JP2018079480A - Bi-In-Sn TYPE SOLDER ALLOY FOR LOW TEMPERATURE, ELECTRONIC PART IMPLEMENTATION SUBSTRATE USING THE ALLOY, AND APPARATUS MOUNTING THE IMPLEMENTATION SUBSTRATE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Bi-In-Sn type solder alloy for a low temperature, which can lower a junction temperature more higher than that of a solder alloy for medium and low temperatures of the prior art, which is excellent in bondability, stress relaxation property, and junction temperature, and a lower melting point, an electronic part mounting substrate, and a device mounting that implementation substrate.SOLUTION: A Pb-free solder alloy of Bi-In-Sn type contains In of 42.0 mass % or more and 50.0 mass % or less, Sn of 7.0 mass % or more and 23.0 mass % or less, preferably In of 43.0 mass % or more and 49.0 mass % or less, Sn of 8.0 mass % or more and 21.0 mass % or less, and the remainder is composed of Bi excepting the element which is contained inevitably on the production.SELECTED DRAWING: None

Description

  The present invention relates to a Pb-free solder alloy, and more particularly to a Bi—In—Sn solder alloy suitable for low temperature use.

  In recent years, regulations on chemical substances harmful to the environment have become stricter, and this regulation is no exception for solder alloys used for the purpose of joining electronic components to a substrate. Pb (lead) has been used as a main component in solder alloys for a long time, but lead has already been a regulated substance under the RoHS directive and the like. For this reason, development of solder alloys that do not contain lead (hereinafter also referred to as Pb-free solder alloys) has been actively conducted.

  Solder alloys used when joining electronic components to a substrate are roughly classified into high temperature (about 260 ° C. to 400 ° C.) and medium to low temperature (about 140 ° C. to 230 ° C.) depending on the limit temperature of use. The low-temperature solder alloy generally refers to a solder alloy having a melting point lower than the melting point 183 ° C. of the eutectic alloy of Pb-63Sn. However, some electronic components have very low heat resistance, and their functions may deteriorate or be destroyed when exposed to high temperatures. For bonding such electronic components, the temperature is lower than 140 ° C. Therefore, there is a demand for a low-temperature solder alloy having a lower melting point for soldering in such an environment.

Conventionally, as such a low-temperature solder alloy having a lower melting point, for example, a lead-containing solder alloy such as a Sn-52Bi-32Pb alloy having a melting point of 95 ° C. or a Sn-40Pb-40Bi alloy having a melting point of 113 ° C. is used. It has been.
As a Pb-free technology for such a low-temperature solder alloy having a lower melting point, Patent Document 1 discloses a low-melting Pb-free solder having a lower melting point that can be soldered in an environment lower than 130 ° C. As an alloy, Pb-free solder containing 48% by mass to 52.5% by mass of In, the balance being Bi, the solidus temperature (melting point) being 85 ° C. or higher and the liquidus temperature being 110 ° C. or lower. Alloys are described.

WO2007 / 21006

In recent years, with the miniaturization of electronic components, heat generation from electronic devices has decreased, and at the same time, the heat-resistant temperature of electronic devices has become lower due to the thinning of circuits of electronic devices. As a solder alloy for use, there is a need for a low-temperature Pb-free solder alloy having a lower melting point that can be soldered in a lower temperature environment than the Pb-free solder alloy described in Patent Document 1. In addition to joining the target member by melting at a desired temperature, the joined body formed of the solder alloy exhibits sufficient stress relaxation properties and has long-term joining reliability. It is also required.
However, conventionally, as a low-temperature Pb-free solder alloy having a lower melting point for soldering in an environment at a temperature lower than 130 ° C., a joined body formed of the solder alloy after joining exhibits sufficient stress relaxation properties. None of them has long-term bonding reliability.

  The present invention has been made in view of such a problem, and can greatly reduce the bonding temperature as compared with conventional solder alloys for medium and low temperatures, and is excellent in bonding property, stress relaxation property, bonding reliability, and the like. Another object of the present invention is to provide a Pb-free solder alloy suitable for low temperature use having a lower melting point.

  In order to achieve the above object, the present inventor has combined various elements that do not contain an environmentally regulated substance, and as a result of earnest research, the inventors have simply set the melting point to a suitable composition range by combining Bi, In, and Sn. Not only lowers, but also makes it possible to produce a Pb-free Bi-In-Sn solder alloy with excellent bondability with various metals to be bonded and excellent stress relaxation, and manufactures electronic components with excellent bonding reliability. The present invention has been found and the present invention has been completed. Further, the inventors have found that the Pb-free Bi—In—Sn solder alloy further contains P, thereby further improving the wettability and producing an electronic component with more excellent bonding reliability. The present invention has been completed.

  That is, the Pb-free Bi—In—Sn solder alloy according to the present invention contains 42.0% by mass to 50.0% by mass of In, 7.0% by mass to 23.0% by mass of Sn, and the balance Is made of Bi except for elements inevitably contained in production.

  The Pb-free Bi—In—Sn solder alloy according to the present invention contains 42.0% by mass to 50.0% by mass of In, 7.0% by mass to 23.0% by mass of Sn, P is contained 0.001 mass% or more and 0.500 mass% or less, and the balance is made of Bi except for elements inevitably contained in production.

  In the Pb-free Bi—In—Sn solder alloy of the present invention, In is contained 43.0 mass% or more and 49.0 mass% or less, and Sn is contained 8.0 mass% or more and 21.0 mass% or less. Is preferred.

  In addition, an electronic component mounting board according to the present invention is characterized by having an electronic component joined using any of the Pb-free Bi—In—Sn solder alloys according to the present invention.

  An apparatus according to the present invention includes the electronic component mounting board according to the present invention.

  Since the Pb-free Bi—In—Sn solder alloy of the present invention does not contain a regulated substance such as Pb, it is environmentally friendly, and the solidus temperature can be set to a very low temperature of about 62 ° C. It is possible to manufacture the low heat resistant component suitably without causing thermal damage. Moreover, since the Pb-free Bi—In—Sn solder alloy of the present invention is extremely excellent in bondability, stress relaxation property, bond reliability, and the like, a highly reliable bonded body can be formed.

It is the schematic which looked at the joined body which joined the solder alloy to Ni plating Cu board | substrate from the upper direction of the solder alloy. It is the cross-sectional schematic of the joined body which joined the solder alloy and also the Si chip on it on Ni plating Cu board | substrate.

  Hereinafter, a technique related to the Pb-free Bi—In—Sn solder alloy according to the present invention in which Bi contains a predetermined amount of In and Sn will be described.

The Pb-free Bi-In-Sn solder alloy of the present invention contains 42.0% to 50.0% by mass of In, 7.0% to 23.0% by mass of Sn, and the remainder is manufactured. It is made of Bi except for elements inevitably contained.
Further, the Pb-free Bi—In—Sn solder alloy according to another embodiment of the present invention has an In content of 42.0 mass% to 50.0 mass% and an Sn content of 7.0 mass% to 23.0 mass%. It is contained below, and further contains P in an amount of 0.001% by mass to 0.500% by mass, and the balance is made of Bi except for elements which are inevitably contained in production.
In addition, the Pb-free Bi—In—Sn solder alloy of the present invention and the Pb-free Bi—In—Sn solder alloy of other embodiments of the present invention preferably include 43.0% by mass or more of In and 49.0% by mass. % By mass or less, Sn is contained in an amount of 8.0% by mass or more and 21.0% by mass or less.

  An electronic component mounting board that performs solder bonding using a Pb-free Bi-In-Sn solder alloy having the above composition and an apparatus having the board mounted thereon have a low heat resistant electron that does not have a general heat resistant temperature. Components, boards, etc. are used. If the Pb-free Bi—In—Sn solder alloy of the present invention is used, in addition to the effect of forming a highly reliable bonded body with excellent bonding properties, stress relaxation properties, bonding reliability, and the like described above, Since the joining temperature at the time of production can be greatly lowered as compared with conventional solder alloys for medium and low temperatures, it also has an effect of suppressing the manufacturing cost for heating the solder alloy. Hereinafter, each element used for the Pb-free Bi—In—Sn solder alloy of the present invention will be described in detail.

<Bi>
Bi is an element which forms a main component together with In and Sn described later in the Pb-free Bi—In—Sn solder alloy of the present invention. Bi belongs to the Va group element (N, P, As, Sb, Bi), and its crystal structure is a trigonal crystal (rhombohedral crystal) with low symmetry, and is a very brittle metal. Bi is a metal that expands during solidification, and the contraction rate (− means expansion and + means contraction) during solidification is −3.2% to −3.4%.
By incorporating In and Sn into a solder alloy containing Bi like the Pb-free Bi—In—Sn solder alloy of the present invention, it is possible to improve the problem that Bi expands during solidification. That is, In and Sn shrink in volume during solidification. Therefore, by adding In and Sn to Bi, the amount of expansion of Bi is reduced by the amount of contraction of In and Sn, the volume change of the entire solder alloy is reduced, and the residual stress in the solder alloy is reduced. Is possible.
Furthermore, by using a ternary alloy of Bi—In—Sn, the solidus temperature becomes about 60 ° C., and the melting point is significantly lower than that of the Sn—Pb eutectic solder alloy (solidus temperature 183 ° C.). Can do. Moreover, the melting point should be lower than that of a low-temperature lead-containing solder alloy having a lower melting point, such as a Sn-52Bi-32Pb alloy having a melting point of 95 ° C. or a Sn-40Pb-40Bi alloy having a melting point of 113 ° C. Can do. In this way, the melting point is very low, so the temperature of the soldering environment can be lowered, it is possible to suitably solder an object with a low heat-resistant temperature, and the running cost such as electricity bill at the time of soldering can be reduced. In addition, the progress of oxidation can be suppressed. Moreover, since the Pb-free Bi—In—Sn solder alloy of the present invention is extremely flexible, it has excellent stress relaxation properties and bonding reliability.

<In>
In is an element which forms a main component together with the above-described Bi and Sn described later in the Pb-free Bi—In—Sn solder alloy of the present invention. As described above, by incorporating In together with Sn in a solder alloy containing Bi, a solder alloy with low residual stress and a low melting point can be obtained.
The In content in the Bi—In—Sn solder alloy of the present invention is 42.0 mass% or more and 50.0 mass% or less. When In is contained in this range, the crystal becomes finer, the workability and stress relaxation properties are improved, and high reliability is also obtained. If the In content is less than 42.0% by mass or exceeds 50.0% by mass, the liquidus temperature becomes high and the solder alloy cannot be sufficiently melted and melted during soldering at a low temperature. There may be a case where a good separation cannot be obtained because a separation phenomenon occurs and sufficient workability and stress relaxation properties cannot be obtained. It is preferable that the content of In is 43.0% by mass or more and 49.0% by mass or less because better characteristics can be obtained.

<Sn>
Sn is an element which forms a main component together with the aforementioned Bi and In in the Pb-free Bi—In—Sn solder alloy of the present invention. As described above, by adding Sn to the solder alloy containing Bi together with In, the residual stress can be reduced and the melting point of the solder alloy can be greatly reduced.
Further, Sn is excellent in reactivity with Cu, Ni and the like often used for the members to be joined, so that wetting and joining properties with the members to be joined are improved, and as a result, there is an effect of improving the joining reliability.
The Sn content in the Bi—In—Sn solder alloy of the present invention is 7.0% by mass or more and 23.0% by mass or less, and preferably 8.0% by mass or more and 21.0% by mass or less. If the Sn content is less than 7.0% by mass, the content is too small to produce a sufficient intermetallic compound with the joint surface, or the difference between the liquidus temperature and the solidus temperature becomes large. In some cases, the solder alloy cannot be sufficiently melted, causing a detachment phenomenon and the like, and sufficient workability and stress relaxation properties cannot be obtained. If the Sn content exceeds 23.0% by mass, the liquidus temperature becomes too high, and the solder alloy cannot be sufficiently melted, resulting in a detachment phenomenon, and sufficient workability and stress relaxation properties are obtained. In some cases, good bonding cannot be achieved.

<P>
The Pb-free Bi—In—Sn based solder alloy according to another embodiment of the present invention improves the wettability and bonding properties of the Bi—In—Sn based solder alloy in addition to Bi, In, and Sn as contained elements. Therefore, P is contained. The reason why the effect of improving wettability is increased by the inclusion of P is that P is highly reducible and suppresses oxidation of the solder alloy surface by oxidizing itself.
By containing P, the effect of reducing the generation of voids at the time of bonding can also be obtained. This is because P tends to oxidize itself, and oxidation proceeds preferentially over Bi, In, and Sn, which are the main components of the solder alloy at the time of joining, thereby suppressing the oxidation of the solder matrix and This is considered to be because the oxide can be reduced. Since P is vaporized at the same time as an oxide, the oxide of P does not disturb the bonding property. As a result, wettability is improved and good bonding is possible.
Since P is very reducible as described above, it exhibits the effect of improving wettability with a very small amount. However, when the P content reaches a predetermined amount, the effect of improving the wettability does not change even if the P content is further increased. Conversely, the oxide of P due to the excessive content is taken into the solder alloy and becomes a void. There is a risk that P forms a brittle phase and segregates, making the solder alloy brittle. In particular, it was confirmed that wire breakage could be caused when processing wires. Therefore, the P content is preferably a trace amount. Specifically, the P content in the solder alloy that sufficiently exhibits the effect of improving wettability is 0.001% by mass or more and 0.50% by mass or less.

Bi, In, Sn, and P having a purity of 99.99% by mass or more were prepared as raw materials. Large flakes and bulk materials were cut and pulverized to a size of 3 mm or less so that the alloy after melting was uniform without variation in composition depending on the sampling location. In addition, P is difficult to melt and easily oxidizes and volatilizes. Moreover, P is a second kind of hazardous material, and if it is contained as it is, it will ignite, so an alloy with Sn is made in advance and the size is 3 mm or less. I made it fine.
Next, a graphite crucible for a high-frequency melting furnace was prepared, and a predetermined amount of the prepared raw materials and alloys were weighed and put into the crucible.
A crucible containing raw materials and alloys was placed in a high-frequency melting furnace, and nitrogen was flowed at a flow rate of 0.7 L / min or more per kg of the raw materials in order to suppress oxidation during melting, and the melting area was set to a nitrogen atmosphere. In this state, the melting furnace was turned on to heat and melt the raw materials and alloy. After the raw materials and alloys began to melt, they were thoroughly stirred with a mixing rod and mixed uniformly so as not to cause local compositional variations. After confirming sufficient melting, the high frequency power supply was turned off, the crucible was quickly taken out, and the molten metal in the crucible was poured into the mold for forming the solder mother alloy. As the mold, a mold was used from which a plate-like solder mother alloy having a thickness of 5 mm, a width of 40 mm, and a length of 250 mm was obtained.
The mixing ratio of each raw material was changed variously, and the solder mother alloys of Samples 1 to 18 were produced by the method described above. The compositions of the solder mother alloys of Samples 1 to 18 were analyzed using an ICP emission spectroscopic analyzer. The analysis results are shown in Table 1 below. Sample 18 is a reference example and is an example of a solder alloy having a melting point for medium and low temperatures for soldering in a conventional environment of about 140 ° C. to 230 ° C., which is different from the solder alloy of the present invention.

（注）表中の※を付した試料１３〜１７は比較例、試料１８は参考例としての中低温用はんだ合金組成を有するはんだ合金の一例である。

(Note) Samples 13 to 17 marked with * in the table are comparative examples, and sample 18 is an example of a solder alloy having a medium and low temperature solder alloy composition as a reference example.

  Next, for each of the solder mother alloys of Samples 1 to 18 shown in Table 1 above, as shown below, as a wettability evaluation, the determination of the spread of the solder alloy on the substrate visually, A void ratio was measured as an evaluation of 1, a shear strength was measured as a second evaluation of bondability, and a heat cycle test was performed as an evaluation of reliability. In addition, since the evaluation of the wettability of the solder alloy does not normally depend on the solder shape, it may be evaluated with the shape of a wire, a ball, a paste, etc. In this example, the evaluation is performed by forming a punched product. did.

<Processing to punched products>
The prepared plate-shaped mother alloy sample having a thickness of 5 mm, a width of 40 mm, and a length of 250 mm was rolled with a warm rolling mill. Each sample was rolled 5 times, rolled at a speed of 15 to 30 cm / sec, and rolled at a temperature of 250 ° C., so that it rolled into a ribbon shape with a thickness of 30.0 ± 1.2 μm by rolling 5 times. Rolled.
Each sample processed into a ribbon shape was punched into a rectangular shape of 0.4 mm × 0.5 mm with a press machine, and 1000 samples were punched out to produce punched products.

<Evaluation of wettability>
The evaluation of wettability was carried out using the solder alloy punched product. First, a wettability tester (device name: atmosphere control type wettability tester) was started, a double cover was applied to the heater part to be heated, and nitrogen was flowed from four locations around the heater part (nitrogen flow rate: each 12 L / min). Thereafter, the heater was set to a temperature higher than the melting point by 50 ° C. and heated.
After the heater part becomes a nitrogen atmosphere and the heater temperature is stabilized, the Cu substrate 1 (plate thickness: about 0.70 mm) on which the Ni plating layer 2 (film thickness: 5.0 μm) is formed is set in the heater part. And heated for 25 seconds. Next, the solder alloy 3 was placed on the Cu substrate and further heated for 25 seconds. After the heating was completed, the Cu substrate 1 was picked up from the heater portion, temporarily moved to a place where the nitrogen atmosphere next to the Cu substrate 1 was maintained, and cooled to obtain a sample for wettability evaluation (see FIG. 1). After sufficiently cooling, it was taken out into the atmosphere and the bonding state was confirmed. “X” when the bonding was not possible, “△” when the bonding was successful but the wetting and spreading was poor (the solder was swelled), and when the welding was performed with the wetting and spreading well (the solder was thin on the Cu substrate) (When spread) was evaluated as “◯”.

<Evaluation of bondability 1 (measurement of void fraction)>
Using the joined body shown in FIG. 1 manufactured in the same manner as that used for the evaluation of the wettability, the void ratio of the joined body of the solder alloy joined to the Cu substrate was measured using an X-ray transmission device. Specifically, X-rays are transmitted perpendicularly from the top to the bonding surface of the solder alloy and the Cu substrate, and the void area and the bonding area of the solder alloy and the Cu substrate are obtained from the obtained X-ray image. Was used to calculate the void fraction. Table 2 shows the calculation results of the void ratio of the joined body.
[Calculation Formula 1]
Void ratio (%) = void area / (void area + solder alloy / Cu substrate bonding area) × 100

<Evaluation of bondability 2 (Comparison of shear strength)>
For the second evaluation for confirming the bondability of each solder alloy, a Cu substrate 1 (plate thickness: 0) having a Si chip 4 and a Ni plating layer 2 (film thickness: 3.0 μm) using the solder alloy 3 is used. .3 mm) (see FIG. 2) and a shear strength was measured. A die bonder was used for manufacturing the joined body. That is, first, while flowing nitrogen gas through the heater part of the apparatus, the temperature was set to 50 ° C. higher than the melting point of each solder sample. After the heater part was filled with a nitrogen atmosphere and reached a predetermined temperature, the heater The Cu substrate 1 having the Ni plating layer 2 was placed on the part and heated for 15 seconds. Thereafter, the solder alloy 3 of each sample was placed thereon and heated for 20 seconds, and the Si chip 4 was placed on the molten solder alloy 3 and scrubbed for 3 seconds. After scrubbing, the joined body was quickly transferred to a cooling part in a nitrogen atmosphere and cooled to room temperature. Thereafter, the joined body was taken out into the atmosphere and the shear strength was measured. Next, the relative value of the measured value of the shear strength of each sample was calculated by setting the measured value of the shear strength in the sample 18 which is an example of a solder alloy having a conventional solder alloy composition for medium and low temperatures as 100%. Table 2 shows the ratios of the calculated share strengths.

<Reliability evaluation (heat cycle test)>
A heat cycle test was performed to evaluate the reliability of the solder joint. This test was performed using a Cu substrate made by bonding a Si chip with a solder alloy, which was produced in the same manner as that used in the evaluation 2 of the bondability. First, a heat cycle test was performed on a Cu substrate bonded with a Si chip with a solder alloy, with cooling at −55 ° C. and heating at 50 ° C. as one cycle, and repeating this for 500 cycles and 700 cycles. Thereafter, a Cu substrate bonded with a Si chip with a solder alloy, which was subjected to a heat cycle test, was embedded in a resin, subjected to cross-sectional polishing, and the bonded surface was observed with an SEM (Scanning Electron Microscope). The case where the joint surface was peeled off or the solder was cracked was indicated as “X”, and the case where there was no such defect and the same joint surface as in the initial state was maintained as “◯”. In addition, although it can be used as a product as long as no defect is confirmed up to 500 cycles in this heat cycle test, among samples having a solder alloy composition within the scope of the present invention, In and Sn have more preferable contents. For a comparative evaluation of reliability between a sample having a solder alloy composition within the range and a sample having a solder alloy composition other than that, confirmation was performed up to 700 cycles. The evaluation results are shown in Table 2.

（注）表中の※を付した試料１３〜１７は比較例についての評価結果、試料１８は参考例としての中低温用はんだ合金組成を有するはんだ合金の一例についての評価結果である。

(Note) Samples 13 to 17 marked with * in the table are evaluation results for the comparative example, and sample 18 is an evaluation result for an example of a solder alloy having a medium and low temperature solder alloy composition as a reference example.

As can be seen from the results in Table 2 above, Samples 1 to 12 having a solder alloy composition within the scope of the present invention exhibited generally good characteristics in each evaluation item.
In the evaluation of wettability, Samples 1 to 3, 8 to 10 in which the In content is 43.0% by mass or more and 49.0% by mass or less and the Sn content is 8.0% or more and 21.0% by mass or less. Has good wettability to a Cu substrate having a Ni plating layer, and in particular, Samples 8 to 10 containing P in an amount of 0.001% by mass to 0.500% by mass are very fast and good in spreading. Yes, the sample spread thinly and wet at the moment of contact with the Cu substrate. Although either the In content or the Sn content is outside the above range, the In content is 42.0 mass% or more and 50.0 mass% or less, and the Sn content is 7.0 mass%. Among samples 4 to 7, 11, and 12 that are 23.0% by mass or less, Samples 11 and 12 that contain P in an amount of 0.001% by mass to 0.500% by mass have good wettability. . On the other hand, in Samples 4 to 7 not containing P, the solder was slightly raised and the wet spread was slightly deteriorated, but the wettability to the extent that bonding was possible was obtained.
In the measurement of the void ratio as the bondability evaluation 1, no void was confirmed in all of the samples 1 to 12.
In the measurement of the shear strength as the bondability evaluation 2, in all the samples 1 to 12, the Sure strength was 110% or more, and it was confirmed that high joint strength was obtained. In particular, Samples 1 to 3 and 8 to 10 had a Sure strength of 120% or more, and it was confirmed that higher bonding strength was obtained.
Also in the heat cycle test as an evaluation of the bonding reliability, good results were obtained, and none of the samples 1 to 12 was confirmed by observation after 500 cycles. In particular, Samples 1 to 3 and 8 to 10 were not confirmed to be defective even when observed after 700 cycles.

On the other hand, Samples 13 to 17 having a solder alloy composition outside the scope of the present invention, which is a comparative example, gave undesirable results in at least any of the characteristics.
In the evaluation of wettability, Samples 13 and 15 had poor wettability to a Cu substrate having a Ni plating layer and could not be joined.
In the measurement of the void ratio as the bondability evaluation 1, at least 5% or more voids were generated in all the samples 13-17. In particular, Sample 17 in which the P content greatly exceeds the upper limit of 0.500% by mass in the present invention has a void generation rate of 15%.
In the measurement of the shear strength as the bondability evaluation 2, the Sure strength was 90% or less in all the samples 13 to 17. In particular, the sample 17 had a shear strength of 75% or less.
In the heat cycle test as an evaluation of reliability, defects occurred in all samples except sample 18 by 500 cycles. Sample 18 is a conventional solder alloy for medium and low temperatures, has good wettability, and has good results although the bondability and shear strength are inferior to the scope of the present invention. As well as the above, good evaluation results were obtained, but the melting point was high and soldering could not be performed in an environment lower than 130 ° C.

1 Cu substrate 2 Ni layer 3 Solder alloy 4 Si chip

The present invention relates to a Pb-free solder alloy, and more particularly to a Bi-In-Sn solder alloy suitable for low temperature use, an electronic component mounting board using the same, and an apparatus on which the mounting board is mounted .

WO2007 / 21006

The present invention has been made in view of such a problem, and can greatly reduce the bonding temperature as compared with conventional solder alloys for medium and low temperatures, and is excellent in bonding property, stress relaxation property, bonding reliability, and the like. Another object of the present invention is to provide a Pb-free solder alloy suitable for low temperature use having a lower melting point, an electronic component mounting board using the same, and a device on which the mounting board is mounted .

In order to achieve the above object, the present inventor has combined various elements that do not contain an environmentally regulated substance, and as a result of earnest research, the inventors have simply set the melting point to a suitable composition range by combining Bi, In, and Sn. Pb-free Bi-In-Sn solder alloy having excellent bondability with various bonded metals and excellent stress relaxation properties, and an electronic component mounting board using the same and its mounting It has been found that a bonded body excellent in bonding reliability can be formed in an apparatus equipped with a substrate , and the present invention has been completed. Further, the inventor further improves the wettability by further adding P to the Pb-free Bi-In-Sn solder alloy, and in an electronic component mounting board using the same and an apparatus on which the mounting board is mounted. The present inventors have found that a bonded body with higher bonding reliability can be formed, and have completed the present invention.

Since the Pb-free Bi—In—Sn solder alloy of the present invention does not contain a regulated substance such as Pb, it is environmentally friendly, and the solidus temperature can be set to a very low temperature of about 62 ° C. An electronic component mounting substrate and a device on which the mounting substrate is mounted can be suitably manufactured without causing thermal damage to the low heat resistant component. Moreover, since the Pb-free Bi—In—Sn solder alloy of the present invention is extremely excellent in bondability, stress relaxation, and bonding reliability, an electronic component mounting board using the same and mounting the mounting board is mounted. A highly reliable bonded body can be formed in the above apparatus .

An electronic component mounting board that performs solder bonding using a Pb-free Bi-In-Sn solder alloy having the above composition, and a device mounted with the mounting board have a low heat resistance that does not have a general heat resistance temperature. Electronic parts, substrates, etc. are used. If the Pb-free Bi—In—Sn solder alloy of the present invention is used, the above-described bonding property, stress relaxation property, bonding reliability, etc. are extremely high in an electronic component mounting substrate using the same and a device mounting the mounting substrate. In addition to the effect of forming an excellent and reliable bonded body, the manufacturing temperature for heating the solder alloy can be greatly reduced because the bonding temperature at the time of fabrication can be greatly reduced compared to conventional solder alloys for medium and low temperatures. It also has the effect of suppressing Hereinafter, each element used for the Pb-free Bi—In—Sn solder alloy of the present invention will be described in detail.

Claims (5)

  It contains 42.0% to 50.0% by mass of In, 7.0% to 23.0% by mass of Sn, and the balance is made of Bi except for elements inevitably contained in production. A Pb-free Bi-In-Sn solder alloy characterized.   In is contained 42.0 mass% or more and 50.0 mass% or less, Sn is contained 7.0 mass% or more and 23.0 mass% or less, P is further contained 0.001 mass% or more and 0.500 mass% or less, A Pb-free Bi—In—Sn solder alloy characterized in that the balance is made of Bi except for elements inevitably contained in production.   The Pb-free Bi-In- according to claim 1 or 2, wherein In is contained 43.0 mass% or more and 49.0 mass% or less, and Sn is contained 8.0 mass% or more and 21.0 mass% or less. Sn solder alloy.   The electronic component mounting board | substrate with which the electronic component was joined using the Bi-In-Sn type solder alloy in any one of Claims 1-3.   An apparatus on which the electronic component mounting board according to claim 4 is mounted.

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