WO2022270282A1

WO2022270282A1 - Solder paste and method for producing electronic device

Info

Publication number: WO2022270282A1
Application number: PCT/JP2022/022745
Authority: WO
Inventors: 愛浅見; 陽也佐久間; 久彦吉田; 晶子 ▲高▼木
Original assignee: 千住金属工業株式会社
Priority date: 2021-06-25
Filing date: 2022-06-06
Publication date: 2022-12-29
Also published as: JP7014992B1; TW202308838A; JP2023004119A; CN117545585A; KR20240027027A

Abstract

A solder paste according to the present invention contains a flux composition and a solder powder and is configured such that, with respect to a flux residue that is obtained from this solder paste in accordance with a specific production procedure, if G'₁₀₀ is the storage elastic modulus thereof at 100°C and G"₁₀₀ is the loss elastic modulus thereof at 100°C as determined under specific measurement conditions with use of a rheometer, G'₁₀₀ and G"₁₀₀ satisfy G'₁₀₀ > G"₁₀₀.

Description

Solder paste and electronic device manufacturing method

The present invention relates to a solder paste and an electronic device manufacturing method.

Various developments have been made on solder paste. As this type of technology, for example, the technology described in Patent Document 1 is known. Patent Document 1 describes a solder paste containing a rosin-based resin having a softening point of 90° C. or lower.

Japanese Patent Application Laid-Open No. 2018-140429

However, as a result of investigation by the present inventors, it was found that there is room for improvement in terms of high-temperature migration in the solder paste described in Patent Document 1 above.

In recent years, with the increasing popularity of devices, the operating temperature of devices has risen to 100°C or higher. When the high-temperature heat history that occurs during the operation of the device is applied to the flux residue for a long time, the tin ions etc. eluted in the flux residue move to the cathode and precipitate, causing high-temperature migration. As a result, the inventors have found that insulation failure may occur.
As a result of further intensive research based on such knowledge, it was found that high-temperature migration can be suppressed by appropriately controlling the viscoelastic properties of the flux residue in the solder paste, leading to the completion of the present invention.

According to the invention,
A solder paste comprising a flux composition and a solder powder,
Regarding the flux residue obtained from the solder paste according to the following preparation procedure, the storage elastic modulus at 100° C. was measured using a rheometer under the following measurement conditions, G′ ₁₀₀ and the loss elastic modulus were G″ ₁₀₀ . when
G′ ₁₀₀ and G″ ₁₀₀ are configured to satisfy G′ ₁₀₀ >G″ ₁₀₀ ;
Solder paste is provided.
<Procedure for preparing flux residue>
1. Prepare two copper trays having a bottom surface of 45 mm×45 mm, a height of 5 mm, and a thickness of 0.3 mm.
2. A copper box having a height of about 10 mm is prepared by laying one of the copper trays on the bottom surface of the other copper tray so that the opening of the other copper tray faces the other opening and fixing with tape.
3. 5 g of the solder paste is taken as a sample. The sample is spread onto the bottom surface inside one of the copper trays to cover 80% of the area of the bottom surface.
4. Using a reflow furnace, the copper box containing the sample is subjected to reflow treatment in the atmosphere according to the following temperature profiles A to E.
(Temperature profile A to E)
A. It is heated from a room temperature of 25° C. to 150° C. at a heating rate of 1.9° C./sec.
B. The temperature is held in the temperature range of 150°C to 180°C for 80 seconds.
C. Heat up to 220° C. at a rate of temperature increase of 1.2° C./sec.
D. The temperature is maintained at 220°C or higher for 40 seconds, and the peak temperature is 240°C.
E. After that, it is cooled to room temperature of 25°C.
5. After the reflow process, the flux residue remaining on the inner bottom surface of one of the copper trays is collected.
<Measurement conditions>
Measuring device: Rheometer Measuring temperature: 20°C to 180°C
Geometry (upper): 25mmφ, stainless steel, parallel plate Plate (lower): 60mmφ
Mode: 5°C/min
Strain: 1%
Frequency: 10Hz
Gap: 0.2mm

Also according to the present invention,
a step of printing the solder paste on a soldering portion of an electronic circuit board;
a step of mounting an electronic component on the soldering portion;
joining the electronic component and the electronic circuit board by heating the soldering portion to a temperature at which the solder powder in the solder paste melts, in a state where a closed structure exists around the soldering portion;
A method of manufacturing an electronic device is provided, comprising:

According to the present invention, a solder paste with excellent high-temperature migration resistance and a method for manufacturing an electronic device using the same are provided.

It is a figure for demonstrating the manufacturing method of a flux residue. It is a figure for demonstrating a high temperature migration test. A standard reflow profile for producing flux residue is shown.

Embodiments of the present invention will be described below with reference to the drawings. In addition, in all the drawings, the same constituent elements are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. Also, the drawings are schematic diagrams and do not correspond to actual dimensional ratios.

The outline of the solder paste of this embodiment will be explained.

The solder paste of the present embodiment contains a flux composition and solder powder,
Regarding the flux residue obtained from the solder paste according to the following preparation procedure, the storage elastic modulus at 100° C. was measured using a rheometer under the following measurement conditions, G′ ₁₀₀ and the loss elastic modulus were G″ ₁₀₀ . when
G′ ₁₀₀ and G″ ₁₀₀ are constructed such that G′ ₁₀₀ >G″ ₁₀₀ .

<Procedure for preparing flux residue>
1. Two copper trays having a bottom surface of 43-45 mm×43-45 mm, a height of 5-7 mm, and a thickness of 0.2-0.4 mm are prepared.
2. A copper box having a height of 10 to 14 mm is prepared by laying one copper tray on the bottom surface of the other copper tray so that the opening of the other copper tray faces the opening of the other tray and fixing with tape.
3. About 5 g of the solder paste is sampled. The sample is spread on the bottom surface inside one of the copper trays to cover approximately 80% of the area of the bottom surface.
4. Using a reflow furnace (manufactured by Senju Metal Industry Co., Ltd., SNR-825), the copper box containing the sample is subjected to reflow treatment under the following temperature profiles A to E in the atmosphere.
(Temperature profile A to E)
A. It is heated from a room temperature of 25° C. to 150° C. at a heating rate of 1.9° C./sec.
B. The temperature is held in the temperature range of 150°C to 180°C for 80 seconds.
C. Heat up to 220° C. at a rate of temperature increase of 1.2° C./sec.
D. The temperature is maintained at 220°C or higher for 40 seconds, and the peak temperature is 240°C.
E. After that, it is cooled to room temperature of 25°C.
5. After the reflow process, the flux residue remaining on the inner bottom surface of one of the copper trays is collected.

<Measurement conditions>
Measuring device: rheometer (manufactured by Malvern Panalytical, KINEXUS 1b+)
Measurement temperature: 20°C to 180°C
Geometry (upper): 25mmφ, stainless steel, parallel plate Plate (lower): 60mmφ
Mode: 5°C/min
Strain: 1%
Frequency: 10Hz
Gap: 0.2mm

In recent high-power devices, the ambient temperature of heat-generating components may reach 100° C. or more. Normally, the humidity around a heat-generating component of 100°C or higher is lower than normal humidity, so it was thought that ion migration was difficult to occur in the environment. The inventors have confirmed that migration can occur.
However, since a general ion migration test is performed under the conditions of a temperature of 85° C. and a humidity of 85%, it cannot be said that it corresponds to the actual situation described above.
Therefore, the present inventor newly devised a high-temperature migration test for evaluating migration of metal ions in a temperature environment of 100° C. or higher. In the high-temperature migration test, environmental conditions such as a low-humidity environment with a humidity of 20% or less and a high-humidity environment with a humidity of 85% or more can be used.
According to the findings of the present inventors, it was found that high-temperature migration can be suppressed by appropriately controlling the viscoelastic properties of the flux residue in the solder paste. It was also found that high-temperature migration can be suppressed even in a more severe high-humidity environment.
The viscoelastic properties of the flux residue were measured using a _rheometer under the above-described measurement conditions for the flux residue obtained by the above preparation procedure. can be stably evaluated by using G″ ₁₀₀ as an index. This point was supported based on the relationship between the viscoelastic properties of the flux residue and the evaluation results of the high-temperature migration test using the same flux residue.
Then, it was found that the high-temperature migration can be suppressed by forming the solder paste so that the flux residues _G'100 and _G''100 satisfy _G'100 >_G''100 .

Although the detailed mechanism is not clear, by making the storage elasticity at 100°C larger than the loss elastic modulus, deformation at high temperatures can be suppressed and flux residue with low fluidity can be achieved, so tin ions and the like can be generated. It is considered that high-temperature migration of metal ions can be suppressed.

In the procedure for producing the flux residue, the temperature profiles described above (temperature profiles A to E) are employed, but may be set according to the standard reflow profile shown in FIG. 3, if necessary. Temperatures in the temperature profile refer to work temperatures.
The reflow treatment may employ a method of circulating hot air using a heater.

Moreover, in the procedure for producing the flux residue, the sample amount may be about 5 g, and 4.5 to 5.5 g is acceptable. The area spread on the copper tray may be about 80%, but if it is about 60% or more, a sufficient amount of flux residue can be obtained.
The copper tray may be made by bending a copper plate having a thickness of 0.2 to 0.4 mm.

The phase angle at 100°C is δ ₁₀₀ , which is determined from the storage modulus and loss modulus at 100°C measured using a rheometer under the above measurement conditions, and the storage modulus and loss modulus at 140°C. Let δ ₁₄₀ be the phase angle at 140°C.

The lower limit of _δ140 is, for example, 1° or more, preferably 2° or more, more preferably 3° or more.
On the other hand, the upper limit of _δ140 is, for example, less than 45°, preferably 44° or less, more preferably 30° or less. As a result, it is possible to improve high-temperature migration resistance in a high-temperature operating environment exceeding 100.degree.

δ ₁₄₀ and δ ₁₀₀ may be configured to satisfy 0.1≦δ ₁₄₀ /δ ₁₀₀ ≦3.0.
The lower limit of _δ140 / _δ100 is, for example, 0.1 or more, preferably 0.15 or more, and more preferably 0.2 or more.
On the other hand, the upper limit of _δ140 / _δ100 is, for example, 3.0 or less, preferably 2.5 or less, and more preferably 2.0 or less.
By setting the value within the above numerical range, it is possible to improve high-temperature migration resistance in a high-temperature operating environment exceeding 100°C.

Using the above ^rheometer , the ^viscosity of the solder paste was measured at 25°C. Let η3 be the viscosity at ⁻¹ .

The lower limit of the viscosity η1 is, for example, 5 Pa·s or more, preferably 20 Pa·s or more, more preferably 50 Pa·s or more.
On the other hand, the upper limit of the viscosity η1 is, for example, 400 Pa·s or less, preferably 300 Pa·s or less, more preferably 280 Pa·s or less.
The printability of the solder paste can be improved by setting the value within the above numerical range.

The lower limit of the thixotropic ratio obtained by Log(η2/η3) is, for example, 0.3 or more, preferably 0.4 or more, and more preferably 0.5 or more.
On the other hand, the upper limit of the thixotropic ratio is, for example, 1.8 or less, preferably 1.5 or less, and more preferably 1.0 or less.
The printability of the solder paste can be improved by setting the value within the above numerical range.

In the present embodiment, for example, by appropriately selecting the type and amount of each component contained in the solder paste, the preparation method of the solder paste, and the like, the storage elastic modulus at 100° C. and 140° C., the loss elastic modulus, the phase It is possible to control the angle, the viscosity η1 and the thixotropic ratio. Among these, for example, using a first rosin-based resin with a high softening point, appropriately adjusting the content of the first rosin-based resin with a high softening point, and not using a third rosin-based resin with a low softening point By appropriately adjusting the content of the solvent and / or activator, the storage elastic modulus at 100 ° C. or 140 ° C., the loss elastic modulus, the phase angle, the viscosity η1 and the thixotropic ratio are in the desired numerical range. It can be cited as an element for

The solder paste of the present embodiment can be used for bonding an electronic circuit board and electronic components. may be used. High-temperature migration can be suppressed even when flux residue remains in the sealed structure.
Moreover, such a solder paste can be suitably used for manufacturing a device in which the temperature of the heat generated at the junction between the electronic circuit board and the electronic component is 100° C. or higher during device operation.

The configuration of the solder paste of this embodiment will be described in detail below.

The solder paste contains a flux composition and solder powder.

The flux composition may be configured to contain one or more selected from the group consisting of activators, base resins, thixotropic agents, and solvents.

(activator)
The flux composition may include an activator that has metal oxide removal properties.
Inclusion of an activator can enhance solder wettability during the solder bonding process.

Specific examples of activators include organic acids, amines, halogen-based activators, phosphorus-based activators, and the like. These may be used alone or in combination of two or more.
Although the detailed mechanism is not clear, these activators are thought to be able to remove the solder and the metal oxide film on the surface of the metal to be soldered by reducing the metal oxide and forming a salt with the metal. .

The content of the activator in 100% by weight of the flux composition may be, for example, 0 to 30% by weight, or may be 1 to 20% by weight.
In the present specification, "-" means including upper and lower limits unless otherwise specified.

Examples of organic acids include monocarboxylic acids, dicarboxylic acids, anhydrides of dicarboxylic acids, and oxyacids. These may be used alone or in combination of two or more.

Specific examples of organic acids include glutaric acid, adipic acid, azelaic acid, eicosanedioic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, dipicolinic acid, dibutylaniline diglycolic acid, and suberin. acid, sebacic acid, thioglycolic acid, terephthalic acid, dodecanedioic acid, p-hydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, isocyanuric acid tris(2-carboxyethyl), glycine, 1,3-cyclohexanedicarboxylic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, malic acid, p-anisic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid and the like.

Among these, the organic acid may contain an organic acid having 11 or less carbon atoms from the viewpoint of low residue.
Examples of organic acids having 11 or less carbon atoms include glycolic acid (2 carbon atoms), thioglycolic acid (2 carbon atoms), glycine (2 carbon atoms), malonic acid (3 carbon atoms), fumaric acid (3 carbon atoms), 4), maleic acid (4 carbon atoms), succinic acid (4 carbon atoms), diglycolic acid (4 carbon atoms), tartaric acid (4 carbon atoms), malic acid (4 carbon atoms), glutaric acid (5 carbon atoms) , 2,2-bis(hydroxymethyl)propionic acid (5 carbon atoms), adipic acid (6 carbon atoms), citric acid (6 carbon atoms), picolinic acid (6 carbon atoms), benzoic acid (7 carbon atoms), 2,2-bis(hydroxymethyl)butanoic acid (6 carbon atoms), salicylic acid (7 carbon atoms), dipicolinic acid (7 carbon atoms), 2,3-dihydroxybenzoic acid (7 carbon atoms), 3-hydroxybenzoic acid (C 7), suberic acid (C 8), phthalic acid (C 8), isophthalic acid (C 8), terephthalic acid (C 8), parahydroxyphenylacetic acid (C 8), 1, 3-cyclohexanedicarboxylic acid (8 carbon atoms), p-anisic acid (8 carbon atoms), azelaic acid (9 carbon atoms), 2,4-diethylglutaric acid (9 carbon atoms), sebacic acid (10 carbon atoms), Phenylsuccinic acid (10 carbon atoms), 2-quinolinecarboxylic acid (10 carbon atoms), 4-tert-butylbenzoic acid (11 carbon atoms) and the like can be mentioned.

Examples of the organic acid include dimer acid, trimer acid, hydrogenated dimer acid which is a hydrogenated product obtained by adding hydrogen to dimer acid, and hydrogenated trimer acid which is a hydrogenated product obtained by adding hydrogen to trimer acid. be done.

The content of the organic acid in 100% by weight of the flux composition may be, for example, 0 to 25% by weight, or may be 1 to 20% by weight. By setting the content to be equal to or less than the above upper limit value, the viscoelastic property of the flux residue can be made suitable.

Examples of amines include monoethanolamine, diphenylguanidine, ethylamine, triethylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2- ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1- Cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2- phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl- (1′)]-ethyl-s-triazine, 2,4-diamino-6-[2′-ethyl-4′-methylimidazolyl-(1′)]-ethyl-s-triazine, 2,4-diamino- 6-[2′-methylimidazolyl-(1′)]-ethyl-s-triazine isocyanurate, 2-phenylimidazole isocyanurate, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl- 4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2 -phenylimidazoline, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s- triazines, epoxy-imidazole adducts, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzo imidazole, benzimidazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3' -tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy- 5′-tert-octylphenyl)benzotriazole, 2,2′-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4 -tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl] benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino] bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6 -bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole and the like.

The content of amines in 100% by weight of the flux composition may be, for example, 0 to 15% by weight, or may be 0.1 to 10% by weight.

Examples of halogen-based activators include organic halogen compounds and amine hydrohalides.

Examples of organic halogen compounds include trans-2,3-dibromo-1,4-butenediol, triallyl isocyanurate hexabromide, 1-bromo-2-butanol, 1-bromo-2-propanol, 3-bromo -1-propanol, 3-bromo-1,2-propanediol, 1,4-dibromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 2,3- dibromo-1,4-butanediol, 2,3-dibromo-2-butene-1,4-diol and the like.
Other organic halogen compounds include, for example, chloroalkanes which are organic chloro compounds, chlorinated fatty acid esters, het acids, het acid anhydrides, and the like. Furthermore, fluorine-based surfactants which are organic fluoro compounds, surfactants having a perfluoroalkyl group, polytetrafluoroethylene, and the like are included.

Examples of amine hydrohalides include hydrohalic acids such as hydroiodic acid (HI), hydrobromic acid (HBr), hydrochloric acid (HCl) and hydrofluoric acid (HF), and aniline , diphenylguanidine, diethylamine, isopropylamine, and other amine compounds.
Further, as an amine hydrohalide equivalent, a salt obtained by combining tetrafluoroboric acid (HBF ₄ ) and an amine compound can also be used.

Examples of amine hydrohalides include stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, isopropylamine hydrobromide, Cyclohexylamine hydrobromide, diethylamine hydrobromide, monoethylamine hydrobromide, 1,3-diphenylguanidine hydrobromide, dimethylamine hydrobromide, dimethylamine hydrochloride, rosin amine odor Hydrochloride, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, 2-pipecoline hydrobromide, 1,3-diphenylguanidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazine hydrate odor Hydrochloride, dimethylcyclohexylamine hydrochloride, trinonylamine hydrobromide, diethylaniline hydrobromide, 2-diethylaminoethanol hydrobromide, 2-diethylaminoethanol hydrochloride, ammonium chloride, diallylamine hydrochloride salt, diallylamine hydrobromide, monoethylamine hydrochloride, monoethylamine hydrobromide, diethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydrochloride, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monohydrochloride Hydrochloride, hydrazine dihydrobromide, pyridine hydrochloride, aniline hydrobromide, butylamine hydrochloride, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine hydrochloride, dimethylcyclohexylamine bromide hydrochloride, ethylenediamine dihydrobromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzylpyridine hydrobromide, L-glutamic acid hydrochloride, N-methylmorpholine hydrochloride Salt, betaine hydrochloride, 2-pipecoline hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoride, diethylamine hydrofluoride, 2-ethylhexylamine hydrofluoride , cyclohexylamine hydrofluoride, ethylamine hydrofluoride, rosinamine hydrofluoride, cyclohexylamine tetrafluoroborate, and dicyclohexylamine tetrafluoroborate.

The content of the halogen-based activator in 100% by weight of the flux composition may be, for example, 0 to 10% by weight, or may be 0.1 to 5% by weight.
The content of organic halogen compounds in 100% by weight of the flux composition may be, for example, 0 to 10% by weight, or may be 0.1 to 5% by weight.
The content of amine hydrohalides in 100% by weight of the flux composition may be, for example, 0 to 5% by weight, or may be 0.1 to 3% by weight.

Phosphorus-based activators include, for example, phosphonic acid esters, phenyl-substituted phosphinic acid phosphonic acids, and phosphoric acid esters.

Phosphonate esters include, for example, 2-ethylhexyl (2-ethylhexyl) phosphonate, n-octyl (n-octyl) phosphonate, n-decyl (n-decyl) phosphonate, and n-butyl (n-butyl) phosphonate. be done.
Phenyl-substituted phosphinic acids include, for example, phenylphosphinic acid and diphenylphosphinic acid.

The content of the phosphorus-based activator in 100% by weight of the flux composition may be, for example, 0 to 10% by weight, or may be 0.1 to 5% by weight.

(base resin)
The flux composition may contain a base resin.
Examples of base resins include rosin resins, (meth)acrylic resins, urethane resins, polyester resins, phenoxy resins, vinyl ether resins, terpene resins, modified terpene resins (e.g., aromatic modified terpene resins, hydrogenated terpene resin, hydrogenated aromatic modified terpene resin, etc.), terpene phenol resin, modified terpene phenol resin (e.g., hydrogenated terpene phenol resin, etc.), styrene resin, modified styrene resin (e.g., styrene acrylic resin, styrene maleic resin, etc.) , xylene resins, modified xylene resins (eg, phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified resol-type xylene resins, polyol-modified xylene resins, polyoxyethylene-added xylene resins, etc.). These may be used alone or in combination of two or more.
In addition, in this specification, "(meth)acrylic resin" means a concept including methacrylic resin and acrylic resin.

Among these, the base resin may contain a rosin-based resin.
Examples of rosin-based resins include starting rosins such as gum rosin, wood rosin and tall oil rosin, and derivatives obtained from starting rosins. Derivatives include, for example, purified rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, α,β unsaturated carboxylic acid modified product (acrylated rosin), maleated rosin, fumarated rosin, etc., and polymerized rosin. Purified products, hydrides and disproportionated products, and purified products, hydrides and disproportionated products of α,β-unsaturated carboxylic acid-modified products are included. These rosin-based resins are used singly or in combination of two or more.

The content of the base resin in 100% by weight of the flux composition may be, for example, 0 to 50% by weight, 10 to 49% by weight, or 15 to 48% by weight. By setting the content of the base resin to 15% by weight or more, the viscoelastic properties of the flux residue can be made suitable.

The flux composition preferably contains a first rosin-based resin having a softening point of 135° C. or higher. The softening point of the first rosin-based resin is preferably 138°C or higher, more preferably 140°C or higher.
If necessary, the flux composition may contain a second rosin-based resin having a softening point of 120°C or higher and lower than 135°C.
The flux composition preferably does not contain a third rosin-based resin having a softening point of 90° C. or lower.
By including the first rosin-based resin and/or including the second rosin-based resin or not including the third rosin-based resin, the viscoelastic properties of the flux residue can be made suitable.
The softening point can be measured according to the softening point test method (ring and ball method) of JIS K 2207:1996.

The content of the first rosin resin in 100% by weight of the flux composition may be, for example, 1 to 50% by weight, 3 to 30% by weight, or 5 to 30% by weight. By making the amount equal to or higher than the above lower limit, the viscoelastic property of the flux residue can be made suitable. By making it equal to or less than the above upper limit, it is possible to suppress deterioration of the printing characteristics of the solder paste.
The content of the first rosin-based resin in 100% by weight of the total rosin-based resin may be, for example, 3 to 100% by weight, 10 to 90% by weight, or 12 to 80% by weight. By making the amount equal to or higher than the above lower limit, the viscoelastic property of the flux residue can be made suitable.

(solvent)
The flux composition may contain a solvent.
A solid or liquid solvent can be used as the solvent in a 25° C. environment. These may be used alone or in combination of two or more.

As the solid solvent, for example, an alcohol-based solid solvent, a phenol-based solid solvent, or the like is used.
These may be used alone or in combination of two or more.

The alcohol-based solid solvent may be a solid solvent having one or more hydroxy groups in the molecule, preferably a polyhydric alcohol-based solid solvent having two or more than three hydroxy groups.

Specific examples of polyhydric alcohol-based solid solvents include pentaerythritol, trimethylolpropane, 2,5-dimethyl-2,5-hexanediol, and neopentyl glycol.

The phenol-based solid solvent may be a solid solvent having one or two or more phenol groups in the molecule, and one or two or more hydroxy groups may be bonded to the benzene ring of the phenol group.

For liquid solvents, for example, alcohol solvents, glycol ether solvents, terpineols, hydrocarbons, esters, water, etc. are used. These may be used alone or in combination of two or more. Among these, at least one of an alcohol-based solvent and a glycol ether-based solvent may be used as the liquid solvent.

Examples of alcohol solvents include isopropyl alcohol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 1,1,1-tris ( hydroxymethyl)ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2′-oxybis(methylene)bis(2-ethyl-1,3-propanediol), 2,2-bis( hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, bis[2,2,2-tris(hydroxymethyl)ethyl]ether, 1-ethynyl-1-cyclohexanol, 1,4 -cyclohexanediol, 1,4-cyclohexanedimethanol, erythritol, threitol, guaiacol glycerol ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5- Decyne-4,7-diol and the like can be mentioned.

Examples of glycol ether solvents include hexyl diglycol, diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, 2-methylpentane-2,4-diol, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, and triethylene glycol. monobutyl ether, tetraethylene glycol monomethyl ether, and the like.

The solvent content in 100% by weight of the flux composition may be, for example, 0 to 65% by weight, 1 to 50% by weight, or 5 to 40% by weight. By setting the content to be equal to or less than the above upper limit value, the viscoelastic property of the flux residue can be made suitable.
The content of the liquid solvent in 100% by weight of the flux composition may be, for example, 0 to 65% by weight, 1 to 50% by weight, or 5 to 40% by weight.

(thixotropic agent)
The flux composition may contain a thixotropic agent.
Examples of thixotropic agents include wax-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.
Examples of wax-based thixotropic agents include castor hardened oil.
Examples of amide thixotropic agents include monoamides, bisamides and polyamides. For example, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, p-toluenemethanamide, aromatic amide, methylenebisstearic acid amide, ethylenebislauric acid amide, ethylenebishydroxystearic acid amide, saturated fatty acid bisamide, methylenebisoleic acid amide, unsaturated fatty acid bisamide, m-xylylene bisstearic acid amide, aromatic bisamide, aliphatic polyamide (saturated fatty acid polyamide, unsaturated fatty acid polyamide), aromatic polyamide, substituted amide, methylol stearamide, methylol amide, fatty acid ester amide, cyclic amide oligomer, non-cyclic amide oligomer and the like.

The content of the thixotropic agent in 100% by weight of the flux composition may be, for example, 0 to 20% by weight or 1 to 15% by weight.

(Additive)
The flux composition may contain additives that are commonly added to flux as long as they do not impair the effects of the present invention.
Examples of additives include antioxidants, rust inhibitors, antifoaming agents, matting agents, surfactants, colorants, and the like. These may be used alone or in combination of two or more.
For example, antioxidants include hindered phenol-based antioxidants, phosphorus-based antioxidants, and the like.

The solder powder can be Sn alone, Sn--Ag-based, Sn--Cu-based, Sn--Ag--Cu-based, Sn--Bi-based, Sn--In-based, etc., or alloys thereof containing Pb, Sb, Bi, In , Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P or the like may be added to the solder powder.

The solder powder may have a predetermined particle size distribution measured by a particle size distribution measurement test according to JIS Z 3284:2014.
In the solder powder, for example, the mass fraction of powder having a particle diameter in the range of 2 to 150 μm is 80% or more, preferably the mass fraction of powder having a particle diameter in the range of 5 to 75 μm is 80% or more, more preferably may be configured such that the mass fraction of powder having a particle size in the range of 5 to 45 μm is 80% or more.

According to a particle size distribution measurement test according to JIS Z 3284:2017, the solder powder can be classified into types 1 to 8 according to the particle size distribution.
In the present embodiment, among these, type 2 to type 7 solder powders are preferred, and type 3 to type 6 solder powders are more preferred.
Type 3 satisfies 80% or more by mass fraction of powder having a particle size in the range of 25 to 45 μm.
Type 4 satisfies 80% or more by mass fraction of powder having a particle size in the range of 20 to 38 μm.
Type 5 satisfies 80% or more by mass fraction of powder having a particle size in the range of 15 to 25 μm.
In type 6, the mass fraction of powder having a particle size in the range of 5 to 15 μm satisfies 80% or more.

The content of the flux composition in 100% by weight of solder paste containing solder powder and flux composition is, for example, 7 to 30% by weight, preferably 8 to 25% by weight, more preferably 10 to 20% by weight.

The manufacturing method of the flux composition and solder paste is not limited, and they can be manufactured by mixing raw materials simultaneously or sequentially by any method.

The flux composition can be produced by finally mixing all the components of the flux composition, and the other components may be sequentially mixed with the solvent, or the mixture of the other components may be added to the solvent. Alternatively, the solvent and all other ingredients may be mixed simultaneously.
Also, in the manufacture of solder paste, it is not always necessary to prepare a flux composition in advance and mix it with solder powder. As long as the additives to be added are mixed, the order of mixing does not matter. For example, after mixing some of the components of the flux composition with the solder powder, the remaining components of the flux composition are added. good too.

The solder paste of this embodiment can be used, for example, in a method for manufacturing an electronic device such as a semiconductor device.
The method of manufacturing an electronic device includes the step of applying the solder paste to the electrodes, and heat-treating a substrate such as a lead frame or a printed wiring board and a semiconductor element, and joining them via molten solder. and a step.

An example of a method for manufacturing an electronic device includes the steps of printing the above solder paste on a soldering portion of an electronic circuit board, mounting an electronic component on the soldering portion, and forming a sealing structure around the soldering portion. heating the soldering portion to a temperature at which the solder powder in the solder paste melts to join the electronic component and the electronic circuit board.
A high output device such as a power semiconductor may be used as the electronic component.

Screen printing, film printing, etc. can be cited as methods for printing the solder paste, and printing may be performed using methods other than jet dispensing.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can be adopted. Moreover, the present invention is not limited to the above-described embodiments, and includes modifications, improvements, etc. within the scope of achieving the object of the present invention.
Examples of reference forms are added below.
1. A solder paste comprising a flux composition and a solder powder,
Regarding the flux residue obtained from the solder paste according to the following preparation procedure, the storage elastic modulus at 100° C. was measured using a rheometer under the following measurement conditions, G′ ₁₀₀ and the loss elastic modulus were G″ ₁₀₀ . when
G′ ₁₀₀ and G″ ₁₀₀ are configured to satisfy G′ ₁₀₀ >G″ ₁₀₀ ;
solder paste.
<Procedure for preparing flux residue>
1. Prepare two copper trays having a bottom surface of 45 mm×45 mm, a height of 5 mm, and a thickness of 0.3 mm.
2. A copper box having a height of about 10 mm is prepared by laying one of the copper trays on the bottom surface of the other copper tray so that the opening of the other copper tray faces the other opening and fixing with tape.
3. 5 g of the solder paste is taken as a sample. The sample is spread on the bottom surface inside one of the copper trays to cover 80% of the area of the bottom surface.
4. Using a reflow furnace, the copper box containing the sample is subjected to reflow treatment in the atmosphere according to the following temperature profiles A to E.
(Temperature profile A to E)
A. It is heated from a room temperature of 25° C. to 150° C. at a heating rate of 1.9° C./sec.
B. The temperature is held in the temperature range of 150°C to 180°C for 80 seconds.
C. Heat up to 220° C. at a rate of temperature increase of 1.2° C./sec.
D. The temperature is maintained at 220°C or higher for 40 seconds, and the peak temperature is 240°C.
E. After that, it is cooled to room temperature of 25°C.
5. After the reflow process, the flux residue remaining on the inner bottom surface of one of the copper trays is collected.
<Measurement conditions>
Measuring device: Rheometer Measuring temperature: 20°C to 180°C
Geometry (upper): 25mmφ, stainless steel, parallel plate Plate (lower): 60mmφ
Mode: 5°C/min
Strain: 1%
Frequency: 10Hz
Gap: 0.2mm
2. 1. The solder paste according to
When δ140 is the phase angle at ₁₄₀ °C obtained from the storage modulus and loss modulus at ₁₄₀ °C measured using a rheometer under the above measurement conditions, δ140 is 1° or more and less than 45°. Yes, solder paste.
3. 2. The solder paste according to
When the phase angle at ₁₀₀ °C is δ100, which is obtained from the storage modulus and loss modulus at 100°C measured using a rheometer under the above measurement conditions, _δ140 and _δ100 are 0.1. A solder paste configured to satisfy ≤ δ ₁₄₀ /δ ₁₀₀ ≤ 3.0.
4. 1. ~3. The solder paste according to any one of
The solder paste, wherein the flux composition contains a rosin-based resin having a softening point of 135° C. or higher.
5. 1. ~ 4. The solder paste according to any one of
A solder paste in which the content of the flux composition is 7% by weight or more and 20% by weight or less in 100% by weight of the solder paste.
6. 1. ~ 5. The solder paste according to any one of
A solder paste having a viscosity η1 of 5 Pa·s or more and 400 Pa·s or less when measured using the above rheometer at a shear rate of 6 sec ⁻¹ and 25°C.
7. 1. ~6. The solder paste according to any one of
Using the above ^rheometer , the ^viscosity of the solder paste was measured at 25°C. A solder paste having a thixotropic ratio calculated by Log(η2/η3) of 0.3 or more and 1.8 or less.
8. 1. ~7. The solder paste according to any one of
Solder paste used to join an electronic circuit board and electronic components around a sealed structure.
9. 1. ~8. The solder paste according to any one of
A solder paste, wherein the flux composition contains one or more selected from the group consisting of an activator, a base resin, a thixotropic agent, and a solvent.
10. 9. The solder paste according to
A solder paste, wherein the activator contains one or more selected from the group consisting of organic acids, amines, halogen-based activators, and phosphorus-based activators.
11. 1. ~ 10. The solder paste according to any one of
A solder paste, wherein the solder powder has a mass fraction of 80% or more of powder having a particle diameter in the range of 2 to 150 μm.
12. 1. ~ 11. A step of printing the solder paste according to any one of 1 to a soldering portion of an electronic circuit board;
a step of mounting an electronic component on the soldering portion;
joining the electronic component and the electronic circuit board by heating the soldering portion to a temperature at which the solder powder in the solder paste melts, in a state where a closed structure exists around the soldering portion;
A method of manufacturing an electronic device, comprising:

Although the present invention will be described in detail below with reference to examples, the present invention is not limited to the description of these examples.

Information on raw material components in Table 1 is shown below.
(base resin)
・ Rosin resin 1: acrylic acid-modified hydrogenated rosin (softening point: 131 ° C., manufactured by Arakawa Chemical Industries, Ltd., KE-604)
· Rosin resin 2: hydrogenated rosin (softening point: 74 ° C., manufactured by EASTMAN CHEMICAL, FORAL AX-E)
・ Rosin resin 3: Polymerized rosin (softening point: 141 ° C., manufactured by Arakawa Chemical Industries, Ltd., KR-140)
The softening point of the rosin resin is measured according to the softening point test method (ring and ball method) of JIS K 2207: 1996, and the average value of two measurements (rounded to the first decimal place) and did.
・Acrylic resin 1: acrylic resin (activator)
・Organic acid 1: dimer acid ・Organic acid 2: adipic acid ・Organic acid 3: azelaic acid ・Amines 1: 2-phenyl-4-methylimidazole (abbreviation: 2P4MZ)
・Amine hydrohalides 1: diphenylguanidine hydrobromide ・Organic halogen compound 1: 2,3-dibromo-2-butene-1,4-diol (solvent)
・Solvent 1: Glycol ether solvent (diethylene glycol monohexyl ether)
(thixotropic agent)
・Thixotropic agent 1: Polyamide (additive)
・Antioxidant 1: Hindered phenolic antioxidant (solder powder)
Solder powder 1: Solder powder (SEC305: Sn-3.0Ag-0.5Cu, type 4, manufactured by Senju Metal Industry Co., Ltd.)

<Preparation of Solder Paste>
A flux composition was obtained by mixing the raw material components at the blending ratios shown in Table 1 below.
After that, 11.5% by weight of the obtained flux composition and 88.5% by weight of solder powder were mixed to obtain a solder paste.

The obtained solder paste was evaluated for the following evaluation items.

<Measurement of storage modulus and loss modulus>
Flux residue was collected from the solder paste according to the following preparation procedure.
(Procedure for preparing flux residue)
1. As shown in FIG. 1, two

copper trays

12 and 14 having a bottom surface of 45 mm×45 mm, a height of 5 mm, and a thickness of 0.3 mm were prepared.
2. A copper box 10 having a height of 10 mm was prepared by laying one of the copper trays 12 on the bottom surface of the other copper tray 14 so that the opening of the other copper tray 14 faced the one opening, and fixing them with tape.
3. 5 g of the obtained solder paste is sampled. The sample was spread onto the bottom surface inside one of the copper trays 12 so as to cover 80% of the area of the bottom surface.
4. Using a reflow furnace (SNR-825, manufactured by Senju Metal Industry Co., Ltd.), the copper box 10 containing the sample was subjected to reflow treatment under the following temperature profiles A to E in the atmosphere.
(Temperature profile A to E)
A. It is heated from a room temperature of 25° C. to 150° C. at a heating rate of 1.9° C./sec.
B. The temperature is held in the temperature range of 150°C to 180°C for 80 seconds.
C. Heat up to 220° C. at a rate of temperature increase of 1.2° C./sec.
D. The temperature is maintained at 220°C or higher for 40 seconds, and the peak temperature is 240°C.
E. After that, it is cooled to room temperature of 25°C.
5. After the reflow treatment, the residual flux remaining on the inner bottom surface of one of the copper trays 12 was collected.

The storage modulus of the obtained flux residue was measured at 25° C. to 180° C. using a rheometer under the following measurement conditions.
(Measurement condition)
Measuring device: rheometer (manufactured by Malvern Panalytical, KINEXUS 1b+)
Measurement temperature: 20°C to 180°C
Geometry (upper): 25mmφ, stainless steel, parallel plate Plate (lower): 60mmφ
Mode: 5°C/min
Strain: 1%
Frequency: 10Hz
Gap: 0.2mm

The storage modulus at 100° C. was G′ ₁₀₀ , the loss modulus was G″ ₁₀₀ , the storage modulus at 140° C. was G′ ₁₄₀ , and the loss modulus was G″ ₁₄₀ , measured using the rheometer.
Based on the relational expression tan δ=G′/G″, the phase angle at 100° C. obtained from G′ ₁₀₀ and G″ ₁₀₀ is defined as δ ₁₀₀ , the phase at 140° C. obtained from G′ ₁₄₀ and G″ ₁₄₀ The angle was taken as _δ140 . Table 1 shows the results.

<Measurement of viscosity>
Using the above ^rheometer , the ^viscosity of the solder paste was measured at 25°C. Taking the viscosity at ⁻¹ as η3, η1, η2 and η3 were obtained. Also, a thixotropic ratio obtained by Log (η2/η3) was calculated. The results are shown in Table 1

<High temperature migration test>
The obtained solder paste was printed on the copper electrodes 30 on the printed circuit board by imitating an actual process, and subjected to a reflow treatment at 240° C. to join the solder 50 to the copper electrodes 30 . Subsequently, the residual flux remaining around the printed portion was cleaned and removed. As a result, a device for evaluation (a structure including a printed circuit board, copper electrodes 30, and solder 50) shown in FIG. 2 was produced.
Subsequently, a high-temperature migration test was performed using the evaluation apparatus shown in FIG. 2 as follows.
The evaluation device shown in FIG. 2 includes a substrate, a copper electrode 30 provided on the substrate, and a tin-containing solder 50 provided on the copper electrode 30 .
Using 0.002 to 0.005 g of the flux residue 22 collected in the above (procedure for producing flux residue), the gap between the copper electrodes 30 adjacently arranged at fine intervals is filled without gaps, and the filled flux residue 22 is The glass cover 60 was placed so that the was sealed by the substrate and the solder 50 .
A constant voltage of 10 V was applied between the copper electrodes 30, and the device for evaluation was stored in a temperature environment of 105.degree.
After that, metal migration was observed in the flux residue 22 in the spaced portion of the copper electrode 30 (high temperature migration test).
When gray dendritic precipitation was confirmed in the flux residue 22 in the spaced portion, it was determined that the tin contained in the solder had migrated.
A high-temperature migration test was performed three times to confirm the presence or absence of precipitation in each test.
In Table 1, "excellent" when precipitation is not confirmed 3 out of 3 times, "good" when precipitation is confirmed 1 time out of 3 times, and "good" when precipitation is confirmed 2 or more times out of 3 times. Impossible.”

The solder paste of each example showed better resistance to high-temperature migration than the solder paste of each comparative example because precipitation in the high-temperature migration test was suppressed.

This application claims priority based on Japanese Patent Application No. 2021-105629 filed on June 25, 2021, and the entire disclosure thereof is incorporated herein.

10 copper box 12 copper tray 14 copper tray 20 solder paste 22 flux residue 30 copper electrode 50 solder 60 glass cover

Claims

A solder paste comprising a flux composition and a solder powder,
the flux composition comprises a base resin, an activator, a solvent, and a thixotropic agent;
The base resin contains a rosin-based resin,
Regarding the flux residue obtained from the solder paste according to the following preparation procedure, the storage elastic modulus at 100° C. was measured using a rheometer under the following measurement conditions, G′ 100 and the loss elastic modulus were G″ 100 . when
G′ 100 and G″ 100 are configured to satisfy G′ 100 >G″ 100 ;
solder paste.
<Procedure for preparing flux residue>
1. Prepare two copper trays having a bottom surface of 45 mm×45 mm, a height of 5 mm, and a thickness of 0.3 mm.
2. A copper box having a height of about 10 mm is prepared by laying one of the copper trays on the bottom surface of the other copper tray so that the opening of the other copper tray faces the other opening and fixing with tape.
3. 5 g of the solder paste is taken as a sample. The sample is spread on the bottom surface inside one of the copper trays to cover 80% of the area of the bottom surface.
4. Using a reflow furnace, the copper box containing the sample is subjected to reflow treatment in the atmosphere according to the following temperature profiles A to E.
(Temperature profile A to E)
A. It is heated from a room temperature of 25° C. to 150° C. at a heating rate of 1.9° C./sec.
B. The temperature is held in the temperature range of 150°C to 180°C for 80 seconds.
C. Heat up to 220° C. at a rate of temperature increase of 1.2° C./sec.
D. The temperature is maintained at 220°C or higher for 40 seconds, and the peak temperature is 240°C.
E. After that, it is cooled to room temperature of 25°C.
5. After the reflow process, the flux residue remaining on the inner bottom surface of one of the copper trays is collected.
<Measurement conditions>
Measuring device: Rheometer Measuring temperature: 20°C to 180°C
Geometry (upper): 25mmφ, stainless steel, parallel plate Plate (lower): 60mmφ
Mode: 5°C/min
Strain: 1%
Frequency: 10Hz
Gap: 0.2mm
The solder paste according to claim 1,
δ is the phase angle at 140° C. obtained from the storage modulus and loss modulus at 140° C. of the flux residue obtained from the solder paste according to the above preparation procedure, measured using a rheometer under the above measurement conditions. 140 , δ140 is 1° or more and less than 45°.
The solder paste according to claim 2,
δ is the phase angle at 100° C. obtained from the storage modulus and loss modulus at 100° C. of the flux residue obtained from the solder paste according to the above preparation procedure, measured using a rheometer under the above measurement conditions. A solder paste configured such that δ140 and δ100 , when 100 , satisfy 0.1≤δ140 / δ100≤3.0 .
The solder paste according to any one of claims 1 to 3,
The solder paste, wherein the flux composition contains a rosin-based resin having a softening point of 135° C. or higher.
The solder paste according to any one of claims 1 to 4,
A solder paste in which the content of the flux composition is 7% by weight or more and 20% by weight or less in 100% by weight of the solder paste.
The solder paste according to any one of claims 1 to 5,
A solder paste having a viscosity η1 of 5 Pa·s or more and 400 Pa·s or less when measured using the above rheometer at a shear rate of 6 sec −1 and 25°C.
The solder paste according to any one of claims 1 to 6,
Using the above rheometer , the viscosity of the solder paste was measured at 25°C. A solder paste having a thixotropic ratio calculated by Log(η2/η3) of 0.3 or more and 1.8 or less.
The solder paste according to any one of claims 1 to 7,
Solder paste used to join an electronic circuit board and electronic components around a sealed structure.
The solder paste according to any one of claims 1 to 8,
A solder paste in which the activator contains one or more selected from the group consisting of organic acids, amines, halogen-based activators, and phosphorus-based activators.
The solder paste according to any one of claims 1 to 9,
A solder paste, wherein the solder powder has a mass fraction of 80% or more of powder having a particle diameter in the range of 2 to 150 μm.
A step of printing the solder paste according to any one of claims 1 to 10 on a soldering portion of an electronic circuit board;
a step of mounting an electronic component on the soldering portion;
joining the electronic component and the electronic circuit board by heating the soldering portion to a temperature at which the solder powder in the solder paste melts, in a state where a closed structure exists around the soldering portion;
A method of manufacturing an electronic device, comprising: