JP2001294901A - Solder powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of solder balls in particular for a Zn solder powder easily oxidized which is melted with a flux with a weak activity in an atmospheric reflowing by maintain the property. SOLUTION: A phosphoric anion surface active agent 4 is adsorbed on the surface of solder powder 1, by which, in the process of reflowing, the surface active agent prevents the oxidation of Zn through flux, so that its solderability is improved and maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solder powder used as a solder paste together with a flux.

[0002]

2. Description of the Related Art Sn-Pb alloy is generally used as a solder alloy used for soldering electronic equipment, and has been used for a long time since ancient times. The Sn-Pb alloy has a low melting point of a eutectic composition (63Sn-Pb) of 183 ° C., and its soldering temperature is 220 to 230 ° C., which may cause thermal damage to electronic components that are weak to heat. No temperature. Moreover, the Sn-Pb alloy has an excellent feature that it solidifies immediately upon soldering and does not crack or peel off even when vibrations or impacts are applied to the soldered portion.

[0003] Generally, electronic devices such as televisions, radios, videos, tape recorders, computers, and copiers are disposed of when they break down or become old and inconvenient. In these electronic devices, the exterior and the printed circuit board are made of synthetic resin such as plastic,
Also, since the conductor and the frame are made of metal, they cannot be incinerated and are almost buried underground.

[0004] In recent years, due to the heavy use of petroleum fuels such as gasoline and heavy oil, a large amount of sulfur oxides has been released into the atmosphere, and as a result, the rain falling on the ground has been acid rain. Acid rain dissolves solder in electronic equipment buried underground and soaks into the ground, polluting groundwater. If the groundwater containing lead has been drunk for many years, lead may accumulate in the human body and lead to poisoning. Due to such momentum, the appearance of solder that does not contain lead, that is, a so-called “lead-free solder alloy” has been desired in the electronic equipment industry.

[0005] Conventionally, lead-free solder alloys include Sn-Ag alloys, Sn-Sb alloys, Sn-Cu alloys, Sn-Bi alloys and Sn-Zn alloys, which are mainly composed of Sn.
The n-Zn alloy has a eutectic composition of Sn-9Zn, a eutectic temperature of 199 ° C, and a melting temperature of 63Sn-Pb.
It has a temperature advantage that it is close to the eutectic temperature of 183 ° C. of the eutectic solder.

However, the Sn—Zn alloy has a problem that solderability is not so good. In order to improve the solderability of the Sn-Zn alloy and further improve the mechanical strength, Ag, Cu, B
Using Sn-Zn-based solder powder to which i, In, Ni, P, etc. are appropriately added, and a powder in which a metal plating film or a resin film is formed on the surface of Sn-Zn-based solder powder to prevent oxidation of Zn. Many proposals have been made, such as a solder paste mixed with a flux, a solder paste mixed with a special flux having a high activity and a Sn-Zn-based solder powder.

[0007]

However, when soldering is performed using an Sn-Zn-based solder paste (hereinafter referred to as Zn-based solder paste) in which the above is improved, compatibility between solderability and viscosity stability is insufficient. Met. That is, with a certain Zn-based solder paste, continuous printing is possible with little change in the solder over time, but a phenomenon has occurred in which the soldered portion is not completely wet and the copper foil land portion of the printed circuit board remains as it is. In addition, the solder paste oxidized from the copper foil land flows between the lead frames of the semiconductor element, and has poor solderability such as being attached to a printed board as a solder ball. In another Zn-based solder paste, the soldering property is improved by removing the oxide film of the solder powder and adding an activator that promotes the spread of the solder to the flux to improve the solderability. That is, when the Sn-Zn-based solder alloy comes into contact with a strong activator, it oxidizes or corrodes in a short period of time, and the metallic performance is completely lost. It has a viscous property immediately after production and is easy to stir with a spatula or a stick. However, the viscosity increases with aging and the stirring becomes difficult. Then, the printing supply of the solder paste to the printed circuit board becomes difficult due to the metal mask or the like.

Although many proposals have been made to apply a surface treatment to the solder powder to prevent oxidation, the surface treatment process is complicated, mass production is difficult, and it has not been practically used due to an increase in cost. Also, there were few solder pastes having good solderability and little change over time.

It is an object of the present invention to provide a Sn—Zn-based solder powder which hardly changes with time and has good solderability even in reflow soldering in the air.

[0010]

In order to solve the above-mentioned problems, a phosphate-based anionic surfactant forms a film around a Sn—Zn-based solder alloy powder, thereby dissolving Zn ions into a flux. The present invention has been found to have an effect of suppressing the oxidation of Zn by oxygen in atmospheric reflow, and has further completed the present invention.

[0011] The present invention is a solder powder characterized in that a phosphate-based anionic surfactant is provided on the surface thereof. By covering the surface of the solder powder, the elution of Zn into the flux is prevented and the change over time is prevented. Less. Further, as the temperature of the solder paste increases in the reflow furnace, the phosphate-based anionic surfactant is melted to shield the solder powder from oxygen, thereby preventing oxidation of the solder powder and suppressing the generation of solder balls. Thereby, a highly reliable printed circuit board can be provided. further,
Similar effects can be obtained by providing a polypropylene copolymer or an alkyl ether-based nonionic surfactant in place of the phosphate-based anionic surfactant.

Further, the present invention is a solder powder characterized in that a phosphoric acid-based anionic surfactant and a polypropylene copolymer are provided on the surface, and the solderability is improved by covering the surface of the solder powder. It is possible to provide a solder paste with little change over time.

The present invention also provides a solder powder characterized in that a phosphate-based anionic surfactant and an alkyl ether-based nonionic surfactant are sequentially provided on the surface, and the solder powder covers the surface of the solder powder. Accordingly, it is possible to provide a solder paste having good solderability and little change over time. Furthermore, it is a solder powder characterized by sequentially providing a polypropylene copolymer and an alkyl ether-based nonionic surfactant on the surface, and has the same effect.

Further, the present invention is a solder powder characterized in that a metal salt of dicarboxylic acid is provided on the surface. By covering the surface of the solder powder, a solder paste having good solderability and little change over time is obtained. It is possible to provide.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) A first embodiment of the present invention is a solder powder characterized in that a phosphate-based anionic surfactant is provided on the surface. The phosphate-based anionic surfactant used in the present invention is easy to bond with the solder powder, easily separated from the solder powder at the preheating temperature during reflow, and the flux residue of the soldered portion after reflow. Those that can ensure reliability are preferable.

For example, polyoxethylene alkyl ether phosphoric acid, particularly "DDP-2", which is commercially available from Nikko Chemicals Co., Ltd., is preferred.

The solvent for dissolving the phosphate anionic surfactant is not particularly limited as long as it is soluble.
Heptane and hexane are preferred from the viewpoint of safety as a solvent, ease of drying of the solder powder when forming a phosphate-based anionic surfactant, non-polarity, and cost.

The formation of the phosphate-based anionic surfactant on the surface of the solder powder is carried out by adding the solder powder to a solution of the phosphate-based anion surfactant and stirring for a certain period of time. Adsorb the activator. Thereafter, the solution and the solder powder are separated, the solder powder is washed with a solvent to remove excess phosphate-based anionic surfactant, and then dried. The amount by which the phosphate-based anionic surfactant is adsorbed is controlled by the concentration of the solution and the amount of the solder powder added.

For example, when DDP2 is used as a phosphate-based anionic surfactant and heptane is used as a solvent,
2 1 cc, heptane 100 cc, solder powder 10
Put it in 0g beaker and use magnet stirrer for about 800r
Stir at pm for 15 minutes. Further, the solution and the solder powder were separated, the solder powder was washed with heptane for 15 minutes, and the solder powder was dried in an oven maintained at 60 ° C. for 30 minutes to obtain a phosphate anion as shown in the conceptual diagram of FIG. A solder powder provided with a surfactant can be obtained.

FIG. 1 shows a solder powder 1 according to a first embodiment of the present invention. The surface of the solder powder 1 is provided with a phosphate anionic surfactant 4 composed of a hydrophilic group 2 and a lipophilic group 3. This solder powder 1 exists in the same state as the lipophilic flux even in the state of the solder paste mixed with the flux, and the phosphate-based anionic surfactant 4 prevents oxidation of the flux into the solder powder. , The change with time is reduced. Also, during the reflow, when the phosphate-based anionic surfactant 4 reaches the melting point, it melts and separates from the surface of the solder powder 1, so that the solder powder is melted and solidified, and soldering becomes possible. The surface of the solder powder 1 is covered with the phosphate anion surfactant 4 until the melting point of the phosphate anion surfactant 4 is reached, so that the solder powder 1 is prevented from being oxidized from the atmosphere during reflow, and soldering is performed. Performance can be improved.

Conventionally, plating and the like have been proposed as a method for surface treatment of solder powder. However, it has been difficult to control a plating solution and to retain the solder powder, and this method has been expensive. However, in the present invention, it is not necessary to hold the solder powder, and the surface treatment of the solder powder can be performed very easily by mixing the solution and the solder powder. It is possible to manufacture.

Further, the same effect can be obtained by providing a polypropylene copolymer or an alkyl ether-based nonionic surfactant in place of the phosphate-based anionic surfactant.

The polypropylene copolymer used in the present invention, like the phosphate-based anionic surfactant, is easily bonded to the solder powder, and is easily separated from the solder powder at the preheating temperature during reflow. It is preferable that the reliability of the flux residue in the soldered portion after the reflow can be ensured. For example, a "polyol prepolymer" commercially available from Nikko Chemicals Co., Ltd. is preferable.

Further, the alkyl ether nonionic surfactant used in the present invention can be easily bonded to the solder powder similarly to the phosphate anionic surfactant, and can be melted at the preheating temperature during reflow and reflowed. Those that can ensure the reliability of the flux residue at the later soldering part are preferable,
For example, “PBC-41” commercially available from Nikko Chemicals Co., Ltd. is preferable.

(Embodiment 2) A second embodiment of the present invention is a solder powder characterized in that a phosphate-based anionic surfactant and a polypropylene copolymer are provided on the surface.

The formation of the phosphate-based anionic surfactant and the polypropylene copolymer on the surface of the solder powder is performed by adding the solder powder to a mixed solution of the phosphate-based anionic surfactant and the polypropylene copolymer and stirring the mixture for a certain period of time. Then, a phosphate-based anionic surfactant and a polypropylene copolymer are adsorbed on the surface of the solder powder. Thereafter, the solution and the solder powder are separated, the solder powder is washed with a solvent to remove the excess solvent, and dried. The amount by which the phosphate anionic surfactant and the polypropylene copolymer are adsorbed is controlled by the concentration of the solution and the amount of the solder powder added.

For example, DDP2 is used as a phosphate anionic surfactant, a polyol prepolymer is used as a polypropylene copolymer, and heptane is used as a solvent. D
1 cc of DP2, 1 cc of polyol prepolymer, 100 cc of heptane, and 100 g of solder powder are placed in a beaker and stirred with a magnetic stirrer at about 800 rpm for 15 minutes. Further, the solution and the solder powder were separated, and the solder powder was washed with heptane for 15 minutes.
By drying in a furnace maintained at a temperature of 30 minutes, solder powder 11 as shown in the conceptual diagram of FIG. 2 can be obtained. FIG.
Indicates a solder powder 11 according to the second embodiment of the present invention. The solder powder 11 has two kinds of organic substances formed on the surface. The hydrophilic group 12 of the surfactant of the phosphate-based anionic surfactant 14 and the hydrophilic group 15 of the copolymer of the polypropylene copolymer 17 are adsorbed on the surface of the solder powder 11.

This solder powder 11 exists in the same state as the lipophilic flux even in the state of the solder paste mixed with the flux, and the solderability and the suppression of the change over time are the same as those of the phosphate anion. Surfactant 1
By the action of No. 4, it is possible to further improve, and at the same time, to form the polypropylene copolymer 17, it is possible to further reduce the change with time. That is, since the lipophilic group 16 of the copolymer of the polypropylene copolymer 17 has a higher molecular weight than the lipophilic group 13 of the surfactant of the phosphate-based anionic surfactant 14, the polypropylene copolymer 17 is not adsorbed. The distance between the solder powder on which the polypropylene copolymer 17 is adsorbed and the other adsorbed solder powder is larger than the distance between the solder powder and other unadsorbed solder powder. Due to this effect, it becomes difficult for the solder powder to approach from the distance of the lipophilic group 16 of the copolymer in the flux,
It is possible to prevent agglomeration of the solder powder and further reduce the change with time.

(Embodiment 3) In a third embodiment of the present invention, a phosphate-based anionic surfactant is provided on the surface,
An alkyl ether-based nonionic surfactant is sequentially provided.

The formation of the phosphate-based anionic surfactant and the alkyl ether-based nonionic surfactant on the surface of the solder powder can be performed by adding the solder powder to a solution of the phosphate-based anionic surfactant and stirring for a certain period of time. A phosphate-based anionic surfactant is adsorbed on the surface of the solder powder. afterwards,
The solution and the solder powder are separated, the solder powder is washed with a solvent to remove excess solvent, dried, and further, the phosphate-based anionic surfactant is adsorbed to a solution of an alkyl ether-based nonionic surfactant. The solder powder is added and stirred for a certain time. By this process, a phosphate-based anionic surfactant is formed into an alkyl ether-based nonionic surfactant, the solution and the solder powder are separated, the solder powder is washed with a solvent to remove excess solvent, and dried. Performs a surface treatment. The amount by which the phosphate-based anionic surfactant and the alkyl ether-based nonionic surfactant are adsorbed is controlled by the concentration of the solution and the amount of the solder powder added.

For example, when DDP2 is used as a phosphate-based anionic surfactant, PBC-41 is used as an alkyl ether-based nonionic surfactant, and heptane is used as a solvent, 1 cc of DDP2 and 100 cc of heptane are used.
100 g of the solder powder is placed in a beaker and stirred with a magnetic stirrer at about 800 rpm for 15 minutes. Further, the solution and the solder powder were separated, and the solder powder was
After washing for 30 minutes, the solder powder is dried in a furnace maintained at 60 ° C. for 30 minutes to obtain a solder powder having a first layer surface treated. Further, 1 cc of PBC-41, 100 cc of heptane and 100 g of the solder powder were placed in a beaker, and similarly stirred,
By separating, washing and drying, a double-layered solder powder as shown in the conceptual diagram of FIG. 3 can be obtained. FIG. 3 shows a solder powder 21 according to a third embodiment of the present invention. An organic film composed of two layers is formed on the surface of the solder powder 21. A layer of a phosphate-based anionic surfactant 24 is formed as a first layer around the solder powder 21, and a layer of an alkyl ether-based non-ionic surfactant 27 is formed outside the layer as a second layer. Each layer is composed of the surface of the solder powder 21 and the hydrophilic group 22 of phosphoric acid of the phosphate-based anionic surfactant 24, and the lipophilic group 23 of phosphoric acid of the phosphate-based anionic surfactant 24 and the alkyl ether-based The nonionic surfactant 27 is formed by adsorption with the alkyl ether hydrophilic group 26 of the nonionic surfactant 27.

The solder paste obtained by mixing the solder powder with the double-layered organic material and the flux is soldered in an air reflow oven, and the same action as described above causes the first and second layer surfactants to remove from the air. Prevents oxidation of Zn, suppresses solder balls, improves wettability, and improves solderability. Furthermore, the change in viscosity in the flux is due to the fact that the hydrophilic group of the alkyl ether in the second layer is in contact with the flux, and the hydrophilic group covers the outside of the solder powder. It is possible to prevent the solder paste from being entangled and agglomerated as in the case of the formed solder powder, and to reduce the time-dependent change of the solder paste.

Further, the same effect can be obtained by a double-layered solder powder having a surface provided with a polypropylene copolymer and an alkyl ether-based nonionic surfactant in this order.

(Embodiment 4) A fourth embodiment of the present invention is a solder powder characterized in that a metal dicarboxylate is provided on the surface of the solder powder.

The metal dicarboxylate used in the present invention is a metal dicarboxylate containing copper which is easily bonded to Zn in the solder alloy. As the dicarboxylic acid, the reliability of the flux residue of the soldered portion after reflow is considered. And organic substances contained in the flux are preferred. For example, succinic acid, adipic acid and fumaric acid are preferred.

The solvent for dissolving the metal salt of dicarboxylic acid is as follows:
Solvents such as heptane and hexane are preferred from the viewpoints of safety as a solvent, ease of drying of solder powder when forming a metal dicarboxylate, cost, and non-polarity, although there is no particular limitation on solubility, insolubility, and the like.

For the formation of the metal dicarboxylate on the surface of the solder powder, a solution of the metal dicarboxylate is used. The solder powder is added to the solution and stirred for a certain period of time. By drying. The amount of forming the metal dicarboxylate is controlled by the concentration of the solution, the amount of the solder powder added, and the stirring time. For example, copper adipate is produced by reacting adipic acid and copper hydroxide, and 90 g of solder powder is added to a solution obtained by adding 9 g of copper adipate to 300 cc of heptane, followed by stirring with a magnetic stirrer at about 800 rpm for 15 minutes. Furthermore, by separating the solution and the solder powder, and drying the solder powder in a furnace maintained at 60 ° C. for 30 minutes,
Copper adipate 34 can be formed on the surface of solder powder 31 as shown in FIG.

FIG. 4 shows a solder powder 31 according to Embodiment 4 of the present invention. 2 hydrophilic groups 32 on the surface of solder powder 31
And the lipophilic group 33 forms one dicarboxylic acid metal salt. Solder powder 31 and metal dicarboxylate 34
Are attached by a hydrophilic group 32.

The solder paste obtained by mixing the solder powder with the metal dicarboxylate and the flux is soldered in an air reflow oven. When the metal dicarboxylate covers the solder powder, the oxidation of Zn from oxygen Can be prevented, and the generation of solder balls can be prevented. Further, by forming a metal salt having two hydrophilic groups, it becomes possible to prevent the terminal of the lipophilic group from facing outward with respect to the solder powder. 1
By providing the kinds of organic substances, the lipophilic groups are entangled with each other as in Examples 2 and 3, and it is possible to prevent changes over time due to aggregation.

As described above, in the conventional Zn-based solder paste, there is a problem that the oxidation of Zn causes a temporal change, a solder ball is generated, and the wettability to a printed circuit board copper foil is reduced. However, by forming an organic substance on the surface of the solder powder as described above, oxidation of Zn during reflow can be prevented, generation of solder balls can be suppressed, and a change with time can be prevented.

[0042]

Embodiments of the present invention are described below.

The solder paste has a flux composed of rosin, a thixotropic agent, an activator and a solvent and a particle size of 20 to 40 μm.
m is a mixture of spherical solder powders. In the present invention, 10% by weight of flux and 90% by weight of solder powder
To make a solder paste. The solder powder is an alloy composed of 8 wt% Zn and 3 wt% Bi remaining Sn (hereinafter referred to as Zn powder), and shows an example of components when various organic substances are adsorbed and surface treated.

Example 1 Flux: 10% by weight Rosin (pine resin) 50% by weight Hardened castor oil (thixotropic agent) 5% by weight Diphenylguanidine HBr (activator) 2% by weight α-Teleneol (solvent) 43 % DOP2 treated Zn powder: 90% by weight Example 2 Flux: 10% by weight Rosin (pine resin) 50% by weight Hardened castor oil (thixotropic agent) 5% by weight Diphenylguanidine HBr (activator) 2% by weight α -TVneol (solvent) 43% by weight ○ DDP2 + polyol prepolymer-treated Zn powder: 9
0% by weight [Example 3] ○ Flux: 10% by weight Rosin (pine resin) 50% by weight Hardened castor oil (thixotropic agent) 5% by weight Diphenylguanidine HBr (activator) 2% by weight α-Teleneol (solvent) 43 Weight% ○ DDP2 + PBC-41 treated Zn powder: 90% by weight [Example 4] ○ Flux: 10% by weight Rosin (rosin) 50% by weight Hardened castor oil (thixotropic agent) 5% by weight Diphenyl guanidine HBr (activator) 2% by weight % Α-TVneol (solvent) 43% by weight ○ Zn powder treated with copper adipate: 90% by weight [Comparative Example 1] ○ Flux: 10% by weight Rosin (rosin) 50% by weight Hardened castor oil (thixotropic agent) 5% by weight Diphenyl guanidine HBr (activator) 2% by weight α-Teleneol (solvent) 43% by weight ○ Untreated Zn powder: 90% by weight [Comparative Example 2] ○ Flux: 10% by weight Rosin (pine resin) 50% by weight Hardened castor oil (thixotropic agent) 5% by weight Diphenylguanidine HBr (activator) 2% by weight α-Teleneol (solvent) 43% by weight ○ Acrylic resin-treated Zn powder Comparative Example 1 is a Zn powder having the same component flux as that of Example 1 and an untreated solder powder. Comparative Example 2 is a Zn powder in which an acrylic resin is coated around the solder powder with the same component flux as in Example 1.

Using the solder pastes of the above-described examples and comparative examples, test substrates are prototyped and their reliability is evaluated.

The test board is a printed wiring board. The land portion to be soldered with glass epoxy is copper plating, the solder paste is printed and supplied by a metal squeegee using a metal mask having a thickness of 180 μm and having an opening by etching. I do. Electronic components are surface mount components.
It is a semiconductor consisting of Pd-plated leads with 84 pins at 8 mm pitch. The surface mount component is mounted on the land portion on which the solder paste is printed, and the solder is melted and joined using an atmospheric hot air reflow furnace so that the maximum temperature of the soldered portion is 210 ° C.

The evaluation of the solder paste is performed by counting the number of solder balls generated around one semiconductor lead to determine whether there is an effect of suppressing the oxidation of the solder powder. In addition, the evaluation of the change over time is preferably performed by placing the solder paste in a closed container and leaving it in a thermostat at 25 ° C., measuring the viscosity change with a Malcolm viscometer, and increasing the standing time with a small viscosity change. (If it is 7 days or more, there is no problem in actual use.) The evaluation results are shown in Table 1, and photographs of the state of occurrence of solder balls are shown in FIGS. FIG.
Reference numeral 41 denotes semiconductor leads, and reference numeral 42 denotes solder balls generated between the leads.

[0048]

[Table 1]

In Example 1, since the phosphate-based anionic surfactant was formed in the solder powder, the generation of solder balls in an air reflow furnace was smaller than that of Comparative Example 1 in which the untreated solder powder was used, and the change with time was less. It's late,
It can be seen that oxidation of Zn is prevented. However, no matter what effect is obtained by coating with powder, the same effect is obtained. As shown in Comparative Example 2, the generation of solder balls is slightly prevented by coating with acrylic resin.
The change with time is the same as that of Comparative Example 1, and it is considered that the change with time is caused by the aggregation of the solder powder.

In Example 2, the formation of solder balls in an atmospheric reflow furnace was smaller than that of Comparative Example 1 in which the untreated solder powder was formed by simultaneously forming the phosphate-based anionic surfactant and the polypropylene copolymer on the solder powder. In addition, agglomeration of the solder powder can be prevented, and the change over time is slower than in Example 1.

In the third embodiment, the formation of the phosphate-based anionic surfactant and then the formation of the alkyl ether-based ionic surfactant in the solder powder are the same as in the second embodiment. The occurrence is small, the aggregation of the solder powder can be prevented, and the change over time is slower than in Example 1.

Further, in Example 4, since the metal salt of dicarboxylic acid was provided around the solder powder, the generation of solder balls was small in an air reflow furnace as in Example 1, and the end of the lipophilic group was added to the solder powder. On the other hand, since it does not protrude outward, the entanglement and aggregation of the solder powder due to the lipophilic group can be prevented, and the change with time is slower than in Examples 2 and 3.

[0053]

As described above, in the solder paste of the present invention, by providing an organic substance on the surface of the solder powder, it is possible to perform soldering with less generation of solder balls and high reliability, and the aging at room temperature. During manufacturing such as solder paste printing on printed circuit boards with little change,
It has the same workability as conventional lead-containing solder.

In the method for treating the surface of a solder powder according to the present invention, the solution and the solder powder can be mixed and dried, and the surface treatment of the solder powder can be easily performed without increasing the cost.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a cross section of a solder powder according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram of a cross section of a solder powder according to a second embodiment of the present invention.

FIG. 3 is a conceptual diagram of a cross section of a solder powder according to a third embodiment of the present invention.

FIG. 4 is a conceptual diagram of a cross section of a solder powder according to a fourth embodiment of the present invention.

FIG. 5 is a view showing a semiconductor lead portion mounted using the solder paste according to the first embodiment of the present invention;

FIG. 6 is a view showing a semiconductor lead portion mounted using the solder paste of Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solder powder 2 Hydrophilic group 3 Lipophilic group 4 Phosphate-based anionic surfactant 11 Solder powder 12 Hydrophilic group of surfactant 13 Lipophilic group of surfactant 14 Phosphate-based anionic surfactant 15 Hydrophilicity of copolymer Group 16 Lipophilic group of copolymer 17 Polypropylene copolymer 21 Solder powder 22 Hydrophilic group of phosphoric acid 23 Phosphoric acid group 24 Phosphate-based anionic surfactant 25 Hydrophilic group of alkyl ether 26 Hydrophilic group of alkyl ether Group 27 Alkyl ether ionic surfactant 31 Solder powder 32 Hydrophilic group 33 Lipophilic group 34 Metal salt of dicarboxylic acid 41 Lead of semiconductor 42 Solder ball

Continued on the front page (72) Inventor Takashi Nagashima 1006 Kadoma, Kadoma, Osaka Prefecture F-term (reference) in Matsushita Electric Industrial Co., Ltd. 4K018 BA20 BC29 BD04

Claims (8)

[Claims] 1. A solder powder comprising a surface provided with a phosphate-based anionic surfactant. 2. A solder powder having a surface provided with a polypropylene copolymer. 3. A solder powder characterized in that an alkyl ether-based nonionic surfactant is provided on the surface. 4. A solder powder having a surface provided with a phosphate-based anionic surfactant and a polypropylene copolymer. 5. A solder powder characterized in that a phosphate anionic surfactant and an alkyl ether nonionic surfactant are sequentially provided on the surface. 6. A solder powder characterized in that a polypropylene copolymer and an alkyl ether nonionic surfactant are sequentially provided on the surface. 7. A solder powder characterized in that a metal salt of dicarboxylic acid is provided on the surface. 8. The solder powder according to claim 1, wherein the solder powder contains Sn and Zn.