JP4409990B2 - A method of manufacturing a solder circuit board. - Google Patents

Description

  In the present invention, a uniform and high-definition solder powder circuit (for example, a solder thin layer formed in advance on the pad surface of a metal circuit in order to attach the electronic component to a printed circuit board) And an electronic component on which the solder powder is fixed is efficiently mounted on the electronic component.

  In recent years, printed circuit boards (printed boards or printed boards) in which electronic circuits are formed by an appropriate method on insulating parts such as electronic parts such as plastic boards (also with films), ceramic boards, metal boards coated with plastics, etc. (Also referred to as a wiring board) has been developed, and means for configuring electronic devices by soldering electronic components such as IC elements, semiconductor chips, resistors, and capacitors on the wiring surface is widely adopted.

  By the way, in the manufacture of the mounting circuit device, in order to solder the lead terminals of the electronic component to a predetermined pad, a so-called cream solder containing a flux is printed in advance on the pad surface, and the required electronic component is positioned and arranged. After that, the soldering is usually performed by reflowing the cream solder. On the other hand, the demand for forming a solder thin layer on the pad surface in advance is increasing as the mounting density is improved. This is because the cream solder cannot avoid defects such as solder bridges.

  In order to form a solder circuit (solder thin layer) in electronic parts, plating methods, solder bath dipping methods (immersion methods), etc. have been performed. Patterns are becoming increasingly finer, and these methods are becoming difficult to cope with due to demands for circuit pattern miniaturization as well as improvement in work efficiency and on-spec ratio.

  Among these conventional solder circuit forming methods, there is a plating method that can be applied to a solder circuit having a high-definition pattern. However, there are cases where the target portion to be a solder circuit portion of an electronic component exists as an independent pattern. In many cases, the application of electrolytic plating is difficult in terms of electrical conduction between patterns. On the other hand, the electroless plating solves the problem of electrical conduction in the electrolytic plating, but has a technical problem that the solder layer is thin and it is difficult to obtain a necessary thickness.

  Also, a solder powder whose surface is coated with a flux is applied to a circuit part by an electrostatic coating method (see, for example, Patent Document 1), a flux is printed and applied to the circuit part, and the solder powder is adhered thereon. After that, there are many proposals such as a method of forming a solder circuit (for example, refer to Patent Document 2) by heating and melting above the melting point of solder, blowing a gas on the solder melting surface, and performing leveling. However, there is a problem in forming a solder circuit having a high definition pattern.

  In recent years, a metal circuit exposed portion of an electronic component is treated with a composition containing a tackifier compound that develops tackiness by acting with a metal, thereby giving the metal exposed portion tackiness, and soldering the tackifier portion. A method of forming a solder circuit (see, for example, Patent Document 3) in which a powder is attached and then heated and fixed has been developed, and a high-definition solder pattern can be easily obtained. When applied to the solder powder fixing part using a flux, the flux does not completely cover the surface of the solder powder, the solder powder has poor meltability after reflow of the solder powder, and the flux residue also remains on the solder circuit, This flux residue has a problem of reducing the reliability of the solder circuit board. Particularly in the case of a microchip mounting substrate, the pitch interval is as narrow as about 300 μm, which adversely affects reliability. Although it is possible to remove the remaining flux residue by a cleaning process or the like, such a cleaning process leads to an increase in the cost of the circuit board. In the future, it is expected that the pattern of the circuit board will become increasingly finer, and it is required to remove the remaining flux as much as possible. Furthermore, in order to improve the meltability after reflow of the solder powder, a flux that stably covers the surface of the solder powder has been required.

It is well known that soldering flux plays an important role in soldering. However, after soldering, the flux residue will deteriorate the quality of the printed wiring board and shorten the product life. is necessary.
The effect of flux residue is
(1) Corrosion of parts, etc. over a long period.
(2) Causes poor electrical insulation.
(3) In-circuit test pins malfunction due to poor continuity due to flux residue. There are adverse effects such as.
For this reason, high detergency products have also been developed. However, these soldering fluxes should be used as they are because of differences in usage temperature due to differences in solder reflow temperature and usage methods. However, it was difficult in terms of solder meltability and flux cleaning ability after reflow.

Japanese Patent Laid-Open No. 3-50853 Japanese Patent Laid-Open No. 4-10694 Japanese Patent No. 3362079

  The present invention aims to solve these problems, and is applicable to the solder circuit forming method described in Patent Document 3 by providing a flux with high meltability of solder powder and high cleaning performance of the flux after reflow. It is an object of the present invention to provide a circuit board manufacturing method in which residual flux is reduced only by a simple cleaning process.

As a result of diligent efforts to solve the above problems, the present inventor has reached the present invention. That is, the present invention
[1] A metal circuit exposed portion of an electronic component is treated with a composition containing at least one tackifying compound that acts with a metal to develop tackiness to impart tackiness, and solder powder is adhered thereto. Next, after heat-fixing this, a water-soluble flux composition containing a surfactant is applied to the solder powder fixing part, then the solder powder is reflowed, and then the flux residue is washed with water. Solder circuit board manufacturing method,
[2] A metal circuit exposed portion of an electronic component is treated with a composition containing at least one tackifying compound that exhibits tackiness by acting with a metal to impart tackiness, and solder powder is adhered thereto. Next, after this is fixed by heating, other mounting parts are aligned and arranged corresponding to the solder powder fixing portion, and a water-soluble flux composition containing a surfactant is arranged in the other mounting parts. A method for producing an electronic circuit board, wherein the solder powder is reflowed by applying before or after the step, and then the flux residue is washed with water.

[3] A method for producing a solder circuit board according to the above [1] or [2], wherein glycol is added to the water-soluble flux.
[4] A water-soluble flux composition comprising a surfactant (nonionic) mixed with a composition comprising an activator, water or a water-soluble organic solvent,
[5] The mixing ratio of the water-soluble flux composition is such that water or a water-soluble organic solvent is within a range from 30 parts by mass to 100 parts by mass with respect to 10 parts by mass of the active agent, and the surfactant (nonionic) is 5 parts. 10 parts by mass of glycol is added to 100 parts by weight of the water-soluble flux composition according to [6] and [5], wherein the water-soluble flux composition is blended in a range of from 20 parts by mass to 20 parts by mass. The above-mentioned problems have been solved by developing a water-soluble flux composition characterized by blending the range of 40 parts by mass.

  The manufacturing method of the present invention can greatly improve the cleaning performance of a circuit board after reflow by using a surfactant having improved cleaning performance or a water-soluble flux composition containing glycol and a surfactant in the reflow process. As a result, the flux remaining after the cleaning is reduced, and it is possible to obtain a highly reliable solder circuit board and electronic circuit board with little corrosion over a long period of time and less insulation failure.

  Examples of the electronic components targeted by the present invention include a printed wiring board and various mounting components. Examples of the printed wiring board include a plastic substrate, a plastic film substrate, a glass cloth substrate, and a paper base epoxy resin substrate. A single-sided electronic component, a double-sided printed wiring board, a multilayer printed wiring board, or a circuit in which a circuit is formed by a suitable method on a substrate in which a metal plate is laminated on a ceramic substrate or the like, or an insulating substrate in which a metal base is coated with plastic or ceramics Applicable to flexible printed wiring boards. Examples of various mounting parts include IC elements (bare chips, various packages), resistors, capacitors, and the like.

  In most cases, copper is mainly used as a metal for forming circuits of electronic components, and is the most preferable metal material for the tackifying compound of the present invention, but other metals may be used. In other metals, the adhesiveness tends to be weaker than copper.

The tackifying compound used in the present invention is not particularly limited as long as it is a compound that acts with a metal and expresses tackiness.
A benzotriazole derivative represented by the general formula (1),

A naphthotriazole derivative represented by the general formula (2),

An imidazole derivative represented by the general formula (3),

A benzimidazole derivative represented by the general formula (4),

Mercaptobenzothiazole derivatives represented by general formula (5),

Ｎ，Ｓ，Ｏ，Ｐなどの元素を有する有機化合物が特に好ましい。 Benzothiazole thio fatty acid derivatives represented by the general formula (6),

An organic compound having an element such as N, S, O, or P is particularly preferable.

  When applying a dipping or spraying method in the form of an aqueous solution as a method for treating these tackifying compounds, in order to dissolve at least one of the tackifying compounds in water, it is acidic, preferably about pH 3-5 A composition adjusted to be slightly acidic is used. When applying the coating method, it is easy to use it by adding a thickening agent such as a carboxymethyl cellulose derivative to the composition used in the dipping or spraying method and using it in an ink form. At this time, the concentration of the solution is preferably about 0.05% by mass to 20% by mass as a whole.

  The treatment temperature is slightly higher than room temperature, and the formation rate and generation amount of the adhesive film are better, and it varies depending on the tackifying compound concentration, the type of metal, etc., but is generally 30 ° C. to 60 ° C. A range of about is suitable. Although the immersion time is not limited, it is preferable to adjust other conditions so that the working efficiency is in the range of about 5 seconds to 5 minutes.

  In this case, it is preferable to coexist 100 to 1000 ppm as copper ions in the composition for forming a solder circuit because the production efficiency such as the production rate and the production amount of the adhesive film is increased.

  The electronic parts to be processed are treated with a composition for forming a solder circuit while the other metal circuit portion is covered with a resist or resin and only the metal circuit of the solder circuit portion is exposed.

  It is immersed, sprayed or coated in a composition containing the above-described tackifier compound used here, and this is appropriately washed and dried with a solvent to impart tackiness only to the exposed metal surface. Next, solder powder is sprinkled on the electronic components to adhere to the adhesive surface, and excess solder powder is removed, followed by heat treatment.

The heat treatment temperature for fixing the solder is preferably set to 50 to 250 ° C. However, it is necessary to set a longer time when the heat fixing temperature is low and to shorten it when the heat fixing temperature is high. Therefore, it is necessary to select conditions under which the solder powder does not melt and flow out.
Thereafter, a water-soluble flux composition is applied, followed by reflow, and the remaining flux is washed with water to form a solder circuit. Further, after the solder powder is fixed, the other electronic components are arranged after alignment in accordance with the solder powder pattern, and the water-soluble flux composition is applied before or after the other electronic components are arranged. This is done by reflowing and washing the remaining flux with water, so that other electronic components can be mounted efficiently and precisely while ensuring reliability. The solder material used here is a lead-based eutectic alloy or a lead-free alloy such as silver or bismuth, such as Sn-Ag, Sn-Zn, or Sn-Bi. Can be arbitrarily selected.

  The water-soluble flux is a product obtained by adding water or a water-soluble organic solvent to the activator. Activators include amine and amino acid inorganic acid salts (eg, dimethylamine or glutamic acid hydrochloride, pyridine hydrobromide), amine and amino acid organic acid salts (eg, glutamic acid oxalate, dimethylamine) Succinate), organic acids (eg glycolic acid, lactic acid, malic acid, formic acid, acetic acid, oxalic acid, malonic acid, succinic acid), inorganic acids (eg hydrofluoric acid, hydrochloric acid, hydrogen bromide) Acid, hydroiodic acid, borohydrofluoric acid, phosphoric acid, zinc chloride, ammonium chloride, sodium chloride, stannous chloride, stannous fluorochloride, sodium fluoride) and the like. Among these, it is particularly preferable to use an inorganic acid salt of amine and amino acid or an organic acid salt of amine and amino acid. Moreover, as a water-soluble organic solvent, what added glycerol, polyethylene, a polypropylene, and phenyl ether to C1-C3 alcohol or high boiling-point alcohol ether can be used.

  As a water-soluble flux used in the production method of the present invention, water or a water-soluble organic solvent is added to 10 parts by mass of the active agent, preferably within a range of 30 parts by mass to 100 parts by mass, and more preferably 50 parts by mass to 90 parts by mass. It is preferable to contain within the range of a mass part. When the addition amount of the water-soluble organic solvent is higher than 100 parts by mass, the effect of the flux at the time of reflow is reduced, and when the addition amount is less than 30 parts by mass, the residual amount of the flux after the reflow is increased.

  In the water-soluble flux composition of the present invention, a surfactant is blended in order to ensure the uniformity of flux application and to improve the removal rate of the flux residue after reflow so that there is no application leakage in the solder powder fixing part. . A commercially available surfactant can be used as the surfactant, but nonionic surfactants are particularly preferably used. For example, polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, It is preferable to use oxyethylene sterol ether, polyoxyethylene lanolin derivative, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropylene alkyl ether.

  The addition amount of the surfactant to the water-soluble flux used in the production method of the present invention is preferably within a range of 5 to 20 parts by mass, more preferably 8 to 10 parts by mass per 10 parts by mass of the surfactant. It is in the range of 15 parts by mass. When the addition amount of the surfactant is higher than 20 parts by mass, the effect of the flux is lowered, and when the addition amount is less than 5 parts by mass, the addition effect of the surfactant is insufficient.

In the production method of the present invention, it is preferable to further add glycol to the surfactant-containing water-soluble flux composition in order to improve the cleaning property. Glycol includes ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, and the like. In the present invention, it is particularly preferable to use ethylene glycol and polyethylene glycol.
The amount of glycol added to the water-soluble flux composition used in the production method of the present invention is in the range of 10 to 40 parts by weight, preferably 15 to 35 parts by weight, per 100 parts by weight of the water-soluble flux. Within range. When the addition amount of glycol is higher than 40 parts by mass, the performance of the flux is lowered. When the addition amount is less than 10 parts by mass, the effect of addition of glycol becomes insufficient, and the meltability of the solder powder and the cleaning property of the flux are poor. Become.

  After applying the flux, the solder powder is melted using a reflow furnace, etc., the remaining flux is washed with water, and the metal exposed surface of the electronic component circuit has a high-definition and uniform thickness without flux reliability A high solder circuit can be formed. Also, other electronic components can be mounted at a high mounting density without fear of a solder bridge or the like.

Example 1
In order to connect a TAB component having a pitch of 0.25 mm, a printed wiring board in which the copper of the corresponding 0.25 mm pitch copper pad portion was exposed was adjusted to a pH of about 4 with acetic acid in 1 part by mass aqueous solution of 2-dodecylimidazole. The film was soaked at 40 ° C. for 30 seconds, washed with water and dried to selectively form an adhesive substance layer on the surface of the copper pad portion. A eutectic solder powder having an average particle size of about 50 μm was sprinkled on the printed wiring board, and the excess solder powder was blown off with air to selectively adhere to the adhesive substance portion to obtain a high-definition solder pattern.

After the electronic components were heat-fixed at 170 ° C. for 30 seconds, a small amount of unnecessary part of the solder powder was removed by brushing, and as a water-soluble flux, 10 parts by mass of dimethylamine hydrobromide and 80 parts by mass of isopropyl alcohol In order to improve the uniformity and cleaning properties of the coating, 10 parts by mass of the above was applied with a flux containing 1.5 parts by mass of polyoxyethylene alkyl ether and 3.5 parts by mass of polyethylene glycol as a surfactant. Thereafter, the solder powder was melted in a reflow furnace at 230 ° C. for 1 minute to produce a solder circuit board. The obtained solder circuit board was a circuit board having a uniform and high-definition 30 μm thick solder circuit on the surface of the copper pad portion. After the solder circuit board was washed with water, the surface of the circuit board and the inside of the through hole were observed, and no flux residue was observed. As a result of measuring the ionic residue on the circuit board with an omega meter, it was 1 μg · NaCl / inch ² , which was a level with no problem.

(Examples 2 to 4)
The above Example 4 is shown as a reference example.
As shown in Table 1, using a water-soluble flux composition containing a water-soluble flux, a surfactant, and a glycol, solder powder meltability, flux residue status (appearance inspection) under the same conditions as in Example 1 and The ion residue was measured. The results are shown in Table 1.

(Comparative Example 1)
In Example 1, a solder circuit board was produced in the same manner as above except that the surfactant was not added to the water-soluble flux composition. After the solder circuit board was washed with water, the surface of the circuit board was observed, and a flux residue was observed. As a result of measuring the ion residue with an omega meter, it was 40 μg · NaCl / inch ² .

In the present invention, a uniform and high-definition solder powder circuit (for example, a solder thin layer formed in advance on the pad surface of a metal circuit in order to attach the electronic component to a printed circuit board) ) Can be efficiently mounted on an electronic component on which the solder powder is fixed and a circuit board with reduced residual flux can be manufactured by only a simple cleaning process.
Since the circuit board or the like has a very small amount of flux remaining after cleaning, it can be applied to the manufacture of solder circuit boards and electronic circuit boards with very high reliability with little corrosion for a long period of time and little occurrence of insulation failure.

Claims (2)

The metal circuit exposed portion of the electronic component is treated with a composition containing at least one tackifying compound that acts with metal to develop tackiness to impart tackiness, and solder powder is adhered thereto, and then this is applied. After heat-fixing, 30 to 100 parts by mass of water or a water-soluble organic solvent , polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl with respect to 10 parts by mass of the activator on the solder powder fixing part Water-soluble flux containing 5 to 20 parts by mass of surfactant selected from ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropylene alkyl ether and composition, water-soluble flux sets Object relative to 100 parts by weight, coated with a water-soluble flux composition containing 10 to 40 parts by weight of glycol, then allowed to reflow the solder powder, then the flux residue of solder circuit board, characterized in that washing with water Production method. The metal circuit exposed portion of the electronic component is treated with a composition containing at least one tackifying compound that acts with metal to develop tackiness to impart tackiness, and solder powder is adhered thereto, and then this is applied. After heat-fixing, other mounting parts are aligned and arranged corresponding to the solder powder fixing part, and 30 to 100 parts by weight of water or a water-soluble organic solvent with respect to 10 parts by weight of the activator , polyoxyethylene alkyl Selected from ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropylene alkyl ether water-soluble by incorporating a 5 to 20 parts by weight surfactant And Lux composition, to water-soluble flux composition 100 parts by weight, coated with a water-soluble flux composition containing 10 to 40 parts by weight of glycol before or after placement of the other mounting parts such, the solder powder The method of manufacturing an electronic circuit board is characterized in that the flux residue is washed with water.