KR102069276B1 - Electronic parts soldering cream and method thereof - Google Patents

Abstract

The present invention relates to solder cream for electronic component and a manufacturing method thereof. The solder cream for electronic component is manufactured by mixing solder alloy powder consisting of the remainder of Bi, Cu, Co, and Sn and other unavoidable impurities and flux. In addition, the present invention increase the work efficiency since the solder alloy powder and flux are mixed and a process is simplified through the manufacturing of the cream.

Description

Solder cream for electronic component and manufacturing method {ELECTRONIC PARTS SOLDERING CREAM AND METHOD THEREOF}

The present invention relates to a solder cream for an electronic component and a method of manufacturing the same, comprising an alloy composed of bismuth, copper, cobalt, cobalt, tin residues, and other unavoidable impurities. The present invention relates to a solder cream for an electronic component containing a flux and a method of manufacturing the same.

In general, in order to connect a component to a substrate such as an electric or electronic device, a soldering operation is used in which a solder, which is an alloy of tin and lead, is melted and rubbed into a joint, whereby the solder melts into a gap in the joint.

However, the soldering process produces smoke, which is caused by the vaporization of the flux.

Flux mainly contains small amounts of chlorine, such as rosin, zinc chloride, and ammonium chloride, and very few dioxins are generated from the soldering smoke.

In addition, as the flux is vaporized, lead included in the solder is also released into the air.

Lead in the air can travel around the body through the lungs through the lungs, accumulate in bones and teeth, and only a small amount is excreted in the urine and feces when a person breathes.

Lead accumulated in the body causes diseases such as anemia, kidney failure, nervous system changes, and cardiovascular disease.

In addition, lead causes environmental problems that pollute not only the human body but also soil, water, and the like.

For this reason, researches on lead-free solders containing no lead have been actively conducted in recent years.

As a background art of the present invention, Korean Unexamined Patent Publication No. 10-2018-0002606 (hereinafter referred to as Document 1), Japanese Unexamined Patent Publication No. 2018-43264 (hereinafter referred to as Document 2), Republic of Korea Patent Publication No. 10-1538293 (Hereinafter, Document 3) and Japanese Patent No. 6060199 (hereinafter, Document 4).

Document 1 is a paste used for electronic and mechanical parts by mixing a first alloy having a solidus temperature of more than 260 ° C and a second alloy and a flux having a solidus temperature of less than 250 ° C with a mixed alloy solder paste.

The paste of Document 1 is used by mixing alloys having different temperatures. However, since the paste is melted in the range of 230 to 260 ° C, if the heat resistance temperature of the component is exceeded at the time of mounting the substrate, the component may be damaged.

In addition, the paste uses a Sn-Ag-X-based alloy for the second alloy, and Ag forms Sn ₃ Ag in the form of a rough and large plate by variables such as long reaction time and slow cooling rate.

Ag ₃ Sn can be a site of crack generation and propagation, and in severe cases, it may squeeze into the appearance of the joint and cause appearance defects.

Document 2 is a solder alloy that has excellent wettability to prevent solder defects from solder alloys, solder balls, and joints, and has high joint joint strength after soldering, thereby preventing breakage of the bonding interface or suppressing the occurrence of electro migration. .

The solder alloy of Document 2 improves the strength and current density by adding Fe and P to Sn-Bi-Cu-Ni-Ge-Co-based alloys to flow a current having a high current density, but has a problem that it can only be used for electronic components. have.

Document 3 is a paste containing a Sn-Ag-Cu-based solder alloy as a solder alloy, a solder paste, and an electronic circuit board.

In the paste of Document 3, weak Cu ₆ Sn ₅ is formed in the vibration fatigue, and cracks are generated at the solder interface, and thus thermal fatigue cracks are simultaneously generated.

When the paste is applied to a semiconductor chip, cracks are generated along the chip plating layer where the chip and the solder meet each other, thereby lowering a production rate due to chip damage.

Document 4 is a solder paste composed of an alloy and a flux composed of Sn-Ag-Cu-Bi-Sb-In-Ni based on a solder alloy, a solder paste and an electronic circuit board.

As the solder paste of Document 4 uses expensive Ag, Cu, In, and Ni, the raw material price increases, and this also causes Ag ₃ Sn to form, causing a problem of component damage.

Background literature

(Document 1) Republic of Korea Patent Publication No. 10-2018-0002606

(Document 2) Japanese Unexamined Patent Publication No. 2018-43264

(Document 3) Republic of Korea Patent Publication No. 10-1538293

(Document 4) Japanese Patent Publication No. 6060199

The present invention is to solve the problems of the background art, to provide a solder cream for an electronic component and a method for manufacturing the same in order to simplify the process and increase the work efficiency by mixing the alloy powder and flux by creaming.

The solder cream for an electronic component of the present invention has a low thermal shock even at a low temperature even when mounting components such as semiconductors, diodes, and chips on a printed circuit board (PCB) using surface mount technology (SMT), and selects components and substrates. I want to use

In addition, the present invention is to provide a solder cream for an electronic component excellent in adhesive strength without using expensive Ag.

Furthermore, the present invention seeks to reduce the occurrence of defects such as whiskers, voids, bridges, migrations, and the like.

In order to achieve the above object, the solder cream for electronic components of the present invention is a mixture of 89 ~ 91% by weight solder and 9 ~ 11% by weight of flux, the solder alloy is Bi 56 ~ 58% by weight, 0.05 ~ 0.15% by weight Cu %, Co 0.01 ~ 0.03% by weight, Sn balance and other unavoidable impurities.

The melting point of the solder alloy is characterized in that 139 ~ 141 ℃.

The flux is characterized by comprising 90 to 95% by weight of the base, 3 to 7% by weight of the active agent, 1 to 3% by weight of the thixotropic agent and 1 to 5% by weight of the solvent.

Solder cream manufacturing method for an electronic component of the present invention comprises the steps of combining the solder alloy (S110); Combining the fluxes (S120); Mixing the solder alloy and flux (S130); comprising, the step of combining the solder alloy (S110) is Bi 56 ~ 58% by weight, Cu 0.05 ~ 0.15% by weight, Co 0.01 ~ 0.03% by weight, Sn balance and It is characterized by being composed of other unavoidable impurities.

The step of combining the flux (S120) is characterized by mixing, including 90 to 95% by weight of the base, 3 to 7% by weight of the active agent, 1 to 3% by weight of the thixotropic agent and 1 to 5% by weight of the solvent.

Mixing the solder alloy and the flux (S130) is characterized by mixing the solder alloy 89 ~ 91% by weight and the flux 9 ~ 11% by weight.

The present invention is characterized in that the solder cream for electronic components manufactured by the solder cream manufacturing method for electronic components.

Solder cream of the present invention can be performed at a lower temperature than the normal temperature (250 ~ 300 ℃), the thermal shock is less, improve the productivity of the electronic component manufacturing process, the effect that can be selectively used parts and substrate There is.

In addition, the present invention has the effect of excellent durability and low price at the same time than the solder alloy containing Ag, even without using a durable Ag.

Furthermore, since the Ag ₃ Sn is not formed because Ag is not used, which causes cracks and appearance defects, the present invention has an effect of reducing defects such as whiskers, voids, bridges, migrations, and the like.

1 is a solder cream according to the present invention.
2 is a graph confirming the viscosity of the solder cream.
3 shows the results according to the fluoride content test.
4 is a result of the insulation resistance.
5 is a sheet corrosion result of the flux residue.
6 is a result of the adhesion test.
7 is the wettability test result.
8 shows the solder ball test results.
9 shows the results of the migration test.
10 is a solder drop test method.
11 shows the state according to the solder drop test.
12 is a drop impact test method.
13 shows the drop impact test results.
14 is a drop shock test results of the Examples and Comparative Examples.
15 is a graph showing the reflow process temperature.
16 is an exemplary diagram divided by the degree of agglomeration of solder by a grade.
17 shows the solder cream according to the present invention applied to a circuit board.

Hereinafter, the present invention will be described in detail through examples.

The objects, features and advantages of the present invention will be readily understood through the following examples.

The invention is not limited to the embodiments disclosed herein, but may be embodied in other forms. The embodiments disclosed herein are provided to sufficiently convey the spirit of the present invention to a person having ordinary skill in the art to which the present invention pertains, and all the transformations included in the technical spirit and technical scope of the present invention. It should be understood to include equivalents, substitutes, or substitutes.

Therefore, the present invention should not be limited by the following embodiments, and it should be understood that all transformations included in the technical spirit and technical scope of the present invention are included. That is, a person having ordinary knowledge in the technical field to which the present invention belongs may variously modify or modify the present invention by adding, changing, deleting or adding components within the scope not departing from the spirit of the present invention described in the claims. It will be possible to change, which will also be within the scope of the invention.

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail. In the drawings, the size of elements or the relative sizes between elements may be somewhat exaggerated for clarity of understanding of the present invention. In addition, the shape of the elements shown in the drawings may be somewhat changed due to variations in the manufacturing process.

Therefore, the embodiments disclosed herein are not to be limited to the shapes shown in the drawings unless otherwise stated, it is to be understood to include some variation.

On the other hand, various embodiments of the present invention can be combined with any other embodiment unless clearly indicated to the contrary. Any feature indicated as particularly preferred or advantageous may be combined with any other feature and features indicated as preferred or advantageous. That is, various aspects, features, embodiments or implementations of the invention may be used alone or in various combinations.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limited by the claims. All technical and scientific terms used herein are commonly described unless otherwise indicated. It has the same meaning as is generally understood for a person with Singular expressions include plural expressions unless the context clearly indicates otherwise.

In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

<Example 1>

1) combining the solder alloy (S110)

In order to manufacture the solder alloy powder, Bi 56 to 58% by weight, 0.05 to 0.15% by weight of Cu, 0.01 to 0.03% by weight of Co and the balance of Sn are essentially included, and other unavoidable impurities may be included.

Preferably, 57 wt% Bi, 0.1 wt% Cu, 0.02 wt% Co, and Sn balance may be included.

In general, Sn-Bi alloy has a solidification and liquid phase coexistence area when soldering with solidification temperature range of 139 ~ 190 ℃, causing lift-off due to segregation during solder solidification. Becomes

In addition, the Sn-Cu alloy has a melting point of 221 ° C, and its wettability is not close to that of pure tin. When applied to wave soldering of a double-sided substrate, the molten solder is sufficiently filled with through-holes depending on the working conditions. There is a problem that is difficult to come.

Therefore, the present invention uses a solder alloy having excellent adhesion strength and low melting point without using Ag, which forms Ag ₃ Sn in the solder alloy and causes poor appearance.

In addition, since the melting point of the solder alloy of the present invention is 139 ~ 141 ℃ solid phase and liquid coexistence area is not significantly different, segregation does not appear during solidification can be minimized defects.

In particular, Bi has an effect of lowering the melting point, and the wettability is improved, and when used in a Cu plate, the wettability is improved.

Therefore, when Bi is out of the above range, the liquidus and the solidus may be degraded and lift off failure may occur.

As Cu increases the mechanical properties as the coarsening of the Bi-rich phase decreases, Cu ₆ Sn ₅ is formed and cracks are generated at the solder interface, and thermal fatigue cracks may occur at the same time. .

Co has the advantages of improved tensile strength, resistance to high temperatures, and strong corrosion and abrasion, so that corrosion may occur due to metal fatigue, heat, and the like.

Sn is used to lower the melting point of the solder alloy at the melting point of 231.9 ℃, and if out of the above range, the solid phase and the liquid coexistence area becomes large, the failure rate may increase due to the lift off occurs.

Other unavoidable impurities may include 0.1 wt% or less of any one or more of Pb, Sb, Au, In, Ag, Al, As, Cd, Fe, Ni, and Zn.

Preferably Pb 0.05% or less, Sb 0.1% or less, Au 0.05% or less, In 0.1% or less, Ag 0.1% or less, Al 0.001% or less, As 0.03% or less, Cd 0.002% or less Fe, 0.02% by weight or less, Ni 0.01% by weight or less, and Zn 0.001% by weight or less may be included.

At this time, the metal used in the solder alloy may be composed of a spherical powder, the powder size may be composed of 5 ~ 55㎛, but is not limited thereto.

In particular, if the powder size is less than 5㎛ size may be too small, defects such as omission, solder ball, adhesiveness, collapse, etc. may occur, if the powder size is larger than 55㎛ may not be used for 0.65mmPitch QFP (Quad Flat Package) .

In addition, when used for 0.4-0.5 mm Pitch QFP, it is preferable that the powder size of a solder alloy is 20-45 micrometers.

Furthermore, when used for 0.3 to 0.4 mm Pitch QFP or CSP (Chip Size Package), it is most preferable that the solder alloy has a powder size of 22 to 38 μm.

The oxygen concentration of the solder alloy powder may include 70 ppm or less, preferably 57 to 68 ppm, most preferably 65 ppm, but is not limited thereto.

If the oxygen concentration is out of the above range, the printability during soldering is deteriorated may cause defects.

The solder alloy powder was put in a metal powder in a mixer and mixed 90 ~ 120rpm, 30 ~ 60 minutes, preferably 100 ~ 110rpm, 40 ~ 60 minutes, most preferably 100rpm, 60 minutes, but depending on the metal powder size The mixing speed and temperature can vary.

If the mixing is performed at 90 rpm or less than 30 minutes, the metal components may not be evenly mixed and bonding may occur at the time of joining. If the mixing is performed at 120 rpm or more than 60 minutes, static electricity may be generated as the metal powder is stirred in the mixer. This may cause an explosion or fire.

When metal powder is mixed and used, the dissolved gas remains in the atmosphere, and the dissolved gas remains, which hinders the wettability of the surface of the solder base material, resulting in poor solderability or voids in the joint, thereby causing problems in thermal conductivity and reliability. Can be improved.

Reliability means that products bonded to printed circuit boards and components with solder cream will not have defects over their lifetime.

The method of preparing the solder alloy powder is not limited to the above method because mechanical, physical, electrochemical, and chemical methods may be used.

As the mechanical method, a grinding method, a cutting method, an impact method, a molten metal spray method, a spray method, a polishing method, or the like can be used.

Physical methods include vaporization and condensation, and electrochemical deposition can be performed using electrolytic precipitation.

As the chemical method, a solid phase decomposition method using a gas, a thermal decomposition method, a reduction method, a precipitation method from a gas phase, a solid-phase reaction synthesis method, or the like can be used.

If melting process is required when manufacturing solder alloy powder, melting in a vacuum state minimizes impurities or water generated in reaction with the atmosphere and dissolved gases in the alloy to improve solderability and minimize dross generation. This is preferred, but the melting method is not limited thereto.

In the manufacture of the solder alloy, the melting temperature may be prepared by mixing at more than 50 ℃ than the general alloy melting temperature, but the melting temperature may vary depending on the powder or content of the solder alloy is not limited thereto.

In the present invention may be melted at 145 ° C or higher, preferably 150 to 200 ° C, more preferably 185 to 195 ° C, most preferably 189 to 191 ° C.

When the solder alloy melting temperature is carried out below 145 ° C, some of the alloy powder is not melted and does not mix well, resulting in poor solderability and thus lowering the joint strength.

The molten solder alloy may be made of solder alloy powder using a mechanical method.

2) combining the flux (S120)

In order to combine the flux, a base, an active agent, a thixotropic agent and a solvent may be included and mixed.

Flux is a solvent for removing contaminants or surface oxide film during soldering. 90 ~ 95% by weight of base, 3 ~ 7% by weight of activator, 1-3% by weight of thixotropic agent and 1 ~ 5% by weight of solvent can be mixed. Preferably, 91 to 94% by weight of the base, 4 to 6% by weight of the activator, 1 to 2% by weight of the thixotropic agent and 1 to 3% by weight of the solvent may be mixed, most preferably 92% by weight of the base, 4% by weight of the active agent. %, 2% by weight of thixotropic agent and 2% by weight of solvent may be mixed.

In addition, the weight ratio of the flux is not limited since it can be changed fluidly.

The base may use rosins and / or resins, but is not limited thereto.

When using rosin, when heated in the soldering process, the rosin begins to melt first, thermally assisting it, and when cooled, it solidifies to act as a hydrophobic capsule on certain ionic active ingredients.

The encapsulation operation allows high soldering yields without compromising reliability and competitive advantages at low cost.

Resin can be used to increase the spreading efficiency.

The combination of rosin and resin can solve the problem of rosin, which turns black at too high a temperature, and the problem of resin producing smoke.

At this time, the mixing ratio of the rosin and the resin may be composed of 1: 0.1 to 1, preferably 1: 0.5, but is not limited thereto.

This does not solve the problem that smoke occurs when the resin is mixed in a higher proportion than rosin.

The resin is composed of an epoxy resin, a phenol resin, a polyimide resin, a silicone resin or a modified resin thereof, a thermosetting resin group composed of an acrylic resin or a polyamide resin, a polystyrene resin, a polymethacryl resin, a polycarbonate resin, and a cellulose resin. One or more kinds of thermoplastic resin groups may be included, but is not limited thereto.

Active agents are used to clean surfaces, to prevent reoxidation and to increase solderability.

In particular, when the active agent exceeds 7% by weight, a problem occurs that adversely affects the environment and the human body.

In addition, the active agent may be one containing chlorine or bromine, preferably may include one or more selected from amine hydrochloride, amine bromine salt, organic carboxylic acid, but is not limited thereto.

The thixotropic agent is used to prevent separation of the flux and the solder alloy powder.

Therefore, the flux and the alloy powder may be separated when the thixotropic agent is included in less than 1% by weight, and when the content exceeds 3% by weight, the viscosity is increased to reduce the fluidity, so that the coating may not be smoothed when mounted.

The thixotropic agent may include one selected from oils and waxes, preferably, hydrogenated castor wax, carnauba wax, ethylene glycol, polyglycols ), 1 selected from polypropylene glycol, acrylate oligomer, glyceride, simethicone, tributyl phosphate or silica compounds It may include more than one species, but is not limited thereto.

The silica-based compound may be selected from dimethylsilicone (dimethylsilicone) or polydimethylsiloxane (polydimethylsiloxane).

The solvent is heat stable and is used for melting the solid raw materials.

The solvent may include one or more kinds of alcohols, glycol ethers, glycidyl ethers.

Alcohol may be used as one of n-hexanol, n-decanol, n-dodecanol, n-dodecanol, and trimethylnonyl alcohol, but is not limited thereto.

In particular, when the solvent is used in excess of 5% by weight, volatile organic compounds (VOC) may be evaporated into the atmosphere when heated, causing air pollution.

3) mixing the solder alloy and the flux (S130)

The solder alloy powder prepared in step 1) and the flux prepared in step 2) are mixed.

The weight ratio of the solder alloy powder and the flux may be changed fluidly, and preferably, 89 to 91 wt% of the solder alloy powder and 9 to 11 wt% of the flux may be mixed, most preferably 90 wt% of the solder alloy powder and 10 wt% flux may be mixed.

That is, the solder cream is completed as the solder alloy powder and the flux are mixed.

Such solder cream has an excellent economical effect by increasing the adhesive strength of electronic components, long shelf life and print life, and excellent work stability.

Since the flux has effects such as surface cleaning, reoxidation prevention, and surface tension reduction, when used too little, viscosity becomes difficult to work.

<Example 2>

Rare earth may be further included in the solder alloy of the first embodiment.

1) combining the solder alloy (S110 ′)

In order to prepare the solder alloy powder, Bi 56 to 58% by weight, 0.05 to 0.15% by weight of Cu, 0.01 to 0.03% by weight of Co, 0.01 to 0.5% by weight of rare earths, and the remainder of Sn are essential, and other unavoidable impurities may be included. .

Preferably, 57 wt% Bi, 0.1 wt% Cu, 0.02 wt% Co, 0.01-0.3 wt% rare earth, and the balance of Sn may be included.

In addition, duplicated content is omitted.

Rare earths are a total of 17 elements including 15 La (lanthanum) elements, scandium (Sc) and yttrium (Y).

The rare earths used in the present invention may be those containing any one or more of La, Ce (cerium), Y, but are not limited thereto.

La is ductile, and its electrical resistivity is about 20 times that of aluminum at 615 nΩ · m at 20 ° C, so it is included to improve the malleability, impact resistance and ductility when used as an alloy.

However, when using a rare earth composed of La corresponds to the melting point of 920 ℃ so that the melting point of the solder alloy is best to use 0.1% by weight.

Ce is a silver-gray metal with a color and luster similar to iron, soft, malleable and ductile, and is included to improve the diffusion and fixation ability while reacting well with other metals.

In particular, when using a rare earth composed of Ce, since the melting point corresponds to 795 ° C, it is best to use 0.3% by weight in order to prevent the melting point of the solder alloy from increasing.

Y is resistant to corrosion and wear at high temperatures, and is included to prevent oxidation by forming an oxide (Y ₂ O ₃ ) protective film in air.

However, when using a rare earth composed of Y, the melting point of 1,526 ℃ belong to the ultra-high temperature, it is best to use 0.01% by weight because there is almost no malleability and ductility.

In addition, the powder size of the rare earth may be composed of 5 to 55㎛, as in Example 1, preferably 20 to 45㎛, more preferably 22 to 38㎛, but is not limited thereto.

In particular, if the rare earth powder size is less than 5㎛ the size is too small to react before the solder alloy may change the physical properties, if it exceeds 55㎛ may not react with the solder alloy may increase the failure rate during soldering.

When the solder alloy powder is a metal powder, the metal powder and the rare earth powder are put in a mixer and mixed 90 to 120 rpm, 30 to 60 minutes, preferably 100 to 110 rpm, 40 to 60 minutes, most preferably 100 rpm, 60 Although mixed minute, the mixing speed and temperature may vary depending on the metal powder size.

When the mixing is performed at 90 rpm or less than 30 minutes, the metal component and the rare earth may not be evenly mixed, so that bonding may occur at the time of joining, and when the mixing is performed at 120 rpm or more than 60 minutes, the metal powder is stirred in the mixer. Static electricity may cause explosion or fire.

If the solder alloy is melted into a powder and then used, the metal powder is melted in the same manner as in Example 1 to prepare an alloy to form a powder, and then the alloy powder and the rare earth powder are mixed.

When the rare earth powder is mixed using the molten alloy powder, it may be put in a mixer and mixed at 50 to 100 rpm and 30 minutes or less, preferably 60 to 80 rpm, 10 to 30 minutes, more preferably 70 rpm and 15 minutes. However, the mixing speed and time may vary depending on the powder size.

Thereafter, the step of combining the flux (S120) and the step of mixing the solder alloy and the flux (S130) are performed in the same manner as in Example 1, and thus a detailed description thereof will be omitted.

The melting point of the solder alloy containing rare earth has a melting point higher than that of Example 1 at 140 to 143 ° C.

However, this also has an effect that segregation does not occur during solidification because the coexistence area is not significantly different in the melting point temperature range from 140 ° C. to 143 ° C. in the liquid phase.

In addition, the effect of preventing the impact resistance and oxidation by the rare earth is doubled.

Experimental Example 1

Solder creams were prepared by the method described in the Examples to confirm general properties.

Table 1 shows the results of confirming the general characteristics according to the test method.

Item characteristic Test Methods Melting Point (℃) 139 ~ 141 DSC Solder Alloy Powder Particle Size (㎛) 22 ~ 38, Spherical JIS Z 3284 1 FLUX content (% by weight) 9 ~ 11 JIS Z 3197 8.1.2 Viscosity (Pas) 100-160 JIS Z 3284 6 Chixo index (TI) 0.3 ~ 0.5 JIS Z 3284 6 Halogen content test (%) 0.15 or less JIS Z 3197 8.1.4.2.1 % Diffusion 75% or more, 75% min JIS Z 3197 8.3.1.1 Fluoride Content Test none JIS Z 3284 2 Insulation resistance 40 ° C / 90% R.H, 168h 1 × 10 ¹¹ or more JIS Z 3284 3 85 ° C / 85% R.H, 168h 5 × 10 ^８ or more Flux residue copper plate corrosion test No corrosion JIS Z 3284 4 Sticky 0h 0.98N JIS Z 3284 9 8h 0.98N Wetting test Class 1-3 JIS Z 3284 10 Solder ball test Class 1-3 JIS Z 3284 11 Migration No occurrence JIS Z 3284 14

As shown in [Table 1], the melting point of the solder alloy powder of the present invention is 139 ~ 141 ℃ do not significantly differ in the coexistence area between the liquid and solid phase, there is an effect that minimizes the failure rate because segregation does not occur during solidification.

In addition, the solder cream of the present invention can also be inferred that the melting point is 139 ~ 141 ℃ because it contains a solder alloy powder.

In particular, when performing reflow soldering using the solder cream of the present invention, since the temperature is very low, energy and CO ₂ required for soldering are reduced.

Furthermore, as the temperature is lowered during reflow soldering, the thermal shock of the component is low, and the component and the substrate can be selectively used.

That is, it can be inferred that the present invention can be used not only for ceramic substrates but also for plastic packages, glass epoxy substrates, and the like.

In addition, the particle size of the solder alloy powder is 22 ~ 38㎛ can be confirmed that no defects such as omission, solder ball, adhesiveness, collapse, even when used for 0.3 ~ 0.4mmPitch QFP or CSP.

The thixotropic index refers to a property in which the viscosity decreases due to wet solder cream and the viscosity decreases again when left untreated.

It was confirmed that the solder cream had a viscosity of 100 to 160 Pa · s and a thixotropy of 0.3 to 0.5.

In particular, when the Nixo index is 0.5 or less, the coating becomes smooth at the time of the coating operation, the rolling property is good, and the solder cream does not flow down even after the coating.

Wetting test and solder ball test confirmed that it belongs to class 1-3.

Class is a criterion divided by grade for the degree of solder agglomeration and the resulting defect phenomenon, as shown in FIG.

Class 1 refers to an agglomerated state in which solder is melted into one large mass, and there are no solder balls around, as shown in FIG. It means the aggregation state which has three or less solder balls of 75 micrometers or less.

Class 3 refers to an agglomerated state in which the solder is melted into a large mass and there are three or more solder balls with a diameter of 75 μm or less around them and are not arranged in a semi-continuous round shape.

Class 4 refers to an agglomerated state in which solder is melted into a large mass, and a plurality of solder balls are arranged in a semi-continuous round shape around it. Class 5 refers to an agglomerated state other than that of Class 1 to 4 it means.

If the class 4 and 5 show a cohesive state, it is a bad phenomenon and cannot be used beyond the application criteria.

Solder cream of the present invention shows a cohesive state of class 1 to 3, it can be seen that it meets the application criteria.

In addition, the solder cream of the present invention has an insulation resistance of at least 1 × 10 ¹¹ Pa at 40 ° C, 90% RH, and 168h, and at least 5 × 10 ⁸ Pa at 85 ° C, 85% RH, and 168h. As a result, there is no corrosion and it can be confirmed that it has excellent soldering characteristics.

In particular, the solder alloy powder of the present invention is composed of Sn-57Bi-0.1Cu-0.02Co, the solder cream containing 10% by weight of flux melting point of 139 ~ 141 ℃, viscosity of 130 Pa.s, thixotropic index 0.4 It can be inferred that the rolling property is good while the wettability is excellent.

Experimental Example 2

The composition of the solder alloy powder described in Example 1 was confirmed.

Table 2 shows the results of confirming the composition of the solder alloy powder of the present invention.

ingredient Sn Pb Sb Bi Cu Au In Ag weight% Balance 0.05 or less 0.1
Below 56-58 0.05 ~ 0.15 0.05
Below 0.1
Below 0.1
Below ingredient Al As CD Fe Ni Zn Co weight% 0.001
Below 0.03
Below 0.002
Below 0.02
Below 0.01
Below 0.001
Below 0.01 ~ 0.03

As shown in Table 2, it can be confirmed that the essential components of the solder alloy powder of the present invention are Sn, Bi, Cu and Co.

In addition, it was confirmed that 0.1 wt% or less of Pb, Sb, Au, In, Ag, Al, As, Cd, Fe, Ni, and Zn were included as other inevitable impurities.

It can be inferred that even if a small amount of the other unavoidable impurities is contained, the solder alloy powder of the present invention does not have a large effect.

Experimental Example 3

The melting point of the solder alloy described in Example 1 was confirmed.

The measurement method was performed based on IEC61189-11 by extracting 10 mg of the solder alloy.

Table 3 below shows the results of confirming the melting point of the solder alloy of the present invention.

Item characteristic Melting Point (℃) Solid temperature 139 Liquidus temperature 141

Looking at Table 3, it was confirmed that the melting point of the solder alloy of the present invention is 139 ° C in solid state and 141 ° C in liquid phase.

That is, it can be seen that the melting point of the solder alloy of the present invention is 139 ~ 141 ℃, the coexistence area is not significantly different in the melting point temperature range, there is an effect that segregation does not occur during solidification.

Therefore, the present invention has the advantage that the defect due to segregation is minimized because there is no significant difference in the coexistence area of the melting point according to Sn-Bi-Cu-Co.

Experimental Example 4

The viscosity, ie, the flow characteristic, was confirmed using the solder cream described in Example 1.

For the test method, refer to JIS Z 3284 6 and the test device used malcom pcu-2,5,205.

The solder cream prepared through the above example was used, and the measurement time was performed to confirm the flow characteristics at 1 to 6 minutes and the rotation speed to 3 to 30 rpm.

Table 4 shows the results of the flow characteristics.

Measuring time (min) 6 3 3 3 One One One Viscosity (Pas) TI Rpm 3 4 5 10 20 30 10 Viscosity (Pas) 216 193 176 130 99 86 127 130 0.4

Based on Figure 2 and [Table 4], the viscosity of the solder cream has a viscosity of 1 ~ 6 minutes, 86 ~ 216 Pa.s at 3 ~ 30rpm, 3 minutes at 10rpm results viscosity 130Pa.s, thixotropy 0.4 It was confirmed that the optimum condition.

In particular, when the same rotational speed 10rpm, when the measurement time is compared to 1, 3 minutes as a result of measuring time increase, it was confirmed that the viscosity rises from 127Pa.s to 130Pa.s.

That is, the solder cream of the present invention can be inferred that there is no problem in reliability at the time of soldering with time-dependent change.

In addition, when the measurement time is 1 minute, as a result of checking the viscosity according to the rotation speed (10, 20, 30rpm) it can be seen that the viscosity decreases as the rotation speed increases.

Experimental Example 5

The flux content of the solder cream of Example 1 was confirmed.

The test method referred to JIS Z 3197 8.1.2.

Table 5 below shows the flux content results.

Count One 2 3 4 5 Average Content (% by weight) 10 10.1 9.9 10 10 10

Looking at Table 5, it was confirmed that the flux mixed in the solder cream used an average of 10% by weight to 3.9 ~ 10.1% by weight.

Experimental Example 6

The halogen content of the solder cream of Example 1 was confirmed.

The test method referred to JIS Z 3197 8.1.4.2.1.

Table 6 below shows the halogen content results.

Count One 2 3 4 5 Average Result (CI%) 0 0 0 0 0 0

Looking at Table 6, it can be seen that the solder cream of the present invention does not contain halogen.

In other words, it can be inferred that it does not contain halogen and harmless to the human body.

Experimental Example 7

The diffusion rate was confirmed using the solder cream of Example 1.

The test method referred to JIS Z 3197 8.3.1.1.

Table 7 shows the results of confirming the diffusion rate.

Count One 2 3 4 5 Average % Diffusion 82.1 80 80.3 81.1 80.5 80.8

Looking at [Table 7], it was confirmed that the diffusion rate, that is, the spreadability of the solder cream of the present invention is an average of 80.8% to 80 ~ 82.1%.

That is, the spreadability of the lead-free solder cream without the use of lead increases the defect rate to 50% or raises the unit price.

In the present invention, the spreadability is 80% or more and 83% or less, and when compared to the lead-free solder cream having 50% spreadability, it can be confirmed that the spreadability is improved by 1.6 times or more.

Experimental Example 8

The fluoride content of the solder cream of Example 1 was confirmed.

The test method referred to JIS Z 3284 2.

As shown in Figure 3, it can be confirmed that the solder cream of the present invention does not contain fluoride.

Fluoride will decompose when heated with strong acids to produce toxic hydrogen fluoride.

That is, the present invention does not contain fluoride and no toxic hydrogen fluoride is produced.

Experimental Example 9

Insulation resistance was confirmed using the solder cream of Example 1.

The test method referred to JIS Z 3284 3.

After solder cream application, the insulation resistance was checked at 40 ° C./90% R.H or 85 ° C./85% R.H for 0, 24, 96, 168, 500, 1000 hours.

Table 8 shows the results of checking the insulation resistance.

Ω 0h 24h 96h 168h 500h 1,000h 40 ℃ / 90% R.H 7.8 × 10 ¹⁴ 7.53 × 10 ¹² 6 × 10 ¹¹ 5.1 × 10 ¹¹ 6 × 10 ¹¹ 6.3 × 10 ¹¹ 85 ℃ / 85% R.H 7.6 × 10 ¹⁴ 9.5 × 10 ⁸ 7.1 × 10 ⁸ 8.1 × 10 ⁸ 9 × 10 ⁸ 9.9 × 10 ⁸

Referring to Figure 4 and Table 8, the solder cream of the present invention has a 5.1 × 10 ¹¹ ~ 7.8 × 10 ¹⁴ 에서 at 40 ℃ / 90% RH conditions, 7.1 × 10 at 85 ℃ / 85% RH conditions ^It can be seen that it has ⁸ to 7.6 × 10 ¹⁴ mV.

In addition, when comparing the insulation resistance of 0h and the insulation resistance of 1,000h, it can be seen that the insulation resistance value of the solder cream decreases with time.

Furthermore, it can be seen that the solder cream of the present invention has an insulation resistance slightly higher than each condition standard value.

Experimental Example 10

The copper plate corrosion of the flux residue was confirmed using the solder cream of Example 1.

The test method referred to JIS Z 3284 4.

Figure 5 shows that no corrosion occurs even after 96h as a result of the plate corrosion of the flux residue.

That is, it was confirmed that the corrosion does not occur, the reliability is improved.

Experimental Example 11

Adhesiveness was confirmed using the solder cream of Example 1.

For the test method, refer to JIS Z 3284 9, and the standing environment was performed under conditions of 40 to 60% RH at 23 to 27 ° C.

Table 9 below shows the results of checking the tackiness.

Storage time (h) 0 2 4 8 16 24 Adhesiveness (N) 1.03 1.13 1.17 1.15 1.13 1.04

Looking at Figure 6 and Table 9, it was confirmed that the adhesion of the solder cream of the present invention is 1.03 ~ 1.17N.

In addition, it can be seen that the solder cream of the present invention has increased adhesion as the storage time is 2h to 4h over time, and the adhesion decreases with time from 4h to 24h.

In addition, the initial 0h tackiness of 1.03N can be seen that there is no big difference when compared with the tackiness 1.04N of 24h.

Therefore, it can be seen that the solder cream of the present invention exhibits the best adhesiveness of 1.13 to 1.17 N at 2 to 16 h.

Experimental Example 12

The wettability and the solder ball were confirmed using the solder cream of Example 1.

Wetting test method was referred to JIS Z 3284 10.

The solder ball test method was referred to JIS Z 3284 11, and the standing environment was performed at 23 to 27 ° C. under 45 to 55% RH and 24 h.

7 can be visually confirmed that the wettability is excellent as a result of the wettability test.

In particular, it can be seen that the solder cream of the present invention belongs to class 1 by visually confirming that the solder is melted to form a large mass and there is no solder ball around it.

FIG. 8 shows that the cohesion test results belong to class 1 as a result of the solder ball test.

Experimental Example 13

Migration was confirmed using the solder cream described in Example 1.

The test method referred to JIS Z 3284 14.

9 confirmed that no migration occurred at 40 ° C./90% RH and 85 ° C./85% RH conditions as a result of the migration test.

Experimental Example 14

It was confirmed whether the solder did not fall through the solder drop test using the solder cream described in the Examples.

The test method, as shown in Figure 10, bend the copper plate in the U-shape, and then apply solder cream in the shape of bamboo shoots on the inside of the bent copper plate.

At this time, the solder cream was applied in 0.05g, 0.1g, 0.2g.

Then, after heating for 60 seconds on a hot plate at 170 ℃, as shown in Figure 11 it was confirmed whether the solder is dropped.

At this time, the rising temperature rate was to be increased by 10 ℃ per second.

Table 10 shows the results of the drop test (○: no dropout, ×: dropout).

Count One 2 3 4 5 0.05g ○ ○ ○ ○ ○ 0.1g ○ ○ ○ ○ ○ 0.2 g ○ ○ ○ ○ ○

As shown in Table 10, the solder cream of the present invention was confirmed that the solder does not drop out at all 0.05g, 0.1g, 0.2g.

Experimental Example 15

The drop impact test was confirmed using the solder cream of Example 1.

In the test method, as shown in FIG. 12, after dropping a weight of 70 g on the soldered part, the impact resistance of the alloy was evaluated at a height by checking whether the part was peeled off or a crack occurred at the joint due to the impact.

As shown in Figure 13, the solder cream of the present invention was confirmed that the drop impact test results up to 11cm.

Experimental Example 16

The drop shock test was confirmed using the solder cream described in the Example and a comparative example.

The test method was carried out in the same manner as in Experiment 15.

Solder cream prepared in the manner described in Example 1 and Example 2 and Comparative Example 1 is 57Bi-0.1Cu-0.4Ag-0.02Co-Sn-based solder alloy, Comparative Example 2 is 0.5Cu-3Ag-Sn-based solder alloy, Comparative Example 3 prepared a mixed alloy in which 2.5 parts by weight of Comparative Example 1 and 7.5 parts by weight of Comparative Example 2 were prepared, and the drop impact test was performed.

As shown in FIG. 14, the drop height of Example 1 is up to 11 cm, the drop height of Example 2 is up to 15 cm, the drop height of Comparative Example 1 is up to 5 cm, and the drop height of Comparative Example 2 is up to 15 cm, Comparative Example The drop height of 3 was confirmed to be up to 18 cm.

In particular, it can be seen that in Example 2, as the rare earth is further included in Example 1, the drop impact is improved.

In addition, when compared with Comparative Example 2 which is a 0.5Cu-3Ag-Sn based solder alloy, Example 2 has the same drop height, and it can be deduced that it has an impact resistance even if Ag is not included.

Example 1 has a drop height of 2.2 times compared to Comparative Example 1, which is a 57Bi-0.1Cu-0.4Ag-0.02Co-Sn-based solder alloy, and it can be seen that the impact resistance is improved even if Ag is not included.

That is, it can be seen that the solder cream manufactured according to the embodiment of the present invention has improved durability even without using Ag.

Experimental Example 17

Corrosion, insulation, solderability, dryness, and migration were compared using the solder creams described in the Examples and Comparative Examples.

The comparative example used the same thing as what was described in Experiment 16.

Table 11 below shows the results of comparing corrosiveness, insulation, solderability, dryness, and migration (◎: very good, ○: good, Δ: normal, ×: bad).

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 causticity ○ ◎ △ ○ ○ Insulation ◎ ◎ × △ ○ Solderability ◎ ◎ △ ○ ○ Dryness ◎ ◎ × △ ○ Migration ◎ ◎ ○ ○ ○

As shown in Table 11, it can be seen that the corrosion, insulation, solderability, dryness and migration of Examples 1 and 2 showed very excellent characteristics compared to Comparative Examples 1 to 3.

In addition, although the corrosiveness of Example 1 was favorable and it fell slightly compared with Example 2, it turns out that it is excellent when compared with the comparative example 1.

This can be inferred from the fact that the rare earth is included in Example 2, and an oxide film is formed to prevent corrosion.

Experimental Example 18

The reflow process was performed using the solder cream described in Example 1 or 2.

After selecting a substrate to be soldered (for example, a PCB), the solder cream described in the embodiment is applied to mount a component on the substrate, and then put into a reflow apparatus, and a reflow process is performed.

15 is a graph showing the reflow process temperature, in which a preheating step is first performed.

The preheating step means a section starting at 50 ° C. up to a preheating temperature (110 ° C.), and the temperature increase rate is gradually increased to 2 to 4 ° C./sec.

If the temperature rises sharply, a slump of solder cream may deteriorate.

In addition, in order to have a small temperature deviation on the substrate (Δt), the preheating time is performed at 60 to 90 sec at a preheating temperature of about 110 to 130 ° C.

At this time, if the preheating temperature is low and the time is short, there may be a problem that the temperature deviation Δt on the substrate becomes severe and unmelting occurs.

In addition, when the preheating temperature is high and the time is long, the active force of the solder cream may be lost during preheating, which may cause a problem of unmelting.

After this, the main heating step is performed.

This heating step sets the melting test to 30 to 60 sec at 150 ° C or higher.

At this time, the maximum temperature may be 170 ~ 200 ℃.

That is, when mounting a component using the solder cream of the present invention, the maximum temperature does not exceed 200 ℃ can minimize the damage to the component by the heat, and there is an advantage that can be used by selecting the component and the substrate .

Thereafter, a cooling step is performed.

The cooling step may be performed at 4 ~ 10 ℃ / sec.

At this time, if the cooling is cooled too slowly, the component may be distorted or the bonding strength may be lowered, thereby causing a problem in reliability.

In addition, if the cooling is reversed too quickly, a problem may occur in which parts are damaged by thermal shock.

The solder cream of the present invention is carried out after 7 hours to 9 hours, preferably 8 hours, until the mounting of the component, but is not limited thereto.

That is, the solder cream of the present invention, as shown in Figure 17, it can be confirmed that the component is stably bonded to the substrate through the above reflow process.

In addition, the solder cream of the present invention can improve reliability by removing defects caused by instability of the temperature profile through a reflow process.

The present invention is an industrially available invention that simplifies the process and increases the working efficiency by mixing the solder alloy powder and flux with the solder cream for electronic components and the manufacturing method thereof and creaming.

Claims (7)

In the solder cream for electronic components,
Solder cream is a mixture of 89 to 91% by weight solder alloy and 9 to 11% by weight flux,
The solder alloy is composed of Bi 56 to 58% by weight, 0.05 to 0.15% by weight of Cu, 0.01 to 0.03% by weight of Co, the balance of Sn and other unavoidable impurities, the melting point is 139 to 141 ℃,
The flux contains 90 to 95% by weight of the base consisting of 1 to 0.1 to 1 of rosin and resin, 3 to 7% by weight of active agent, 1 to 3% by weight of thixotropic agent and 1 to 5% by weight of solvent. Become,
The solder cream has a viscosity of 100 to 160 Pa.s, thixotropy index (TI) of 0.3 to 0.5, and adhesion of 1.03 to 1.17 N. Solder cream for electronic components, characterized in that.
delete delete In the solder cream manufacturing method for electronic components,
Combining the solder alloy (S110);
Combining the fluxes (S120);
And mixing the solder alloy 89 to 91% by weight and the flux 9 to 11% by weight (S130).
The solder alloy is composed of Bi 56 to 58% by weight, 0.05 to 0.15% by weight of Cu, 0.01 to 0.03% by weight of Co, the balance of Sn and other unavoidable impurities, the melting point is 139 to 141 ℃,
The flux contains 90 to 95% by weight of the base consisting of 1 to 0.1 to 1 of rosin and resin, 3 to 7% by weight of active agent, 1 to 3% by weight of thixotropic agent and 1 to 5% by weight of solvent. Become,
The solder cream has a viscosity of 100 to 160 Pa · s, a thixotropy index (TI) of 0.3 to 0.5, and an adhesiveness of 1.03 to 1.17 N, wherein the solder cream manufacturing method for an electronic component is used.
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