JPH0671478A - Cream soldering material and reflow soldering method using cream soldering material - Google Patents

Abstract

PURPOSE:To reduce the ratio of generation of the chip erection phenomenon by specifying the composition of the cream soldering material, and thereby increasing the time required for melting the cream soldering material, together with gradual application of the parts-tensioning force of the molten solder. CONSTITUTION:The cream solder has a composition consisting of by weight, 55-80% solder powder, 20-45% solid flux, <=0.1% halogen. This cream soldering material is printed on the printed board to the thickness of 0.15mm, and the 1005 chips are soldered thereon by a mounting equipment. During the soldering operation, reflow is executed in the nitrogen atmosphere of 1000ppm. This reflow soldering method allows gradual application of the parts-tensioning force of the molten solder, and reduces the rate of generation of the chip erection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cream solder material used for soldering an electronic circuit board and a reflow soldering method using the same.

[0002]

2. Description of the Related Art In recent years, surface mounting on electronic circuit boards has been progressing toward miniaturization and high-density mounting of electronic parts. Resistors and capacitors having a size of 1 mm × 0.5 mm (hereinafter referred to as 1005 chips Called) is beginning to be used. In addition, the development of non-cleaning cream solder materials and reflow soldering methods has been actively promoted in order to completely abolish the cleaning of electronic circuit boards with a specific flon.

A conventional cream solder material and a reflow soldering method using the same will be described.

The solder powder of the conventional cream solder is tin 6
3% by weight, 37% by weight of lead, and had a eutectic point at 183 ° C. Further, in order to impart appropriate viscosity and adhesive strength to the cream solder, a solid content mainly composed of natural rosin was added as a flux in an amount of about 60% by weight. Also,
As an activator for removing the solder powder and the oxide film of the copper foil on the electronic circuit board, halogen was added so as to be about 0.2% by weight of the entire cream solder. The cream solder printing and the reflow soldering after mounting the components were performed in the atmosphere, and the flux residue was washed with chlorofluorocarbon.

In response to recent CFC regulations, as an example, a low-residue cream solder material having a solid content of 35% by weight and a halogen component of 0.06% by weight has been developed. Cleaning is being realized.

[0006]

However, in the above-described conventional cream solder material and the reflow soldering method in nitrogen using the same, the re-oxidation at the time of heating is less than that in the reflow in the atmosphere, so that the solder spreads and spreads. Get faster, 100
There is a problem that chip standing is likely to occur due to a difference in solder melting time between the left and right electrodes of 5 chips or the like.

An object of the present invention is to solve the above-mentioned problems and to provide a cream solder material in which chip standing is less likely to occur in reflow in nitrogen and a reflow soldering method using the same.

[0008]

In order to achieve the above object, the cream solder of the present invention comprises 55-80% by weight of solder powder composed of tin, lead and bismuth, 20-45% by weight of solid flux, and halogen. Is 0.1 wt% or less.

[0009]

According to the present invention, the time required for melting the cream solder material is longer than before, and the force for the molten solder to pull the component is gradually added.

[0010]

EXAMPLE An example of the present invention will be described below.

The cream solder material used in the present embodiment is A powder containing 60% by weight of tin and 40% by weight of lead and B powder containing 21% by weight of tin, 71% by weight of lead and 8% by weight of bismuth in a weight ratio of 50: Solder powder consisting of tin, lead and bismuth mixed with 50, 70% by weight, solid flux 30% by weight, halogen 0.06% by weight.

The above cream solder material was printed on a printed board to a thickness of 0.15 mm, and 1005 chips were soldered by a mounting machine. For soldering, reflow was performed in a nitrogen atmosphere having an oxygen concentration of 100 ppm, and the occurrence rate of chip standing was measured. The results are shown in (Table 1).

[0013]

[Table 1]

As is clear from (Table 1), according to the present embodiment, the chip rising occurrence rate was reduced to 1/50.

In the conventional example shown in the same table, 64.94% by weight of eutectic point solder consisting of 63% by weight of tin and 37% by weight of lead, 35% by weight of solid content mainly composed of natural rosin, 0 of halogen component Reflow was performed under the same conditions as in the example using a low residue cream solder material of 0.06% by weight.

In the present invention, the reason why the solder powder consisting of tin, lead and bismuth is limited to 55 to 80% by weight, the solid flux to 20 to 45% by weight, and the halogen to 0.1% by weight or less is exceeded. This is because the occurrence rate of chip standing exceeds 1.5%.

[0017]

As is apparent from the above description, according to the cream solder material of the present invention and the reflow soldering method using the same, the time required for melting the cream solder material is longer than before, and the molten solder is Since the force for pulling the component is gradually applied, the effect that the occurrence rate of chip standing is reduced can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Fukushima 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A cream solder material comprising 55-80% by weight of solder powder composed of tin, lead and bismuth, 20-45% by weight of solid flux, and 0.1% by weight or less of halogen. 2. A reflow soldering method of melting and soldering the cream solder material according to claim 1 in a nitrogen atmosphere.