JPH0692033B2 - Additives for flux and solder paste - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flux and an additive for solder paste, a flux containing this additive, and a solder paste containing this flux. Flux is widely used in the electronic industry field for the purpose of removing an oxide film on a metal substrate. Even if the flux of the present invention remains on the metal substrate, it does not corrode the metal substrate,
It is a new flux.

[Conventional technology]

A common method for soldering an electronic component onto a substrate of an electronic circuit is to treat the substrate (copper) surface with flux to remove the oxide film, and then immerse the substrate surface in a molten solder bath.

However, this method requires two steps: fluxing and dipping in a solder bath. Further, according to this method, the electronic component placed on the board may drop from the board during the work.

Therefore, as a method for solving such a problem, a method using a solder paste containing a flux and solder particles has been developed. According to this method, the solder paste is applied onto the substrate by a method such as a dispenser method, and then the soldering is completed by heating or irradiating with ultraviolet rays.
Since the solder paste has a viscosity, the electronic component is easily held on the substrate.

[Problems to be Solved by the Invention]

However, the method using the above solder paste also has drawbacks. The solder paste contains an activator for the purpose of strongly removing the oxide film on the substrate. However, if the activator remains in the solder after the soldering is completed, it corrodes the substrate. Therefore, the substrate needs to be cleaned after the soldering is completed.

Furthermore, Freon solvent and water are generally used for this cleaning. However, the use of the Freon solvent is being prohibited due to the influence on the environment. Further, when water is used for washing, there is a problem that the water cannot be drained as it is because the water is contaminated by heavy metals and may cause pollution problems.

Therefore, an object of the present invention is to provide a flux and a solder paste containing this flux, which does not corrode the substrate even if the substrate is not cleaned after the soldering is completed. That is, an object of the present invention is to provide a non-cleaning type flux and solder paste.

[Means for Solving the Problems]

The present invention is a flux and an additive for a solder paste containing an organic acid or an organic acid salt as an activator, which contains, as a main component, a blocked isocyanate that reacts with the organic acid or the organic acid salt under heating for soldering. The present invention relates to the above additive.

Further, the present invention relates to a flux containing an organic acid or an organic acid salt, which further comprises a blocked isocyanate which reacts with the organic acid or the organic acid salt under heating for soldering.

In addition, the present invention relates to a solder paste containing this flux and solder particles.

The present invention will be described in detail below.

The flux and solder paste targeted by the present invention are
It contains an organic acid or an organic acid salt as an activator.

The present invention utilizes the reaction of these organic acids and organic acid salts with blocked isocyanates at relatively high temperatures.

In the present invention, "blocked isocyanate" means that the NCO of an isocyanate compound (R-NCO) is reacted with a volatile active hydrogen compound (HB) to make it inactive at room temperature, and the reactivity derived from NCO only under heating. Compound with (RNHCOB)
Is. Examples of the active hydrogen compound used as the blocking agent include alcohols, phenols, ε-caprolactam, oximes and active methylene compounds. However, it is not limited to these compounds.

Although there are a monomer and a polymer in such a blocked isocyanate, any of them can be used in the present invention.

The concentration of the blocked isocyanate in the additive of the present invention is not particularly limited, but is preferably 50 to 100% by weight, for example.

Various catalysts can be added to the additive, flux and solder paste of the present invention for the purpose of controlling the reactivity of the blocked isocyanate. Specific examples of this catalyst include N-methylmorpholine.

The addition amount of this catalyst can be determined by the type and amount of blocked isocyanate and the type of catalyst.
For example, HDI-based (hexamethylene diisocyanate) isocyanate using phenol as a blocking agent is used as the blocked isocyanate, and N is used as the catalyst.
When using methylmorpholine, it is appropriate to use 0.001 to 1 part by weight of catalyst per 100 parts by weight of blocked isocyanate.

During soldering, "organic acids and acid salts" act as activators. The activator contained in the flux has a function of removing an oxide film on the substrate when a solder paste containing the flux and the solder is applied to the metal substrate.

In the present invention, as the organic acid, monocarboxylic acids (formic acid, acetic acid, propionic acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid,
Lauric acid, myristic acid, palmitic acid, stearic acid), dicarboxylic acids (oxalic acid, malonic acid, succinic acid,
Glutaric acid, adibic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid,) oxycarboxylic acid (oxysuccinic acid, citric acid, tartaric acid, hydroxyacetic acid, salicylic acid, (m-, p-) hydroxybenzoic acid, 12-hydroxy Dodecanoic acid, 12-hydroxyisobutyric acid, (o-, m
-, P-) hydroxyphenylacetic acid, 4-hydroxyphthalic acid, 12-hydroxystearic acid) and the like.

Further, examples of the organic acid salt include salts of the above-mentioned organic acid with an amine (for example, diethylaminoethanol), ammonia and an alkali metal (for example, sodium, potassium, etc.).

Next, the flux of the present invention will be described.

The blocked isocyanate, organic acid and organic acid salt contained in the flux of the present invention are as described above.

Further, the flux of the present invention contains a solvent. The solvent is not particularly limited as long as it is a solvent capable of dissolving other components such as organic acid. However, it is preferable to use a solvent having a boiling point lower than the melting temperature of the solder during soldering, from the viewpoint that the physical properties of the solder after soldering are not impaired. Further, in the solvent having a carboxyl group or a hydroxyl group, it is preferable that the boiling point is equal to or lower than the decomposition temperature of the blocked isocyanate from the viewpoint of reacting the organic acid or the organic acid salt as the activator with the isocyanate. Examples of such a solvent include aliphatic compounds [n-hexane (bp68.7) (boiling points in parentheses below), isohexane (60 to 64), n-heptane (98.4)], esters [isopropyl acetate (89.0) , Methyl propionate (79.
7), ethyl propionate (99.1)], ketones [methyl ethyl ketone (79.6), methyl-n-propyl ketone (103.3), diethyl ketone (102.2)], alcohols [ethanol (78.3), n-propanol (97.2)] , Isopropanol (82.3), isobutanol (107.9),
Second butanol (99.5)] and the like can be exemplified.

In addition, the above-mentioned flux and solder paste additive,
In addition to the blocked isocyanate, the above solvent can be contained.

In the flux and the additive for solder paste of the present invention, the flux and the solder paste, the use amount or content of the blocked isocyanate with respect to the organic acid or the organic acid salt (or a mixture thereof) is COOH contained in the organic acid or the organic acid salt. The molar ratio of NCO groups of blocked isocyanate to groups is 1: 0.05-3, preferably 1: 3.
The range of 0.5 to 1.5 is suitable from the viewpoint of effectively preventing the corrosion of the metal substrate.

In the flux of the present invention, the content of organic products, organic acid salts, blocked isocyanates and solvents is 0.1 to 30 parts by weight of organic acid or organic acid salt, 0.1 to blocked isocyanate.
Appropriately 50 parts by weight and 20 to 99.8 parts by weight of solvent are suitable.

The flux of the present invention may contain rosin in addition to the components such as the organic acid. Various rosins can be used as the rosin. Examples thereof include maleic acid-modified rosin, maleic acid-modified rosin ester, hydrogenated rosin, disproportionated rosin, polymerized rosin, gum rosin, wood rosin, tall oil rosin and the like. Particularly, considering the corrosiveness of the solder, it is preferable to use an esterified rosin, for example, a maleic acid-modified rosin ester.

The main component of rosin is abietic acid-based compound such as abietic acid or its isomers and polymers. These abietic acid and abietic acid-based compounds do not exhibit activity at room temperature, and when heated at about 90 ° C. or higher, they dissolve and exhibit excellent activity, exhibiting the effect of removing an oxide film on a metal substrate. Therefore, it is hardly corrosive when stored at room temperature.

Therefore, in the present invention, the rosin only needs to include abietic acid and abietic acid compounds.

The content of rosin can be, for example, 10 to 10000 parts by weight based on 100 parts by weight of the organic acid or the organic acid salt.

The solder paste of the present invention further contains solder in the above flux. Here, the "solder" includes not only a tin-lead alloy generally known as solder but also a mixture of silver, bismuth, gold, iridium and the like.

The shape of the solder powder is not particularly limited. Particle size is 10 to 10
Suitable is 00 mesh, preferably 250-400 mesh.

In the solder paste of the present invention, the amount ratio of the solder and the flux is not particularly limited, for example, solder 40 ~
It is suitable that the flux is 5 to 60 parts by weight with respect to 95 parts by weight.

Hereinafter, the present invention will be described in more detail with reference to Examples.

〔Example〕

Example 1 (Flux composition) An organic acid (or organic acid salt), a rosin, an activator and a solvent were added to a production kettle equipped with a stirrer and stirred to completely dissolve each component. Next, after confirming the dissolution, an additive is added to obtain a flux composition. The blending amount of each component is shown in Table 1.

The spreadability and corrosiveness of the obtained flux composition were evaluated. Spreadability was measured according to the American standard QQ-S-571E. Corrosion was measured according to JIS-Z-3197 6.6. The results are shown in Table 3.

Additive (block type isocyanate) Orestar NP-1060PB: Mitsui Toatsu Chemicals, Inc. Epokey EPR-170: Mitsui Toatsu Chemicals, Inc. Orestar PB3537: Mitsui Toatsu Chemicals, Inc. Orestar XQ5095PB: Mitsui Toatsu Chemical Co., Ltd. Coronate 2507: Nihon Poe Urethane Industry Co., Ltd. Coronate 2513: Nihon Poe Urethane Industry Co., Ltd. Corrosion evaluation judgment Ex: Compatible flux (evaporated copper or plated copper is not corroded by flux) P: Incompatible flux A: Copper under the flux is corroded and disappears B: Under the edge of the flux If the copper in the center of the flux disappears due to corrosion C: If the copper under the center of the flux disappears, D: The area around the flux discolors due to corrosion and looks like a bulk E: The center of the flux Is discolored due to corrosion F: Edge of flux appears to be opaque dark brown Example 2 (solder paste) Yoshikawa Kako Co., Ltd., high viscosity kneader Pencer (PS-501
Type), a thixotropic agent is added to the flux composition obtained in Example 1 and completely dissolved. Next, solder powder is added to the melted flux composition, and the mixture is stirred until it becomes uniform to obtain a solder paste. The compounding amounts of the flux composition and the solder powder are shown in Table 4.

The spreadability, solder ball property and corrosiveness of the obtained solder paste were evaluated. Spreadability is American standard, QQ-
It measured according to S-571E. The solder ball property was measured according to the American standard ANSI / IPC-SP-819. Corrosion is JIS-
It was measured according to Z-3197 6.6. The results are shown in Table 5.

Solder ball property evaluation A: Preferred B: Allowable range C: No Corrosion evaluation judgment Ex: Compatible flux (evaporated copper or plated copper is not corroded by flux) P: Incompatible flux A: Copper under the flux is corroded B: When the copper under the edge of the flux is corroded and disappears C: When the copper under the center of the flux is obscured D: The area around the flux is discolored due to corrosion When it looks like a lump, E: When the center part of the flux is discolored due to corrosion F: When the edges of the flux appear as an opaque dark brown color

Claims (3)

[Claims] 1. A flux and solder paste additive containing an organic acid or an organic acid salt as an activator, comprising:
The above-mentioned additive, which contains, as a main component, a blocked isocyanate that reacts with the organic acid or the organic acid salt under heating for soldering. 2. A flux containing an organic acid or an organic acid salt as an activator, further comprising a blocked isocyanate which reacts with the organic acid or the organic acid salt under heating for soldering. . 3. A solder paste containing the flux according to claim 2 and solder particles.