JPH0454555B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to cream solder. Conventionally, cream solder is made by preparing a cream solder flux made by dissolving a base resin, such as a polymerized rosin, an activator (such as an amine hydrohalide), a viscosity modifier, a corrosion inhibitor, and an antioxidant in a solvent, and then aging it. After cooling, solder powder is added and kneaded. Another method is to prepare a flux base in advance by dissolving the base resin and activator in a suitable solvent, and then add a suitable solvent or dissolved thickener (for example, hydrogenated castor oil, synthetic wax polyamide) to the flux base. is added to adjust the flux viscosity, and after aging and cooling, solder powder is added and kneaded. Still another method is known, in which an inorganic powder such as silica, bentonite, etc. is dispersed and mixed in the flux base, and solder powder is added thereto to produce cream solder. In the above method, the viscoelastic properties under high shear force are insufficient, and if the viscosity is lowered to increase fluidity in order to improve print ejection properties, the cream solder bleeds or drips after printing ejection. Therefore, it is unsatisfactory when used in precision electronic parts, etc. In particular, when hardened castor oil or waxes are precipitated as a gel, the gel structure is crushed by printing or ejection, so the viscoelasticity changes greatly during use. On the other hand, if a large amount of hydrogenated castor oil or wax is added for the purpose of increasing the thixotropic properties of cream solder to prevent bleeding or dripping after printing, the viscoelastic properties will improve, but other problems will occur. That is, depending on the type of thickener used, these thickening components may crystallize during manufacture and storage and grow into large crystal particles, causing trouble during use. Further, many thickeners do not contribute to improving soldering properties, such as soldering properties and cleanability, but rather cause deterioration of soldering properties when used in large amounts. In addition, in the method of using inorganic fine powder as a viscosity modifier, it inhibits the wetting of the solder to the metal substrate during soldering and the fusion of molten solder particles with each other.
This may cause solder balls to form. Furthermore, the viscosity adjusting effect is weak, and in order to obtain a sufficient effect as a thickener, it is necessary to use a large amount, which leads to the formation of more and more solder balls. Therefore, inorganic viscosity modifiers are not substantially used. The present invention improves the above-mentioned drawbacks of the prior art and provides a cream solder that has excellent viscoelastic properties under high shear force and is particularly suitable for soldering precision electronic components. That is, the present invention has a softening point or melting point of 55 to 180.
Cream solder containing 0.5 to 15% by weight of the total amount of cream solder, fine particles selected from rosin-based thermoplastic resin with a particle size of 5 to 150 μm,
and its manufacturing method. The rosin-based thermoplastic resin that can be used in the present invention is natural rosin, hydrogenated rosin, disproportionated rosin or a mixture. It is particularly preferable that these rosin-based resins be made highly purified by distillation or the like, or those made by further crystallization treatment. Although rosin contains various isomers, Chinese gum rosin has a high content of abietic acid and has few impurities such as sulfur and metal salts that deteriorate solderability, and shows good results. Comparing natural rosin, disproportionated rosin, and hydrogenated rosin, natural rosin is susceptible to air oxidation, but disproportionated rosin and hydrogenated rosin are stable, so the flux after joining using cream solder is Good residue cleaning properties. Comparing disproportionated rosin and hydrogenated rosin, disproportionated rosin tends to crystallize, but crystallized resin particles are stable. Since rosins purified by distillation or the like are free of impurities such as low volatile components and polymers and are easily crystallized, fine powder added to cream solder is particularly effective. The softening point of rosin is 60 to 80℃, but by crystallization, the melting point of rosin can be increased to 150 to 80℃.
The temperature rises to 180℃. This improves the temperature stability of the cream solder containing fine particles obtained by the crystallization treatment. Therefore, cream solder containing fine particles obtained by further crystallizing a resin obtained by distilling a disproportionated product of purified Chinese rosin exhibits excellent properties with good viscoelastic properties and thermal stability. Ta. These resin particles are stored at the normal storage temperature of cream solder, e.g.
Use a material that does not substantially dissolve in cream solder at ~30°C. Although "substantially" does not necessarily have a strict meaning, it does mean that it does not dissolve in the cream solder and affect the viscoelastic properties, at least at the cream solder storage temperature. Generally, it is appropriate to use cream solder that does not separate the metal powder and flux when stored overnight at 40°C or below. The rosin-based thermoplastic resin fine particles may be swollen by the solvent in the flux during the manufacturing process and aging, but the particle size is particularly suitable for use in cream solder at 200 μm or less, preferably 80 μm. The softening point of the fine particles is 55-180℃, particularly preferably
The temperature is 150-180℃. The rosin thermoplastic resin particles are 2 to 70% by weight of the cream solder flux.
More preferably, it is used in an amount of 15 to 50% by weight. This corresponds to 0.5 to 15% by weight, particularly 1 to 12% by weight of the total amount of cream solder. Other thermoplastic resins that can be used in addition to the rosin thermoplastic resin of the present invention include esters of higher fatty acids or higher aliphatic alcohols that have been conventionally used as thickeners for cream solders; coconut oil, beef tallow; Hydrogenated oils such as castor oil and rapeseed oil; Waxes such as wax wax, beeswax, yellowtail wax, and carnauba wax; stearic acid amide,
Amides such as ethylene bisstearic acid amide and N,N'-distearyl adipic acid amide; free fatty acids, adipic acid, sebacic acid, myristic acid, palmitic acid, stearic acid, behenic acid,
Montanic acid, other natural and animal and vegetable oil fatty acids, aliphatic or aromatic fatty acids such as benzoic acid, etc. may also be used. The blended amount of thermoplastic resins other than rosin-based thermoplastic resins is 15% of the total amount of cream solder.
It is not more than 0.3% by weight, more preferably 0.3 to 8% by weight. The cream solder of the present invention includes a base resin (e.g., polymerized rosin, natural rosin, hydrogenated rosin, maleated rosin, disproportionated rosin, etc.) commonly used in cream solder, an activator (e.g., a hydrogen halide salt of a nitrogen-containing base), an organic Acid salts, organic acids, amino acids, etc., in a suitable solvent (e.g. diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, triethylene glycol, diethylene glycol, tripropylene). glycol, dipropylene glycol, hexylene glycol, ethylene glycol, propylene glycol, butanediol and their esters (e.g. diethylene glycol monobutyl ether acetate),
Plasticizers, such as phosphate esters (e.g. tricresyl ester), acid phosphate esters (e.g. octyl acid phosphate, dibutyl phosphate), phthalate esters (e.g. dibutyl phthalate), dibasic acid esters (e.g. diisobutyl Adipate) etc. to prepare a flux base, and after cooling, add the above-mentioned rosin-based thermoplastic resin fine particles as they are or dispersed in a suitable dispersion medium to a flux base at a suitable temperature, e.g. 5 to 40°C.
Preferably, the flux for cream solder is prepared by sufficiently kneading at 10 DEG C. to 30 DEG C., and then solder powder is added thereto and mixed. Flux bases can be prepared by dissolving the base resin and activator in solution at the same time, or by simply dissolving the base resin in a solvent under heat and adding the activator after cooling. After the resin fine particles are dispersed in a dispersion medium containing an activator, they may be added and kneaded to the flux base containing the base resin and a solvent. Additionally, additives commonly added to base resins, such as hydrogenated castor oil, organic acids, antioxidants,
Corrosion inhibitors and the like may be added as appropriate. As the base resin for the flux, resins that are difficult to crystallize such as polymerized rosin, phenol-modified rosin, and maleated rosin are suitable, and natural rosin, hydrogenated rosin, and disproportionated rosin, especially those that are purified or crystallized, are suitable. It is undesirable to add a large amount of such a substance because crystals are likely to precipitate during the cooling process after preparing the flux base, and this may grow during storage and cause trouble during use. The amounts of these base resins, activators, additives and solvents may be the same as in the case of cream solder fluxes commonly used in the past. However, when natural rosin, hydrogenated rosin or disproportionated rosin is used as the rosin-based thermoplastic resin fine particles, the amount of these base resins can be reduced. The dispersion medium for rosin-based thermoplastic resin particles may be appropriately selected from the above-mentioned cream solder solvents, but it must be one that does not substantially dissolve the particles during the cream solder manufacturing process and storage temperature. Therefore, this solvent should be selected appropriately. Generally, it is preferable to use the same solvent as that used for the flux base from the viewpoint of the process. The flux base and thermoplastic resin fine particles are kneaded using a homomixer, triple roll, dissolver, etc.
It is appropriate to carry out the kneading at 40°C, more preferably 10 to 30°C, and kneading the obtained flux and solder powder at 5 to 20°C. The crystallization method for rosin thermoplastic resin is as follows:
There is a method in which the molten resin is maintained at 120° C. to 150° C. and crystallized, and a method in which the resin is dissolved or mixed in a suitable solvent and crystallized or precipitated in the solvent system. Although it is possible to crystallize using either method, the method performed in a liquid contains a high concentration of unprecipitated or uncrystallized resin in the solvent solution. Cream solder has lower storage stability than cream solder using fine particles obtained by melt crystallization because crystals grow in the cream solder during storage. There are two methods for producing cream solder containing fine particles of rosin-based thermoplastic resin: a powder addition method in which fine resin powder is added to base flux or cream solder, and a method in which the fine resin particles that are desired to function are dispersed in a dispersion medium. A paste addition method in which fine particle paste is added to base flux or cream solder. After heating and dissolving the base resin, activator, solvent, etc., the resin is precipitated and crystallized by aging and cooling.
There is an in-liquid production method that miniaturizes and disperses particles. Among the above manufacturing methods, the paste addition method is superior in terms of manufacturing method and cream solder properties. The cream solder of the present invention has excellent viscoelastic properties even under high shearing forces, and does not cause poor removal from the printing plate or blurring even at high printing speeds.
Also, no sagging or bleeding occurs after printing. Furthermore, even when stored at relatively high temperatures, the flux and solder powder do not separate. Furthermore, when a high melting point material (for example, 150 to 180 DEG C.) is used as the resin fine particles, thermal stability is high, and therefore there is a significant advantage in reflow soldering. In other words, in reflow soldering, cream solder is discharged and printed onto a board, the specified electronic components are mounted, preheated at 150°C for about 2 minutes to remove volatile components in the cream solder, and then reflow soldering is performed. Perform heating. In conventional cream solder, the viscosity adjustment effect of the viscosity modifier is limited to about 35°C, and therefore thermal sagging occurs during the preheating stage of reflow soldering, which limits precision soldering. In the cream solder of the present invention, thermoplastic resin fine particles exist in the system as independent particles, so if resin fine particles whose softening point is higher than the reflow preheating temperature are used, bleeding during reflow soldering may occur. More precise soldering is possible without sagging. Furthermore, when using distillation-refined natural rosin, hydrogenated rosin, disproportionated rosin, etc. as the resin particles of the cream solder of the present invention, and crystallized products of these, the melting points are approximately 170°C, 180°C, and 175°C, respectively. Therefore, it is suitable for the above-mentioned reflow soldering. Furthermore, since it itself has an acid value and performs the same function as the base resin in flux (behavior as a flux carrier), it does not have the disadvantages caused by the addition of conventional thickeners. Therefore, a large amount of these can be blended, and the range of viscosity adjustment based on this can be widened.
Furthermore, when using rosin-based thermoplastic resin fine particles, the solderability and cleanability are very high, and the residue after soldering is easily washed away with a Freon-based solvent. The present invention will be explained below with reference to Examples. Example 1 20g of polymerized rosin and 34g of dipropylene glycol
was added to the solution, heated and dissolved at 120°C, and 1 g of diethylamine HBr was added thereto to prepare a flux base.
Separately crystallized disproportionated rosin fine powder (15-44μm) 70g
was added to 30 g of dipropylene glycol and kneaded and dispersed. 45 g of this was taken, added to 55 g of flux base cooled to 20° C., mixed and kneaded, and further 670 g of solder powder (325 mesh or more) was added and sufficiently kneaded to obtain cream solder. Example 2 24g of polymerized rosin, 27g of diethylene glycol monobutyl ether, butylated hydroxytoluene
0.5g, benzotriazole 0.5g, silicone defoamer
A flux base was prepared at 120° C. by adding 0.5 g of malic acid, 0.5 g of maleic acid, 1 g of hydrogenated castor oil, and 1 g of diethylamine HBr. Separately crystallized disproportionated rosin fine powder (15
~44μm) was added to 30g of dipropylene glycol and kneaded and dispersed. 45g of this was added to 55g of flux base cooled to 20°C, mixed and kneaded, and 670g of solder powder (325mesh or more) was added to obtain cream solder. Example 3 20g of polymerized rosin, 47g of propylene glycol monophenyl ether, butyl hydroxytoluene
0.5g, benzotriazole 0.5g, silicone defoamer
A flux base was prepared at 120° C. by adding 0.5 g, 0.5 g of maleic acid, 1 g of hydrogenated castor oil, and 1 g of diethylamine HBr. Flux base cooled to 20℃
Add 29g of crystallized disproportionated rosin fine powder to 71g.3
After dispersing with this roll, 670 g of solder powder was further added and thoroughly kneaded to obtain cream solder. Example 4 Tripropylene glycol to 20g of polymerized rosin
31g, butylated hydroxytoluene 0.5g, benzotriazole 0.5g, silicone defoamer 0.5g, maleic acid 0.5g, hydrogenated castor oil 1g, diethylamine
A flux base was prepared by adding 1 g of HBr. Separately crystallize 70g of disproportionated rosin fine powder (15-44μm) and 30g of propylene glycol monophenyl ether
and kneaded and dispersed. 45g of this was added to 55g of flux base, mixed and dispersed, and 670g of solder powder was added to obtain cream solder. Example 5 Polymerized rosin 32g, benzoic acid 3g, hydrogenated castor oil 2g
and 1 g of diethylamine HBr were dissolved in a mixed solvent of 12 g of diethylene glycol monobutyl ether acetate and 18 g of diisobutyl adipate,
A flux base was prepared. Separately, 80 g of crystallized disproportionated rosin fine powder was added to 20 g of diethylene glycol monobutyl ether acetate, and 32 g of the dispersed fine particle compound was added to the flux base to prepare a cream solder flux.
670 g of solder powder was added to cream solder flux to obtain cream solder. Example 6 Polymerized rosin 32g, benzoic acid 3g, hydrogenated castor oil 2g
A flux base was prepared by dissolving 1 g of diethylamine HBr in 18 g of a mixed solvent of 12 g of diethylene glycol monobutyl ether acetate and diisobutyl adipate. Separately, crystallize 80g of disproportionated rosin fine powder into diisobutyl adipate.
Fine particle compound added to 20g and dispersed
A cream solder flux was prepared by adding 32g to the flux base. 670 g of solder powder was added to cream solder flux to obtain cream solder. Example 7 20g of polymerized rosin and 34g of dipropylene glycol
was added to the solution, heated and dissolved at 120°C, and 1 g of diethylamine HBr was added thereto to prepare a flux base.
Separately, 70 g of crystallized hydrogenated rosin fine powder (15 to 44 μm) was added to 30 g of dipropylene glycol, and the mixture was kneaded and dispersed. 45 g of this was taken, added to 55 g of flux base cooled to 20° C., mixed and kneaded, and further 670 g of solder powder (325 mesh or more) was added and sufficiently kneaded to obtain cream solder. Example 8 24g of polymerized rosin, 27g of diethylene glycol monobutyl ether, butylated hydroxytoluene
0.5g, benzotriazole 0.5g, silicone defoamer
A flux base was prepared at 120° C. by adding 0.5 g of malic acid, 0.5 g of maleic acid, 1 g of hydrogenated castor oil, and 1 g of diethylamine HBr. Separately crystallized distilled hydrogenated rosin fine powder (15~44μm) 70g dipropylene glycol 30g
and kneaded and dispersed. Add 45g of this to 55g of flux base cooled to 20℃, mix,
Knead and add 670g of solder powder (325mesh or more)
was added to obtain cream solder. Example 9 20g of polymerized rosin, 47g of propylene glycol monophenyl ether, butylated hydroxytoluene
0.5g, benzotriazole 0.5g, silicone defoamer
A flux base was prepared at 120° C. by adding 0.5 g, 0.5 g of maleic acid, 1 g of hydrogenated castor oil, and 1 g of diethylamine HBr. Flux base cooled to 20℃
Add 29g of crystallized distilled medium-sized gum rosin fine powder to 71g, disperse with three rolls, and then add solder powder.
670g was added and thoroughly kneaded to obtain cream solder. Example 10 Tripropylene glycol to 20g of polymerized rosin
31g, butylated hydroxytoluene 0.5g, benzotriazole 0.5g, silicone defoamer 0.5g, maleic acid 0.5g, hydrogenated castor oil 1g, diethylamine
A flux base was prepared by adding 1 g of HBr. Separately, 70 g of distilled disproportionated rosin is dissolved in 70 g of diisobutyl adipate by heating, and the solution is cooled. The resin precipitates over time, so after ten minutes of precipitation, it is passed through three rolls to form a compound. Particulate Comb Pound
45g of solder powder was added to 55g of flux base, mixed and dispersed, and further 670g of solder powder was added to obtain cream solder. Comparative example 1 47g of polymerized rosin, 49g of dipropylene glycol,
Butylated hydroxytoluene 0.5g, benzotriazole 0.5g, silicone antifoaming agent 0.5g, maleic acid 0.5g,
A flux was prepared by adding 1 g of hydrogenated castor oil and 1 g of diethylamine HBr, and 670 g of solder powder was added and thoroughly kneaded to obtain cream solder. Comparative Example 2 43g of polymerized rosin and 50g of dipropylene glycol,
Butylated hydroxytoluene 0.5g, benzotriazole 0.5g, silicone antifoaming agent 0.5g, maleic acid 0.5g,
Mix 4g hydrogenated castor oil with 1g diethylamine HBr,
A flux was prepared by heating and melting at 120°C. After the flux was left to cool and mature, 670 g of solder powder was added and thoroughly kneaded to obtain cream solder. Comparative Example 3 43g of polymerized rosin and 50g of dipropylene glycol,
Butylated hydroxytoluene 0.5g, benzotriazole 0.5g, silicone antifoaming agent 0.5g, maleic acid 0.5g,
Mix 4g of finely powdered silica and 1g of diethylamine HBr,
The mixture was heated and melted to prepare a flux, and 670 g of solder powder was added and thoroughly kneaded to obtain cream solder. Note that although the above example uses a eutectic solder of Sn/Pb:63/37, the composition is not limited to the above, and it is preferable to select and use a commercially available soft solder with a suitable composition. The printing characteristics of the screen printing machine were evaluated in terms of the ability to remove from the printing plate, sagging after printing, bleeding, etc.
The cream solder sag during preheating was evaluated. Leave the cream solder at 40℃ for 12 hours,
The separation of flux and metal powder was evaluated. The solderability and the amount of solder balls generated were evaluated. The cleaning performance was evaluated using a fluorine-based cleaning agent. The above evaluation results are shown in Table-1.

[Table] 〓Evaluation〓 ○: Good, △: Fair, ×: Not good

Claims (1)

[Claims] 1. Softening point or melting point is 55°C to 180°C, particle size 5
Cream solder containing ~150μm rosin thermoplastic resin particles. 2. The cream solder according to item 1, wherein fine particles of rosin-based thermoplastic resin are precipitated in a flux solvent system. 3. The cream solder according to item 1, which contains fine particles by adding fine powder of a rosin-based thermoplastic resin. 4. The cream solder according to item 1, which contains fine rosin thermoplastic resin particles dispersed in a dispersant. 5. Cream solder according to item 1, wherein the rosin-based thermoplastic resin is rosin. 6. The cream solder according to item 1, wherein the rosin-based thermoplastic resin is selected from tall oil rosin, oil rosin, gum rosin, or derivatives thereof. 7. The cream solder according to item 6, wherein the rosin derivative is selected from hydrogenated rosin or disproportionated rosin. 8. The cream solder according to item 1, wherein the fine particles of rosin-based thermoplastic resin are substantially purified into a single component. 9. The cream solder according to item 1, wherein the rosin-based thermoplastic resin fine particles are selected from tall oil rosin, oil rosin, gum rosin, or distillation-purified products of hydrogenated or disproportionated products thereof. 10 The melting point of fine particles of rosin thermoplastic resin is
1. The cream solder according to item 1, which has a temperature of 150 to 180°C. 11. The cream solder according to item 1, wherein fine particles of a rosin thermoplastic resin are crystallized. 12. The cream solder according to item 1, wherein the fine particles of rosin-based thermoplastic resin are crystallized from a solution. 13. The cream solder according to item 1, wherein fine particles of a rosin-based thermoplastic resin are crystallized from a molten resin system. 14. The cream solder according to item 1, wherein the rosin-based thermoplastic resin fine particles are pulverized in a gas phase or in a vacuum. 15. The cream solder according to item 1, wherein the rosin-based thermoplastic resin fine particles are pulverized in a liquid phase. 16 Add thermoplastic resin fine particles to the flux base obtained by adding and dissolving additives and base resin in a solvent, grinding, kneading, and dispersing to prepare flux for cream solder, then add and mix solder powder. Cream solder manufacturing method. 17. The production method according to item 16, wherein the base resin is selected from resins that are difficult to crystallize, such as polymerized rosin, phenol-modified rosin, and maleated rosin. 18 The particle size of the fine particles of rosin thermoplastic resin is 5
17. The manufacturing method according to item 16, wherein the particle size is 150 μm and the melting point and softening point are 55 to 180°C. 19. The manufacturing method according to item 16, wherein the rosin thermoplastic resin fine particles are added as a powder. 20. The manufacturing method according to item 16, wherein the rosin-based thermoplastic resin fine particles are dispersed in a dispersion medium and added. 21. The production method according to item 16, wherein the addition, crushing, kneading, and dispersion of the flux base and rosin-based thermoplastic resin particles are carried out at 5 to 40°C. 22 The first stage where cream solder flux and solder powder are added, crushed, kneaded, and dispersed at 5 to 40°C.
The manufacturing method described in Section 6. 23 Add additives and rosin-based thermoplastic resin fine particles to the flux base obtained by dissolving the base resin in a solvent, grind, knead, and disperse to prepare flux for cream solder, then add and mix solder powder. Cream solder manufacturing method. 24. The production method according to item 23, wherein the base resin is selected from resins that are difficult to crystallize, such as polymerized rosin, phenol-modified rosin, and maleated rosin. 25 The particle size of the fine particles of rosin thermoplastic resin is 5
24. The method according to item 23, wherein the particle size is 15 μm and the melting point and softening point are 55 to 180°C. 26. The manufacturing method according to item 23, wherein the rosin thermoplastic resin particles are dispersed in a dispersion medium and added. 27. The manufacturing method according to item 23, wherein the rosin thermoplastic resin fine particles are added as a powder. 28. The production method according to item 23, wherein the addition, pulverization, kneading, and dispersion of the flux base and the rosin-based thermoplastic resin particles are carried out at 5 to 40°C. 29 The second stage where cream solder flux and solder powder are added, crushed, kneaded, and dispersed at 5 to 40°C.
The manufacturing method described in Section 3.