JP2641841B2 - Cream solder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cream solder.

[0002]

2. Description of the Related Art A cream solder is a mixture of a solder powder and a liquid or paste-like flux to form a cream, and is widely used for screen printing of electronic parts and the like.

[0003] The typical performance required for a cream solder is that, in addition to the original solderability, there is little change in viscosity over time, a long tacking time, a large tacking force, good continuous printability, and a horizontal component. No ball occurs,
It shows good corrosion resistance to voltage application and little oxide residue after standing. It is very difficult to obtain a cream solder having all of these properties, and various improvements have been attempted.

[0004] Among these properties, it is difficult to obtain the stability of the solder over time, and the conventional cream solder gradually increases in viscosity even when stored in a refrigerator, and becomes loose in six months to one year. And become unusable. To improve this, it has been proposed to add a chelating agent to the cream solder (JP-A-62-187595). However, even with this method, it is difficult to achieve long-term stability over time. In addition, the tacking time is short, and horizontal balls tend to occur.

[0005]

SUMMARY OF THE INVENTION The present invention addresses the above-mentioned problems,
In particular, it is an object of the present invention to obtain a cream solder which has stability over time, a long tacking time, and does not generate horizontal balls.

[0006]

SUMMARY OF THE INVENTION The present invention provides a chelating agent comprising one or more amino groups and at least two carboxyl groups, wherein at least one of the carboxyl groups is esterified with a hydrocarbon group, and / or The present invention relates to a cream solder, characterized by containing a compound having at least one hydrocarbon group bonded to the group.

In the present invention, a chelating agent containing an amino group and a carboxyl group refers to a conventional chelating agent of this kind, for example, polymethylenediaminetetraacetic acid (especially ethylenediaminetetraacetic acid), (alkyl) iminodiacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid. Acetic acid, triethylenetetramine hexaacetic acid, cyclohexane-1,2
-Diaminetetraacetic acid, N-hydroxyethylethylenediaminetriacetic acid, ethyleneglycolethyletherdiaminetetraacetic acid, ethylenediaminetetrapropionic acid and the like.

The chelating agent is esterified with at least one of its carboxyl groups and / or a hydrocarbon group, or has at least one hydrocarbon group bonded to an amino group. The hydrocarbon group has 1 to 40 carbon atoms, more preferably 8 to 20 carbon atoms. As the hydrocarbon group, an aliphatic hydrocarbon group which may have an unsaturated bond or a branch, for example, methyl, ethyl, propyl, isopropyl, butyl,
t-butyl, amine, 2-ethylhexyl, lauryl,
Oleyl, stearyl, etc .; alicyclic hydrocarbon group, for example, cyclohexyl group; optionally substituted aromatic group, for example, phenyl group, naphthyl group, alkylphenyl group, halogenated phenyl group, nitrophenyl group, etc .: Aliphatic aromatic groups such as a benzyl group are exemplified.

A typical chelating agent has the general formula:

Embedded image (Wherein, R ₁ to R ₄ are a hydrocarbon group having 1 to 40 carbon atoms,
Preferably, it is a hydrocarbon group, a carboxyl group, or a carboxylic ester having 8 to 20 carbon atoms, and the alkyl group forming the ester has 1 to 40 carbon atoms, preferably 8 to 20 carbon atoms. However, at least two of R ₁ to R ₄ are carboxyl groups. X is a hydrogen atom or a C 1-6 branched or halogen, an aliphatic hydrocarbon group which may have a substituent such as a nitro group, an alicyclic group, an aromatic group,
And aliphatic aromatic groups. n is a number of 1-8, especially 2-6. )

The amount of the chelating agent to be added to the cream solder is from 0.01 to 5% by weight, more preferably from 0.1 to 5% by weight, based on the total amount of the cream solder. If it is more than 10% by weight, a good paste is not obtained. 0.01% by weight
If less, there is no effect.

The cream solder of the present invention can be obtained by further mixing a solder powder and a flux suitably containing a resin, an activator, a solvent, a viscosity modifier, an antifoaming agent, a plasticizer and the like used in conventional cream solder.

As the resin, rosins such as rosin, polymerized rosin, disproportionated rosin, hydrogenated rosin, maleated rosin, and polybutadiene carboxylic acid can be used.

Examples of the activator include a hydrogen halide of a nitrogen-containing base, for example, a hydrobromide salt of cyclohexylamine, and an organic acid, for example, an amino acid such as adipic acid and sebacic acid, for example, glutamic acid.

Examples of the solvent include organic solvents, particularly alcohols, glycols, esters, ethers, glycol ethers, terpenes, alicyclic hydrocarbons, aliphatic hydrocarbons and aromatic hydrocarbons. Preferably, the boiling point is 160 ° C. or more, particularly 220 ° C. to 290 ° C.
It is preferable to use a resin which has low hygroscopicity and dissolves resins and chelates well. Specific examples of particularly preferred solvents for the present invention are glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, mono- or diethers thereof with lower alcohols, or mono- or diesters, cyclic ethers, especially crown ethers. Ethers, glycerin, pentaerythritol, trimethylolpropane, and esters thereof.

As the viscosity modifier, those having properties such as increasing the viscosity by dissolving or dispersing in the above-mentioned solvents or imparting thixotropic properties are mentioned. Specific examples thereof include high molecular weight polyethylene glycol and polypropylene. Glycols, thickeners soluble in organic solvents such as ethyl cellulose, hardened castor oil, fats and oils such as coconut oil,
Waxes of higher alcohols and fatty acids, saturated higher fatty acids or alcohols, esters of polyhydric alcohols and higher fatty acids, amides or bisamides of higher fatty acids, carnauba wax, acacia gum, tragacanth gum, guar gum, locust bean gum, Natural or semi-synthetic gums such as arabinogalactone, karaya gum, iris moss, gelatin, sodium alginate, propylene glycol alginate, synthetic resins,
Examples thereof include inorganic viscosity modifiers such as low molecular weight phenol formaldehyde resin and low molecular weight polyethylene wax, for example, ultrafine silica.

These viscosity modifiers are used in an amount of 0.1 to 10% by weight, preferably 2 to 5% by weight, based on the total amount of the flux. It is preferable that the viscosity when adjusted to a paste is in the range of 50,000 to 1,000,000 cps at 23 ° C., more preferably 150,000 to 800,000 cps.

The amount of the resin used is 10 to 90% by weight, more preferably 40 to 80% by weight of the total amount of the flux. The amount of the solvent used is 10 to 70% by weight, more preferably 20 to 60% by weight of the total amount of the flux. The amount of activator is 0 to 30% by weight of the total flux, more preferably 0 to 5% by weight.

The thickener may be appropriately compounded so that the viscosity of the cream solder becomes the optimum use viscosity. Usually 50,000 at room temperature
Adjust from cps to 1 million cps.

The antifoaming agent may be a silicone-based antifoaming agent or an alcohol-based antifoaming agent, for example, 2-ethylhexanol or a mixture thereof.
And lauryl alcohol.

Examples of the antioxidant include 2,6-di-t-butyl-p-cresol.

As the plasticizer, esters, for example, dioctyl phthalate, cream solder, and solder powder are blended in addition to the above components. The solder powder may include tin, lead, and other components containing silver, copper, antimony, phosphorus, and the like.

The particle size of the solder powder ranges from 10 μm to 100 μm.
m, more preferably from 20 μm to 50 μm. The amount of solder powder used is from 1% by weight to 95% of the total amount of cream solder.
%, More preferably from 85% to 92% by weight.

Hereinafter, the present invention will be described with reference to examples. Example 1 The flux was adjusted according to the formulation shown in Table 1.

[Table 1] Solder powder (tin / lead = 63) was added to 10 parts by weight of this flux.
/ 37 weight ratio, average particle size 20 μm) and 90 parts by weight.
The mixture was mixed for 1 minute to obtain a cream solder.

The following properties of this cream solder were evaluated. Evaluation method (1) Test method for tacking time The paste was printed to a thickness of 6.5 Φ and a thickness of 200 μm, and the temperature was 2
The sample is placed in an environment of 5 ° C. and a humidity of 50%, and after a certain period of time, the tackiness is measured with a tacking tester TAC-II manufactured by Resca under the following conditions. Probe diameter: 5.1Φ Pushing speed: 120mm / min Pulling speed: 600mm / min Pressure: 50gf Pressing time: 0.2sec ◎: Greater than 80g at 8h ○: Greater than 80g at 3h ×: Smaller than 80g at 3h (2) Component lateral ball test method Chip lateral solder ball test board (1608 and 2
The paste is printed to a thickness of 200 μm on a chip resistor (175 chip resistors can be mounted thereon), and the chip resistors are mounted. Reflow under standard conditions and check the solder balls generated on the side of the chip. ◎: Occurrence of less than 0.01% ：: Occurrence of 1 to 0.01 ×: Occurrence of 1% or more (3) Stability over time ：: Viscosity increase rate of 5% or less in 3 weeks at room temperature ○: Room temperature 3 Viscosity increase rate of 10% or less in a week ×: Viscosity increase rate of more than 10% in a room temperature of 3 weeks (4) Continuous printability ◎: Continuous print 8h possible ○: Continuous print 4h possible ×: Continuous print 4h not possible (5) Oxide residue after standing ◎: No oxide residue is generated even after standing for 8 hours. ：: No oxide residue was generated even after standing for 4 hours. ×: Oxide residue is generated when left for 4 hours.

The same test was carried out for a cream solder using no chelating agent and a cream solder using a conventional chelating agent (comparative example). Table 2 shows the properties of the cream solder.

[0026]

[Table 2]

[0027]

The cream solder of the present invention is excellent in stability over time, has little formation of oxide residues over time, has a long tacking time, and is unlikely to generate horizontal balls. In addition, it has excellent properties of continuous printing.

Claims (1)

(57) [Claims] 1. A chelating agent comprising one or more amino groups and at least two carboxyl groups, wherein at least one of the carboxyl groups is esterified with a hydrocarbon group, and / or at least one carboxyl group on the amino group. A cream solder containing a compound having a hydrogen group bonded thereto.