JP2002086292A - Solder paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide solder paste having excellent preservation stability, to provide a soldering method corresponding to pitches becoming increasing finer and the diversification of parts and having high reliability and to provide a joined article. SOLUTION: The concentration of halogen ions in 1 g of flux in this solder paste containing a halogen compound is controlled to 3,000 ppm or below in terms of chlorine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder paste used for surface mounting of an electronic component.
The present invention relates to a solder paste having excellent storage stability, a soldering method using the solder paste, and a joined product.

[0002]

2. Description of the Related Art Solder pastes are used in the electronics industry for surface mounting electronic components.
Solder paste is suitable for automation due to its printability and adhesiveness, and its use has increased in recent years.

[0003] In the electronics industry, solder paste is applied on a printed circuit board by screen printing or dispenser, electronic components are placed, and then reflowed to fix the electronic components. Here, reflow refers to a series of operations for preheating a substrate on which electronic components are mounted and thereafter heating the solder paste to a temperature equal to or higher than the melting temperature to join the components.

On the other hand, in recent years, fine pitch has been required to reduce the size of electronic products, and fine pitch components such as a 0.3 mm pitch QFP (Quad Flat) have been demanded.
Package) Type LSI and CS
P (Chip Size Package) and the like are often used. For this reason, the solder paste is required to have a printing performance compatible with fine pitch. In order to respond to such demands of the industry, the average particle diameter of the solder particles has been reduced.On the other hand, the specific surface area of the entire solder particles has been increased, so that the reaction between the solder particles and the flux has been promoted, and There was a problem that the storage stability of the paste was further deteriorated.

[0005] The biggest cause of the decrease in the storage stability of the solder paste is that the solder powder reacts preferentially with the flux during storage, the oxidation of the solder powder progresses, the activator in the flux is consumed, and the activity of the flux is reduced. At the same time
This is because the reaction product increases the viscosity of the solder paste. For this reason, when using the solder paste, there arises a problem that proper printing characteristics cannot be maintained and that the solder paste does not melt during reflow.

Conventionally, in order to improve the storage stability of the solder paste, efforts have been made to protect the surface of the solder particles and reduce the reactivity of the metal particles.

For example, a method of coating a solder powder with glycerin (Japanese Patent Publication No. 5-26598), a method of coating a solder powder with a coating agent that is insoluble or hardly soluble in a solder paste solvent (Japanese Patent Laid-Open No. 1-113).
197). Preferred examples of the latter coating agent include silicone oil, silicone-based high molecular weight compound, fluorinated silicone oil, fluorosilicone resin, and fluorinated hydrocarbon-based polymer compound.

Also, a method of coating a solder powder with a resin mainly composed of rosin which is incompatible with the flux at room temperature but is compatible with the soldering temperature (Japanese Patent Laid-Open No. 18469/1991).
No. 8, JP-A-4-251691).

In the above-mentioned method, coating with a relatively large amount of a coating agent is effective in suppressing the oxidation of the solder powder, but a large amount of the coating material is rather inconvenient to reflow of the solder paste. There is a possibility that solder balls are frequently generated. In addition, since these coatings are only performed physically, the adhesion is considered to be very weak, and there is a strong possibility that the coatings may be peeled off during kneading when producing a solder paste or during handling such as transfer and printing during use. Further, it is hard to say that the above-mentioned resin coating agent mainly composed of rosin contains a large amount of reactive organic acid itself and protects the powder.

In addition, a method of adding a phenol-based, phosphite-based or sulfur-based antioxidant as an activator for the soldering flux (Japanese Patent Publication No. 59-22632, Japanese Patent Application Laid-Open No. 3-124092), A method of adding 1 to 30% by weight of one or more antioxidants containing one or more phenol skeletons having a tertiary butyl group (JP-A-5-185283); Using an activator (Japanese Patent Laid-Open No. 2-147194)
Publication).

Recently, due to environmental problems, lead-free P
b Free solder paste is recommended, and development is underway to meet this requirement. Above all, Sn—Zn based solder paste is advantageous in resources and cost, and moreover, Sn
Since the reflow temperature is reduced to the same level as that of the -Pb solder, the life of the mounted components can be extended, and the components can be diversified. However, the Sn—Zn-based solder paste has poorer storage stability than ordinary Pb-based solder paste, and the viscosity of the solder powder over time increases due to the progress of oxidation of Zn in the solder powder and the reaction between Zn and flux. To rise. In particular, Zn reacts with the halogen compound in the flux at room temperature to deteriorate the storage stability of the solder paste. Further, the halogen compound in the flux reacts with Zn in the solder powder to generate a small amount of hydrogen gas,
Since the generated hydrogen gas is incorporated in the solder fillet even after the parts are joined, it has been found that the reliability is seriously affected.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a solder paste having excellent storage stability. Further, by using this solder paste, a highly reliable solder paste is provided. It is an object of the present invention to provide an attachment method and a joint.

[0013]

Means for Solving the Problems The inventors of the present invention have made intensive efforts to solve the above-mentioned problems, and as a result, have reached the present invention. That is, the present invention relates to [1] a solder paste containing a halogen compound, wherein the halogen ion concentration per gram of flux is 3000 ppm or less in terms of chlorine, and [2] the halogen ion is bromine. 2. The solder paste according to claim 1, wherein the solder paste is an ion, and [3] the solder paste contains Zn as a solder powder.
Or the solder paste according to 2, [4].
A method for soldering a circuit board, comprising: a step of applying the solder paste according to any one of the above, on a circuit board; and a step of reflowing the solder paste.
[5] A joined article manufactured by the circuit board soldering method according to claim 4.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The flux contained in the solder paste includes a resin component of rosin or a synthetic resin, a halogen compound and / or an organic acid component as an activator, a solvent,
It contains a thixotropic agent and the like. Among these components, the components effective for removing the surface oxide of the solder metal at the time of reflow and obtaining a good bond are a halogen compound and / or an organic acid component used as an activator. Although these activators can enhance the ability to remove surface oxides, they react with the solder powder when formed into a solder paste and during storage, and deteriorate the solder paste. In particular, a halogen compound has a high effect as an activator, but has a strong effect of deteriorating a solder paste.

The present inventors have studied the reaction between the solder powder and the activator in the solder paste. As a result, the halogen ion concentration per gram of the flux of the solder paste was 3000 ppm or less in terms of chlorine, preferably 1 ppm or less.
000 ppm or less, more preferably 500 ppm or less,
It has been found that by setting the content to 300 ppm or less most preferably, the reaction between the solder powder and the activator can be suppressed, the deterioration of the solder paste can be prevented, and the storage stability can be increased.

It is not clear why the halogen ions adversely affect the storage stability of the solder paste, but in the presence of the halogen ions, the oxidizing power of the halogen compound added to the flux is enhanced, and the reaction with the solder metal is increased. Is considered to be promoted.

The chlorine equivalent value of the halogen ion concentration is determined by measuring the concentration of the halogen ion contained in the aqueous layer when the solder paste is weighed and extracted with an organic solvent-water system by ion chromatography, and further converted to chlorine to obtain a flux. 1
It is determined from the value converted per gram. The chlorine conversion value is a value when the contained halogen ion is converted to chloride ion. For example, when a bromine compound is used as the activator, the quantitative value of the bromine ion in the solder paste (μ
g / g) may be multiplied by a value of 35.453 / 79.904 (atomic weight of chlorine / atomic weight of bromine). When an iodine compound is used as the activator, the quantitative value (μg / g) of the ion may be multiplied by the value of 35.453 / 126.9045 (atomic weight of chlorine / atomic weight of iodine).

Here, the organic solvent used for the extraction may be any solvent which does not react with flux, is insoluble in water, and does not contain halogen ions, which is conventionally used in organic synthesis and the like. Examples include methylene chloride, toluene, xylene, benzene, diethyl ether, petroleum ether and the like. Chloroform, toluene, xylene, diethyl ether and petroleum ether are preferably used from the viewpoints of the solubility of the flux and the ease of the extraction operation. The water used for the extraction need not contain halogen ions. For example, ultrapure water is most preferably used. The measurement of the halogen ion concentration by extraction with an organic solvent-water can be performed on a solder paste using either a water-soluble flux or a water-insoluble flux.

In the present invention, the concentration of halogen ions in the flux of the solder paste is 3000 ppm or less in terms of chlorine. For example, isopropylamine hydrobromide, which is a hydrohalide of an organic base, preferably used as an activator,
In the case of amine salts of hydrohalic acid such as butylamine hydrochloride and cyclohexylamine hydrobromide, and 1,3-diphenylguanidine hydrobromide, the total amount of halogen contained in these compounds is halogen. It is an ion. Therefore, when the halogen compound is not used in combination, the chlorine equivalent of the halogen ion is 3,000.
What is necessary is just to calculate and add so that it may become ppm or less.

As the halogen compound, a halogen compound used as a normal solder flux may be used. However, in order to further improve the solderability and wettability of the solder paste, the halogen compound is used during storage of the solder paste. It is preferable to use a halogen compound, particularly an organic bromine compound, which stably exists at a reflow temperature and decomposes to exhibit an activity at a reflow temperature so that the chlorine equivalent of halogen ions is 3000 ppm or less.

As an example of an organic bromine compound having such performance, a benzyl bromide compound having an alkyl substituent having 10 or more carbon atoms, or a fatty acid or alicyclic compound having 10 or more carbon atoms in one molecule. Examples thereof include polybromine compounds containing four or more bromines, and these may be used as a mixture.

Benzyl bromide compounds having an alkyl chain having at least 10 carbon atoms include, for example, 4-stearoyloxybenzyl bromide, 4-stearyloxybenzyl bromide, 4-stearylbenzyl bromide,
Compounds such as 4-bromomethylbenzyl stearate, 4-stearoylaminobenzyl bromide, 2,4-bisbromomethylbenzyl stearate and the like can be mentioned. Other than this, 4-palmitoyloxybenzyl bromide, 4-myristoyloxybenzyl bromide,
4-lauroyloxybenzyl bromide, 4-undecanoyloxybenzyl bromide and the like.

The polybromine compounds include, for example, carboxyl groups, ester groups, alcohol groups, ether groups,
It is a compound which may have a ketone group or the like and is bonded to four or more bromine atoms.

Specific examples of these compounds include 9.1
0,12,13,15,16-hexabromostearic acid, 9,10,12,13,15,16-hexabromostearic acid methyl ester, the same ethyl ester,
10,12,13-Tetrabromostearic acid, methyl ester, ethyl ester, 9,10,12,1
3,15,16-hexabromostearyl alcohol,
9,10,12,13-tetrabromostearyl alcohol, 1,2,5,6,9,10-hexabromocyclododecane and the like. Hexabromostearic acid and hexabromocyclododecane are particularly preferred.

In addition to the above, examples of organic bromine compounds include 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,
1,4-dibromo-2,3-butanediol, 2,3-dibromo-2-butene-1,4-diol, 1-bromo-
3-methyl-1-butene, 1,4-dibromobutene, 1
-Bromo-1-propene, 2,3-dibromopropene,
Ethyl bromoacetate, ethyl α-bromocaprylate, α-
Ethyl bromopropionate, ethyl β-bromopropionate, α-bromo-ethyl acetate, 2,3-dibromosuccinic acid, 2-bromosuccinic acid, 2,2-bromoadipic acid, 2,4-dibromoacetophenone, 1,1 Bromide such as -dibromotetrachloroethane, 1,2-dibromo-1-phenylethane, and 1,2-dibromostyrene; and the like, but is not limited to these examples. An organic halogen compound containing chlorine and iodine may be used instead of bromine.

The amount of the halogen compound added is such that the halogen ions in the solder paste fall within 3000 ppm or less in terms of chlorine per gram of flux. One or more halogen compounds may be added, or an organic halogen compound and an organic base hydrohalide may be used in combination.

Examples of the organic acid component in the present invention include conventionally known succinic acid, phthalic acid, stearic acid, sebacic acid and the like, and an organic acid derivative which is a compound which generates an organic acid when the reflow temperature is reached is preferable. Used for Examples thereof include various aliphatic carboxylic acid esters, aromatic carboxylic acid esters, aliphatic sulfonic acid esters, aromatic sulfonic acid esters, and the like.

Alcohol residues of these esters include alkyl and allyl, especially t.
-A butyl group, an isopropyl group and an isobutyl group are preferred, and these compounds may contain a halogen atom.

Specific examples include n-propyl paratoluenesulfonate, isopropyl paratoluenesulfonate, isobutyl paratoluenesulfonate, n-butyl paratoluenesulfonate, and n-butylbenzenesulfonate.
Propyl, isopropyl benzenesulfonate, isobutyl benzenesulfonate, n-propyl salicylate, isopropyl salicylate, isobutyl salicylate, n-butyl salicylate, isopropyl 4-nitrobenzoate,
4-t-butyl 4-nitrobenzoate, t-methacrylic acid
Butyl, t-butyl acrylate, t-butyl malonate, t-butyl bromoacetate and the like. Of these, n-propyl paratoluenesulfonate, isobutyl salicylate, and t-butyl bromoacetate are particularly preferred. The addition amount is 0.01 to the total amount of the flux.
-20% by weight, preferably 0.05-5% by weight.

Since the decomposable organic acid ester alone has low decomposability even at a reflow temperature, it is effective to add a small amount of an ester decomposing catalyst to accelerate the decomposition. As the ester decomposition catalyst, any catalyst may be used as long as the decomposable organic acid ester has a function of decomposing at the reflow temperature to promote the generation of an acid. Among them, a hydrohalide of an organic base is particularly effective. is there.

As the resin component blended in the solder paste of the present invention, a well-known resin blended in a conventional flux can be used. For example, natural rosin, disproportionated rosin, polymerized rosin, modified rosin, etc. As the resin, polyester, polyurethane, acrylic resin or the like is used.

As the solvent, alcohols, ethers, esters, or aromatic solvents can be used as in the case of conventional fluxes and solder pastes. For example, benzyl alcohol, butanol, ethyl cellosolve, butyl cellosolve, butyl carbitol, Diethylene glycol hexyl ether, propylene glycol monophenyl ether, dioctyl phthalate, xylene and the like are used alone or in combination.

As the thixotropic agent added to improve printability, inorganic agents such as fine silica particles and kaolin particles, or organic agents such as hydrogenated castor oil and amide compounds are used. Is done.

In the solder paste of the present invention, the storage stability can be further improved by using a reducing agent as a stabilizer.

As the reducing agent, a phenolic compound, a phosphorus compound, a sulfur compound, tocopherol and its derivatives, L-ascorbic acid and its derivatives, which are usually used as antioxidants for resins and the like, are soluble in solvents. Derivatives and the like.

Specifically, phenolic compounds include hydroquinone, catechol, 2,6-di-t-butyl-p-cresol, butylhydroxyanisole,
2,2'-methylenebis (4-methyl-6-t-butylphenol) and the like can be mentioned.

Examples of the phosphorus compound include triphenyl phosphite, trioctadecyl phosphite, tridecyl phosphite and the like.

As the sulfur compound, dilauryl-
3,3'-thiodipropionate, distearyl-3,
3'-thiodipropionate, dimyristyl-3,3 '
-Thiodipropionate and the like.

As tocopherol and its derivatives, and L-ascorbic acid and its derivatives, any compound having a reducing property and soluble in a solvent, such as esters thereof, can be used. Particularly good results are obtained when two kinds of tocopherol or its derivative and L-ascorbic acid or its derivative are used in combination. The compounding ratio is preferably 0.5: 1 to 1: 0.5 by weight, particularly preferably about 1: 1.

Specific examples of the L-ascorbic acid derivative include ascorbic acid-2-phosphate, ascorbic acid-2
-Sulfuric acid, ascorbic acid-2-glucoside, ascorbic acid-2,6-dibutyrate, ascorbic acid-2,6
-Distearate, ascorbic acid-2,6-dimyristylate, ascorbic acid-6-palmitate, ascorbic acid-6-stearate, ascorbic acid-6-myristylate, ascorbic acid-2,3,5,6-tetrapalmitate , Ascorbic acid-2,3,5,6-tetramyristylate, ascorbic acid-2,3,5,6
Tetrastearate, ascorbic acid-2-glucoside-6-palmitate, ascorbic acid-2-glucoside-6-myristylate, ascorbic acid-2-glucoside-6-stearate, ascorbic acid-5,6-benzylidene, ascorbic acid -5,6-propylidene,
Ascorbic acid-2-phosphate-5,6-benzylidene,
Ascorbic acid-2-phosphate-5,6-propylidene and the like, and specific examples of tocopherol derivatives include tocol, tocopherol acetate, tocopherol phosphate,
And tocopherol sorbate, tocopherol nicotinate and the like.

These reducing agents may be used alone or as a mixture. The amount of the reducing agent added may be an amount sufficient to sufficiently secure the storage stability of the solder paste, but is generally 0.005% by mass or more and 20% by mass or less based on the total amount of the flux, and more preferably. Is 0.
It is at least 01% by mass and at most 10% by mass. If the addition amount is too small, there is no stabilizing effect, and even if it is added in an amount of 20% by mass or more, no improvement in the effect corresponding to high concentration addition is observed, which is not preferable.

The flux used in the solder paste of the present invention is, for example, 20 to 60 with respect to the total amount of the flux.
0.1% by mass of a resin component, 0.04% by mass to 20% by mass of a thixotropic agent, 0.01% by mass to 20% by mass of an organic acid component, and a halogen compound satisfying the above-mentioned range of halogen ions.
A reducing agent of 005 to 20% by mass and a solvent and others are used as the balance. This flux is kneaded with, for example, 14 to 8% by mass and 86 to 92% by mass of the solder powder based on the total amount of the solder paste to obtain a solder paste of the present invention. In this case, the amount of halide added is such that the concentration of halogen ions in the flux after kneading the solder paste is 3 in terms of chlorine.
It is necessary to make it below 000 ppm.

In the preparation and kneading of the mixture, the moisture such as the flux and the humidity of the atmosphere are adjusted so that the moisture content in the solder paste is 0.5% by mass or less, more preferably 0.1% by mass or less.
It is preferable to control it to 3% by mass or less. If the paste contains more than 0.5% by weight of water, dissociation of the halide is promoted, and the dissociated halogen reacts with the solder alloy powder, which is not preferable. Further, the pH value of the solder paste is preferably in the range of 4 to 9, and more preferably in the range of 6 to 8, from the viewpoint of suppressing the reaction between the solder powder and the flux. In this case, it is preferable to use amine compounds such as alkanolamines, aliphatic primary to tertiary amines, aliphatic unsaturated amines, alicyclic amines, and aromatic amines as the pH adjuster.

Specific examples of these amine compounds include ethanolamine, butylamine, aminopropanol, polyoxyethylene oleylamine, polyoxyethylene laurelamine, polyoxyethylene stearylamine, diethylamine, triethylamine, methoxypropylamine and dimethylaminopropyl. Amine,
Examples thereof include dibutylaminopropylamine, ethylhexylamine, ethoxypropylamine, ethylhexyloxypropylamine, bispropylamine, isopropylamine, and diisopropylamine.

The amount of the amine compound used is preferably 0.05 to 20% by mass based on the total amount of the solder paste flux. If the amount is less than 0.05% by mass, the effect as a pH adjuster is not sufficient. If the amount exceeds 20% by mass, the pH generally exceeds 9, and the composition shifts to the alkali side, and the solder paste easily absorbs moisture.

Further, azoles, for example, benzotriazole, benzimidazole, tolyltriazole and the like may be added to the flux to prevent rust of copper in the circuit. The amount of rust inhibitor added is 0.0
5-20 mass% is preferable.

The solder powder used for the solder paste of the present invention may have a conventionally known metal composition, but a solder powder containing Zn which is easily oxidized is preferably used. For example, Sn-Zn-based, Sn-Ag-Zn-based, Sn-Bi-
Sb-Zn system, Sn-Bi-Cu-Zn system, Sn-Ag
-Sb-Zn system, Sn-Ag-Cu-Zn system, Sn-Z
An n-Bi system is mentioned.

As a specific example, a eutectic solder containing 91% by mass of Sn and 9% by mass of Zn (hereinafter referred to as 91Sn / 9Z
Expressed as n. ) And 95.5Sn / 3.5Ag
/ 1Zn, 51Sn / 45Bi / 3Sb / 1Zn, 84
Sn / 10Bi / 5Sb / 1Zn, 88.2Sn / 10
Bi / 0.8Cu / 1Zn, 88Sn / 4Ag / 7Sb
/ 1Zn, 97Sn / 1Ag / 1Sb / 1Zn, 91.
2Sn / 2Ag / 0.8Cu / 6Zn, 89Sn / 8Z
n / 3Bi, 86Sn / 8Zn / 6Bi, 89.1Sn
/2Ag/0.9Cu/8Zn. The solder powder of the present invention may be a mixture of two or more types of solder powders having different compositions.

The solder paste of the present invention is suitably used when a substrate, for example, a printed wiring board and an electronic component are joined together to produce a joined product. In the method of using the solder paste of the present invention, and in the method of manufacturing an electronic component joint, for example, a solder paste is applied to a portion where soldering is desired by a printing method or the like, the electronic component is placed, and then heated. The electronic component can be joined to the substrate by melting and solidifying the solder particles.

As a bonding method (mounting method) between the substrate and the electronic component, there is, for example, a surface mount technology (SMT).
In this mounting method, first, a solder paste is applied to a desired portion on a substrate, for example, a wiring board by a printing method. Next, electronic components such as chip components and QFPs are placed on the solder paste, and are collectively soldered by a reflow heat source. As the reflow heat source, a hot blast stove, an infrared stove, a steam condensation soldering device, a light beam soldering device, or the like can be used.

Although the reflow process of the present invention differs depending on the solder alloy composition, 91Sn / 9Zn and 89Sn / 8Zn
Sn-Zn such as / 3Bi, 86Sn / 8Zn / 6Bi
In the case of a system, it is preferable to carry out the preheating and the reflow in a two-step process, and the conditions are as follows.
To 180 ° C, preferably 130 to 150 ° C, and a preheating time of 60 to 120 seconds, preferably 60 to 90 seconds,
The reflow is performed at a temperature of 210 to 230 ° C., preferably 21 ° C.
The temperature is 0 to 220 ° C and the reflow time is 30 to 60 seconds, preferably 30 to 40 seconds. The reflow temperature in other alloy systems is +20 to +50 with respect to the melting point of the alloy used.
° C, preferably +20 to + 30 ° C with respect to the melting point of the alloy, and the other preheating temperature, preheating time, and reflow time may be in the same ranges as described above.

With the solder paste of the present invention, the above-mentioned reflow process can be carried out in nitrogen or in air. In the case of nitrogen reflow, by setting the oxygen concentration to 5 vol% or less, preferably 0.5 vol% or less, the wettability of solder to a substrate such as a wiring board is improved and the generation of solder balls is reduced as compared with the case of atmospheric reflow. Stable processing is possible.

Thereafter, the substrate is cooled to complete the surface mounting. In the method for manufacturing a bonded electronic component by this mounting method, bonding may be performed on both surfaces of a substrate (plate to be bonded) such as a printed wiring board. In addition, as an electronic component to which the solder paste of the present invention can be used, for example, LS
I, resistor, capacitor, transformer, inductance,
Examples include a filter, an oscillator and a vibrator, but are not limited thereto.

Further, according to the present invention, an adhesive film is formed in advance only on a predetermined surface of a substrate, for example, a predetermined surface of a circuit metal of a printed circuit board by a chemical reaction, a solder powder is adhered to this, and then a flux is applied. Then, the solder paste is heated to the melting temperature of the solder, reflowed, and mounted on a circuit board (JP-A-7-7244) on which solder bumps are formed using the solder paste of the present invention by SMT (surface mounting technology). Has excellent solderability.

The solder paste of the present invention can cope with fine pitch of joining of electronic parts by a solder alloy which does not contain Pb and has little environmental pollution, for example, fine pitch of a mounting wiring board and diversification of parts. A wiring board having an excellent component life can be provided.

[0056]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto.

[Test Method] Measurement of Halogen Ion Concentration 5 ml of chloroform was added to 1 g of the solder paste, and the mixture was stirred to dissolve the flux. Then, 10 ml of ultrapure water was added to extract the halogen ions into water, and the aqueous layer was subjected to ion chromatography. Measured by graphy. Apparatus was used: Yokogawa IC-100 separation column: SAM3-125 Filler: hydrophilic low exchange capacity strong ion exchange resin particle size: 10 [mu] m exchange capacity: 60μeq / ml eluent and _{flow: 4mM Na 2 CO 3 / 4mM} NaHC
O ₃ , 2 ml / min Removal solution and flow rate: 0.05 M n-dodecylbenzenesulfonic acid, 2 ml / min Temperature: 40 ° C. Sample volume: 100 μl

Viscosity measurement 10 r of the solder paste at the time of production and after 25 days at 25 ° C.
The viscosity at pm was measured using a Malcolm PCU-205 spiral viscometer.

Observation of voids (reliability of bonding) A pattern of 6 mm in diameter × 6 was printed on a 60 mm square copper plate using a 150 μm thick metal mask, and then reflowed in an air atmosphere, and then soldered with a cutter. After cutting the copper plate together, the solder portion was observed with a microscope to observe the occurrence of voids. Voids having a size of 10 μm or more were measured for six patterns, and the case where the average number per one pattern was two or more was rejected.

(Examples 1 to 9, Comparative Examples 1 to 3) <Production of flux and solder paste> 17.5% by mass of polymerized rosin, 27.5% by mass of disproportionated rosin as a resin component, and water as a thixotropic agent 7% by mass of castor oil, diphenylguanidine hydrobromide and cyclohexylamine hydrobromide as organic base hydrohalides, hexabromocyclododecane and 2,3-dibromo-2-butene-1 as halogen compounds , 4-diol, 4-stearoyloxybenzyl bromide, isobutyl salicylate and n-propyl p-toluenesulfonate as organic acid components in the amounts shown in Table 1, respectively.
2% by mass of triethanolamine as an H regulator, 0.3% by mass of hydroquinone as a reducing agent, 1% by mass of benzimidazole as a rust preventive agent, and 100% by mass of diethylene glycol mono-2-ethylhexyl ether as a solvent. Was prepared.

[0061]

[Table 1]

The amount of 89Sn / 8 was added to 11% by mass of this flux.
89 mass% of Zn / 3Bi Pb-free solder powder was added and kneaded with a planetary mill to produce a 3 kg solder paste.

<Manufacture of Electronic Component Joint> SMT was used as a mounting method. Each of the solder pastes having the compositions of Examples 1 to 9 and Comparative Examples 1 to 3 was printed on one circuit board, and LS
After placing I, the chip resistor, and the chip capacitor on the solder paste, they were soldered by heating with a reflow heat source. A hot blast stove was used as the reflow heat source.

The reflow conditions are as follows:
° C, preheating time was 80 seconds, and reflow was performed at a peak temperature of 220 ° C and a reflow time of 200 ° C or more for 50 seconds.

The characteristics of the produced printed wiring board and the used solder paste were compared by the measurement method described above. Table 2 shows the measurement results. In addition, the halogen ion concentration in Table 2 shows a chlorine conversion value.

[0066]

[Table 2]

Further, similarly, 91Sn / 9Zn, 86Sn
A similar experiment was performed using a / 8Zn / 6Bi Pb-free solder powder, but exactly the same results were obtained.

Further, when the solder alloy structure after reflow in Examples 1 to 9 was compared with the solder alloy structure of the conventional Sn—Pb solder paste, it was found that in the case of Sn—Pb, the crystal coarseness in a high temperature environment was large. , While S of the present invention
In the case of the n-Zn-based alloy, the tendency of coarsening is small, whereby the mechanical properties of the solder were improved, and the improvement of the life characteristics of the mounting wiring board using the same was confirmed.

[0069]

According to the solder paste of the present invention, the reaction between the solder alloy and the flux is greatly suppressed, and extremely excellent storage stability is obtained. In particular, the present invention significantly improved the storage stability of Sn-Zn-based solder paste, which was considered to have poor storage stability, and its effectiveness was confirmed.

Further, by developing the solder paste of the present invention, it is possible to provide a highly reliable circuit board soldering method and a soldered joint corresponding to the fine pitch of the mounting wiring board and diversification of components. It became.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takashi Shoji 1-1-1 Onodai, Midori-ku, Chiba-shi, Chiba F-term in the Research Institute, Showa Denko KK (reference) 5E319 BB05 CC33

Claims (5)

[Claims] 1. A solder paste containing a halogen compound, wherein the concentration of halogen ions per gram of flux is not more than 3000 ppm in terms of chlorine. 2. The solder paste according to claim 1, wherein the halogen ions are bromine ions. 3. The method according to claim 1, wherein the solder paste is Zn powder.
The solder paste according to claim 1, further comprising: 4. A solder for a circuit board, comprising: a step of applying the solder paste according to claim 1 on a circuit board; and a step of reflowing the solder paste. Attachment method. 5. A joined article manufactured by the circuit board soldering method according to claim 4.