JP2001170796A - Resin flux cored solder and soldering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide resin flux cored solder which is capable of sufficiently preventing migration and well preventing flux splashing and allows the effective utilization of flux residues as insulating films in soldering by the resin flux cored solder. SOLUTION: The flux containing 1 to 50 wt.%. more preferably 5 to 30 wt.% ethylene-vinyl acetate copolymer having a melt flow rate of >=500 g/10 min or/and 1 to 50 wt.%. more preferably 5 to 30 wt.% ethylene-vinyl acetate copolymer having a melt flow rate of >=500 g/10 min or/and 5 to 40 wt.% fatty acid amide or/and fatty acid bisamide and rosin or/and denatured rosin and activator is built into the solder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cored solder and a soldering method using the cored solder.

[0002]

2. Description of the Related Art Flux is indispensable for soldering. For soldering of electronic and electric equipment, particularly for consumer electronic equipment and precision electronic equipment, a linear solder having a built-in flux, that is, a flux. Solder is frequently used. The effect of this flux is to remove the oxide film on the surface of the base material to clean it, to form an air barrier film on the surface of the base material and solder to prevent oxidation, and to reduce the interfacial tension of the solder and get wet. To improve the performance.

[0003] Conventional flux in flux cored solder has a weak active power only with rosin as a main component, and it is difficult to sufficiently achieve the above-mentioned effects. Therefore, hydrohalides of organic amines, organic acids, Activators such as salts of acids and organic amines are added.

However, under the addition of an activator, conductor erosion is likely to occur due to a reaction of forming a complex between the flux residue after soldering and the base material. Therefore, a corrosion-resistant flux capable of preventing the corrosion of the base material (conductor) due to the flux residue has been proposed (Japanese Unexamined Patent Publication No. Hei 3-238195, Japanese Patent Publication No. 4-335).
No. 57, etc.), and a low solid differentiation flux for avoiding poor probe pin contact of an in-circuit tester has been proposed.

[0005]

However, the present inventor has set forth the following problems associated with the flux residue.
It was found that the migration caused by cracking of the flux residue due to the heat cycle during use of the circuit board was important.

That is, heat stress cracks occur in the flux residue due to the heat cycle during use of the circuit board,
In the cracks, an electrolyte solution is generated due to moisture absorbed and ions eluted from the flux residue (eg, halogen ions), and a weak current flows through the electrolyte solution under the application of a voltage to a circuit board. Is eluted by the electrolysis reaction, and the eluted conductor material ions are discharged and precipitated in the cathode-side conductor, and the conductor material atoms grow in a dendritic shape toward the anode side, eventually causing a short circuit between both conductors. There is

However, it is difficult to effectively prevent such migration with the above corrosion-resistant flux. The inventor of the present invention has intensively studied means for preventing the generation of cracks in the heat cycle of the flux residue, and as a result, the melt flow rate was 500 g.
It has been found that it is effective to include an ethylene / vinyl acetate copolymer of / 10 min or more in the flux.

Hitherto, it has been known to use an ethylene / vinyl acetate copolymer having a low melt flow rate and a high molecular weight as one component of a flux. For example, Japanese Patent Application Laid-Open
JP-A-54298 and JP-A-56-6798 disclose a flux in which a flux layer is coated on a solder surface in order to prevent the explosion of the flux of a flux cored solder (linear solder with built-in flux) due to thermal expansion. Addition of an ethylene / vinyl acetate copolymer to a flux in a coated linear solder ”.

However, in this case, it is necessary to impart a certain degree of contact wear resistance to the flux-coated linear solder, and the melt flow rate is 500 g / 10 min or more, an ultra-low molecular weight low-strength ethylene / vinyl acetate. Copolymers are unsuitable because of their low mechanical strength.

However, the present inventor has found that if an ethylene / vinyl acetate copolymer having a melt flow rate of 500 g / 10 min or more is added to a normal flux, the occurrence of cracks due to the heat cycle of the flux residue will be prevented. It has been found that migration can be sufficiently prevented, migration can be eliminated, and the flux residue can be used as an effective insulating film by maintaining its insulating property stably. In addition, in the case of the conventional cored solder, flux scatter during the soldering work cannot be avoided, but the melt flow rate is 500 g / 10 min.
With the addition of the ethylene / vinyl acetate copolymer described above, it has been found that the scattering can be prevented well and the use as the insulating film can be effectively achieved.

The object of the present invention is based on this finding,
When soldering with flaky solder,
It is an object of the present invention to provide a flux cored solder and a soldering method using the flux cored solder, which can sufficiently prevent the application of flux and effectively prevent the flux from scattering and can effectively utilize the flux residue as an insulating film.

[0012]

According to the present invention, the sheath solder contains 1 to 50% by weight, preferably 5 to 30% by weight of an ethylene / vinyl acetate copolymer having a melt flow rate of 500 g / 10 min or more. Flux containing rosin and / or modified rosin and activator, or ethylene / vinyl acetate copolymer 1 having a melt flow rate of 500 g / 10 min or more
A flux containing ５０50% by weight, preferably 5-30% by weight, fatty acid amide or / and fatty acid amide 5-40% by weight, preferably 10-25% by weight, rosin or / and modified rosin and an activator; Melt flow rate 500 g
/ 10min or more ethylene-vinyl acetate copolymer 1-50
% By weight, preferably 5 to 30% by weight, with the balance being rosin and / or modified rosin and an activator as a main component, or a melt flow rate 500 g / 10 m
1 to 50% by weight, preferably 5 to 30% by weight of ethylene-vinyl acetate copolymer of at least
And fatty acid bisamide 5 to 40% by weight, preferably 1
It can be carried out in a mode in which a flux containing 0 to 25% by weight, the balance being rosin or / and modified rosin, and a composition which is an activator as a main component is incorporated.

The soldering method according to the present invention is characterized in that soldering is performed using the above-mentioned solder for soldering, and the flux residue after soldering is left as an insulating film.

The above melt flow rate is JIS K72.
Measured based on 10-1976, inner diameter φ9.50 ±
It has a through hole of 0.03 mm, and the inner diameter φ
A sample is filled in the hole of a heater cylinder equipped with a 2.095 ± 0.005 mm die, and the lower end of a piston having a weight attached to the upper end is inserted into the above hole using a test apparatus. , Weight of weight 325gf {3.185N},
The amount of extrusion X (g) for 10 minutes when the test temperature is set to 125 ° C. is measured, and is obtained from Xg / 10 minutes.

The above-mentioned fatty acid amide / fatty acid bisamide is used for suppressing the stickiness of the flux residue and for preventing the flux from being cut off (the occurrence of a flux deficient portion in the entangled solder). One or more kinds of amide / stearic acid bisamide, palmitic amide and the like can be used.

The rosin and / or modified rosin includes natural rosin, polymerized rosin, phenol-modified rosin,
Maleated rosin, hydrogenated rosin and the like can be used.

As the activator, a hydrohalide of an organic amine, an organic acid, a salt of an organic acid and an organic amine, and the like can be used. For example, diethylamine hydrochloride, cyclohexylamine hydrochloride, dioctylamine hydrochloride, propylamine hydrochloride, diethylamine hydrobromide, cyclohexylamine hydrobromide, dioctylamine hydrobromide, propylamine hydrobromide Salts, glutaric acid, adipic acid, sebacic acid, methyl maleic acid, cyclohexylamine adipate and the like can be used.

A flux containing 1 to 50% by weight, preferably 5 to 30% by weight of an ethylene / vinyl acetate copolymer having a melt flow rate of 500 g / 10 min or more and rosin or / and modified rosin and an activator, or 1 to 50% by weight, preferably 5 to 30% by weight of an ethylene / vinyl acetate copolymer having a melt flow rate of 500 g / 10min or more, 5 to 40% by weight of a fatty acid amide or / and a fatty acid bisamide and rosin or / and modified rosin If necessary, an additive may be added to the flux containing the and the activator. For example, a corrosion inhibitor (for example, phthalic acid, benzotriazole compound, gallic acid ester such as n-propyl gallate, etc.) for suppressing conductor corrosion due to flux residue, an antioxidant (for example, dibutyl cresol, etc.) and the like are used. It can be added, and the amount of addition is 1 to 3 parts by weight based on 100 parts by weight of the main component.

The solder of the cored solder according to the present invention is:
There is no particular limitation, and 63% by weight of Sn-remainder Pb
In addition, for example, Sn 60% by weight-balance Pb, Sn 50% by weight-balance Pb, Sn 45% by weight-balance Pb, Sn 40% by weight-balance Pb, Sn 62% by weight-Ag 2% by weight-balance Pb, Sn 60% by weight-Ag 4% by weight -Balance Pb, Sn
46% by weight-Bi 8% by weight-balance Pb, Sn 57% by weight
-Bi 3% by weight-Residual Pb, Ag 3.5% by weight-Cu
0.75% by weight-balance Sn, Sb 5% by weight-balance Sn and the like can also be used.

The shape of the solder according to the present invention is not particularly limited as long as it has a built-in flux, and a so-called V-cut can also be formed. Also,
The flux amount is usually 1.0% by weight to 4.0% by weight, and the standard amount is 2 to 3% by weight.

The cored solder according to the present invention is mainly used for so-called retrofitting of electronic equipment using a trowel, and a flux residue is left as an insulating film.

The melt flow rate added to the flux in the cored solder according to the present invention is 500 g / 10 m.
The ethylene-vinyl acetate copolymer of in or more has extremely low mechanical strength due to its extremely low molecular weight, but has the function of absorbing rubber stress by exhibiting rubber elasticity due to the vinyl acetate group. Despite being extremely low, the molecular chains are hardly broken by stress, and cracks can be well prevented by repeated heating. Therefore, even when exposed to a heat cycle, the occurrence of thermal stress cracks in the flux residue can be sufficiently prevented, and migration can be eliminated well.

When soldering is performed by using the core solder according to the present invention, scattering of the flux at the time of soldering can be prevented well. The reason is the flow rate 500g
It is presumed that the ethylene / vinyl acetate copolymer of / 10 min or more has a very low molecular weight and a low melting point, but exhibits rubber elasticity and viscoelasticity due to the vinyl acetate group.

The ethylene / vinyl acetate copolymer preferably has a vinyl acetate content of 20 to 40% (2
If it is 0% or less, the rubber property is insufficient and it is not suitable for preventing the occurrence of cracks, and if it is 40% or more, the tackiness increases and dust easily adheres to the flux residue.)

The flux in the cored solder according to the present invention has a melt flow rate of 500 g / 10 m2 despite the addition of the ethylene / vinyl acetate copolymer.
Since an ethylene / vinyl acetate copolymer having fluidity of in or more is used, the wettability of the solder can be promoted well, and the wettability required for soldering can be sufficiently ensured. The preferred range of the melt flow rate of the ethylene / vinyl acetate copolymer is 800 to 2000 g / 10 min or less (20
If it is more than 00 g / 10 min, dust easily adheres to the flux residue.)

The reason why the addition amount of the ethylene / vinyl acetate copolymer in the above flux is 1 to 50% by weight is that if it is less than 1%, it is difficult to satisfactorily prevent the generation of cracks in the flux residue, and if it exceeds 50% by weight. This is because dust easily adheres to the flux residue, and the moisture absorption of the attached dust excessively reduces the surface resistance of the flux residue.

The flux residue in the flux cored solder according to the present invention contains an ethylene / vinyl acetate copolymer having excellent insulation resistance as compared with rosin or the like. It can function as an insulating film and can stably hold a soldered portion without occurrence of electrolytic corrosion or the like. Therefore, the reliability of soldering can be improved by effectively using the flux residue as an insulating film.

[0028]

EXAMPLES Example 1 24% by weight of natural rosin, 23% by weight of hydrogenated rosin, 30% by weight of stearamide, 20% by weight of ethylene / vinyl acetate copolymer of melt flow rate 1000g / 10min, cyclohexyl A flux having a composition of 2% by weight of amine hydrobromide (activator) and 1% by weight of dibromopropanol (activator) was applied to a solder rod (Sn).
63% by weight-the remainder Pb) was filled, and a cored solder having a wire diameter of 1.6 mmφ and a built-in flux of 2% by weight was produced by wire drawing.

Comparative Example 1 The procedure was the same as in Example 1 except that an ethylene / vinyl acetate copolymer having a melt flow rate of 400 g / 10 min was used.

Comparative Example 2 The procedure of Example 1 was repeated except that the blending amount of natural rosin was 34% by weight, the blending amount of hydrogenated rosin was 33% by weight, and the ethylene / vinyl acetate copolymer was not blended. Same as Example 1.

According to these Examples and Comparative Examples, JIS
Z 3197-1986 Resin flux test method for soldering 6.10 The spread rate was measured based on the spread test (the number of each sample was 20).
Is 92%, Comparative Example 2 is 93%, and Comparative Example 1 is 87%. In Example 1, 500 g of the melt flow rate was added even though the ethylene / vinyl acetate copolymer was added to the flux. Since it was / 10 min or more, the same excellent wettability as in the case of using a normal flux (Comparative Example 2) could be guaranteed.

When soldering was performed on the copper lands of the circuit board with a soldering iron at 350 ° C. using the above-mentioned flared solder (both without V-cut) (the number of each sample was 20). In Example 1 and Comparative Example 1, no flux was scattered. On the other hand, in Comparative Example 2, 14 out of 20
Flux was scattered in the section.

Further, regarding these soldering samples,
When a heat cycle test was performed 1000 times (30 samples for 30 minutes at + 30 ° C. and 30 minutes for 30 minutes at + 60 ° C. (the number of each sample was 20)), the flux residue was not found in Examples 1 and Comparative Example 1. While no crack generation was observed, a large number of cracks were generated in Comparative Example 2.

In each of the above Examples 1 and Comparative Examples 1 and 2, each of which was soldered using a cored solder (the number of samples was 20), the temperature was 40 ° C. with the flux residue attached. × Relative humidity 92% × After leaving for 2,000 hours, the surface insulation resistance was measured.
And in the case of Comparative Example 1, the initial surface insulation resistance value was reduced by one digit or less, but in the case of Comparative Example 2, it was 3%.
It was a drop of more than an order of magnitude.

Each of the fluxes used in Example 1 and Comparative Examples 1 and 2 was applied between silver electrodes formed by a thick film method with an interval of 0.5 mm. When a DC voltage of 100 volts was applied for 1000 hours and observed, no migration was observed with the flux of Example 1 and Comparative Example 1, but the migration of Comparative Example 2 was observed. Was observed.

Example 2 14% by weight of natural rosin, 13% by weight of hydrogenated rosin, 30% by weight of stearamide, 40% by weight of ethylene / vinyl acetate copolymer of melt flow rate 1000g / 10min, cyclohexylamine A flux having a composition of 2% by weight of hydrobromide (activator) and 1% by weight of dibromopropanol (activator) was applied to a solder rod (S
n63% by weight-remainder Pb) was filled, and a drawn solder having a wire diameter of 1.6 mmφ and a built-in flux of 2% by weight was produced by wire drawing. When a test was conducted on this example product in the same manner as described above, the spreading rate was 90%, the number of scattered molten flux was 0, the number of cracks generated in the flux residue was 0, the temperature was 40 ° C., the relative humidity was 92%, and the sample was left for 2,000 hours. The subsequent surface insulation resistance value was within one digit, and the result was sufficiently comparable to that of Example 1.

Example 3 32% by weight of natural rosin, 30% by weight of hydrogenated rosin, 30% by weight of stearamide, 5% by weight of ethylene / vinyl acetate copolymer of 1000 g / 10 min melt flow rate, cyclohexylamine A flux composed of 2% by weight of hydrobromide (activator) and 1% by weight of dibromopropanol (activator) was applied to a solder rod (Sn).
63% by weight-the remainder Pb) was filled, and a cored solder having a wire diameter of 1.6 mmφ and a built-in flux of 2% by weight was produced by wire drawing. When a test was performed on the product of this example in the same manner as described above, the spreading rate was 95%, the number of scattered fluxes was 2 out of 20, the number of cracks generated in the flux residue was 1 out of 20, and the temperature was 40 ° C. × relative. Humidity 92% ×
The surface insulation resistance value after leaving for 2,000 hours was within one digit, and the result was sufficiently comparable to that of Example 1.

[0038]

According to the solder of the present invention, good solderability can be obtained without poor wetting due to excellent flux wettability, and flux residue after soldering is exposed to a heat cycle. However, migration can be prevented by preventing the generation of cracks in the residue, and the flux residue is excellent in insulating properties and can be performed while suppressing the scattering of the flux during soldering. Since the insulating property of the residue can be effectively used for insulating the soldering portion by being left at the soldering portion, soldering with a soft solder can be performed with excellent workability and safety.

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Claims (3)

[Claims] 1. A flux containing 1 to 50% by weight of an ethylene / vinyl acetate copolymer having a melt flow rate of 500 g / 10 min or more, rosin or / and a modified rosin, and an activator. Fatigue solder. 2. An ethylene / vinyl acetate copolymer having a melt flow rate of 500 g / 10 min or more, 1 to 50% by weight, fatty acid amide and / or fatty acid bisamide 5 to 40% by weight, rosin or / and modified rosin, activator Flux-cored solder characterized by having a built-in flux. 3. A soldering method, wherein soldering is performed using the solder for soldering according to claim 1 or 2, and a flux residue after soldering is left as an insulating film.