JP3369196B2 - Flux composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux composition used for soldering electronic parts and the like.

[0002]

2. Description of the Related Art In soldering, a flux improves the wettability by dissolving and removing oxides on the surface of a metal substrate, preventing oxidation during heating, or reducing the surface tension of the solder.
Used for the purpose of good soldering. Flux is a composition containing a resin, a solvent, an activator, a viscosity modifier, and other additives. The flux is generally used by coating, dipping or ironing the surface of the metal substrate, but the flux may be coated or clad with the solder in advance and used in preformed solder.

As a flux composition for soldering very fine parts of electronic parts, there is cream solder kneaded with powder solder. This is often used by printing on a printed circuit board. For soldering in this case, cream solder is printed on a printed circuit board, parts are placed thereon, and hot air at 120 to 150 ° C. is passed for 1 to 3 minutes, and then 2
Complete by passing in hot air at 40 ° C for about 1 minute. For this reason, it is required that the cream solder has excellent printing characteristics and ejection characteristics and does not cause bleeding or sagging on the ejected material. Therefore, the flux composition is required to be amorphous and have an appropriate viscosity.

Printed circuit boards for electronic parts and the like have tended to become smaller and smaller in recent years, and the miniaturization of parts, the increase in mounting density, and the high degree of integration are being promoted, and the distance between electrodes of electronic materials and the distance between patterns are increasing. It is getting narrower. Therefore, in addition to the conventional non-corrosiveness, solderability, wettability, etc., there is a high demand for the flux composition in terms of ensuring high insulation and bonding strength.

In the field of electronic parts, a rosin-based flux containing abietic acid as a main component has been mainly used as a flux composition. However, in the conventional rosin-based flux, the flux residue is likely to remain after soldering, and in the cream solder, it may cause generation of solder balls, corrosion, and the like, resulting in short circuit, deterioration of reliability, and checker pin contact failure. Therefore, after soldering, cleaning with a halogen-based solvent is performed to remove the flux residue.

In the present specification, the term "reliability" means reliability with respect to reliability of soldering such as deterioration and corrosion after soldering.

[0007]

[Problems of prior art] In order to cause serious pollution problems such as destruction of the ozone layer surrounding the earth and pollution of groundwater,
The use of conventionally used freon-based and halogen-based solvents is limited, and the cleaning with water and the alternative cleaning liquid is being changed to non-cleaning. However, in the case of no cleaning, the presence of flux residue causes a decrease in reliability and a checker pin contact failure. In order to ensure high reliability, weakly activated rosin, so-called RAM type is generally used. Although this type of flux is less likely to corrode, it is easy for checker pin contacts to fail due to flux residue. However, if the rosin is completely removed from the flux composition in order to reduce the residue, the solderability is remarkably deteriorated and it becomes unusable in actual use. Therefore, there is a demand for a low-residue flux composition that can reduce the amount of rosin while maintaining the solderability, non-corrosiveness, and wettability of the flux and that can realize high reliability without washing.

In order to prevent the checker pin contact failure, it is only necessary to reduce the residual material after soldering, as long as the flux composition evaporates and volatilizes during soldering. On the other hand, the flux composition must coexist as an acid supply source for solder until the end of soldering.
Therefore, a flux composition is desired that quickly evaporates by heating at the final stage of soldering.

Since it evaporates quickly, it must be of high purity in order to obtain a constant evaporation temperature, and it is preferably amorphous in order to ensure the characteristics as a cream solder. However, an amorphous substance generally has a wide molecular weight distribution and a wide boiling point. The appearance of substances that resolve this contradiction was awaited.

[0010]

As a result of the research conducted by the present inventors, alkenylsuccinic acid was found as a substance having the above-mentioned properties. That is, the present invention relates to a soldering flux composition containing a resin, a solvent and an activator and containing alkenylsuccinic acid having a total carbon number of 12 to 20.

The alkenylsuccinic acid used in the soldering flux composition of the present invention is a yellow highly viscous liquid having an acid value of about 400, and as shown by its TG curve in FIG.
Evaporates quickly at temperatures near ℃. This temperature is Sn
Since the temperature is higher than the final reflow temperature in the reflow soldering of the Pb eutectic cream solder, the flux is not completely evaporated until the final stage, and the soldering is completed. Further, compared with the TG curve of rosin in FIG. 1, since the evaporation rate is higher, the flux residue after soldering can be reduced as compared with the conventional product. Also, with high-purity alkenyl succinic acid, the viscosity rapidly decreases due to heat and the solder particles melt,
Since secondary agglomeration occurs quickly, formation of solder balls, which tend to cause a short circuit, can be prevented, and good insulation can be obtained.

Further, alkenyl succinic acid has tackiness by itself, and when mixed with other resin, it plasticizes the other resin, so that when used as a flux composition for cream solder, the tackiness retention time becomes long. . Further, since the compatibility with the solvent and rosin is good, it is possible to supply cream solder of stable quality. The alkenylsuccinic acid of the present invention preferably has the following chemical formula 1:

[0013]

[Chemical 1]

[In the formula, R ₁ and R ₂ each independently represent the same or different hydrogen, or a saturated or unsaturated aliphatic hydrocarbon group which may have a side chain. ] Is represented. As a whole, those having 12 to 20 carbon atoms are preferable, and those having R ₁ + R ₂ having 5 to 13 carbon atoms are preferable. Particularly preferably, R ₁ has 7 to 11 carbon atoms, and the optimum compound is a compound having 16 total carbon atoms in which R ₁ is 9 carbon atoms and R ₂ is hydrogen.

The alkenylsuccinic acid used in the present invention preferably has a high purity, and the alkenylsuccinic acid having a single carbon number is 80% or more, more preferably 90% or more. Although the olefin used as the raw material is free, for example, when a tetramer of propylene is used as the raw material, a preferable alkenylsuccinic acid which is amorphous and has high purity can be obtained because it has a side chain.

The alkenyl succinic acid of the present invention can be used not only as a cream solder but also as a main component or an additive of a flux for solder containing solder, a preform solder, a liquid flux, and a water-soluble cream solder.

The blending amount of alkenylsuccinic acid used in the present invention is appropriately selected depending on the kind of flux and the use. In the case of the flux for cream solder, it is 0.5 to 80% by weight, more preferably 5 to 30% by weight, based on the total amount of the flux. In the case of the flux for solder containing a varnish, it can be arbitrarily blended in the range of 0 to 100% by weight of the total flux in place of the conventional rosin, but more preferably 1 to 80% by weight.
Is. When it is added to the liquid flux, it can be optionally added at a concentration of 1 to 80% by weight of the total amount of flux, more preferably 2 to 40% by weight. The flux for preform solder is 0 to 100% by weight, more preferably 1 to 80% by weight, based on the total amount of flux.

The resin and activator compounded in the flux composition of the present invention may be the general components commonly used in conventional soldering fluxes. The amount of ingredients used is
It is appropriately selected based on the application.

Examples of the resin include rosin, disproportionated rosin, hydrogenated rosin, maleated rosin, polymerized rosin, etc., and the blending amount thereof in the case of flux for cream solder is 0.5 to 80% by weight of the total flux. %, More preferably 5 to 40% by weight. In the case of the flux for solder containing a tar, it is 1 to 100% by weight, more preferably 30 to 100% by weight. 1 for liquid flux
˜90% by weight, more preferably 2 to 40% by weight.
In the case of the flux for preform solder, it is 1 to 100% by weight, more preferably 2 to 50% by weight.

Examples of the activator include hydrogen halide salts of nitrogen-containing bases, organic acid salts, organic acids, amino acids and the like. In the case of the flux for cream solder, the blending amount is 0 to 5% by weight, and more preferably 0.01 to 3% by weight based on the total weight of the flux. In the case of flux containing solder, 0 to 5% by weight, more preferably 0.01 to 3% by weight
% By weight. In the case of liquid flux, 0-3% by weight,
It is more preferably 0.05 to 3% by weight. In the case of the flux for preform solder, it is 0 to 5% by weight, more preferably 0.05 to 3% by weight.

When the flux composition of the present invention is prepared as a flux for preform solder, a liquid flux, or a flux for cream solder, a solvent or a viscosity modifier may be used in the usual manner. It is appropriately selected based on the component and the application. Examples of the solvent include organic solvents, alcohols, aliphatic and aromatic hydrocarbon analogs, terpenes, esters, ethers, glycol ethers, and the like. It is 5 to 80% by weight, more preferably 10 to 70% by weight. In the case of liquid flux, 1 to 90% by weight, more preferably 2 to 6%
It is 0% by weight. In the case of the flux for preform solder, it is 0 to 40% by weight, more preferably 0 to 20% by weight. As the viscosity modifier, alkenyl succinic acid itself is considered as a kind of viscosity modifier, but waxes such as hydrogenated castor oil, ultrafine silica particles, amides, etc. are also exemplified.

Further, the flux composition of the present invention contains an antioxidant (for example, BHT), a plasticizer (for example, dioctyl phthalate), an antifoaming agent (for example, a silicon-based antifoaming agent), and the like.
You may mix | blend a conventional additive suitably.

[0023]

The present invention will be described with reference to the following examples. With respect to Examples 1 to 6 and Comparative Examples 1 to 6, fluxes are prepared according to the formulations shown in Table 1. Powder solder (Sn / Pb = 63/3) for Examples 1 to 3 and 6 and Comparative Examples 1 to 3
7; 250 to 400 mesh (amorphous)) and the above flux were kneaded at a flux content of 10% by weight. Example 4 and Comparative Example 4 are fluxes for solder containing solder, and Example 5 and Comparative Example 5 are liquid fluxes.

[0024]

[Table 1]

* 1 Rosin ester surfactant (Arakawa Chemical) * 2 Rosin ester surfactant (Arakawa Chemical) * 3 Amide surfactant (Lion Akzo) * 4 1: 2 type monoethanolamide (Kawa Lab) Fine chemicals) * 5 PO / EO block polymer (NOF Corporation) * 6 Diethylene glycol mono-2-ethylhexyl ether * 7 N, N'-ethylenebis-12-hydroxystearic acid amide

The solder using the above-mentioned flux is treated with viscosity stability, printability, adhesiveness, solderability, corrosiveness, insulation,
The amount of residue after reflow and the checker pin test were evaluated. The evaluation method is as follows. Viscosity stability : Measured by Brookfield viscometer for viscosity when left at room temperature for 1 month. A: Almost no change, B: Usable change,
C: change there printability degree unusable: pitch pattern 0.65 mm, opening 0.3 × 3.0 m
Clearness to m, t = 0.2mm A: Excellent, B: Usable range, C: Unusable adhesiveness : Mountable time of chip parts after cream solder application A: 12 hours possible, B: 6 hours Possible, C: Not possible for 6 hours Solderability : Soldering to oxidized copper plate A: Excellent, B: Usable, C: Poor corrosiveness : JIS Z 3197 Copper plate corrosion test A: Pass, B: Fail Insulation : JIS Z 3197 Insulation resistance test A: 10 ¹¹ Ω or more, B: 10 ⁹ Ω or more and less than 10 ¹¹ , C:
Less than 10 ⁹ Amount of residue after reflow : Amount of flux remaining as residue A: less than 40%, B: 40% or more and less than 60%, C: 60
However, for the liquid flux (Example 5 and Comparative Example 5), A: less than 10%, B: 10% or more and less than 30%,
C: 30% or more Checker pin test : Conductivity when the checker pin is applied to the soldered part φ1.2 mm with a force of 20 g A: 90% or more, B: 70% or more and less than 90%, C: 70
The results of less than% are shown in Table 2.

[0027]

[Table 2]

[0028]

By adding the alkenylsuccinic acid of the present invention, the viscoelasticity of the flux composition can be freely controlled, and while maintaining good solderability and high reliability, the amount of residue is reduced compared with the conventional product, Enables soldering that shows the contactability of checker pins.

[Brief description of drawings]

Fig. 1 TG curve of rosin

FIG. 2 TG curve of alkenylsuccinic acid having 16 total carbon atoms

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koji Kojima, 3-8-10 Mitsuyanaka, Yodogawa-ku, Osaka City, Osaka Prefecture Nihongenma Co., Ltd. (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 35 / 363

Claims (3)

(57) [Claims] 1. A flux composition containing a resin and an activator, and containing alkenylsuccinic acid having a total carbon number of 12 to 20. 2. The flux composition according to claim 1, wherein the alkenylsuccinic acid contains at least 80% by weight of components having the same carbon number. 3. The flux composition according to claim 1, wherein the alkenylsuccinic acid has 16 carbon atoms in total.