WO2001058639A9

WO2001058639A9 - Solder paste, soldering method using said solder paste and jointed product prepared by said soldering method

Info

Publication number: WO2001058639A9
Application number: PCT/JP2001/000877
Authority: WO
Inventors: Hitoshi Amita; Noriko Murase; Takashi Shoji
Original assignee: Showa Denko Kk; Hitoshi Amita; Noriko Murase; Takashi Shoji
Priority date: 2000-02-08
Filing date: 2001-02-08
Publication date: 2002-01-17
Also published as: WO2001058639A1; AU3224201A; CN1211183C; TW503147B; CN1358123A; JP2002086292A

Abstract

A solder paste which comprises a halogen compound as an activator in such an amount as to give a halogen ion concentration per 1 g of the flux used in the paste of 3,000 ppm or less in terms of a chlorine ion; a method for soldering using the solder paste; and a jointed product prepared by using the soldering method. The solder paste exhibits excellent storage stability.

Description

Description Solder paste, soldering method using the solder paste

And a joint manufactured by the soldering method

The present invention relates to a solder paste used for surface mounting of an electronic component, and more particularly to a solder paste having excellent storage stability, a soldering method using the solder paste, and a joined article. Background art

Solder paste is used in the electronics industry to surface mount electronic components. Solder paste is suitable for automation due to its printability and adhesiveness, and its use has been increasing in recent years.

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. In this specification, "Reflow J" refers to applying a solder paste to a predetermined position on a board, placing the electronic component to be joined on it, and then heating the board above the melting temperature of the solder paste to join the above components. Means a series of operations that perform

On the other hand, fine pitch bonding has recently been required to reduce the size of electronic products, and the use of fine pitch components, for example, a 0.3 mm pitch QFP (Quad Flat Package) type LSI, and the use of CSP (Chi ize Package) is often used. For this reason, solder paste is required to have printing performance that is compatible with fine pitch. In order to respond to the demands of the industry, the average particle size of the solder particles has been reduced.However, 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. However, there is a problem that the storage stability of the solder paste deteriorates. The biggest cause of the decrease in the storage stability of the solder base is that the solder powder reacts preferentially with the flux during storage, the oxidation of the solder powder progresses, and the activator in the flux is consumed, reducing the activity of the flux At the same time, the reaction product increases the viscosity of the solder paste. For this reason, when the solder paste is used, there is a problem that proper printing characteristics cannot be maintained and that the solder paste does not melt during reflow.

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

For example, a method of coating a solder powder with glycerin (Japanese Patent Publication No. 5-265898) and a method of coating a solder powder with a coating agent that is insoluble or hardly soluble in a solder paste solvent (Japanese Patent Publication No. (Kaihei 1-111 1397). Preferable examples of the latter coating agent include silicone oil, silicone base high molecular weight compound, fluorinated silicone oil, fluorosilicone resin and fluorinated hydrocarbon base 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 Application Laid-Open Nos. 3-184696 / 1991, No. 251-26991) has been proposed.

In the above-mentioned method of coating with a coating agent, 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. Therefore, solder balls may be generated frequently. In addition, these coatings are only performed physically, and the adhesion is considered to be very weak, and there is a strong possibility that they will be peeled off during kneading when manufacturing the solder paste, transport during use, printing, etc. . In addition, it is difficult 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 soldering flux (Japanese Patent Publication No. 59-226-32) And Japanese Patent Application No. 3-124092), and one or more antioxidants containing one or more phenol skeletons with tertiary butyl groups in the molecule. A method of adding 0% by weight (Japanese Patent Application Laid-Open No. 5-185283) and use of a specific surfactant (Japanese Patent Application Laid-Open No. 2-147194) are proposed. It has been.

Recently, lead-free Pb-free solder paste has been recommended due to environmental issues, and development is under way to address this. Above all, Sn-Zn solder paste is advantageous in terms of resources and cost, and since the reflow temperature is reduced to the same level as Sn-Pb solder, long life of mounted components It is attracting attention as a particularly promising one because it can be adapted to the diversification of parts as well. However, the Sn-ZII solder paste has poorer storage stability than ordinary Pb-based solder paste, and due to the progress of oxidation of Zn in the solder powder and the reaction between Zn and flux,粘度 Viscosity rises occasionally. In particular, Zn reacts with halogen compounds in the flux at room temperature, deteriorating the storage stability of the solder paste. In addition, the halogen compound in the flux reacts with Zn in the solder powder to generate a small amount of hydrogen gas, and this generated hydrogen gas is built into the solder fillet even after joining the parts, resulting in high reliability. It has been found to have significant consequences.

The present invention has been made in view of the above problems, and has an excellent storage stability, and particularly, a solder paste having an excellent storage stability even when the solder particle size is reduced by fine pitching, and further using this solder paste. An object of the present invention is to provide a reliable soldering method and a joint. Disclosure of the invention

The present invention relates to a solder paste containing a halogen compound, wherein the concentration of halogen ions per gram of flux is 300 ppm or less in terms of chlorine. The halogen ions include bromine ions. In addition, the above-mentioned solder paste contains Zn as solder powder. including.

Further, the present invention provides a method of soldering a circuit board including a step of applying the solder paste on a circuit board, a step of reflowing the solder paste, and a joined product manufactured by the method of soldering a circuit board. Including.

As described above, long-term storage stability can be maintained by setting the halogen ion concentration per gram of the flux of the solder paste to 300 ppm or less in terms of chlorine. BEST MODE FOR CARRYING OUT THE INVENTION

The flux contained in the solder paste is a mixture of a rosin or synthetic resin-based resin component, a halogen compound and / or an organic acid component as an activator, a solvent, a thixotropic agent, and the like. Among these components, the effective components for removing the surface oxide of the solder metal at the time of reflow and obtaining a good bond are a halogen compound used as an activator and a halogen or organic acid component. These activators can enhance the ability to remove surface oxides, but they react with the solder powder during soldering and during storage to deteriorate the solder paste. In particular, a halogen compound has a high effect as an activator, but has a strong effect of deteriorating solder paste.

The present inventors studied the reaction between the solder powder and the activator in the solder paste and found that the halogen ion concentration per gram of the solder paste flux was 300 ppm or less, preferably 100 ppm, in terms of chlorine. ppm or less, more preferably 50 O ppm or less, most preferably 30 O ppm or less, suppresses the reaction between the solder powder and the activator, prevents the solder paste from deteriorating, and increases the storage stability. Found that it is possible.

However, the activator is attached in order to remove the metal surface oxide and obtain a good bond. To obtain the above-mentioned effect, the halogen compound should be at least 1 in terms of the chlorine concentration of the halogen ion concentration. It is necessary to add 0 ppm or more, preferably 100 ppm or more. It is not clear why halogen ions have an adverse effect on the storage stability of the solder paste, but in the presence of halogen ions, the oxidizing power of the halogen compound added to the flux is enhanced, and the reaction with the solder metal is accelerated. It is thought that it will be done.

The chlorine equivalent value of the halogen ion concentration is determined by measuring the solder ion paste, measuring the concentration of the halogen ions contained in the aqueous layer when extracted with an organic solvent / aqueous system using ion chromatography, and converting it to chlorine, and then converting the chlorine to 1 g of flux. Calculated from the value converted to per hit. The chlorine conversion value is the value when the contained halogen ion is converted to chloride ion. For example, when a bromine compound is used as the activator, the amount of the bromine ion in the solder paste (g / g) , 35.4 5 3/7 9.904 (atomic weight of chlorine Z atomic weight of bromine). When an iodine compound is used as the activator, the quantitative value (g / g) of the ion is calculated as 35.545 3 / 126.945 (the atomic weight of chlorine and the atomic weight of iodine). ). Here, the organic solvent used for the extraction may be any solvent which does not react with the flux, is not soluble in conventionally known water used in organic synthesis, etc., and does not contain halogen ions. Examples include methylene, toluene, xylene, benzene, getyl ether, petroleum ether and the like. From the solubility of the flux, the ease of the extraction operation, etc., chloroform-form, toluene, xylene, getyl ether, and petroleum ether are preferably used. The water used for the extraction need not contain halogen ions, and for example, ultrapure water is most preferably used. Note that the measurement of the halogen ion concentration by organic solvent-water extraction can be performed on a solder paste using either a water-soluble flux or a non-water-soluble flux.

In the present invention, the solder paste is adjusted so that the halogen ion concentration in the flux of the solder paste is 300 ppm or less in terms of chlorine. For example, halogens such as isopropylamine hydrobromide, butylamine hydrochloride, and cyclohexylamine hydrobromide, which are preferably used as an activator, are organic base hydrohalides. Ammonium hydride, 1,3-diphenyl In the case of anidine hydrobromide or the like, all of the halogen contained in these compounds is a halogen ion. Therefore, the amount of addition should be calculated and added so that the chlorine-equivalent value of the halogen ion is 300 Oppm or less when no other halogen compound is used in combination.

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 is stable and exists at the reflow temperature and decomposes to exhibit an activity at a reflow temperature such that the chlorine equivalent of the halogen ion is 3000 ppm or less.

Examples of the organic bromine compound having the above-mentioned characteristics include 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 a polybromine compound containing at least two 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-stearoyloxybenzylbutamide, 4-stearyloxybenzyl bromide, 4-stearylbenzylbenzyl bromide, Examples include compounds such as —bromomethylbenzyl stearate, 4-stearoylaminobenzyl bromide, and 2,4-bisbromomethylbenzyl stearate. Other than these, 41 palmitoyloxybenzyl bromide, 41 myristyloxybenzyl bromide, 41 lauroyloxybenzyl bromide, 4-pentadecanyloxybenzyl bromide, etc. No.

The polybromine compound may have, for example, a carboxyl group, an ester group, an alcohol group, an ether group, a ketone group, or the like, and is a compound in which four or more bromine atoms are bonded.

Specific examples of these compounds include 9,10,12,13,15,16-hexabutamostate and 9,10,12,13,15,16-hexabutate methyl stearate. Esters, same ethyl esters, 9, 10, 12, 13—Tet Labromostearic acid, the same nutyl ester, the same ethyl ester, 9,10,12,13,15,16-hexabutamostearyl alcohol, 9,10,12,13-tetrabromostearyl alcohol, 1,2,5 6, 9, 10-hexa-substituted mocyclo dodecane. Particularly preferred are mosabetic mostearic acid and hexabolic mocyclo dodecane.

In addition to the above, examples of organic bromine compounds further include 1-bromo-2-butanol, 1-bromo-12-propanol, 3-bromo-11-propanol, and 3-bromo-1,2-propanediol. 2,4-butanediol 1,1,4-dibutene 2-, butanediol 1,3-dibutene 2-propanol, 2,3-dibromo-1,1-propanol, 1,4-dibutene-1,2-butanediol 1,2-Dibutene 1,2-diol, 1,3-Bromo-3-methyl-1-butene, 1,4-Dibromobutene, 1-Bromo-1-proven, 2,3-Dibromopropene, Bromo Ethyl acetate, ethyl bromocaprylate, ethyl bromopropionate, / 5-ethyl bromopropionate, ethyl bromo-ethyl acetate, 2,3-dibromosuccinic acid, 2-bromosuccinic acid, 2,2-bromoazivic acid, 2, 4 pages Bromoacetates such as bromoacetophenone, 1,1-dibromotetrachloroethane, 1,2-dibutene molybdenum, and 1,2-dibutene mostyrene are listed, but are not limited thereto. is not. An organic halogen compound containing chlorine or iodine may be used instead of bromine.

The addition amount of these halogen compounds is set so that the halogen ions in the solder paste fall below 3000 ppm 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 hydrochloride may be used in combination.

Examples of the organic acid component in the present invention include succinic acid, fumaric acid, stearic acid, sebacic acid, and the like, which are well-known in the art. An organic acid derivative that is a compound that generates an organic acid when the temperature reaches one temperature of the riff port Is preferably used. Examples thereof include various aliphatic carboxylic esters, aromatic carboxylic esters, aliphatic sulfonic esters, and aromatic sulfonic esters. Alcohol residues of these esters are preferably alkyl, aryl, particularly t-butyl, isopropyl, and isobutyl, which have high ester decomposability, and these compounds may contain a halogen atom.

Specific examples include 1-n-propyl paratoluenesulfonate, isopropyl p-toluenesulfonate, isobutyl p-toluenesulfonate, 1-n-butyl paratoluenesulfonate, 1-n-propyl benzenesulfonate, and isopropyl benzenesulfonate. Bil, isobutyl benzenesulfonate, mono-n-butyl salicylate, isopropyl salicylate, isobutyl salicylate, n-butyl salicylate, isoprovir 4-dinitrobenzoate, t-butyl 4-dibenzoate, methyl methacrylate Mono-t-butyl, mono-t-butyl acrylate, mono-t-butyl malonate, mono-t-butyl bromoacetate and the like. Of these, n-propyl paratoluenesulfonate, isobutyl salicylate, and t-butyl bromoacetate are particularly preferred. The addition amount is in the range of 0.01 to 20% by mass, and preferably 0.05 to 5% by mass, based on the total amount of the flux.

Since the above 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 a temperature of the riff to promote the generation of an acid. Among them, especially, a hydrohalide of an organic base is preferable. It is valid.

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. Polyester, polyurethane, acrylic resin and others are 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 solvent, butyl solvent, butyl carbitol , Diethylene glycol hexyl ether, propylene glycol monophenyl ether, dioctyl phthalate, xylene, etc. Used.

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. You.

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

The above-mentioned reducing agent is usually used as an antioxidant for resins and the like, and can be dissolved in a solvent, such as a phenolic compound, a phosphorus compound, a sulfur compound, a tocophere and its derivatives, L-ascorbic acid and its derivatives. Derivatives and the like. Specifically, phenolic compounds include hydroquinone, catechol, 2,6-di-t-butyl-p-cre-v-yl, butylhydroxyanisole, 2,2,1-methylenebis (4-methyl-6-t Monobutylphenol) and the like.

Examples of the phosphorus compound include triphenylphosphite, trioctadecylphosphite, tridecylphosphite and the like.

Examples of the sulfur compound include dilauryl-3,3'-thiodipropionate, distearyl-1,3,3,1-thiodipropionate, and dimyristyl-3,3,3-thiodipropionate.

As tocopherol and its derivatives, and L-ascorbic acid and its derivatives, any compound having a reducing property and soluble in a solvent, for example, 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 mixing ratio is preferably 0.5: 1 to 1: 0.5 by weight, particularly preferably about 1: 1.

Specific examples of L-ascorbic acid derivatives include ascorbic acid-2-phosphate, ascorbic acid-12-sulfate, ascorbic acid-12-glucoside, ascorbic acid-12,6-dibutylate, and ascorbic acid-12,6- Distearate, ascorbic acid- 1,2,6-dimyristate, ascorbic acid-6-palmitate, ascorbic acid-6-stearate, ascorbic acid-16-myristylate, Ascorbic acid 1,2,3,5,6-tetrapalmitate, Ascorbic acid 1,2,3,5,6-tetramyristylate, Ascorbic acid 1,2,3,5,6—Tetrastearate, Ascorbic acid 1-2— Glucosido 6-palmitate, monoascorbic acid 2-glucoside 6-myristylate, mono-ascorbic acid 2-glucosido 6-stearate, mono-ascorbic acid 5,6, -benzylidene, mono-ascorbic acid 5, 6, -prolydene Examples of tocopherol derivatives include tocophoric acid, tocopherol acetate, and ascorbic acid 1-2-phosphate-1,5,6-benzylidene and ascorbic acid-12-phosphate-1,5,6-propylidene. Acid tocopherol, sorbic acid tocopherol, nicotinic acid tocopherol and the like.

These reducing agents may be used alone or in combination. The amount of the reducing agent added may be any amount that is sufficient to ensure the storage stability of the solder paste, but is generally in the range of 0.05% by mass to 20% by mass with respect to the total amount of the flux. Yes, more preferably 0.01% by mass or more and 10% by mass or less. 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 includes, for example, 20 to 60% by mass of a resin component, 0.04 to 20% by mass of a thixotropic agent, and 0.01% to the total amount of the flux. To 20% by mass of an organic acid component, a halogen compound satisfying the above-mentioned range of halogen ions, 0.05 to 20% by mass of a reducing agent, and a solvent or the like as a balance. This flux is kneaded with, for example, 14 to 8% by mass and solder powder of 86 to 92% by mass based on the total amount of the solder paste to obtain a solder paste of the present invention. In this case, the amount of the halide added must be such that the halogen ion concentration in the flux after the solder paste kneading is not more than 300 ppm in terms of chlorine.

Adjust the moisture such as flux and the humidity of the atmosphere in the blending and kneading of the mixture to control the moisture content in the solder paste to 0.5% by mass or less, more preferably 0.3% by mass or less. Is preferred. More than 0.5% by weight of water in the paste If mixed in, the 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, more preferably 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 an amine compound such as an alkanolamine, an aliphatic primary to tertiary amine, an aliphatic unsaturated amine, an aliphatic amine, or an aromatic amine as the pH adjuster.

Specific examples of these amine compounds include ethanolamine, butylamine, aminopropanol, polyoxyethyleneoleylamine, polyoxyethylenelaurelamine, polyoxyethylenestearylamine, getylamine, triethylamine, and methylamine. Toxiprovilamine, Dimethylaminopropylamine, Dibutylaminopropylamine, Ethylhexylamine, Ethoxypropylamine, Ethylhexyloxypropylamine, Bispropylamine, Isopropylamine, Disopropyl Examples include amines.

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 content is less than 0.05% by mass, the effect as a pH adjuster is not sufficient. If the content is more than 20% by mass, the pH generally exceeds 9, shifting to the alkaline side, and the solder paste tends to absorb moisture.

Further, azoles such as benzotriazole, benzimidazole, and tritriazole may be added to the flux to prevent copper in the circuit. The addition amount of the protective agent is preferably 0.05 to 20% by mass based on the total amount of the flux. The solder powder used in 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, Sn_Ag-Zn, Sn-Bi-Sb-Zn, Sn-Bi-Cu-Zn, Sn-Ag-Sb-Zn, Sn- Ag—Cu—Zn system and SnZnBi system.

As a specific example of the above, 95.5 Sn / 3.5 Ag / 1 centered on a eutectic solder having 91% by mass of Sn and 9% by mass of Zn (hereinafter referred to as 91 Sn / 9 Zn). Zn, 51Sn / 45Bi / 3Sb / 1Zn, 84Sn / 10Bi / 5Sb / 1 Zn, 88.2 S n / 10 B i / 0.8 Cu / 1 Z n 88 S n / 4 Ag / 7 S b / 1 Z n, 97 Sn / 1 Ag / 1 Sb / 1 Zn, 91. 2 S n / 2 A g / 0.8 CuZ6 Zn, 89 S n / 8 Z n 3 B i, 86 Sn / 8Zn / 6B i, 89.1 S n / 2 Ag / 0.9 Cu / 8 Z n and the like. The solder powder of the present invention may be a mixture of two or more types of solder powders having different compositions.

By adjusting the content of halogen ions to 3000 ppm or less in terms of chlorine per gram of flux as described above, the prepared solder paste can maintain the wettability of the solder on the substrate even after storage for 10 days. Is maintained well, and a reliable joint can be obtained.

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 joint. In the method of using a solder paste and the method of manufacturing an electronic component joint according to the present invention, for example, a solder paste is applied to a portion where soldering is desired by a printing method or the like, and the electronic component is placed. Thereafter, the electronic component can be joined to the substrate by heating and melting and solidifying the solder particles.

As a bonding method (mounting method) between the substrate and the electronic component, there is, for example, surface mounting 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 soldered collectively by a reflow heat source. As the reflow heat source, a hot blast stove, an infrared stove, a steam condensing 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, Sn—Zn such as 91Sn / 9Zn, 89Sn / 8Zn / 3Bi, 86Sn / 8Zn / 6Bi, etc. In the case of a system, it is preferably carried out in a two-step process of preheating and reflow, and the conditions for the preheating are 130 to 180 ° C, preferably 130 to: I50. C, the bure heat time is 60 to 120 seconds, preferably 60 to 90 seconds, and the reflow temperature is 210 to 230 °, preferably 210 to 220. C, one hour of riff mouth 660 seconds, preferably 30 to 40 seconds. The reflow temperature in other alloy systems is +20 to 150 ° C with respect to the melting point of the alloy used, preferably +20 to 130 ° C with respect to the melting point of the alloy. The temperature, preheat time and reflow time may be in the same ranges as above.

With the solder paste of the present invention, the above reflow process can be carried out both in nitrogen and in air. In the case of nitrogen reflow, by setting the oxygen concentration to 5 vo 1% or less, preferably 0.5 vo 1% or less, the wettability of solder to a substrate such as a wiring board is improved as compared to the case of atmospheric reflow, and the solder ball Generation is reduced and stable processing is possible.

After that, the board is cooled and the surface mounting is completed. In the method of 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. The electronic components on which the solder paste of the present invention can be used include, for example, LSIs, resistors, capacitors, transformers, inductors, filters, oscillators and vibrators. It is not limited.

Further, the present invention provides a method of forming an adhesive film 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, as disclosed in Japanese Patent Publication No. 7-7244, After applying solder powder to this, apply flux, heat it to the melting temperature of the solder, reflow, and mount the circuit board on which the solder bumps are formed using SMT (Surface Mount Technology) using the solder paste of the present invention. In this case, more excellent solderability can be obtained.

INDUSTRIAL APPLICABILITY The present invention can be applied to a solder paste for fine pitch joining of microelectronic components made of a Pb-free solder alloy with low environmental pollution, and a reliable joint can be obtained even if a solder paste prepared in advance is used. As a result, for example, it is possible to cope with fine pitch bonding of a mounting wiring board, and as a result, it is possible to provide a wiring board having an excellent component life.

Hereinafter, the content of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Example

[Test method]

①Halogen ion concentration measurement

To 1 g of the solder paste was added 5 ml of black-mouthed form, and the mixture was stirred. After dissolving the flux, 10 ml of ultrapure water was added to extract halogen ions into water, and the aqueous layer was measured by ion chromatography.

Equipment used: YOKOGAWA I C— 100

Separation column: SAM 3—125

Filler: hydrophilic low exchange capacity strong ion exchange resin

Particle size: 10 m

Exchange capacity: 60 / eq / ml

Eluent and flow rate: 4mM Na 2 CO 3 / 4mM NaHC03, 2mlZ min. Eluent and flow rate: 0.05M n-dodecylbenzenesulfonic acid, 2mlZ min. Temperature: 40 ° C

Sample volume: 100 1

②Viscosity measurement

The viscosity of the solder paste at 10 rpm was measured using a Malco PCU-205 spiral viscometer.

3) Observation of void (reliability of joint)

After printing a pattern of 6 mm diameter x 6 pieces on a 60 mm square copper plate using a 150 micron thick metal mask, reflow under the air atmosphere, then cut the copper plate together with the solder with a cutter, and then microscope the solder part To observe the occurrence of voids. The size of a board with a size of 1 O ^ m or more was measured for 6 patterns, and the case where the average number per pattern was 2 or more was rejected.

(Examples 1-9, Comparative Examples 1-3)

Polymerized rosin 17.5% by mass, disproportionated rosin 27.5% by mass as resin component, 7% by mass of hydrogenated castor oil as a thixotropic agent, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide as an organic base, and hydrocyanic acid hydrochloride; Table 1 shows dodecane, 2,3-dibromo-12-butene-1,4-diol, 4-stearoyloxybenzylbutamate, isoptyl salicylate, and p-toluenesulfonic acid-n-propyl as organic acid components. 2% by mass of triethanolamine as a pH adjuster, 0.3% by mass of hydroquinone as a reducing agent, 1% by mass of benzimidazole as a protective agent, and diethylene glycol monoethyl 2-ethyl as a solvent A flux was prepared by adding xyl ether to 100% by mass.

table 1

89% by mass of Pb-free solder powder of 89 SnZ8 Zn / 3Bi was added to 11% by mass of this flux, and the mixture was kneaded with a Blaner mill to produce a 3 kg solder paste.

As a comparative example, a solder paste was produced in the same manner as in the example by adding the addition amount as shown in Table 1 so that the halogen ion concentration of the hydrohalide and the halogen compound exceeded 3000 ppm. <Manufacture of electronic component joints>

SMT was used as the mounting method. Each of the pastes having the compositions of Examples 1 to 9 and Comparative Examples 1 to 3 was printed on one circuit board, and the LSI, chip resistor, and chip capacitor were mounted on the solder paste and then reflowed. It was heated by a heat source and soldered. A hot blast stove was used as a heat source for the riff opening.

One condition of the riff opening is as follows: preheating temperature is 130 ° C, preheating time is 80 seconds, and reflow is beak temperature of 220 ° C and 200 ° C. The reflow time of C or longer was set to 50 seconds. The solder paste used in both the examples and comparative examples was the one immediately after production and the one stored for 7 days after production.

The characteristics of the produced printed wiring board and the used solder paste were measured by the measurement method described above. Table 2 shows the measurement results. The halogen ion concentration in Table 2 indicates the chlorine equivalent value. Indicates that the bonding is good, and the X mark indicates that the bonding is two or more, indicating that the bonding is poor. Table 2

As is clear from Table 2 above, when the solder paste according to the present invention was stored for 7 days, both the halogen ion concentration and the viscosity increased slightly as compared to the solder paste immediately after the production, but in all cases, the bonding state was good. Was. In addition, similar experiments were performed using Pb-free solder powders of 91SnZ9Zn and 86Sn / 8Zn / 6Bi, and the same results were obtained. .

In addition, when the solder alloy structure after reflow in Examples 1 to 9 was compared with the conventional Sn—Pb based solder alloy structure, in the case of the Sn—Pb based In contrast to the remarkable coarsening of the crystal, the Sn—Zn-based solder alloy of the present invention has a small tendency to coarsen, thereby improving the mechanical properties of the solder and mounting wiring using the solder alloy. Improvement of the life characteristics of the plate was confirmed. Industrial applicability

With the solder paste of the present invention, the reaction between the solder alloy and the flux was significantly suppressed, and extremely excellent storage stability was obtained. In particular, the present invention has significantly improved the storage stability of Sn—Zn-based solder paste, which has been conventionally regarded as having poor storage stability, and its effectiveness was confirmed.

In addition, the application of the solder paste of the present invention makes it possible to provide a highly reliable circuit board soldering method and a soldered joint corresponding to a fine pitch of a mounting wiring board and diversification of components. became.

Claims

The scope of the claims

1. A solder paste containing a halogen compound, wherein the concentration of halogen ions per gram of flux is not more than 300 ppm in terms of chlorine.

2. The solder paste according to claim 1, wherein said halogen ions are bromine ions.

3. The solder paste according to claim 1 or 2, wherein the solder paste contains Zn as solder powder.

4. A circuit board comprising: a step of applying the solder paste according to any one of claims 1 to 3 onto a circuit board; and a step of reflowing the solder paste. Soldering method.

5. A joined body manufactured by the method for soldering a circuit board according to claim 4.