonding.

  A member to be joined by this joining method may be a metal member having conductivity, for example, an electrode or wiring of an electronic component such as a semiconductor device. Although the metal of the joining surface of a to-be-joined member is not prescribed | regulated, copper, silver, or gold | metal | money is good in practice, and it is copper that the effect of this invention appears notably among them. There are two main methods for forming an oxide film on the metal used for the bonding interface: a wet method and a dry method. As typical dry methods, there are high-temperature oxidation exposed to high-temperature air and exposure to high-temperature water vapor. In the wet method, there is a method of immersing in an alkaline solution. In order to shorten the time and increase the efficiency, it is efficient to add an oxidizing agent to the alkaline solution. As this oxidizing agent, for example, ammonium persulfate, iron nitrate, hydrogen peroxide and the like are effective.

The metal compound having an average particle size of 50 μm or less of the bonding material is a substance that is mixed with a reducing agent and reduced by heating to produce metal particles having a particle size of 100 nm or less. The metal compounds are metal oxides, metal carbonates, is preferably 1 or more particle element selected from particles of metal carboxylate. This is because, since the metal content in the metal compound is high, the volumetric shrinkage at the time of bonding is small, and oxygen is generated at the time of decomposition, so that the oxidative decomposition of the organic matter is promoted.

  The average particle diameter of the metal compound used here is 1 nm or more and 50 μm or less. When the average particle diameter of the metal particles is larger than 50 μm, it is difficult to produce metal particles having a particle diameter of 100 nm or less during bonding. This is because the gaps between the particles increase, and it becomes difficult to obtain a dense bonding layer. The reason why the thickness is 1 nm or more is that it is difficult to actually produce a metal compound having an average particle size of 1 nm or less. In the present invention, since metal particles having a particle size of 100 nm or less are produced during bonding, it is not necessary that the metal compound has a particle size of 100 nm or less. From the viewpoint of production, handling properties, and long-term storage stability of the metal compound. It is preferable to use particles having a particle size of 1 to 50 μm. In order to obtain a denser bonding layer, a metal compound having a particle size of 1 nm to 100 nm can be used.

Examples of the metal oxide include silver oxide (Ag ₂ O, AgO), copper oxide, gold oxide, silver carbonate as the metal carbonate, silver acetate as the carboxylic acid metal salt, and at least one kind selected from these groups. It is possible to use a bonding material made of two or more kinds of metals. Among these, metal oxides composed of gold oxide, silver oxide (Ag ₂ O, AgO), and copper oxide generate only oxygen during reduction, so that residues after bonding are hardly left and the volume reduction rate is very small. It is preferable to use a metal oxide.

  In the presence of a reducing agent, these metal oxides, metal carbonates, and carboxylic acid metal salts start to produce metal particles of 100 nm or less at 200 ° C. or less. Therefore, metal particles whose surfaces of 100 nm or less are coated with organic substances are used. Bonding can be achieved even at a low temperature of 200 ° C. or lower, which was impossible when used as a bonding material. As a result, even at a temperature of 250 ° C. or lower, which is difficult with the prior art, it becomes possible to perform strong bonding with a shear strength of 5 MPa or more at the bonding interface of the bonding layer, and deterioration of chip peripheral members during bonding is 300 ° C. or higher. Can be significantly reduced.

  As the reducing agent composed of an organic substance, one or more mixtures selected from alcohols, carboxylic acids, and amines can be used.

  Examples of the compound containing an alcohol group that can be used include alkyl alcohols, such as ethanol, propanol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, and dodecyl. There are alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, nonadecyl alcohol, icosyl alcohol. Furthermore, not only the primary alcohol type, but also an alcohol compound having a secondary alcohol type, a tertiary alcohol type such as ethylene glycol or triethylene glycol, an alkanediol, or a cyclic type structure can be used. In addition, compounds having four alcohol groups such as citric acid and ascorbic acid may be used.

  Moreover, there exists alkylcarboxylic acid as a compound containing carboxylic acid which can be utilized. Specific examples include butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, Examples include octadecanoic acid, nonadecanoic acid, and icosanoic acid. Further, similarly to the amino group, it is possible to use not only the primary carboxylic acid type but also a secondary carboxylic acid type, tertiary carboxylic acid type, dicarboxylic acid, and a carboxyl compound having a cyclic structure.

  Moreover, an alkylamine can be mentioned as a compound containing an available amino group. For example, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, There are nonadecylamine and icodecylamine. In addition, the compound having an amino group may have a branched structure, and examples thereof include 2-ethylhexylamine and 1,5 dimethylhexylamine. Moreover, not only a primary amine type but also a secondary amine type and a tertiary amine type can be used. Further, such an organic material may have an annular shape.

  Further, the reducing agent to be used is not limited to the organic substance containing the alcohol, carboxylic acid, and amine, but may be an organic substance containing an aldehyde group, an ester group, a sulfanyl group, a ketone group, or the like.

Here, reducing agents that are liquid at 20 to 30 ° C., such as ethylene glycol and triethylene glycol, are reduced to silver after one day if mixed with silver oxide (Ag ₂ O) and left to stand. Need to be used immediately. On the other hand, myristyl alcohol, laurylamine, ascorbic acid, etc., which are solid in the temperature range of 20-30 ° C., do not proceed to a large extent even if left for about a month with metal oxides, etc. These are preferably used when stored for a long time after mixing. Further, it is desirable that the reducing agent used has a certain number of carbon atoms in order to function as a protective film for purified metal particles having a particle size of 100 nm or less after reducing metal oxides and the like. Specifically, it is desirably 2 or more and 20 or less. This is because, when the number of carbon atoms is less than 2, metal particles are produced at the same time as particle size growth occurs, making it difficult to produce metal particles of 100 nm or less. On the other hand, if it exceeds 20, the decomposition temperature becomes high and the metal particles are hardly sintered, resulting in a decrease in bonding strength.

  The amount of the reducing agent used may be in the range of 1 part by mass to 50 parts by mass with respect to the total weight of the metal compound. This is because when the amount of the reducing agent is less than 1 part by mass, the amount of the metal compound in the bonding material is not reduced enough to produce metal particles. Moreover, when it exceeds 50 mass parts, it is because the residue after joining increases and it is difficult to achieve metal joining at the interface and densification in the joining silver layer. Furthermore, as a reducing agent, it is preferable that the thermal weight reduction rate at the time of a heating to 400 degreeC is 99% or more. This is because if the decomposition temperature of the reducing agent is high, the residue after bonding increases, and it is difficult to achieve metal bonding at the interface and densification in the bonding silver layer. Here, the measurement of the thermogravimetric decrease rate at the time of heating up to 400 ° C. is performed using a commercially available apparatus such as TG / DTA6200 manufactured by Seiko Instruments or TGA-50 manufactured by Shimadzu Corporation. It shall be when conducted in air at 10 ° C / min.

  The combination of the reducing agent composed of a metal compound and an organic substance is not particularly limited as long as the metal particles can be produced by mixing them, but from the viewpoint of storage stability as a bonding material, the metal particles are used at room temperature. A combination that is not produced is preferable.

  Moreover, it is also possible to mix and use metal particles having a relatively large average particle diameter of 50 μm to 100 μm in the bonding material. This is because the metal particles of 100 nm or less produced during bonding play a role of sintering metal particles having an average particle diameter of 50 μm to 100 μm. Further, metal particles having a particle size of 100 nm or less may be mixed in advance. Examples of the metal particles include gold, silver, and copper. In addition to the above, at least one metal selected from platinum, palladium, rhodium, osmium, ruthenium, iridium, iron, tin, zinc, cobalt, nickel, chromium, titanium, tantalum, tungsten, indium, silicon, aluminum, etc. It is possible to use an alloy made of more than one kind of metal.

  The bonding material used in this embodiment may be used only with a reducing agent composed of a metal compound and an organic substance, but a solvent may be added when used as a paste. If it is used immediately after mixing, it may be used that has a reducing action such as methanol, ethanol, propanol, ethylene glycol, triethylene glycol, terpineol alcohol, etc. It is preferable to use water, hexane, tetrahydrofuran, toluene, cyclohexane, or the like that has a weak reducing action at room temperature. In addition, when a reducing agent such as myristyl alcohol that is difficult to reduce at room temperature is used, it can be stored for a long time, but when a reducing agent such as ethylene glycol is used, it is mixed at the time of use. And preferably used.

Moreover, in order to improve the dispersibility of the metal compound in the solvent, the periphery of the metal compound may be coated with an organic substance using a dispersant as necessary to improve the dispersibility. As the dispersant used in the present invention, in addition to polyvinyl alcohol, polyacrylonitrile, polyvinyl pyrrolidone, polyethylene glycol and the like, commercially available dispersants such as Dispersic 160, Dispersic 161, Dispersic 162, Dispersic 163, Disperbic 166, Disperbic 170, Disperbic 180, Disperbic 182, Disperbic 184, Disperbic 190 (manufactured by Big Chemie), MegaFuck F-479 (Dainippon Ink), Solsperse 20000, Solsperse 24000, Solsperse 26000 Solsparse 27000, Solsparse 28000
Polymeric dispersants such as (Avisia) can be used. The amount of such a dispersant used is within the range of 0.01 wt% or more and not exceeding 45 wt% in the bonding material of the metal compound.

  These paste materials can be applied using a method in which the paste is ejected from a fine nozzle by an ink jet method and applied to the electrode or the connection part of the electronic component on the substrate, or a metal mask or mesh mask with an open application part. A method of applying only to the surface, a method of applying to a necessary part using a dispenser, a water-repellent resin containing silicone, fluorine, etc., is applied with a metal mask or a mesh-like mask having an opening only on the necessary part, or photosensitive. A method of applying a water-repellent resin on a substrate or electronic component, removing a portion to which the paste composed of the fine particles and the like is applied by exposure and development, and then applying a bonding paste to the opening, and After applying the water-repellent resin to the substrate or electronic component, the paste application part consisting of the metal particles is applied with a laser. Removed, there is then a method of applying a bonding paste in the opening. These application methods can be combined according to the area and shape of the electrodes to be joined. In addition, when a solid at room temperature such as myristyl alcohol or ascorbic acid is used as a reducing agent, there is a method of mixing with a metal compound and applying pressure to form a sheet and using it as a bonding material.

  In bonding using this bonding material, metal particles having a particle size of 100 nm or less are produced from a metal compound at the time of bonding, and metal bonding is performed by fusing metal particles having a particle size of 100 nm or less while discharging organic substances in the bonding layer. Therefore, it is essential to apply heat and pressure. As joining conditions, it is preferable to apply heating of 40 ° C. or more and 400 ° C. or less and pressurization of more than 0 and less than 10 Mpa within 1 second or more and 10 minutes or less. The reason why pressurization is indispensable at the time of joining is that unless pressurization is applied, the area of the joint is not improved, and strong joining cannot be achieved.

  In the bonding method of the present invention, since nanoparticles are not used for the bonding material used for bonding, the metal particles used do not need to protect the surface with organic substances, and yet the bonding surface is equal to or higher than when using nanoparticles. Therefore, it is possible to achieve a simplification of the joining process and a significant cost reduction of the joining material. Of course, the bonded layer after bonding has a very high heat resistance as compared with the conventional solder. In addition, when the metal particles mixed at the same time through this aggregated layer are bonded to the semiconductor element, the electrode formed on the wiring board, etc., it is possible to bond at a low temperature.

  On the other hand, after depositing copper on the surface of the mounting portion of the electrode provided on the active area of the conductor element and the wiring board on which the electrode is mounted by plating or the like, and then oxidizing the surface of the copper, an average of 50 μm or less By forming a bonding layer made of a bonding material containing a reducing agent composed of a metal compound and an organic substance, the semiconductor element mounting portion does not melt in the thermal process after mounting the semiconductor element on the wiring board, so that the wiring board is damaged during bonding. Therefore, the semiconductor device can be downsized and highly reliable.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
In Example 1, a copper pellet was used as a test piece, and the size was 5 mm in diameter and 2 mm in thickness on the upper side, and 10 mm in diameter and 5 mm in thickness on the lower side. As a pretreatment, this test piece was immersed in a 200 g / L, NH ₄ S ₂ O ₈ +5 mL / L, H ₂ SO ₄ solution at 25 ° C. for 90 s and subjected to soft etching, and then 90 g / L, NaClO at 70 ° C. ₂ +30 g / L, immersed in a NaOH solution for a predetermined time to be oxidized. The joining material used for joining was produced by the following method. After 0.8 g of silver oxide having an average particle size of 50 μm or less and 0.2 g of myristyl alcohol were ground and mixed for 10 minutes using a mortar, 0.4 g of toluene was added to the mixed powder to make a paste. This was subjected to vibration for about 1 hour using a vibrator to disperse silver oxide and myristyl alcohol in the mixed solution. The above-mentioned paste was applied to the test piece subjected to the oxidation treatment, followed by drying at 60 ° C. for 5 minutes to remove toluene, and then bonding was performed. The bonding conditions were a bonding temperature of 300 ° C. and 400 ° C., a bonding time of 2.5 min, and a pressure of 2.5 Mpa. In order to investigate the influence of the oxidation treatment time, the bonding strength was measured when changing to 10 s, 1 min, 2 min, and 10 min. The bonding strength was evaluated by pure shear stress. For this shear test, Seishin Shoji Bond Tester SS-100KP (maximum load 100 kg) was used. The shear rate was 300 mm / min, the specimen was broken with a shearing tool, the maximum load at the time of breaking was measured, and the maximum load divided by the joint area was taken as the shear strength. FIG. 2 shows the dependency of the shear strength on the oxidation treatment time. When the oxidation treatment is not performed, an oxide layer of about 2 nm is present on the surface, but the bonding strength in this case is considerably lower than that in the case of the high melting point solder. However, when the oxidation treatment is performed, the bonding strength suddenly increases and then decreases with the oxidation treatment time. When the oxidation treatment time of 10 s is applied, the joint strength increases at least twice as high at 300 ° C and 1.5 times at 400 ° C compared to the case where no oxidation treatment is performed, and the same joint strength as that of the high melting point solder. Can be confirmed. Even when the oxidation treatment is performed for 1 minute, the bonding strength is larger than that when the oxidation treatment is performed. However, when the oxidation treatment is further performed, the bonding strength becomes smaller than that when the oxidation treatment is not performed. When the fracture surface after the test was observed, when the oxidation treatment time was 10 s and 1 minute, it was a fracture in the sintered silver layer, whereas when it exceeded 1 minute, it was an interface fracture. This is presumably because, when the oxide film layer is thickened, the oxide layer remains even after the bonding, so that it exists as a residual and thus breaks in that portion. FIG. 3 shows the change over time of the oxide film thickness when the oxidation treatment is performed in the alkaline solution. The oxide film thickness was measured using the cathode reduction method. That is, 0.1M
A constant current of −20 mA / cm ² was applied in an NaOH solution, and the amount of electricity until the potential changed was converted to the oxide film thickness. From the comparison between FIG. 3 and FIG. 2, it can be seen that the thickness of the oxide film that provides high bonding strength is 100 nm or less. When the oxidation treatment is not performed, that is, the oxide film thickness by natural oxidation is about 2 nm. In this case, the bonding strength is smaller than that when the oxidation treatment is performed within 1 minute. FIG. 4 shows a change in bonding force when the applied pressure during bonding is changed. When the oxidation treatment is not performed, the shear strength increases linearly as the pressure is increased. This is because by increasing the pressing force, the sintered silver layer is densified during bonding, and the contact area at the interface between the sintered silver layer and the bonding member increases, so that metal bonding is achieved in a wider area. It is thought to be like that. On the other hand, when the oxidation treatment is performed, the effect of increasing the bonding force due to the oxidation treatment becomes remarkable in a lower pressure region. Although this mechanism is not necessarily clear, it is thought that the effect of the oxides effectively burning organic substances appears.

  In the present embodiment, the case where the treatment is performed in an alkaline solution containing an oxidizing agent is shown as a representative example of the wet method, but the same effect can be obtained even when another solution is used.

(Example 2)
In this embodiment, an air oxidation method is applied as a typical example of the dry method. The same method was used for portions other than the oxide film treatment with alkali + oxidant in Example 1. The oxidation treatment in this example was performed at a temperature of 200 ° C. to 400 ° C. and an oxidation time of 2 to 10 minutes using a thermostatic bath or an electric furnace. Table 1 shows the shear strength when the test piece subjected to air oxidation treatment is joined using the above-described silver oxide paste, using temperature and oxidation time as parameters. The results are shown in Table 1. The oxide film thickness is shown above the dotted line of the cell in the table, and the shear strength ratio (high melting point solder strength is 1) is shown below. The colored area is an area where the bonding strength is increased by the oxidation treatment. The oxide film thickness increases with increasing time and temperature. The oxide film thickness in which the increase in shear strength was observed was a region of 8 nm to 100 nm thicker than the natural oxide film thickness, and when the oxide film thickness became thicker than that, the shear strength decreased as shown in Example 1. To come.

(Example 3)
This example shows the bonding strength ratio when bonding is performed by changing the combination of the organic substance and metal particles used for bonding. The metals used for the joint surfaces are copper and nickel. When copper was used, 200 g / L at 25 ° C., NH ₄ S ₂ O ₈ +5 mL / L shown in Example 1,
Soft etching by immersing in H ₂ SO ₄ solution for 90 s, followed by oxidation treatment by immersing in 70 g of 90 g / L, NaClO ₂ +30 g / L, NaOH solution for 10 s. When nickel is used, an oxide film is formed by the high temperature treatment shown in Example 2. The generation conditions are 400 ° C. and 2 minutes in air. The used particles are silver oxide, copper oxide, gold oxide, silver carbonate, and silver acetate. In addition, myristyl alcohol, ethylene glycol, triethylene glycol, methanol, ethanol, octyl alcohol, undecyl alcohol, hexylamine, octylamine, lauryl alcohol, tetradecanoic acid and ascorbic acid were used as reducing organic substances. Table 2 shows the bonding strength of 80% I or more of the high melting point solder in either case when joining using each metal particle and organic matter (temperature 400 ° C., time 2.5 min, pressure 2.5 MPa). Can get.

Example 4
FIG. 5 is a view showing the structure of a non-insulated semiconductor device which is one embodiment of the present invention. 5A is a top view, and FIG. 5B is a cross-sectional view taken along the line AA ′ of FIG. 5A. After mounting the semiconductor element (MOSFET) 301 on the ceramic insulating substrate 302 and the ceramic insulating substrate 302 on the base material 303, an epoxy resin case 304, a bonding wire 305, and an epoxy resin lid 306 are provided. Was filled with silicone gel resin 307. Here, the ceramic insulating substrate 302 on the base material 303 is bonded by a bonding layer 308 made of a paste material in which silver oxide and myristyl alcohol are dispersed in toluene, and 8 Si are formed on the copper plate 302a of the ceramic insulating plate 302. A MOSFET element 301 made of is bonded with a bonding layer 309 made of a paste material in which silver oxide and myristyl alcohol are dispersed in toluene. Joining with the joining layers 308 and 309 made of a paste material in which silver oxide and myristyl alcohol are dispersed in toluene is first performed on the copper plate 302a of the ceramic insulating plate 302 and the base material 303 with silver oxide and myristyl alcohol in toluene. The dispersed paste material is applied onto the copper plate 302a and the base material 303, respectively.

  Each of the copper material 302a and the copper base material 303 on the ceramic substrate is subjected to an oxidation treatment (10 s) by the method shown in the first embodiment. In addition, the bonding surface of the element 301 is previously subjected to electroless copper plating and the oxidation treatment of Example 1 before bonding.

  A semiconductor element 301 and a ceramic insulating plate 302 are arranged and connected on a bonding layer of a paste material in which these silver oxide and myristyl alcohol are dispersed in toluene. At this time, heating is performed at about 250 ° C. for 5 minutes under an applied pressure of 1 MPa.

An Al wire 305 having a diameter of 300 μm is used between the gate electrode, emitter electrode, and the like formed on each element 301 and the terminals 310 attached in advance to the electrodes 302a and 302b of the epoxy resin case 304 formed on the insulating substrate. Wire bonding was performed by ultrasonic bonding. Reference numeral 311 denotes a temperature detection thermistor element that has been subjected to copper plating and oxidation treatment. The temperature detection thermistor element 311 is composed of a bonding layer 309 made of a paste material in which silver oxide and myristyl alcohol are dispersed in toluene. Wire bonding is performed with an Al wire 305 of 300 μm and is communicated to the outside.

The epoxy resin case 304 and the base material 303 were fixed using a silicone adhesive resin (not shown). The epoxy resin lid 306 is provided with a recess 306 ′ in the inner thick portion and a hole 310 ′ in the terminal 310, and a screw (not shown) for connecting the insulating semiconductor device 1000 to an external circuit is attached. It is like that. The terminal 310 is a copper plate that has been punched into a predetermined shape and formed and subjected to an oxidation treatment, and is attached to the epoxy resin case 304.

FIG. 6 is a view showing a sub-assembly portion of the insulated semiconductor device of the present invention shown in FIG. 5, in which a ceramic substrate and a semiconductor element are mounted as a base material. A mounting hole 303A is provided in the periphery of the base material. The base material is made of Cu, and the surface is oxidized. A ceramic insulating substrate 302 (copper portion is oxidized) is formed on the base material 303 by a paste layer in which the silver oxide and myristyl alcohol are dispersed in toluene, and on the ceramic insulating substrate 302 (copper portion is oxidized). MOSFET elements 301 are respectively mounted by layers of paste material in which silver oxide and myristyl alcohol are dispersed in toluene.

FIG. 7 is an enlarged schematic view of a cross section of the MOSFET element mounting portion in FIG. 6 before joining. As shown in FIG. 7, a paste material in which silver oxide and myristyl alcohol are dispersed in toluene can be used for the bonding layer. Further, a water repellent film 322 is applied on the base material 303 so as to correspond to the region where the ceramic insulating substrate 302 is mounted in order to prevent a solution flow when applying a paste material in which silver oxide and myristyl alcohol are dispersed in toluene. . Furthermore, a water repellent film 321 is applied on the ceramic insulating substrate 302 so as to correspond to the mounting region of the semiconductor element 301 to prevent solution flow during application of the Ag particle-containing solution.

  Copper present on each joint surface is subjected to an oxide film treatment by the method shown in the first embodiment.

(Example 5)
FIG. 8 is a diagram showing another embodiment of the non-insulated semiconductor device using the present invention.

  Similar to the third embodiment, the semiconductor element 401 and the ceramic insulating substrate 402 are bonded by a paste material bonding layer in which silver oxide and myristyl alcohol are dispersed in toluene after the oxidation treatment of the copper-plated wiring portion 402a. The copper electrode 402b subjected to the oxidation treatment formed on the ceramic insulating substrate via the junction terminal 431 is also connected by a paste material particle layer in which silver oxide and myristyl alcohol are dispersed in toluene.

  FIG. 9 is an enlarged schematic cross-sectional view of the semiconductor element mounting portion in FIG. 8 before joining. The connection terminal 431 uses the copper plate subjected to the oxidation treatment described in the first embodiment, and the semiconductor element 401 (copper plating and oxidation treatment on the bonding surface) is mounted on the wiring 402a (the oxidation treatment is performed) of the insulating substrate. Thereafter, a paste material in which silver oxide and myristyl alcohol are dispersed in toluene is placed on the emitter electrode (upper side) of the semiconductor element. Further, the sheet material is placed on the copper wiring 402b which is oxidized on the surface connected with the emitter electrode of the semiconductor element via the terminal 431 by the copper wiring pattern formed on the insulating substrate 402. After that, the connection terminal 431 is mounted on the upper part of the paste material electrode in which silver oxide and myristyl alcohol whose surfaces are coated with an organic substance are dispersed in toluene, and heat of about 250 ° C. is applied under a pressure of 0.5 MPa. By adding for a minute, the connection between the semiconductor element 401 and the insulating substrate wiring 402b is completed. In the insulating semiconductor device, a large current flows not only in the collector electrode but also in the emitter electrode portion. Therefore, the connection reliability on the emitter electrode side can be further improved by using the connection terminal 431 having a large wiring width.

(Example 6)
When the LED is mounted on the substrate, the heat dissipation can be improved as compared with the conventional solder or heat conductive adhesive by bonding using the bonding method according to the present invention.

The conceptual diagram at the time of joining of this invention. Dependence of shear strength on oxide layer thickness when joining surfaces with oxide layers using paste in which silver oxide and myristyl alcohol are dispersed in toluene. Dependence of oxide thickness on oxide treatment time. Dependence of applied pressure on shear strength. The figure which showed the structure of the non-insulated semiconductor device which is one of the Examples of this invention. The figure which showed the sub-assembly part of the insulated type semiconductor device of this invention. The enlarged schematic diagram of a semiconductor element and a board | substrate junction part. The figure which showed the other Example structure of the sub-assembly part of the non-insulating semiconductor device. The enlarged schematic diagram of a semiconductor element and a board | substrate junction part.

Explanation of symbols

301 Semiconductor device (MOSFET)
302, 403 Ceramic insulating substrate 302a, 302b Copper part 303 on ceramic insulating plate Base material (copper)
304 Epoxy resin case 305 Al material 308, 309 Bonding layer 310 Terminal 311 Temperature detection thermistor 322 Water repellent film 401 Semiconductor element 402a, 402b Copper wiring 402b Copper wiring 431 Connection terminal

Claims (14)

Forming an oxide layer containing oxygen at the bonding interface of the members to be bonded;
Disposing a bonding material including a metal compound particle having an average particle diameter of 1 nm to 50 μm and a reducing agent made of an organic substance at a bonding interface;
A joining method comprising joining members to be joined by heating and pressurizing the members to be joined. In claim 1, the joining method wherein said metal compound is a metal oxide is one or more particle element selected from particles of a metal carbonate or a metal carboxylate.   The joining method according to claim 1, wherein the metal compound is at least one compound of silver, gold, and copper.   The joining method according to claim 1, wherein the reducing agent is one or a mixture of two or more selected from alcohols, carboxylic acids, and amines.   2. The reducing agent according to claim 1, wherein the reducing agent is represented by ethylene glycol, triethylene glycol, methanol, ethanol, octyl alcohol, undecyl alcohol, or myristyl alcohol, or hexylamine, octylamine, or laurylamine. And a mixture of at least one or a mixture of two or more alkylamines, carboxylic acids typified by tetradecanoic acid, and ascorbic acid.   2. The bonding method according to claim 1, wherein the oxide layer has a thickness of 5 nm or more and 100 nm or less. The joining method according to claim 1, wherein the member to be joined is immersed in an alkaline solution containing an oxidizing agent to form an oxide layer on the surface .   The joining method according to claim 7, wherein the oxidizing agent is sulfite, hydrogen peroxide, nitrate, or persulfate.   The bonding method according to claim 1, wherein an oxide layer is formed on a surface by exposing the member to be bonded to a high-temperature steam environment. The bonding method according to claim 1, wherein an oxide layer is formed on a surface by exposing the member to be bonded to high-temperature air.   2. The joining method according to claim 1, wherein copper, silver or nickel is deposited on the joining surface of the member to be joined by electroless plating or electroplating, and then the plated metal surface is oxidized.   The bonding method according to claim 1, wherein the oxide layer is a copper oxide.   The bonding method according to claim 1, wherein the metal compound particles are reduced by the heating to generate metal particles having an average particle diameter of 100 nm or less. A bonding method for bonding an electrode of a semiconductor element and a wiring for taking out an electric signal of the semiconductor element to the outside,
Forming an oxide layer containing oxygen on at least one surface of the electrode of the semiconductor element or the wiring;
Disposing a bonding material including metal compound particles having an average particle diameter of 1 nm or more and 50 μm or less and a reducing agent made of an organic substance between the electrode and the wiring;
Heating between the electrode and the wiring, joining method characterized by a step of bonding by pressing.

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