JP2001179487A - Flux for soldering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensively and easily producible noncleaning type flux for soldering. SOLUTION: This flux is composed of one kind of thermosetting resin and one kind of curing agent. By preparing such a composition, the noncleaning type flux for soldering free from the need of removing flux residue by cleaning can inexpensively and easily be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering flux used in a process of manufacturing an electronic component.

[0002]

2. Description of the Related Art Conventionally, when a lead wire or the like is soldered to an electrode of an electronic component, a flux is generally used in order to avoid the occurrence of poor connection at the soldered portion or insufficient bonding strength. In addition, soldering has been performed by reducing the surface tension between the solder and the base material and dissolving and removing the metal oxide on the surface of the soldered portion.

[0003] Fluxes conventionally used generally have the following composition.

[0004]

[Table 1] In the composition as described above, as the activator, an amine hydrohalide such as an organic amine hydrochloride,
As a solvent, an alcoholic solvent having a boiling point of 280 ° C. or lower such as isopropyl alcohol is generally used.

[0005] However, if the heat-softening rosin of the above-mentioned components remains in the soldered portion, there is a problem that poor contact of the checker pins for inspection and poor painting are caused. Further, if the activator remains, there is a problem in that corrosion of the electrode and a decrease in insulation resistance are caused.

Therefore, conventionally, flux residues were removed by cleaning the soldered portion using a chlorofluorocarbon-based cleaning agent or a chlorine-based solvent such as trichloroethane. However, in recent years, destruction of the ozone layer and groundwater have been attempted. At present, the use of these cleaning agents and solvents is gradually being banned in consideration of environmental problems such as pollution.

Therefore, various detergents such as an aqueous detergent containing a surfactant, a hydrocarbon detergent and an alcohol detergent such as ethanol have been developed as substitutes for these detergents. However, the cleaning agent cannot eliminate the possibility of environmental pollution, and requires equipment costs and running costs for waste liquid and wastewater treatment, which causes a problem of increasing product prices.

In order to address these problems, there has been an increasing industrial demand for the development of a flux that does not require cleaning and has a low flux residue such as rosin (hereinafter referred to as a non-cleaning type flux). In fact, some non-cleaning type fluxes have been proposed.

For example, JP-A-8-90283 describes a non-cleaning type flux having the following compositions (a) and (b).

[0010]

[Table 2] The composition (a) has an effect of reducing the amount of flux residue, but has a problem in that the soldering strength is insufficient and the reliability is low. Pointed out that although the soldering strength is secured, the adhesion between the thermoplastic resin used and the exterior resin of the electronic component is poor, and there is a problem that the reliability of the product is reduced, and the composition It is stated that the above-mentioned problems of the compositions (a) and (b) can be solved by using only the thermosetting resin as the resin component therein.

As such a flux, a flux having the following composition (c) has been proposed.

[0012]

[Table 3] In addition to the above, some fluxes containing a thermosetting resin as a composition component have been proposed, for example, JP-A-6-269.
No. 980 discloses that, for 50 to 80 parts by weight of solder,
A conductive paste for bonding having a composition (hereinafter, referred to as (d) composition) obtained by adding a total of 20 to 50 parts by weight of a thermosetting resin containing an organic acid that cures at a temperature equal to or higher than the melting point of solder and a curing agent. Is described.

Japanese Patent Application Laid-Open No. Hei 7-169646 discloses a method of manufacturing an electronic component which does not require cleaning and removing a flux by using a flux having a composition in which a resin content is a thermosetting resin. A method for manufacturing a part is described.

The composition of such a flux is
It is described that the composition is in the range of the following (e).

[0015]

[Table 4] Japanese Patent Application Laid-Open No. 10-85884 discloses a solid or paste-like soldering flux containing a resin and an activator, and adding or not adding an activator and a solvent thereto. A composition characterized by containing a thermosetting resin in part or all (hereinafter, referred to as
(Often referred to as (f) composition).

[0016]

However, at present, it is difficult to say that the conventional flux can sufficiently respond to industrial requirements.

The flux having the compositions (a) and (b) has the problems as described in the above-mentioned Japanese Patent Application Laid-Open No. 8-90283.

In order to solve these problems, the flux having the composition (c) can reduce the amount of the flux residue and secure the soldering strength, but requires an activator and a solvent in addition to the resin component. Due to the use, it is troublesome and costly to uniformly mix the composition.

The bonding conductive paste having the composition (d) described in JP-A-6-269980 is
Rather than flux for soldering, it is a flux cored solder that secures a reliable electrical connection by precipitating and collecting near the base material in the paste applied to the base material with a large specific gravity of the solder. It is. Therefore, since the difference in specific gravity between the solder and the resin component is large, it is considered that it takes time and effort to secure the uniformity of the composition by stirring or kneading the batch during the production and after storage of the paste.

Further, the flux having the composition (e) described in JP-A-7-169646 uses an activator and a solvent in addition to the resin component, similarly to the flux having the composition (c). Therefore, it takes time and effort to uniformly mix the composition.

The flux having the composition (f) described in Japanese Patent Application Laid-Open No. 10-85884 is based on the fact that a thermosetting resin, which is a heat-reactive phenolic resin, is thermoset at the time of soldering to form a base material. This is a flux that does not require chemical cleaning and can be easily peeled off from the base material by a mechanical (physical) method such as rubbing the residue after soldering with a brush or the like after solidifying the attached residue firmly. Therefore, if the flux residue is not removed by any method, the flux residue which is easily cracked and peeled off from the base material will be coated with the exterior resin or the paint, and there is a problem that the reliability of the product is reduced.

As described above, the conventional flux for soldering has a certain effect in terms of avoiding chemical cleaning, but sufficiently satisfies the industrial requirements in terms of manufacturing labor and cost. I couldn't say that.

The present invention has been made in view of the above circumstances, and has as its object to provide an inexpensive and easy-to-manufacture non-cleaning type soldering flux.

[0024]

According to the present invention, there is provided a soldering flux having one type of thermosetting resin and one type of curing agent.

The soldering flux of the present invention comprises 75 to 96% by weight of a thermosetting resin and 4 to 2% of a curing agent.
It is characterized by having 5% by weight.

With such a configuration, the soldering flux of the present invention becomes a non-cleaning type soldering flux which can be manufactured inexpensively and easily.

Further, the thermosetting resin is an epoxy resin.

With such a configuration, it is possible to improve the adhesiveness of the electronic component to the exterior resin and the bonding strength.

Further, the epoxy resin is a bisphenol F type. With such a configuration, insulation properties can be ensured, and bonding strength can be further improved.

Further, the curing agent is an amine-based latent curing agent.

According to such a configuration, the resin component can be cured quickly and reliably, and good bonding strength can be obtained.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The soldering flux of the present invention has one type of thermosetting resin and one type of hardener.

The flux of the present invention can keep the physical properties of the flux uniform by limiting both components in the composition to one type, respectively, without taking any special measures.
It is advantageous in terms of cost and quality control.

The thermosetting resin used in the present invention is not particularly limited. However, if the resin is of the same type as the exterior resin of the electronic part to which the flux is applied, the adhesiveness between the two can be improved, and the physical properties of the two can be further improved. Are also similar, so that impact resistance and moisture resistance are also improved. Therefore, it is preferable to use the same type of thermosetting resin in the present invention according to the exterior resin of the electronic component to be applied. For example, if the exterior resin of the electronic component is an epoxy resin, it is preferable that the thermosetting resin used in the present invention is also an epoxy resin.

However, the thermosetting resin used in the present invention is:
The resin is not limited to the same type of resin as the exterior resin, and can be appropriately selected according to desired characteristics. For example, by using a bisphenol A-type or bisphenol F-type epoxy resin, preferably a bisphenol F-type epoxy resin, it is possible to secure electric insulation and obtain strong bonding strength.

The compounding ratio of the thermosetting resin is preferably 7
It is in the range of 5 to 96% by weight. If the blending ratio of the thermosetting resin is less than 75% by weight, the solderability tends to decrease, and if it exceeds 96% by weight, poor curing may occur and the adhesiveness may decrease. Because there is.

The curing agent used in the present invention is not particularly limited, and can be appropriately selected according to the resin component used. In general, an acid anhydride type, an amine type, an amide type, a dicyandiamide type, or an imidazole type curing agent can be suitably used, but preferably an amine type curing agent, particularly preferably an amine type latent curing agent is used. Good to use.

By using an amine-based latent curing agent in the flux of the present invention, it is possible to cure the resin component quickly and reliably, and to obtain good electrical insulation and good bonding strength.

The compounding ratio of the curing agent is in the range of 4 to 25% by weight. This is because when the compounding ratio of the curing agent is less than 4% by weight, poor curing of the thermosetting resin occurs and the adhesion (bonding property) occurs.
This is because there is a risk that the solderability will decrease if the content exceeds 25% by weight.

The flux for soldering of the present invention is produced as a composition in which a thermosetting resin and a curing agent are mixed and blended according to a conventional method. Then, after applying the composition to a soldered portion of the base material, soldering is performed. Normal,
Under environmental conditions such as temperature and time when the flux is exposed during soldering, the thermosetting resin in the flux does not completely cure, and in the subsequent step of curing the exterior resin on the electronic component, the exterior resin Completely cures with.

When soldering using the soldering flux of the present invention, for example, in a reflow furnace, it is preferable to set the MAX value of the reflow furnace in the range of 250 to 280 ° C. This is 25
If the temperature is less than 0 ° C., the solderability tends to decrease.
If the temperature exceeds 80 ° C., the characteristics of the electronic component may be deteriorated. When soldering with a trowel, the temperature condition may be determined in consideration of the temperature condition in the reflow furnace described above.

Next, examples of the present invention will be described with reference to comparative examples. <Example 1> As a thermosetting resin and a curing agent, bisphenol F type epoxy resin (manufactured by Yuka Shell Co., Ltd., Model No. 80)
7) and an amine-based latent curing agent (Fuji Kasei Co., Ltd., Model No. F)
XE-1000).
The soldering flux of the present invention was prepared by blending and mixing according to a conventional method at a ratio of 2 to 25% by weight of the curing agent.

Using this flux, lead wires were soldered to the electrodes of the ceramic capacitor by reflow soldering.

First, the soldered portion of the lead wire was immersed in a solder bath at 240 ° C. to perform preliminary soldering, and then the soldered portion of the lead wire was immersed in a normal temperature flux bath to apply a flux. Next, the soldered part of the lead wire was brought into contact with the soldered part of the ceramic capacitor electrode, and heat treatment was performed in a reflow furnace to perform soldering. After soldering, without cleaning, apply epoxy resin (Somal, Model No. F375) to the entire surface except for a part of the lead wire as an exterior resin, and heat-treat at 150 ° C for 1 hour for all thermosetting The conductive resin was completely cured.

At this time, a four-stage reflow furnace (manufactured by JAPAN PALSE LABORATORIES, INC., REFLOW SOLD) was used for soldering.
Using ERING MACHINE RF-447), each stage was passed for one minute at a time, and heat treatment was performed for a total of four minutes.

Further, the soldering was carried out while changing the MAX value (temperature) in each stage variously, and the obtained soldering state was evaluated to examine the influence of the difference in the MAX value of the reflow furnace on the solderability. .

The evaluation of the solderability was carried out by measuring the adhesive strength between the soldered lead wire and the electrode of the ceramic capacitor.
8kg or more and 1kg or less are "slightly inferior" and 1
The test was carried out by classifying those exceeding kg as “good” into three stages. The results are shown in Table 5 below as Examples 1 to 6.

[0048]

[Table 5] As shown in Table 5, the flux of the present invention shows good solderability under a wide range of temperature conditions. <Examples 7 to 12> Examples 7 to 12 having the compositions shown in Table 6 below were produced using the same thermosetting resins and curing agents as in Examples 1 to 6 above, and changing the mixing ratios thereof. Then, in the same manner as in the above Examples 1 to 6, the lead wires were soldered to the electrodes of the ceramic capacitors using the fluxes of Examples 7 to 12, and the whole except for a part of the lead wires was covered with an exterior resin. . The setting of the MAX value (temperature) of the reflow furnace is the same as in Examples 1 to 6 above.

Thereafter, the solderability was evaluated in the same manner as in Examples 1 to 6, and the spread ratio (JIS Z
3197 6.10) and insulation resistance (1000 hours)
(JIS Z 3197 6.8) were measured. The results are shown in Table 6 below.

The conventional examples in Table 6 below are 20% by weight of rosin (Gum Rosin WW manufactured by Yashara Chemical Co., Ltd.), 0.5% by weight of an activator (organic acid manufactured by Junsei Chemical Co., Ltd.), and 79. Using a conventional flux having a composition of 5% by weight of a solvent (isopropyl alcohol), the MAX value (temperature) of the reflow furnace was set to 275 in all cases.
゜ C, which was subjected to soldering and coating with an exterior resin in the same manner as in Examples 1 to 6, except that the heat treatment time was 30 seconds as a whole, and the exterior resin was applied after washing with trichloroethane after soldering. It is.

[0051]

[Table 6] From Table 6 above, the mixing ratio of the thermosetting resin and the curing agent in the flux of the present invention is as follows.
It is understood that the content of the curing agent is preferably in the range of 4 to 25% by weight.

In Examples 8 to 11, it can be seen that the thermosetting resin prevents the re-oxidation of the surface of the soldered portion, which plays the role of rosin in the conventional flux, so that good solderability can be obtained. . Further, good results are obtained in each characteristic without performing flux residue cleaning after soldering.

From the above, by using the soldering flux of the present invention, it is possible to reliably manufacture an electronic component having excellent reliability.

It should be noted that the present invention is not limited to the above-described illustrative embodiment, and it is needless to say that various applications and modifications can be made within the scope of the present invention.

[0055]

Since the soldering flux of the present invention has a thermosetting resin and a curing agent, it is not necessary to clean the flux residue after soldering. In addition, since it does not contain an activator and a solvent, it can be manufactured with a simple manufacturing process and a low manufacturing cost without impairing various soldering characteristics. Furthermore, since each of these components is limited to one type, it is possible to keep the properties of the flux uniform without taking any special measures, which is further advantageous in terms of cost and quality control.

Claims (5)

[Claims] 1. A soldering flux comprising one type of thermosetting resin and one type of curing agent. 2. A soldering flux comprising 75 to 96% by weight of a thermosetting resin and 4 to 25% by weight of a curing agent. 3. The soldering flux according to claim 1, wherein the thermosetting resin is an epoxy resin. 4. The soldering flux according to claim 3, wherein the epoxy resin is a bisphenol F type. 5. The soldering flux according to claim 1, wherein the curing agent is an amine-based latent curing agent.