JP5652689B2 - Manufacturing method of electronic component bonded structure and electronic component bonded structure obtained by the manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing an electronic component bonding structure and an electronic component bonding structure obtained by the manufacturing method, and more particularly, to electronic components such as chip components and semiconductor packages using printed materials such as solder, such as printed wiring boards. The present invention relates to a method for manufacturing a lead-free electronic component bonding structure and an electronic component bonding structure to be mounted on a circuit board.

  As electronic devices have become smaller and thinner in recent years, the mounting technology for electronic devices is to screen-print solder paste onto the electrodes on the circuit board, mount the electronic components, and then perform heat treatment using a reflow furnace. Accordingly, surface mounting technology in which an electronic component is bonded to a circuit board to form an electronic component bonded structure has become mainstream. In addition, electronic components used in semiconductor devices, etc., are becoming more sophisticated, lighter, smaller, and thinner, and along with this, the electrode terminals and soldered parts arranged in the electronic components are miniaturized and There is a tendency to increase the number of terminals. There has been a demand for a mounting joint structure for electronic components in which electrode terminals that are miniaturized and multi-terminals are mounted on a circuit board with high reliability.

  The solder used for joining these electrode terminals to the electrode metal on the substrate is generally used for joining metal materials, and has a melting temperature range (solidus temperature to liquidus temperature range) of 450 ° C. The following alloy materials are used. Conventionally, as a solder material used in reflow heat treatment, Sn-37Pb eutectic solder having a melting point of 183 ° C. is generally used, and high-temperature solder used in an electronic component or the like that requires high heat resistance. For example, high-temperature solder such as Sn-90Pb having a solidus of 270 ° C. and a liquidus of 305 ° C. has been widely used.

  However, in recent years, as in EU environmental regulations (WEEE, RoHS directive), the harmfulness of Pb has become a problem, and from the viewpoint of preventing environmental pollution, lead-free solder is rapidly progressing. Currently, as an alternative to Sn-37Pb eutectic solder, for example, lead-free solder made of Sn-3.0Ag-0.5Cu having a melting point of about 220 ° C. (see Patent Documents 1 and 2) has been proposed, and 240 ° C. as reflow heat treatment. A temperature range of approximately 260 to 260 ° C. is becoming common.

  However, each of the above eutectic solder, high temperature solder, and lead-free solder exhibits a liquid phase at a temperature higher than the melting point. Therefore, after printing and applying as a solder paste, it becomes a molten state in a heat treatment process such as reflow. In addition, it was a processing characteristic that spreads in a liquid state with respect to the electrode metal on the substrate. Especially for the electrode metal surface on the substrate on which the solder is printed and applied, the solder is greatly wet and spread, so there is no exposed part of the electrode metal surface on the substrate and the coating thickness is not constant. Stable quality and reliability with one or more other bonding methods (for example, gold wire bonding, mating type connection, pressure contact conductive material addition, etc.) in the margin of the same electrode metal on the substrate There was a situation that could not be implemented due to sex.

  Examples of the bonding material applied to the electrode metal on the substrate that does not spread out when heated include a conductive adhesive (typically, conductive particles dispersed in an adhesive resin). However, unlike solder materials, the continuity of the joint is realized by the contact of conductive particles, and the adhesive strength depends on the adhesive strength of the adhesive resin. Therefore, it is a metal bond in terms of heat resistance and reliability of the joint. It was inferior to the solder to be joined. Therefore, when using a bonding method that combines on the same electrode metal on the substrate to increase the functionality and multi-terminal of the electronic component bonding structure, it has a high heat resistance and high reliability connection material that has the same metal bond as solder. However, a bonding material that can maintain the shape and area during printing without melting into a liquid during the heat treatment of bonding and does not spread even on a minute electrode, and a method of forming a bonded structure using the bonding material are desired. It was rare. However, there was no effective solution at present.

  On the other hand, the present inventors alloyed the lead-free solder represented by Sn-3.0Ag-0.5Cu under reflow heat treatment conditions (specifically, peak 245 ° C.), and after the alloy formation, the peak was less than 300 ° C. A high heat-resistant lead-free connecting material that does not remelt under the reflow heat treatment conditions has been proposed (see Patent Document 3).

JP-A-5-050286 Japanese Patent Laid-Open No. 5-228685 International Publication No. 2006/109573 Pamphlet

  The present invention provides a method for manufacturing an electronic component bonded structure and an electronic component bonded structure in which solder wetting and spreading during heat treatment after coating is reduced, and the electronic component has a higher functionality and can have multiple terminals. Objective.

  The present inventors have studied for solder paste materials with regard to various metal compositions and particle forms, and by using specific solders, printing, component mounting, and reflow heat treatment used in ordinary electronics mounting technology In such a series of steps, the present inventors have found that the change in the solder application area on the electrode metal on the substrate before and after the formation of the joint by heat treatment can be reduced, and the present invention has been completed. That is, the present invention is as follows.

[1] An application step of applying a solder paste onto the electrode metal on the substrate, and heat-treating the solder paste in a state where the electrode terminal of the electronic component is in contact with the electrode metal on the substrate via the solder paste Heat treatment process,
A method for manufacturing an electronic component joint structure including:
When the solder paste is applied to a metal plate of the same material as the electrode metal on the substrate, the contact area between the metal plate and the solder paste is A, and the solder paste is heat-treated at a temperature in the range of 235 ° C. to 260 ° C. A manufacturing method of an electronic component joint structure satisfying 0.7 ≦ B / A ≦ 1.3, where B is a contact area between the metal plate and solder later.

  [2] In the application step, a solder paste is applied to a part of the electrode metal on the substrate, and after the heat treatment step, the electrode metal on the substrate is not covered with solder. The method for manufacturing an electronic component bonding structure according to the above [1], wherein a bonding step of forming a bond by physical signal line connection is performed.

  [3] The solder paste contains first metal particles and second metal particles as a conductive filler, and in differential scanning calorimetry in the range of 30 ° C. to 600 ° C., the first metal particles are at least One exothermic peak and at least one endothermic peak of 300 to 600 ° C., wherein the second metal particle does not have an exothermic peak and has at least one endothermic peak at 210 to 260 ° C. 2] The manufacturing method of the electronic component joining structure according to [2].

  [4] The method for manufacturing an electronic component joint structure according to [3], wherein the second metal particles are particles containing Sn as a main component.

  [5] The first metal particles are made of an alloy having a composition of 50 to 90% by mass of Cu and 10 to 50% by mass of one or more elements selected from the group consisting of Ag, Bi, In, and Sn. The method for producing an electronic component joint structure according to [3] or [4], wherein the second metal particles are made of Sn.

  [6] An electronic component joint structure obtained by the manufacturing method according to any one of [1] to [5].

  According to the method of manufacturing an electronic component bonding structure and the electronic component bonding structure of the present invention, the electronic component capable of reducing the spread of the solder during heat treatment after coating and increasing the functionality of the electronic component and increasing the number of terminals. A method for manufacturing a bonded structure and an electronic component bonded structure can be provided. In addition, according to the present invention, for example, bonding by solder and bonding by other methods (for example, gold wire bonding, fitting type connection, pressure contact conductive material addition, etc.) can be stably performed on the same electrode metal on the substrate. It is also possible to form with high quality and reliability.

  The method for manufacturing an electronic component joint structure according to the present invention includes a coating step of applying a solder paste on an electrode metal on a substrate, and contacting an electrode terminal of the electronic component on the electrode metal on the substrate via the solder paste. A heat treatment step of heat treating the solder paste in a state where

  The solder paste used in the present invention has a contact area between the metal plate and the solder paste when applied to a metal plate made of the same material as the electrode metal on the substrate, and the solder paste has a temperature in the range of 235 ° C. to 260 ° C. When the contact area between the metal plate and the solder after the heat treatment is B, 0.7 ≦ B / A ≦ 1.3 is satisfied. If the contact area between the electrode and the solder decreases due to the shrinkage of the solder after the heat treatment step, the joint part of the electronic component joint structure itself is hidden under the electronic component and becomes invisible, and the appearance inspection becomes difficult, and the joint strength From this point of view, the value of B / A is 0.7 or more. Moreover, the value of B / A is 1.3 or less from the viewpoint of suppressing the influence of diffusion and alteration on the electrode metal and electrode terminal on the substrate. The value of B / A is preferably 0.8 or more and 1.2 or less, and more preferably 0.9 or more and 1.1 or less.

  In the present invention, by using a solder paste having a B / A value within the above range, when the solder paste is heat-treated to form an electrode metal electronic part joint on the substrate, the solder does not spread out. In addition, a blank portion (that is, a portion where no solder coating is formed) can be formed on the electrode metal on the substrate. Thereby, the joining by another physical signal connection can be given to the electrode metal itself on the board | substrate with which the solder joint part was formed, and a smaller area and a small electronic component joining structure can be manufactured. .

Hereinafter, preferable examples of the solder paste that can be used in the present invention will be described.
Preferred solder pastes include those containing a conductive filler, and in particular, a paste composed of a conductive filler and a flux comprising an additive containing a rosin, an activator, a solvent and, if necessary, a thickener. Is particularly preferred.

  The conductive filler more typically includes first metal particles and second metal particles. In this case, in differential scanning calorimetry (hereinafter also referred to as “DSC measurement”) in the range of 30 ° C. to 600 ° C., the first metal particles have at least one exothermic peak and an endothermic peak at 300 to 600 ° C. It is preferable that at least one and the second metal particles have no exothermic peak and have at least one endothermic peak at 210 to 260 ° C.

  In particular, as the first metal particles, at least one metastable alloy phase observed as an exothermic peak in DSC measurement, and melting points observed as endothermic peaks at two locations of 210 to 240 ° C. and 300 to 450 ° C., respectively. It is more preferable to have at least one and not have a melting point observed as an endothermic peak at 50 ° C. or higher and lower than 210 ° C.

  In addition, the temperature range of DSC measurement is 30 to 600 ° C., the rate of temperature increase is 10 ° C./min, and the one having a calorific value or endothermic amount of ± 1.5 J / g or more is quantified as a peak derived from the measurement object Less than peaks are excluded from the viewpoint of analysis accuracy. In the present specification, the “melting point” means a melting start temperature and indicates a solidus boundary temperature in DSC.

  In addition, as a combination of the first metal particles and the second metal particles, a mixture of the first metal particles and the second metal particles is an exothermic peak derived from the first metal particles in DSC measurement. At least one observed metastable alloy phase and at least one melting point observed as an endothermic peak derived from the second metal particles at 210-240 ° C. and observed at 210-240 ° C. of the second metal particles After heat treatment at a temperature equal to or higher than the melting point (the lowest melting point when two or more melting points are present), a new stable alloy phase is obtained as a reaction product between the first metal particles and the second metal particles. It is preferable that at least one melting point observed as an endothermic peak derived from the stable alloy phase is 300 to 450 ° C.

  When heat equal to or higher than the melting point of the second metal particles is applied to the mixture of the first metal particles and the second metal particles by, for example, heat treatment at 235 ° C. to 260 ° C., the second metal particles The particles start to fuse with the first metal particles, the thermal diffusion reaction between the first metal particles and the second metal particles proceeds at an accelerated rate, the metastable alloy phase disappears, and a new stable alloy A phase is formed. That is, the presence of a metastable alloy phase observed as an exothermic peak by DSC has an effect of promoting the progress of the thermal diffusion reaction. Here, the temperature of the heat treatment can be appropriately set within a range of a peak temperature of 235 to 260 ° C. which is a general reflow heat treatment condition of the solder.

  As the above thermal diffusion reaction proceeds, the metal component having a melting point of 210 to 260 ° C. in the second metal particles moves to the newly formed stable alloy phase having a melting point of 300 to 450 ° C. and decreases. To do. That is, after the heat treatment, the endothermic amount at the time of melting of the second metal particles observed as an endothermic peak area of 210 to 240 ° C. is reduced or disappears as compared with that before the heat treatment. On the other hand, a new stable alloy phase that does not melt below 300 ° C. is formed by the reaction between the first metal particles and the second metal particles.

  The endothermic peak area of DSC at 50 to 240 ° C. of the above mixture is 0 to 90% before heat treatment after heat treatment in the range of a peak temperature of 235 to 260 ° C., which is a general reflow heat treatment condition for solder. Preferably, it is 0 to 70%. When the endothermic peak area is 90% or less before heat treatment after heat treatment, high heat resistance can be imparted to the solder by a new stable alloy phase that does not melt below 300 ° C. In addition, 0% means that the endothermic peak of DSC at 50 to 240 ° C. disappears after the heat treatment.

  Solder pastes formed using conductive fillers containing the above combinations of first metal particles and second metal particles are all in the range of peak temperatures of 235 to 260 ° C., which is a general reflow heat treatment condition. The reaction proceeds without passing through a liquid state in which the metal melts, and the fusion of the first metal particles and the second metal particles proceeds. Therefore, the electrode terminal of the electronic component and the electrode metal on the substrate are joined. Therefore, the change of the contact area between the electrode metal on the substrate and the solder paste, which occurs before and after the application of the solder paste and the heat treatment, can be kept within a desired range.

  As the first metal particles, metal particles made of an alloy having a composition of Cu 50 to 90% by mass and one or more elements selected from the group consisting of Ag, Bi, In, and Sn are 10 to 50% by mass. preferable. For example, when the main component of the second metal particles is Sn, the Cu content in the first metal particles is preferably 50% by mass or more from the viewpoint that the bonding strength by heat treatment of the solder paste can be increased. Further, in the DSC measurement, the first metal particles are composed of Ag, Bi, In, and Sn in that it can be easily adjusted to have at least one exothermic peak and at least one endothermic peak at 300 to 600 ° C. The content of one or more elements selected from the group is preferably 10% by mass or more.

  Moreover, as a 1st metal particle, the metal particle which consists of an alloy which has the composition of Cu 50-80 mass%, Sn 5-25 mass%, Ag 5-25 mass%, Bi1-20 mass%, and In1-10 mass%. More preferred. In order to facilitate formation of a metastable alloy phase exhibiting an exothermic peak in DSC measurement, it is more preferable that the Ag content is 5% by mass or more and the Bi content is 1% by mass or more. In order to promote alloying of the first metal particles and the second metal particles during the heat treatment, it is more preferable that the Sn content is 5 mass% or more and the In content is 1 mass% or more. Moreover, in order to make the content rate of Cu 50 mass% or more, the content rates of Sn, Ag, Bi, and In are 25 mass% or less, 25 mass% or less, 20 mass% or less, and 10 mass% or less, respectively. More preferably.

  Even more preferable first metal particles are metal particles made of an alloy having a composition of Cu 50 to 80% by mass, Ag 5 to 15% by mass, Bi 2 to 10% by mass, In 2 to 10% by mass, and the balance Sn.

  As the second metal particles, particles containing Sn as a main component are preferable. In this specification, the metal particle which has Sn as a main component means the metal particle which contains Sn more than 50 mass%. The second metal particles are more preferably metal particles containing 70 to 100% by mass of Sn. For example, when the main component of the first metal particles is Cu, the Sn content in the second metal particles is preferably set to 70% by mass or more in that the bonding strength by heat treatment of the solder paste can be increased. In addition, since the melting point of Sn is 232 ° C., the second metal particles are mainly composed of Sn in that the second metal particles can easily develop a melting point of 210 to 260 ° C. It is preferable to contain 70 mass% or more of Sn. As a component other than Sn in the second metal particles, a metal element usually used in lead-free solder, for example, Ag, Al, Bi, Cu, Ge, In, Ni, Zn, may be contained in an amount of 30% by mass or less. preferable.

Moreover, as a 2nd metal particle, 1-30 mass% of 1 or more types of elements chosen from the metal particle which consists of Sn100 mass%, or Sn70-99 mass%, and the group which consists of Ag, Bi, Cu, and In Metal particles made of an alloy having the following composition are more preferable.
As a preferable typical combination of the first metal particles and the second metal particles, the first metal particles are selected from the group consisting of Cu 50 to 90% by mass, Ag, Bi, In, and Sn. A combination comprising an alloy having a composition of 10 to 50% by mass of the element of at least a seed and a second metal particle comprising Sn can be exemplified.

  As a mixing ratio in the combination of the first metal particles and the second metal particles, the mixing amount of the second metal particles with respect to 100 parts by mass of the first metal particles is preferably 50 to 200 parts by mass, It is more preferably 55 to 186 parts by mass, and most preferably 80 to 186 parts by mass. When the mixing amount of the second metal particles with respect to 100 parts by mass of the first metal particles is 50 parts by mass or more, the connection strength at room temperature of the solder joint after being formed as the joint of the electronic component joint structure is high. When the mixing amount of the second metal particles is 200 parts by mass or less, a high connection strength is obtained, for example, when heat treatment is performed at 260 ° C., which is a general reflow heat treatment condition for solder.

  The particle sizes of the first metal particles and the second metal particles can be appropriately determined according to the solder paste application method. For example, in the screen printing method, it is preferable to use particles having a broad particle size distribution with a volume average particle size in the range of 2 to 40 μm and a relatively high sphericity, with emphasis on the ability to remove the paste plate. In the dispensing method, it is preferable to make the particle size distribution sharper in consideration of the paste fluidity at the time of discharge coating.

  Usually, the surface of fine metal particles is often oxidized. Therefore, for the purpose of promoting melting and thermal diffusion of the solder paste by heat treatment, it is preferable to add an activator for removing the oxide film to the solder paste.

  As a method for producing the first metal particles and the second metal particles constituting the conductive filler, an inert gas atomization which is a rapid solidification method in order to form a metastable alloy phase or a stable alloy phase in the metal particles. It is desirable to adopt the law. In the gas atomization method, an inert gas such as nitrogen gas, argon gas, or helium gas is usually used, but helium gas is preferably used, and the cooling rate is preferably 500 to 5000 ° C./second.

  The solder paste is typically composed of a flux containing the above conductive filler and an additive containing a rosin, an activator, a solvent, and optionally a thickener. As a content rate of the electroconductive filler in a solder paste, 85-95 mass% is preferable. The flux is optimal for the surface treatment of the conductive filler made of metal particles, and promotes melting and thermal diffusion of the metal particles. A known material can be used as the flux, and the known material is described in, for example, Japanese Patent Application Laid-Open No. 2004-223559. More preferably, the flux further contains an organic amine as an oxide film removing agent. Moreover, you may use what adjusted the viscosity by adding a solvent further to well-known flux as needed.

  Examples of the rosin include those containing a natural resin or a modified resin thereof as a main component. Examples of the modified resin include polymerized rosin and phenol resin-modified rosin. The content of rosin in the solder paste is preferably in the range of 40 to 50% by mass, and more preferably in the range of 42 to 48% by mass.

  As the activator, inorganic and organic ones can be used, and examples thereof include halogen activators such as amine hydrochloride, organic acid activators and the like. The content of the activator in the solder paste is preferably in the range of 7 to 12% by mass, and more preferably in the range of 8 to 11% by mass.

  Examples of the solvent include diethylene glycol monohexyl ether and octanediol. The content of the solvent in the solder paste is preferably in the range of 30 to 45% by mass, and more preferably in the range of 35 to 40% by mass.

  As a thickener, a thixotropic agent is mentioned, for example. The content of the additive including the thickener in the solder paste is preferably in the range of 10 to 15% by mass.

  The viscosity of the solder paste is preferably in the range of 150 to 250 Pa · s at 25 ° C., and more preferably in the range of 180 to 230 Pa · s. The viscosity is preferably 250 Pa · s or less from the viewpoint of maintaining good plate slippage in the paste fluidity / print coating process, and the sagging of the electrode metal on the substrate in the paste fluidity / print coating process is preferably reduced. From the viewpoint of prevention, 150 Pa · s or more is preferable. The viscosity is determined by the method specified in the JIS Z 3284 “Solder Paste” standard. Actually, the viscosity is measured using a viscosity measuring device (for example, “PCU-205” manufactured by Malcolm Co., Ltd.). It is a value measured under the conditions described in the standard.

  When the solder paste includes the first metal particles and the second metal particles, the heat treatment step is performed by the action of the second metal particles having a fusion property with other metal particles and the first metal particles not melted. As the solder paste wets and spreads in the solder, the shape close to the time of application is maintained even after the heat treatment process, and the solder paste is applied and heat treated to join between the electrode terminals of the electronic component and the electrode metal on the substrate. The effect of keeping the change in expansion or contraction of the contact area between the electrode metal on the substrate and the solder paste occurring before and after within a desired range is good.

  Examples of the metal constituting the electrode metal on the substrate in the present invention include metals such as Cu, Ag, Au, Ni, Sn, Al, Ti, Pd, and Si, and Cu, Ag, and Au are more preferable. These can be formed as a surface portion of the electrode metal on the substrate by various processes such as plating and bonding. When applying the solder paste to the electrode metal on the substrate, the surface coating treatment is performed on the electrode metal on the substrate in order to improve the connection between the solder and the electrode metal on the substrate. For example, in a copper electrode, for example, a thin film of Sn, Au, Ni or the like formed by plating on the electrode is formed as an example. In particular, since the metal surface other than Au is easily oxidized among the above metals, surface treatment with a flux or the like, or pre-flux coating, or various metal plating or solder coating can be performed before applying the solder paste. preferable.

  In the coating process, as a means for applying the solder paste onto the electrode metal on the substrate, a means for applying the solder paste with a constant thickness or a constant coating amount is generally used, such as screen printing, transfer printing, and dispensing. Etc. are used.

  In screen printing, a printing press using a mask plate can be used. The printing machine typically has a mechanism for fixing the substrate, a mechanism for aligning the metal mask and the electrode portion on the substrate, and a mask plate pressed against the substrate, and from above the mask onto the substrate under the mask. And a mechanism for printing the paste from the opening with an application squeegee. There are various materials such as a mesh type and a metal type as a mask plate, but a metal mask type that is widely used for the particle size and easy to clean in the process is generally widely used.

  Transfer printing is a method of forming a flat coating film with a certain coating thickness of solder paste with a squeegee with a certain clearance, and then extracting the coating film with a stamper and stamping it at a predetermined electrode position on the substrate. This is a system in which a certain amount of solder paste is arranged on the electrode, and a dedicated transfer printing apparatus is used. The transfer printing apparatus has an application mechanism for applying a flat coating film, a mechanism for fixing the substrate and aligning the electrode position of the substrate, and a mechanism for performing extraction and transfer imprinting by driving a stamper three-dimensionally. Yes. In transfer printing, the amount of coating is more variable than in screen printing, and care is required for continuous operation such as stamper cleaning management, and screen printing has become the mainstream printing method.

  Dispensing is a method in which a certain amount of solder paste is discharged to the electrode portion on the substrate, and a dispenser device is used. The dispenser pushes a certain amount of solder paste from the needle at the tip of the syringe by applying the pressure required for discharge to the solder paste contained in the syringe on demand, and the syringe itself is driven three-dimensionally. This is an apparatus for discharging and applying a necessary amount of solder paste on an electrode by determining the position of the electrode portion on the substrate. Due to the method of discharging from the needle, the paste itself has the disadvantage that it is less likely to be thinner than screen printing, but there is little loss of paste in the process, and the position and amount of discharge are variable depending on the program Further, it is possible to apply a paste to a substrate and an electronic component structure having a step or an unevenness that are difficult to press the printing mask plate.

  In the coating process, from the viewpoint of forming a small-area and small-sized electronic component bonding structure, the solder paste coating part is a part of the area of the upper surface of the electrode metal on the substrate (that is, the surface not on the substrate side). Preferably, it is 20 to 80% of the area of the upper surface of the electrode metal on the substrate.

  In the heat treatment step, the solder paste is heat-treated in a state where the electrode terminals of the electronic component are brought into contact with the electrode metal on the substrate via the solder paste. The heat treatment step is typically performed in two parts, a component mounting step and a reflow heat treatment step.

  In the component mounting process, a mounter device is used in which various electronic components such as semiconductors and chip components are picked up and placed in contact with predetermined positions on the substrate. The mounter device has a mechanism for supplying an electronic component, a mechanism for picking up the electronic component, and a mechanism for placing the picked-up electronic component at a predetermined electrode position on a substrate arranged in the device. doing.

  The reflow heat treatment process is a process in which a temperature of a certain specification is applied to a substrate in which electronic components are arranged on the electrode metal on the substrate via a solder paste, and is generally compatible with solder heat treatment. A reflow device with a furnace is used. As the heating method for reflow heat treatment, methods such as infrared ray application and hot air application are the mainstream, and the atmosphere in the furnace at the time of reflow heat treatment may be air or nitrogen. In order to prevent deterioration due to oxidation, reflow in a nitrogen atmosphere is frequently used in recent high-density and high-precision mounting. The reflow heat treatment is usually divided into a preheating part and a main heating part. The main heating part is generally set to a temperature higher than the temperature at which the solder is melted and joined. The maximum temperature of the main heating part is 235 ° C. in the case of eutectic solder. In the case of lead-free solder represented by Sn-3.0Ag-0.5Cu, the temperature is about 245 to 255 ° C. Since the preheating part has the meaning which warms the whole board | substrate and an electronic component uniformly, and arranges the flux component of a solder before it becomes an active state in this heating part, it is hold | maintained at the temperature of about 200 degrees C or less.

  The reflow heat treatment is preferably performed so that the time of 235 ° C. or higher is 3 to 60 seconds. In the case where the first metal particles and the second metal particles are used as the conductive filler, in order for the second metal particles to thermally diffuse, the time of 235 ° C. or higher is preferably 3 seconds or longer. From the viewpoint of protection, the time of 235 ° C. or higher is preferably 60 seconds or shorter. The time of 235 ° C. or higher is more preferably 30 seconds or longer. Further, the reflow heat treatment is preferably performed at a peak temperature of 245 ° C. to 260 ° C. for 5 to 30 seconds. The heat treatment may be performed in the air, but is more preferably performed in a nitrogen atmosphere. More preferably, the heat treatment is performed using a solder reflow apparatus in a nitrogen atmosphere having a peak temperature of 210 ° C. to 250 ° C. and an oxygen concentration of 1000 ppm or less.

  In the conventional electronic component bonding structure, a portion where the solder coating after the reflow heat treatment is not formed is obtained by previously drawing another electrode portion through the wiring pattern on the electrode metal on the substrate to which the electronic component is bonded. In many cases, a step of forming a joint by physical signal line connection other than the solder joint is formed in this portion.

  In this case, since it is necessary to prepare a lead-out wiring and a separate electrode part in advance, an extra area is required for constructing the electronic component joint structure, which hinders downsizing.

In the present invention, since wetting and spreading of the solder paste during the heat treatment is reduced, the solder paste is first applied to a part of the electrode metal on the substrate in the coating process, and after the heat treatment process, the bonding process is performed on the substrate. the portion not covered with the solder of the same electrode metal above, it is possible to further form a bond by physical signal connection (physical signal connections other than joining I).

  That is, in the method for manufacturing an electronic component bonded structure according to the present invention, the electronic component is soldered on the upper surface (that is, the surface not on the substrate side) of the electrode metal on the substrate, which is a portion related to input / output of electric signals. A joined portion and a portion not covered with solder can be formed. The upper surface forms a portion joined by physical signal line connection other than solder (for example, gold wire bonding, fitting type connection, pressure contact conductive material addition, etc.) to express the original function of the electrode metal on the substrate Because this is an important part, the area of the solder formation part is reduced, the part not covered with solder is secured on the electrode metal on the board, and multiple types of signal line connections are made on the same electrode metal on the board The ability to form an electronic component joint structure having the following is advantageous in terms of reduction in area and size.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this.

(1) Production of first metal particles 6.5 kg of Cu particles (purity 99 mass% or more), 1.5 kg of Sn particles (purity 99 mass% or more), 1.0 kg of Ag particles (purity 99 mass% or more), Bi 0.5 kg of particles (purity 99% by mass or more) and 0.5 kg of In particles (purity 99% by mass or more) were put in a graphite crucible and heated to 1400 ° C. with a high frequency induction heating device in a helium atmosphere of 99% by volume or more. Melted.

  Next, after this molten metal is introduced from the tip of the crucible into a spray tank in a helium gas atmosphere, helium gas (purity 99 vol% or more, oxygen concentration 0.1 vol%) is supplied from a gas nozzle provided near the crucible tip. The pressure was reduced to 2.5 MPa, and atomization was performed to produce first metal particles. The cooling rate at this time was 2600 ° C./second.

  When the obtained 1st metal particle was observed with the scanning electron microscope (Hitachi, Ltd. product: S-2700), it was spherical. The metal particles were obtained by classifying the overcut powder again at a setting of 10 μm after classifying the metal particles at a setting of 1.6 μm using an airflow classifier (manufactured by Nissin Engineering Co., Ltd .: TC-15N). Undercut powder was collected. The collected first metal particles had a volume average particle size of 2.7 μm. The first metal particles thus obtained were used as samples, and “DSC-50” manufactured by Shimadzu Corporation was used, and the temperature was 30 to 600 ° C. under a temperature increase rate of 10 ° C./min in a nitrogen atmosphere. Differential scanning calorimetry was performed over the range.

  As a result, it was confirmed that the obtained first metal particles had endothermic peaks at 495 ° C. and 514 ° C. and had a plurality of melting points. Moreover, the exothermic peak of 254 degreeC existed and it has confirmed that it had a metastable alloy phase.

(2) Production of Second Metal Particles 10.0 kg of Sn particles (purity 99% by mass or more) were put in a graphite crucible and heated and melted to 1400 ° C. with a high frequency induction heating device in a helium atmosphere of 99% by volume or more. Next, after this molten metal is introduced from the tip of the crucible into a spray tank in a helium gas atmosphere, helium gas (purity 99 vol% or more, oxygen concentration 0.1 vol%) is supplied from a gas nozzle provided near the crucible tip. The second metal particles were produced by performing atomization by ejecting a pressure of less than 2.5 MPa. The cooling rate at this time was 2600 ° C./second.

  When the obtained 2nd metal particle was observed with the scanning electron microscope (Hitachi Ltd. make: S-2700), it was spherical. The metal particles were classified using an airflow classifier (manufactured by Nissin Engineering Co., Ltd .: TC-15N) at a setting of 5 μm, and then the undercut obtained by classifying the overcut powder again at a setting of 40 μm. The flour was collected. The volume average particle diameter of the recovered second metal particles was 6.5 μm. The second metal particles thus obtained were used as samples, and “DSC-50” manufactured by Shimadzu Corporation was used, and the temperature was 30 to 600 ° C. under a nitrogen atmosphere under a temperature rising rate of 10 ° C./min. Differential scanning calorimetry was performed over the range. As a result, it was confirmed that the obtained second metal particles had an endothermic peak of 242 ° C. and had a melting point of 232 ° C. (melting start temperature: usually a temperature indicated as a solidus temperature). There was no characteristic exothermic peak.

(3) Thermal characteristics of conductive filler and solder paste (Reference Example 1)
Using a conductive filler (average particle size of 3.4 μm) in which the first metal particles and the second metal particles are mixed at a mass ratio of 100: 83 as a sample, “DSC-50” manufactured by Shimadzu Corporation is used. Using a nitrogen atmosphere, differential scanning calorimetry was performed in the range of 30 to 600 ° C. under a temperature rising rate of 10 ° C./min. In the DSC chart obtained by this measurement, it was confirmed that endothermic peaks exist at 233 ° C., 348 ° C., and 378 ° C. The endothermic peak at 233 ° C. has a melting point of 227 ° C. (melting start temperature: a temperature indicated as a solidus temperature) and an endothermic amount of 16.1 J / g. In addition, an exothermic peak was present at 255 ° C. characteristically.

  Next, 90.2% by mass of the conductive filler and 9.8% by mass of rosin-based flux were mixed, and solder softener (manufactured by Malcolm Co., Ltd .: “SPS-1”), defoaming kneader (Matsuo Sangyo Co., Ltd.) ) Manufactured: “SNB-350”) to produce a solder paste. When the viscosity of the solder paste thus obtained was measured with “PCU-205” manufactured by Malcolm Corporation, the viscosity was 204 Pa · s and the thixo index was 0.50.

  The solder paste was placed on an alumina substrate and subjected to reflow heat treatment at a peak temperature of 245 ° C. in a nitrogen atmosphere. As a heat treatment apparatus, a reflow simulator “SRS-1C” manufactured by Malcolm Co., Ltd. was used. The temperature profile shows the rate of temperature rise to the preheating zone: 1 to 3 ° C./second, the preheating temperature range from 130 ° C. to 190 ° C., the preheating time from 110 to 170 seconds, and the main heating zone at 235 ° C. or higher. The conditions of controlling in the range of 30 to 50 seconds and the peak temperature of 245 ° C. were adopted. During this time, the paste was observed from the observation window of the reflow simulator, but the conductive filler in the solder paste did not melt into a liquid state.

  Using this heat-treated solder paste as a sample, differential scanning calorimetry is performed in a range of 30 to 600 ° C. under a temperature increase rate of 10 ° C./min under a nitrogen atmosphere using “DSC-50” manufactured by Shimadzu Corporation. Was done. In the DSC chart obtained by this measurement, the presence of endothermic peaks was detected at 136 ° C, 171 ° C, 347 ° C, and 420 ° C. Of these, the endothermic peaks at 240 ° C. or lower are 136 ° C. and 171 ° C., and the endothermic amount is 3.9 J / g. Therefore, the endothermic amount at 50 to 240 ° C. is reduced to 24% of the endothermic amount at the time of melting observed from the endothermic peak area at 210 to 240 ° C. before the heat treatment, and a new stable alloy phase is formed to form a fusion. It was confirmed that

(Reference Example 2)
Using a conductive filler (average particle size of 4.25 μm) in which the first metal particles and the second metal particles are mixed at a mass ratio of 100: 185 as a sample, “DSC-50” manufactured by Shimadzu Corporation is used. Using a nitrogen atmosphere, differential scanning calorimetry was performed in the range of 30 to 600 ° C. under a temperature rising rate of 10 ° C./min. It was confirmed that endothermic peaks exist at 235 ° C. and 409 ° C. The endothermic peak at 235 ° C. has a melting point of 223 ° C. (melting start temperature: a temperature indicated as a solidus temperature) and an endothermic amount of 2.71 J / g. Further, an exothermic peak was present at 248 ° C. characteristically.

  Next, 89.6% by mass of the conductive filler and 10.4% by mass of rosin-based flux are mixed, and solder softener (manufactured by Malcolm: “SPS-1”), defoaming kneader (Matsuo Sangyo Co., Ltd.) ) Manufactured: “SNB-350”) to produce a solder paste. When the viscosity of the solder paste thus obtained was measured with “PCU-205” manufactured by Malcolm Corporation, the viscosity was 214 Pa · s and the thixo index was 0.45.

  The solder paste was placed on an alumina substrate and subjected to reflow heat treatment at a peak temperature of 245 ° C. in a nitrogen atmosphere. As a heat treatment apparatus, a reflow simulator “SRS-1C” manufactured by Malcolm Co., Ltd. was used. The temperature profile shows the rate of temperature rise to the preheating zone: 1 to 3 ° C./second, the preheating temperature range from 130 ° C. to 190 ° C., the preheating time from 110 to 170 seconds, and the main heating zone at 235 ° C. or higher. The conditions of controlling in the range of 30 to 50 seconds and the peak temperature of 245 ° C. were adopted. During this time, the paste was observed from the observation window of the reflow simulator, but the conductive filler in the solder paste did not melt into a liquid state.

  Using this heat-treated solder paste as a sample, differential scanning calorimetry is performed in a range of 30 to 600 ° C. under a temperature increase rate of 10 ° C./min under a nitrogen atmosphere using “DSC-50” manufactured by Shimadzu Corporation. Was done. The presence of endothermic peaks was detected at 177 ° C., 194 ° C., 401 ° C., and 430 ° C., and it was confirmed that a new stable alloy phase was formed and a fusion was formed.

(4) Application of solder paste, heat treatment and area change evaluation (Example 1, Comparative Example 1)
The solder paste produced in Reference Example 1 was printed and applied to an Au plated Cu plate (surface is Au) having a length of 25 mm × width of 25 mm and a thickness of 0.3 mm. For the printing pattern formation, “MT-320TV” manufactured by Microtech Co., Ltd. was used as a printing machine, and a 0.2 mm thick metal mask was used for the plate. The aperture of the mask is 2 mm × 3 mm (application contact area 6 mm ² ). The printing conditions were speed: 10 mm / sec, printing pressure: 0.1 MPa, squeegee pressure: 0.2 MPa, back pressure: 0.1 MPa, squeegee R80-60 °, and clearance: 0 mm. This printed pattern was subjected to reflow heat treatment at a peak temperature of 245 ° C. in a nitrogen atmosphere. As a heat treatment apparatus, a reflow simulator “SRS-1C” manufactured by Malcolm Co., Ltd. was used. The temperature profile shows the rate of temperature rise to the preheating zone: 1 to 3 ° C./second, the preheating temperature range from 130 ° C. to 190 ° C., the preheating time from 110 to 170 seconds, and the main heating zone at 235 ° C. or higher. The conditions of controlling in the range of 30 to 50 seconds and the peak temperature of 245 ° C. were adopted. As Comparative Example 1, a typical lead-free solder, “Micro Solder” (Sn-3.0Ag-0.5Cu metal composition) manufactured by Harima Chemical Co., Ltd. was evaluated under the same conditions. FIG. 1 shows top view photographs of the solder paste printed pattern formed in this way before and after heat treatment. In Comparative Example 1, since the liquid was completely melted at the heat treatment temperature, the solder paste wets and spreads on the Au surface, and the contact area of the solder after the heat treatment is 2.6 times the original application contact area. However, in the paste of Example 1, no liquid melting was observed, and the area change was within 1.0 times the original application contact area (no change), and the print shape and print area on the original settings. Was kept. In addition, when the paste after the heat treatment on the Au plated Cu plate was subjected to a reflow heat treatment again under the same conditions as described above and a change in the contact area was observed, it was further enlarged in Comparative Example 1, but the example was not changed. It was.

Example 2 and Comparative Example 2
The solder paste produced in Reference Example 1 was printed and applied to a Cu plate having a length of 25 mm × width of 25 mm and a thickness of 0.3 mm. For the printing pattern formation, “MT-320TV” manufactured by Microtech Co., Ltd. was used as a printing machine, and a 0.1 mm thick metal mask was used for the plate. The opening of the mask is 300 μmφ (coating contact area 90000 μm ² ). The printing conditions were speed: 10 mm / sec, printing pressure: 0.1 MPa, squeegee pressure: 0.2 MPa, back pressure: 0.1 MPa, squeegee R80-60 °, and clearance: 0 mm. This printed pattern was subjected to reflow heat treatment at a peak temperature of 245 ° C. in a nitrogen atmosphere to form bumps. As a heat treatment apparatus, a reflow simulator “SRS-1C” manufactured by Malcolm Co., Ltd. was used. The temperature profile shows the rate of temperature rise to the preheating zone: 1 to 3 ° C./second, the preheating temperature range from 130 ° C. to 190 ° C., the preheating time from 110 to 170 seconds, and the main heating zone at 235 ° C. or higher. The conditions of controlling in the range of 30 to 50 seconds and the peak temperature of 245 ° C. were adopted. As Comparative Example 2, a typical lead-free solder, “Micro Solder” (Sn-3.0Ag-0.5Cu metal composition) manufactured by Harima Chemical Co., Ltd. was evaluated under the same conditions. FIG. 2 shows a cross-sectional photograph at the bump central portion after the heat treatment of the solder paste printed bump formed as described above. In Comparative Example 2, since the liquid was completely melted at the heat treatment temperature, the solder paste spreads even when the bump is formed even on the Cu surface where the solder wettability is relatively small compared to Au, and the solder Cu plate contacts the bump part after the heat treatment. The area was 374 μmφ, which was 1.55 times the size of the original coating contact area, but the liquid melt was not seen in the paste of Example 2, the area was also 320 μmφ, and the area change was the original coating contact area The value was 1.14 times that of the original, and 1.3 or less with respect to the print shape and print area on the original setting.

(Example 3, Comparative Example 3)
Two 0.3 mm square copper electrodes with a thickness of 18 μm are arranged at 0.3 mm gap intervals on the surface of an FR-4 substrate (“CS-3287” manufactured by Risho Kogyo Co., Ltd.) having a length of 50 mm × width of 50 mm and a thickness of 0.80 mm. The electrode metal on the substrate was formed by connecting the center of the cake with a copper wiring bridge pattern having a width of 0.1 mm (surface treatment of the electrode was preflux “Toughace” F-2, manufactured by Shikoku Kasei Co., Ltd., solder on the substrate surface The resist is “PSR4000” manufactured by Taiyo Ink Manufacturing Co., Ltd .; thickness 20 μm). The solder paste prepared in Reference Example 1 was printed on the electrode metal on this substrate. The printing pattern was formed using “YVP-Xg-w” manufactured by Yamaha Motor Co., Ltd. as a printing machine, and a 0.1 mm thick metal mask for the plate. The opening of the mask is a square hole having a 60% opening ratio (opening area 0.054 mm ² ) of 0.3 mm square area with reference to the center position of the 0.3 mm square electrode portion. The printing conditions were a double metal squeegee (angle 55 °), a printing pressure of 50 N, a speed of 10 mm / sec, and a clearance of 0 mm. This printed pattern was subjected to reflow heat treatment at a peak temperature of 250 ° C. in a nitrogen atmosphere. As a heat treatment apparatus, a reflow furnace “NIS-20-82C” manufactured by Atec Techtron Co., Ltd. was used. The temperature profile shows the rate of temperature rise to the preheating zone: 1 to 3 ° C./second, the preheating temperature range from 130 ° C. to 190 ° C., the preheating time from 110 to 170 seconds, and the main heating zone at 235 ° C. or higher. A condition of controlling in the range of 30 seconds and a peak temperature of 250 ° C. was adopted.

  A top view photograph of the solder paste after the heat treatment is shown in FIG. The contact area after heat treatment of the solder paste inside the left and right 0.3 mm square electrodes is the same as the area where printing is applied, and is approximately 60% of the electrode area when converted from the area on the photograph. It was found that there was no change in the contact area of the solder on the electrode surface as with the porosity setting.

  As Comparative Example 3, under the same conditions as in Example 3, only a solder paste was used as a representative lead-free solder, an eco solder paste "M705-GRN360-K2-V" (Sn-3.0Ag-) of Senju Metal Industry Co., Ltd. When evaluated by changing to 0.5 Cu), the solder paste spreads within the 0.3 mm square electrode after the heat treatment, and the finished area greatly changes. In some cases, the solder paste flowed to the center 0.1 mm wide copper wiring bridge pattern, and the left and right 0.3 mm square electrodes were connected.

(5) Formation of electronic component joint structure by mounting electronic components (Example 4, Comparative Example 4)
The same conditions, apparatus, and mask as in Example 3 were applied to the solder paste prepared in Reference Example 1 on the same electrode electrode on the substrate as that used in Example 3 (that is, the electrode of the substrate having a matrix-arranged electrode). Was applied by printing. Steps straddling the left and right sides of this printed pattern, that is, in the pair of adjacent left and right electrode patterns, the left side 0.3 mm square electrode on the right side electrode and the left side 0.3 mm square electrode on the right side electrode are stepped evenly. Then, a 0603 size chip resistor (manufactured by KOA Co., Ltd .; the installation area on the substrate is 0.3 mm in length and 0.6 mm in width) is mounted on a chip mounter “YV100Xg” manufactured by Yamaha Motor Co., Ltd. ( Parts pushing pressure 0.8N, pushing height setting 0mm). Thereafter, reflow heat treatment was performed at a peak temperature of 250 ° C. under a nitrogen atmosphere using the same conditions and apparatus as in Example 2.

  FIG. 4 shows a top view photograph of this electronic component bonding structure. The chip resistor was mounted on the upper half of the 0.3 mm square electrode of the component and the electrode portion was exposed in the other half, but the solder paste was within the half electrode area after heat treatment. The solder contact area after the heat treatment was within 1.3 times the contact area at the time of printing application, and the periphery of the electrode left a blank part not covered with the solder.

  As Comparative Example 4, under the same conditions as in Example 4, only a solder paste was used as a representative lead-free solder, an eco solder paste "M705-GRN360-K2-V" (Sn-3.0Ag-) of Senju Metal Industry Co., Ltd. FIG. 5 shows the results of evaluation with the change to 0.5 Cu). The solder paste spreads as a whole in the half of the electrode area that does not have chip resistance after heat treatment, and the solder contact area after heat treatment is more than 1.3 times larger than the contact area during printing application. It was.

  In the so-called “filletless mounting” method in which the electrode metal on the substrate is substantially within the mounting projection area range of the electronic component mounted on the electrode metal on the substrate, the conventional general solder is liquid. Solder that has melted into the electrode terminal of the electronic component gets wet and moves, and the quality of the joint between the electrode metal on the board and the electrode terminal of the electronic component becomes unstable, or a bulge is formed on the side of the electrode terminal portion. As a result, there were concerns about variations in mounting quality, deterioration in strength, and short-circuiting of adjacent components. However, as can be seen in this example, the solder paste used in the manufacturing method of the present invention has a small expansion from the printed contact area of the electrode metal on the substrate during the heat treatment, as described above, and further, Since the electronic component can be mounted with little wetting with respect to the electrode terminal, it can also be used for high-density filletless mounting.

(5) Formation of an electronic component joint structure having a part joined by another physical signal line connection (Example 5)
Same as Example 3, using the electrode metal on the substrate, removing the central 0.1 mm wide copper wiring bridge pattern and combining the left and right 0.3 mm square electrodes (length 0.3 mm, width 0.6 mm), and two of them (that is, a pair) were arranged side by side with a gap of 0.3 mm in the longitudinal direction of the rectangle, and the copper surface was plated with gold under a nickel base. The solder paste prepared in Reference Example 1 was printed and applied to the inner half near the gap of the electrode metal on the obtained substrate. The printing pattern was formed using “YVP-Xg-w” manufactured by Yamaha Motor Co., Ltd. as a printing machine, and a 0.1 mm thick metal mask for the plate. The opening of the mask is a square hole having a 60% opening ratio (opening area 0.054 mm ² ) from the center of 0.3 mm square, which is half of the area of the electrode metal on the rectangular substrate. The conditions, apparatus, and mask for printing application are the same as in Example 3. Crossing the gap between the pair of rectangular electrodes, that is, in the pair of left and right adjacent electrodes, the portion corresponding to the right 0.3 mm square of the left electrode and the portion corresponding to the left 0.3 mm square of the right electrode are evenly distributed. Step-on electronic components equipped with 0603 size chip resistors (KOA Co., Ltd .; installation area on the board is 0.3 mm long and 0.6 mm wide) mounted on Yamaha Motor Co., Ltd. chip mounter “YV100Xg” (Parts indentation pressure 0.8 N, indentation height setting 0 mm). Thereafter, reflow heat treatment was performed at a peak temperature of 250 ° C. under a nitrogen atmosphere using the same conditions and apparatus as in Example 3.

  Since the solder paste did not spread after heat treatment on both sides of the part where the chip resistor of the obtained electronic component bonding structure was mounted and mounted, the surface of the gold plating was exposed as a half of the electrode area. When a gold wire commonly used in semiconductor chips and electronic component modules is bonded to a gold-plated electrode portion of about 0.3 mm square by a wire bonder manufactured by West Bond; model 5400B, solder spreads on the electrode surface. As a result, the surface was in a stable gold plating state, and wire bonding by gold-gold bonding could be performed.

  The present invention can be applied to the mounting of electronic components, and can be suitably applied particularly when electronic components such as chip components and semiconductor packages are mounted on a circuit board such as a printed wiring board with solder. According to the present invention, since the electrode portion can be formed in a minute region by a composite bonding method, it is possible to provide an electronic component bonding structure corresponding to high functionality and multi-terminal.

In Example 1 and Comparative Example 1, it is the photograph replaced with the top view which showed the change of the contact area of the Au plating metal plate and solder before and behind heat processing. In Example 2 and Comparative Example 2, it is the photograph replaced with sectional drawing which showed the contact state and contact area change of Cu board before and behind heat processing, and a solder. It is a photograph replaced with the top view which shows the state after heat processing of the solder paste in Example 3. FIG. 14 is a photograph replacing a top view of the electronic component bonding structure formed in Example 4. FIG. 14 is a photograph replacing a top view of an electronic component bonding structure formed in Comparative Example 4.

Claims (5)

An application step of applying a solder paste on the electrode metal on the substrate, and a heat treatment step of heat-treating the solder paste in a state where the electrode terminal of the electronic component is in contact with the electrode metal on the substrate via the solder paste A method for manufacturing an electronic component joint structure including:
When the solder paste is applied to a metal plate of the same material as the electrode metal on the substrate, the contact area between the metal plate and the solder paste is A, and the solder paste is heat-treated at a temperature in the range of 235 ° C. to 260 ° C. When the contact area between the later metal plate and the solder is B, 0.7 ≦ B / A ≦ 1.3 is satisfied, and in the coating step, the solder is partially applied to the electrode metal on the substrate. After applying the paste and after the heat treatment step, a bonding step of forming a bond by physical signal line connection other than solder bonding is performed on a portion of the electrode metal on the substrate that is not covered with solder. By this, the manufacturing method of the electronic component joining structure which forms the physical signal line connection other than the solder joint and the solder joint on the same electrode metal.   The solder paste includes first metal particles and second metal particles as conductive fillers, and in the differential scanning calorimetry in the range of 30 ° C. to 600 ° C., the first metal particles have at least one heat generation. 2. The peak and at least one endothermic peak of 300-600 [deg.] C., wherein the second metal particle does not have an exothermic peak and has at least one endothermic peak at 210-260 [deg.] C. Manufacturing method of electronic component joining structure.   The manufacturing method of the electronic component joining structure according to claim 2, wherein the second metal particles are particles containing Sn as a main component.   The first metal particles are made of an alloy having a composition of 50 to 90% by mass of Cu and 10 to 50% by mass of one or more elements selected from the group consisting of Ag, Bi, In, and Sn. The manufacturing method of the electronic component joining structure according to claim 2 or 3, wherein the metal particles of 2 are made of Sn.   The electronic component joining structure obtained by the manufacturing method according to claim 1.