KR101865727B1 - Lead-free solder composition - Google Patents

Abstract

The lead-free solder composition according to one embodiment of the present invention is characterized in that 0.1 to 1.7% by weight of silver (Ag), 1.5 to 3.5% by weight of bismuth (Bi), 0.01 to 0.8% by weight of copper %, Nickel (Ni) 0.001 to 0.0099 wt%, and the balance tin (Sn).

Description

[0001] LEAD-FREE SOLDER COMPOSITION [0002]

High-strength lead-free solder composition.

Soldering is mainly used for soldering, but it is prohibited to use soldering to electronic products due to recent environmental regulations. In the automobile field, we will strictly prohibit the use of lead in vehicles from 2016. Accordingly, the solder material based on the lead component used in the past has been replaced by various kinds of metal alloys.

However, lead-free solder materials have lower strength than conventional lead-based alloys, they are weak against corrosion and have a disadvantage that ion migration phenomenon is easy

There are various studies on the improvement of reliability according to the application of new lead-free solder and the increase of usage. As a method for improving the reliability of lead-free solder

1) How to suppress grain growth of solder alloy by thermal fatigue

2) How to suppress corrosion of solder surface

3) a method for suppressing the growth of an intermetallic compound formed between a substrate and a solder

And 4) methods of improving the strength of solder through strengthening of employment.

One of the most basic methods of existing techniques is to enhance the reliability of strength and thermal fatigue by adjusting the alloy phase. Through this method, it is possible to realize various advantages such as solidification of solder alloy, refinement of grain boundary, and change of melting point.

This solder alloy design process is basically used in manufacturing solder in that it can improve the physical properties of the final product.

Sn-Ag-Cu-based, Sn-Bi-based, Sn-Ag-based, and Sn-Zn-Bi based solders are used in general lead-free solder compositions. Is the composition commonly used. The Sn-Ag-Cu-based lead-free solder composition is applied to general electronic products, and a Sn-Ag-Cu-based lead-free solder is used for an automobile or a similar level of products requiring high reliability, that is, excellent thermal fatigue characteristics Add another element to the composition and apply.

When Sn-Ag-Cu-based lead-free solder composition is repeatedly subjected to extreme temperature changes after soldering, cracks are generated in the solder joint due to the stress caused by the difference in coefficient of thermal expansion of the base material. If a crack is generated, the bonding strength is lowered, and a reliability problem is caused in the product.

One embodiment of the present invention provides lead-free solder compositions that are excellent in high temperature stability, strength, and wetting.

Further, one embodiment of the present invention provides a lead-free solder composition harmless to the human body and environment-friendly.

In addition, one embodiment of the present invention provides a lead-free solder composition applicable to electronic products and automobiles.

The lead-free solder composition according to one embodiment of the present invention is characterized in that 0.1 to 1.7% by weight of silver (Ag), 1.5 to 3.5% by weight of bismuth (Bi), 0.01 to 0.8% by weight of copper %, Nickel (Ni) 0.001 to 0.0099 wt%, and the balance tin (Sn).

And silver (Ag) in an amount of 0.3 to 1.5% by weight.

And 2.0 to 3.3% by weight of bismuth (Bi).

And 0.1 to 0.6% by weight of copper (Cu).

And 0.003 to 0.007% by weight of nickel (Ni).

Phosphorus (P), and cobalt (Co).

And 1.0 to 3.0% by weight of phosphorus (P).

And 1.0 to 2.0% by weight of cobalt (Co).

The lead-free solder alloy according to one embodiment of the present invention is made of the lead-free solder composition described above.

An electronic component according to an embodiment of the present invention includes the above-described lead-free solder alloy.

An automobile according to an embodiment of the present invention includes the above-described lead-free solder alloy.

The lead-free solder composition according to one embodiment of the present invention is excellent in high-temperature stability, strength and wettability.

In addition, the lead-free solder composition according to one embodiment of the present invention is useful as a solder alloy for automobiles, electronic products, particularly, microelectronic products.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise.

In the examples of the present invention, the% by weight (wt%) represents the weight of the total composition in terms of the weight of the total composition as a percentage.

The lead-free solder composition according to one embodiment of the present invention includes Ag, Bi, Cu, Ni and Sn. Hereinafter, each component will be described in detail.

The lead-free solder composition according to one embodiment of the present invention comprises silver (Ag) in an amount of 0.1 to 1.7% by weight based on the total weight of the composition. More specifically 0.3 to 1.5% by weight, and more specifically 0.5 to 1.0% by weight. The intermetallic compound of Sn-Ag having a dense needle-shaped structure produced upon soldering within the above-mentioned range strengthens the strength of the solder alloy. Further, the elongation is improved to improve the thermal fatigue characteristics and the dropping resistance.

The lead-free solder composition according to one embodiment of the present invention comprises 1.5 to 3.5% by weight of bismuth (Bi) based on the total weight of the composition. More specifically from 2.0 to 3.3% by weight, and more specifically from 2.3 to 2.8% by weight. When included in the above-mentioned range, the cold resistance is improved even in an environment where an extreme temperature change occurs. In addition, resistance to shear stress can be induced by diffusion of Bi atoms having a large atom size, and crack initiation, cracking speed and crack range can be reduced by repeated thermal fatigue test. Therefore, the thermal fatigue characteristics of the solder alloy can be improved.

The lead-free solder composition according to one embodiment of the present invention contains copper (Cu) in an amount of 0.01 to 0.8% by weight based on the total weight of the composition. More specifically 0.1 to 0.6% by weight, and more specifically 0.1 to 0.5% by weight. When contained within the above-mentioned range, the melting point of the Sn solder alloy is lowered and the reactivity with the base material is improved to improve the spreadability. If the above range is not satisfied, the range of the insoluble compound and the melting point (liquidus line) increases, and the workability can be lowered.

The lead-free solder composition according to one embodiment of the present invention contains nickel (Ni) in an amount of 0.001 to 0.0099% by weight based on the total weight of the composition. More specifically from 0.003 to 0.007% by weight, and more specifically from 0.004 to 0.006% by weight. When included in the above range, the intermetallic compound of Sn-Ni reduces the thickness of the alloy and is effective in securing strength. In the repeated load test (constant temperature / humidity test, thermal fatigue test) It is possible to secure a dense structure and improve the strength of the solder alloy due to its characteristics as a diffusion barrier film for suppressing diffusion.

The lead-free solder composition according to one embodiment of the present invention includes tin (Sn) as the remainder so that the total weight of the composition is 100 wt%. Tin (Sn) is not self-toxic and has excellent solubility with other metals, making it easy to produce various alloys.

The lead-free solder composition according to an embodiment of the present invention may further include at least one of phosphorus (P) and cobalt (Co).

(P) is contained in an amount of 1.0 to 3.0% by weight based on the total weight of the composition. More specifically from 1.3 to 2.5% by weight, and more specifically from 1.5 to 2.0% by weight. When contained within the above-mentioned range, the amount of generation of the molten oxide (Dross) is reduced, the flowability of the molten solder is increased, and the wetting speed and spreadability can be improved.

If it further contains cobalt (Co), it contains 1.0 to 2.0% by weight based on the total weight of the composition. More specifically from 1.0 to 1.8% by weight, and more specifically from 1.0 to 1.5% by weight. When included within the above-mentioned range, the toughness of the solder alloy is increased, and the growth of the intermetallic compound is suppressed to suppress the crack. Exceeding the above range may result in deterioration of workability.

The lead-free solder composition according to an embodiment of the present invention may be applied to various types of solder paste such as solder paste, solder ball, solder bar, solder wire, solder bump, Solder plate, solder powder, solder powder, solder ribbon, and solder ring.

The lead-free solder composition according to an embodiment of the present invention may be made of a lead-free solder alloy, and such a lead-free solder alloy may be usefully used in electronic parts and automobiles.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example  1 to 6, Comparative Example  1 to 3: Lead-free Solder  Preparation of composition

Lead-free solder compositions according to Examples 1 to 6 and Comparative Examples 1 to 3 were prepared with the compositions shown in Table 1 below.

division silver
(weight%) Bismuth
(weight%) Copper
(weight%) nickel
(weight%) sign
(weight%) cobalt
(weight%) Remark Example 1 0.3 1.5 0.5 0.008 - - Balance Example 2 0.5 1.5 0.5 0.005 - - Balance Example 3 0.5 1.5 0.5 0.001 - - Balance Example 4 0.5 2.5 0.5 0.001 1.5 - Balance Example 5 0.5 1.5 0.5 0.005 - 1.0 Balance Example 6 1.5 1.5 0.5 0.005 1.5 1.0 Balance Comparative Example 1 3.0 - 0.5 - - - Balance Comparative Example 2 0.3 - 0.7 - 1.5 - Balance Comparative Example 3 1.5 1.5 0.5 0.015 - - Balance

Manufacturing example : Solder  Manufacture of pastes

Powders having the compositions of Examples 1 to 6 and Comparative Examples 1 to 3 were each prepared using a centrifugal separation method and then classified into a sieve type 4 (type 4 having a diameter of approximately 20 to 38 탆 using a sieve) ) Powder. At this time, the melting temperature was 600 ° C, and argon (Ar) was used as an inert gas for preventing oxidation during production. Thereafter, a halide free flux in which the powder and the harmful substances (Cl, Br) were not added was adjusted to a weight ratio of 88.5: 11.5 to prepare a paste. The conditions were as follows: the stirring speed of the vacuum mixer was 60 rpm, and the mixture was stirred for 15 minutes under a vacuum of 1 atm (1 atm).

Test Example : Lead-free Solder  Evaluation of composition characteristics

The properties of the solder alloys prepared from the lead-free solder compositions of Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated by the following test methods. ROL1 halogen-free flux was used to evaluate the solder paste, and the results are shown in Table 2 below.

In Table 2, spreadability is expressed as numerical value. In the case of thermal shock (125 ° C, -40 ° C, 2000cycle), the occurrence of cracks is expressed as OK or NG, and the thickness of the intermetallic compound layer (IMC) layer is expressed by numerical value. In addition, the rate of decrease in strength was expressed by numerical value.

division Spreadability Crack occurrence during thermal shock 2000 cycles 0
cycle 500 cycles 1000 cycles 1500 cycles 2000 cycles IMC layer change rate burglar
Rate of change Example 1 75.8% OK OK OK NG NG + 37% - 48% Example 2 76.4% OK OK OK NG NG + 35% - 44% Example 3 76.7% OK OK OK OK NG + 33% - 32% Example 4 77.1% OK OK OK OK NG + 28% - 26% Example 5 77.1% OK OK OK OK OK + 25% - 22% Example 6 77.6% OK OK OK OK OK + 26% - 19% Comparative Example 1 76.7% OK OK OK NG NG + 42% - 46% Comparative Example 2 75.5% OK OK NG NG NG + 44% - 56% Comparative Example 3 75.8% OK OK OK OK OK + 34% - 24%

1) Comparison of spreadability

The degree of spreading by heating for 30 seconds at a temperature of + 50 ° C based on the melting point (liquid phase) of each composition was confirmed using a micrometer.

As a result, as shown in Table 2, there was a difference in degree of spreading depending on the kind and content of the added components, and compared with Comparative Examples 1 and 2, which are the conventional ternary system, and spreadability of Examples 4 to 6 was excellent . In addition, as in Comparative Example 3, when nickel (Ni) was included in a large amount, spreadability was deteriorated due to a high melting point of nickel (Ni) and a characteristic of being vulnerable to oxidation.

2) Crack comparison during thermal shock

The alloys of Examples 1 to 6 and Comparative Examples 1 and 3 were soldered to a PCB of FR-4 finished with OSP and allowed to stand for 2000 cycles (30 minutes / cycle) under conditions of 125 캜 and -40 캜 in a thermal shock plant And the presence of cracks was confirmed.

As a result, as shown in Table 2, it was confirmed that the time of occurrence of cracks in the alloys of the Examples was better than that of Comparative Examples 1 and 2 of the prior art.

3) Intermetallic compound (IMC layer) change rate

The change in the intermetallic compound (IMC layer) thickness of the specimens evaluated in the same manner as in the thermal shock cracking test was confirmed. Although there is no precise standard for the influence of IMC layer thickness, IMC layer itself has strong brittleness when it is subjected to thermal shock test (thermal fatigue test) compared with the initial stage of soldering, Compared with the initial characteristics, it is judged to be solder with excellent bonding reliability.

On the other hand, Examples 1 to 6 according to the present invention were found to be better than Comparative Examples 1 and 2.

4) Strength reduction rate

The strength change rate of the specimens evaluated in the same manner as in the thermal shock cracking test and IMC layer change rate test was confirmed. The change in strength varies depending on the coarsening and cracking of the internal metal structure, and the difference between the examples and the comparative examples is clearly confirmed. A lower rate of strength reduction means less internal cracks, which means less change in electrical resistance. Therefore, the rate of reduction in strength is an absolute criterion for separating high strength lead free solder composition and general lead free solder.

As compared with the comparative example, it was confirmed that the rate of decrease in the strength of the alloys of the examples and the alloys of the other examples was remarkably low. As a result, it was concluded that the composition of the examples conformed to the characteristics of the high strength lead-free solder composition.

As shown in Table 2, the solder according to Examples 1 to 6 composed of tin-silver-bismuth-nickel, as compared with the solder according to Comparative Examples 1 and 3, showed good spreading characteristics and thermal shock test ). ≪ / RTI > Also, it was confirmed that it has an improved bonding strength. In Examples 1 to 6, it was confirmed that Examples 4 to 6 containing phosphorus or cobalt were superior in terms of spread characteristics, thermal shock test (heat cycling), and bonding strength.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (11)

For a total of 100% by weight of the lead-free solder composition,
0.1 to 1.7% by weight of silver (Ag)
1.5 to 3.5% by weight of bismuth (Bi)
0.01 to 0.8% by weight of copper (Cu)
0.001 to 0.0099% by weight of nickel (Ni), and
The remainder tin Sn,
1.0 to 3.0% by weight of phosphorus (P) and 1.0 to 2.0% by weight of cobalt (Co). The method according to claim 1,
And 0.3 to 1.5% by weight of silver (Ag). The method according to claim 1,
And 2.0 to 3.3% by weight of the bismuth (Bi). The method according to claim 1,
And 0.1 to 0.6% by weight of copper (Cu). The method according to claim 1,
And 0.003 to 0.007% by weight of nickel (Ni). delete For a total of 100% by weight of the lead-free solder composition,
0.1 to 1.7% by weight of silver (Ag)
1.5 to 3.5% by weight of bismuth (Bi)
0.01 to 0.8% by weight of copper (Cu)
0.001 to 0.0099% by weight of nickel (Ni), and
The remainder tin Sn,
And 1.0 to 3.0% by weight of phosphorus (P). For a total of 100% by weight of the lead-free solder composition,
0.1 to 1.7% by weight of silver (Ag)
1.5 to 3.5% by weight of bismuth (Bi)
0.01 to 0.8% by weight of copper (Cu)
0.001 to 0.0099% by weight of nickel (Ni), and
The remainder tin Sn,
And 1.0 to 2.0% by weight of cobalt (Co). A lead-free solder alloy made from the lead-free solder composition according to any one of claims 1 to 5, 7 and 8. An electronic part comprising the lead-free solder alloy according to claim 9. A vehicle comprising the lead-free solder alloy according to claim 9.