JP5861559B2 - Pb-free In solder alloy - Google Patents

Description

  The present invention relates to a so-called Pb-free solder alloy that does not contain Pb, and particularly to a Pb-free In-based solder alloy that is excellent in all of workability, wettability, and stress relaxation properties.

  Solder alloy is generally workability when processing into the shape when using solder such as sheet and wire, mechanical strength such as elongation rate, tensile strength, shear strength, wettability, and reliability, It is desirable to have various characteristics in a balanced manner. The requirements for these characteristics vary greatly depending on the joining conditions of the solder and the usage environment of the product in which the solder is used.

For example, an excellent stress relaxation property is required for a solder for joining a Si chip or the like used in a computer or a communication device. This is because a large chip having a bonding area of 100 mm ² or more is used, or a current flowing through the chip is frequently interrupted, and thermal stress due to heating and cooling is intensely applied. In addition, even when the usage environment such as an automobile or a solar cell is severe, the stress applied to the solder is very large, and heating and cooling are frequently repeated. Thus, the stress generated by repeated heating and cooling becomes very large because the thermal expansion coefficient of Cu, which is the main component of the Si chip and the substrate, is about five times larger, and the stress increases as the chip becomes larger. Become.

  In order to relieve such a large stress and ensure high reliability, it is preferable to select a soft solder that can relieve the stress. A typical example is In-based solder, but in order to take advantage of the flexible nature of In, it is essential to be able to join well. That is, if good wettability is not obtained, the bonding strength is reduced, and voids are generated in the bonded portion, resulting in a decrease in heat dissipation. Therefore, high reliability utilizing the flexible nature of In cannot be obtained. . However, sufficient wettability cannot be obtained with In alone, and worse, there is a problem that In is too soft and cannot be processed into a sheet shape. That is, if In is processed into a thin sheet, there is a problem that it sticks to a rolling roll or does not have a uniform thickness.

  In is a very soft metal and has the best stress relaxation properties, so it is used as a solder or brazing material for various purposes. However, because of the above problems, it is used by alloying with other elements. Yes. As a specific example of a solder or brazing material using an In-based alloy, for example, Patent Document 1 discloses that 0.001 to 10 wt% Zn, 0.001 to one of Pb, Sn, and In main elements. There is described a solder bump forming material for semiconductor elements, characterized in that 10 wt% Sb is added.

  Patent Document 2 discloses a semiconductor element characterized by adding 0.001 to 1 wt% of Cu and 0.001 to 1 wt% of Ni to any one of main elements of Pb, Sn, and In. A solder bump forming material is described. In Patent Document 3, an intermetallic compound having a NiAs-type crystal structure is formed in a solder joint and / or at a solder joint interface, and the Cu content is 0.1 to 2% by weight, and the Ni content is Lead-free solder alloy composition comprising In—Cu—Ni and / or Sn—In—Cu—Ni, characterized in that 0.01 to 0.1% by weight and the balance comprising In or In and Sn, and A lead-free solder alloy is described.

  In Patent Document 4, 2.5 to 10% by weight of Cu, 0.5 to 2.0% by weight of P, the balance of In, 35% by weight or less of Ag, and 2.5 to 10% by weight of Cu. 0.5 to 2.0 wt.% P, the balance of In composition, 65 to 75 wt.% Sb, 25 to 35 wt.% In composition, or 50 to 60 wt.% Ag, 40 to 50 wt. A low temperature brazing material for metal bonding having a composition of% Sb is described. It is also described that these brazing materials are suitable for a steel plate of a double wall container made of thin stainless steel and can be brazed without flux in a low oxidation potential atmosphere.

Japanese Patent Laid-Open No. 05-251451 Japanese Patent Laid-Open No. 05-251442 JP 2011-005542 A Japanese Patent Application Laid-Open No. 07-223089

  As described above, In-based solder has excellent stress relaxation properties, but with the recent technological advancement, there is an increasing demand for more reliable solder in computers and communication devices. In other words, as a result of the integration of functions in a small number of chips and the increase in chip size as functions become higher, In-based solders used in devices in the communication field that require even higher reliability Therefore, further excellent reliability, that is, wettability and stress relaxation properties are required.

  However, the solder bump forming material described in Patent Document 1 improves the bonding strength by forming an Al solid solution and an Al—Sb intermetallic compound, and further reduces the local battery reaction in a high temperature / high humidity environment. It is intended to improve durability and not to improve the flexibility of the base material itself. For this reason, it is estimated that excellent performance is exhibited in an environment of high temperature and high humidity, but it is difficult to exhibit sufficient performance in a severe environment where thermal stress is frequently applied by repeated heating and cooling. In other words, in addition to the fact that intermetallic compounds generally considered to be brittle are present at the bonding interface, Sb is originally a trigonal and brittle element, so it has a poor function to relieve repeated thermal stress, and thermal stress High reliability cannot be obtained in a severe environment in which is frequently applied.

In addition, the solder bump forming material described in Patent Document 2 is intended to make the wire thinner and improve the ball cutting position. Among In-based solders, it is not particularly excellent in terms of stress relaxation and reliability. I guess it is not. That is, since the additive element Ni generates a phase such as the main element In and many intermetallic compounds, for example, InNi ₃ , InNi ₂ , In ₉ Ni ₁₃ , the alloy becomes brittle when Ni is contained. Therefore, it is unlikely that such an In-based solder alloy has a particularly high reliability.

In the Pb-free solder alloy described in Patent Document 3, an intermetallic compound having a (Cu, Ni) ₆ Sn ₅ composition formed by adding Ni is a structure of an intermetallic compound having an additive-free Cu ₆ Sn ₅ composition. Higher reliability can be obtained by having a miniaturized structure compared to the above, that is, high reliability can be obtained by miniaturizing the crystal structure of the solder with the addition of Ni as essential. However, if the elongation is further improved by the refinement of the crystal, it becomes easy to elastically and plastically deform, and In that is originally soft and difficult to process becomes more difficult to process. There is a drawback that it is difficult to manufacture industrially.

  Furthermore, since the brazing material of Patent Document 4 is intended for brazing stainless steel plates, the bonding temperature is increased, and the low melting point of In (melting point: 156.6 ° C.) is not utilized. It is not suitable for joining semiconductor elements such as. That is, when the bonding temperature is high, the equipment cost becomes expensive and the power consumption increases. Furthermore, when the bonding temperature exceeds 400 ° C., there arises a disadvantage that the heat resistance of each component must be taken into consideration.

  The present invention has been made in view of the problems associated with the above-described conventional In-based solder alloys, and is excellent in all of workability, wettability, and stress relaxation properties, and has high reliability. An object is to provide an alloy, an electronic component mounting substrate bonded using the solder alloy, and a semiconductor device on which the substrate is mounted.

The first Pb-free In-based solder alloy according to the present invention is a Pb-free In-based solder alloy that does not contain Pb and contains In as a main component, and has a Sn content of 3.9 % by mass or more and 11.00% by mass. % or less and characterized in that the remaining portion is composed of in and inevitable impurities. The second Pb-free In-based solder alloy according to the present invention is a Pb-free In-based solder alloy that does not contain Pb and contains In as a main component, and has a Sn content of 0.01 mass% or more and 11. 00 mass% or less, Ag content is 0.01 mass% or more and 21.00 mass% or less, Cu content is 0.01 mass% or more and 0.90 mass% or less, and the balance is It consists of In and inevitable impurities.

The first Pb-free In-based solder alloy may further contain at least one of Cu and Zn, and when Cu is contained, the content thereof is 0.01% by mass or more and 0.90% by mass or less. In the case where Zn is contained, the content is 0.01 mass% or more and 3.00 mass% or less. The second Pb-free In-based solder alloy can further contain Zn, and the content thereof is 0.01 mass% or more and 3.00 mass% or less.

The first and second Pb-free In-based solder alloys can further contain P, and the content is preferably 0.500% by mass or less. Further, the first and second Pb-free In solder alloys preferably have a Vickers hardness (Hv) of 0.80 or more.

  According to the present invention, it is possible to provide a Pb-free In-based solder alloy that is excellent in all of workability, wettability, and stress relaxation properties and has high reliability. By bonding an electronic component or the like to the substrate using this Pb-free In-based solder alloy, a semiconductor device having high reliability can be provided even in a severe environment where a large thermal stress is applied.

  The Pb-free In-based solder alloy according to the present invention does not contain Pb, contains In as a main component, contains at least one of Sn and Ag, and contains an element inevitably included in production. The Pb-free In-based solder alloy of the present invention described above can further contain at least one of Cu and Zn, and can further contain P.

  In is a very soft element and has excellent stress relaxation properties. However, since In alone is too soft, it is difficult to process into a shape for use as solder. For example, when rolling into a sheet shape, In sticks to a rolling roll or the thickness of In does not become uniform. Therefore, in the present invention, various elements described below are included in order to obtain an In-based solder alloy that has sufficient stress relaxation properties, can be easily processed into a use shape, and has excellent wettability. Yes.

  Next, the essential elements contained in the above-described Pb-free In-based solder alloy according to the present invention or elements that can be optionally contained will be described in detail below.

<In>
In is an essential element constituting the main component in the Pb-free In-based solder alloy of the present invention. In is the softest of the elements that can be used practically, and because of its excellent stress relaxation properties, it can absorb thermal stress sufficiently, greatly improving the reliability of chip assemblies. Can be improved. Further, In has a melting point of 156 ° C., and melting at a relatively low temperature is advantageous in soldering. That is, since the chip can be bonded at a low temperature, the equipment cost, the electricity bill, etc. can be kept low.

  However, since In is too soft, In alone cannot be processed into a normal solder shape, for example, a sheet shape, or wettability is not always sufficient. Therefore, in the In-based solder alloy of the present invention, each element described below is added and contained in order to improve workability and improve wettability while maintaining sufficient stress relaxation properties in use. By adding each element, moderate hardness is added to In. For example, if it is Vickers hardness (Hv), it becomes a value of 0.8 or more and can be processed into a sheet shape, etc. In addition, wettability is also obtained. improves.

<Sn>
Sn is an element that should contain at least one of them together with Ag in the Pb-free In-based solder alloy of the present invention. That is, since Sn and Ag exhibit similar effects, any one or both of Sn and Ag may be contained.

  Sn is generally a soft metal, but is harder than In. Therefore, the hardness can be adjusted by adding an appropriate amount of Sn to In, and the workability can be improved. Furthermore, since Sn is less thermally oxidized than In, wettability can be improved by adding Sn.

  When Sn is contained, the content is set to 0.01% by mass or more and 11.00% by mass or less. If the Sn content is less than 0.01% by mass, the content is too small, so that the effect of the addition does not substantially appear. Moreover, when it exceeds 11.00 mass%, a beta phase will be generated and it will enter into a 2 phase field with an In solid solution. Further, this two-phase region is a narrow region with respect to the Sn content (or In content), and the structure control becomes very difficult. Naturally, the β phase is an intermetallic compound and is extremely hard and brittle, so that the solder alloy becomes too hard and the required stress relaxation property cannot be obtained. The Sn content may be determined within the above range in accordance with the required characteristics, but is particularly preferable in the range of 0.2% by mass or more and 6.0% by mass or less because the effect of Sn is more likely to appear.

<Ag>
Ag is an element which should contain at least one of them together with Sn in the Pb-free In solder alloy of the present invention. The effect obtained by containing Ag is roughly divided into two, which are improvement of wettability and improvement of workability.

  First, Ag is very effective in improving wettability, as can be seen from the fact that Ag is used in the metallization layer provided as the uppermost layer on the top of the electrode, substrate, etc. of the chip. In other words, the main cause of the decrease in wettability is that an oxide film is formed on the bonding surface of the solder or the substrate, but Ag is very difficult to oxidize, and naturally it is harder to oxidize than In. Therefore, Ag is an optimal element for improving wettability because it is difficult to form a thick oxide film that lowers wettability, and is easily alloyed with various elements.

In addition, Ag forms a eutectic alloy (composition of eutectic point: Ag = 3.0% by mass) with In, thereby miniaturizing the crystal and improving the elongation rate of the solder. Moreover, since this eutectic alloy is comprised from In solid solution and AgIn ₂ intermetallic compound, hardness can be provided by the effect of the intermetallic compound. Therefore, the amount of intermetallic compounds can be adjusted by adjusting the Ag content, and as a result, the hardness, elongation, and workability can be adjusted.

  Naturally, the workability of the solder is affected by the manufacturing conditions such as cooling because the size of the crystal grains changes depending on the cooling conditions at the time of solder manufacture. As the solder manufacturing conditions, for example, when attention is paid to the size of crystal grains, rapid cooling is preferable when miniaturizing, and when the cooling is slow, the crystal grains become coarse and good workability cannot be obtained. Therefore, the Ag content may be adjusted in consideration of the balance of workability, stress relaxation, etc., including wettability.

  When Ag is contained, the content is set to 0.01% by mass or more and 21.00% by mass or less. If the content of Ag is less than 0.01% by mass, the content is too small, so that the effect is not substantially exhibited. Conversely, if the content exceeds 21.00% by mass, the liquidus temperature will exceed 400 ° C, and the difference between the solidus temperature and the liquidus temperature will become too large at 250 ° C, resulting in the phenomenon of melting. As a result, the Ag content should not exceed 21.00% by mass.

  In particular, by making the Ag content in the range of 1.50 mass% or more and 5.00 mass% or less, the effect of the eutectic structure appears more remarkably and the workability and the like can be easily adjusted, which is more preferable. In this way, Ag exhibits a greater effect than Sn, but since Ag is an expensive metal, either or both of Sn and Ag are selected in consideration of the balance between cost and effect, and its content You can decide.

<Cu>
Cu is an element that can contain at least one of them together with Zn in the Pb-free In-based solder alloy of the present invention. That is, Cu can be added and contained as necessary in consideration of workability, wettability, stress relaxation, and cost.

  The effect expected by containing Cu is similar to the case of Sn or Ag. That is, since Cu is less likely to oxidize than In, it exists near the solder surface when the solder is melted, so that the oxidation of the solder can be suppressed and the wettability can be improved.

  However, in the case of Cu, the amount contained is small, as can be seen from the binary phase diagram with In. That is, the upper limit of the Cu content is 0.90% by mass, and when this value is exceeded, the liquidus rises sharply as Cu increases, the liquidus temperature becomes too high, and the liquidus temperature Since the difference in the solidus temperature becomes too large, a melting phenomenon occurs when the solder melts. When melting and separation occur, the bonding strength is remarkably reduced, and high reliability cannot be obtained. Moreover, although the lower limit of Cu content is 0.01 mass%, since it will be too small if it becomes less than this value, the effect of containing Cu is not acquired.

<Zn>
Zn is an element that can contain at least one of them together with Cu in the Pb-free In-based solder alloy of the present invention. The effect which can be expected by containing Zn is improvement of wettability and workability.

  First, regarding the improvement of wettability, Sn, Ag, and Cu suppress the surface oxidation of the solder because the metals themselves are hardly thermodynamically oxidized, whereas Zn is the opposite. That is, since Zn is more easily oxidized than In, Zn itself is preferentially oxidized over In to form a thin oxide film, thereby improving wettability. In other words, since the oxidation of the solder mother phase is suppressed by the oxidation of Zn, the oxide film does not become thick.

  Zn also has an effect on workability. That is, Zn and In form a eutectic alloy (eutectic point composition: Zn = 2.2% by mass). Generally, crystals become finer and soft In becomes softer, which reduces workability. It might be. However, since Zn itself is harder than In, Zn is a suitable metal for finely adjusting the softness (workability) of solder.

  The Zn content may be determined based on the above-described action of Zn while considering the balance of workability, wettability, and stress relaxation properties. Specifically, the content is 0.01 mass% or more and 3.00 mass%. The following is preferred. If the Zn content is less than 0.01% by mass, the content is too small, so that the effect of Zn content does not appear. Conversely, if the Zn content exceeds 3.00% by mass, the composition of the eutectic point will be exceeded, the difference between the liquidus temperature and the solidus temperature will widen, and melting or segregation will occur. It becomes difficult to control processability due to coarsening.

<P>
P is an element that can be optionally added to the Pb-free In solder alloy of the present invention, and the expected effect is improved wettability.

  P is highly reducible and suppresses oxidation of the solder alloy surface by oxidizing itself. When sufficient wettability cannot be secured, the role of improving wettability obtained by adding P to the solder is great.

  In addition, the inclusion of P also has the effect of reducing the generation of voids during bonding. That is, as already described, since P is easily oxidized by itself, oxidation proceeds preferentially over In which is a main component of the solder alloy at the time of bonding. As a result, it is possible to prevent the solder mother phase from being oxidized and reduce the joint surface of the electronic component or the like to ensure wettability. In this joining, since solder and oxides on the surface of the joining surface disappear, gaps (voids) formed by the oxide film are hardly generated, and the joining property, reliability, and the like can be improved.

  Note that P does not remain on the solder, the substrate or the like because it reduces the solder alloy or the substrate to become an oxide and vaporizes and flows into the atmospheric gas. For this reason, there is no possibility that the residue of P adversely affects reliability and the like, and it can be said that this is an excellent element.

  Content in the case of containing P is 0.500 mass% or less. As described above, since P is very reducible, the effect of improving wettability can be obtained even with a very small amount. However, even if the content exceeds 0.50% by mass, the effect of improving the wettability is hardly changed, and excessive inclusion increases the generation rate of voids by generating a large amount of P and P oxide gases. There is a risk that P may form a fragile phase and segregate, embrittle the solder joint and reduce reliability. In particular, when processing into a wire shape or the like, it has been confirmed that it tends to cause disconnection.

[Example 1]
As raw materials, In, Sn, Ag, Cu, Zn and P having a purity of 99.9% by mass or more were prepared. Large flakes and bulk-shaped raw materials were reduced to a size of 3 mm or less by cutting and crushing while paying attention to ensure that the alloy after melting did not vary in composition depending on the sampling location. Next, a predetermined amount of these raw materials was weighed and put into a graphite crucible for a high-frequency melting furnace.

  The crucible containing the raw materials was placed in a high-frequency melting furnace, and nitrogen was flowed at a flow rate of 0.7 liter / min or more per kg of the raw materials in order to suppress oxidation. In this state, the melting furnace was turned on to heat and melt the raw material. When the raw material began to melt, it was 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 of the solder mother alloy. A mold having the same shape as that generally used in the production of a solder mother alloy was used.

  Thus, the Pb free In type | system | group solder mother alloy of the samples 1-18 was produced by changing the mixing ratio of each said raw material. The compositions of the obtained solder mother alloys of Samples 1 to 18 were subjected to composition analysis using an ICP emission spectroscopic analyzer (SHIMAZU S-8100), and the obtained composition analysis results are shown in Table 1 below.

  Next, the workability of each Pb-free In-based solder mother alloy of Samples 1 to 18 was evaluated by processing it into a sheet with a rolling mill as described below. Moreover, about each solder alloy of the samples 1-18 processed into the sheet form, while measuring Vickers hardness, the following method evaluated the wettability (joinability) and the reliability evaluation by the heat cycle test. The evaluation of solder wettability or bondability does not depend on the solder shape, and may be evaluated by the shape of a wire, a ball, a paste, or the like.

<Evaluation of workability>
Each solder mother alloy (plate-shaped ingot having a thickness of 7 mm) of Samples 1 to 18 shown in Table 1 was rolled to a thickness of 100 μm using a rolling mill. In-based solder alloys are very soft, so care must be taken when rolling. First, rolling was performed while applying an appropriate amount of oil as required so that the sample did not stick to the roll. Thus, by making an oil film between a roll and a sheet | seat and between a sheet | seat and a sheet | seat, it can suppress that a roll, a sheet | seat, or sheets adhere. Also, sufficient consideration must be given to the feed rate of the sample. If the feed rate is too high, the sheets may be easily adhered to each other, or the tension may be applied too much and the sheets may be cut off. On the other hand, if the feeding speed is too slow, bending may occur and winding may be lost, or a sheet having a uniform thickness may not be obtained.

  For this reason, it rolled, adjusting feed rate, tension, etc. according to the softness of each sample. The rolled sheet was oil-washed with alcohol and then cut into a width of 25 mm by slitting. Further, Vickers hardness was measured according to JIS Z 2244-1961 for the obtained sheet-like In-based solder alloys of each sample, and the results are shown in Table 2 below.

  As evaluation 1 of workability, the obtained sheet-like In-based solder alloy was observed, and “◯” when no scratches, cracks, or deflections were observed, and scratches, cracks, or deflections per sheet length of 10 m were 1 to 3. “△” when there are places, if there are 4 or more scratches, cracks, or deflections per 10 m of sheet length, if the sheet breaks during sheet processing, and the sheet sticks to the rolling roll and can be processed into a sheet The case where there was not was set as "x".

  Furthermore, as a workability evaluation 2, the sheet thickness of a sheet-like In-based solder alloy having a length of 10 m was measured with a micrometer every 1 m, and the measured sheet thickness was in a range of 100 ± 3 μm at all measurement points. The case where it was included was evaluated as “◯”, and the case where it was outside this range at one or more measurement points was evaluated as “x”. The evaluation results of these processability evaluations 1 and 2 are shown in Table 2 below.

<Evaluation of wettability (bondability)>
Each solder alloy of Samples 1 to 18 processed into a sheet shape was evaluated using a wettability tester (device name: atmosphere control type wettability tester). That is, the heater part of the wettability tester is covered with a double cover, and the heater set temperature is about 30 ° C. higher than the melting point of each sample while flowing nitrogen at a flow rate of 12 liters / minute from four places around the heater part. Heat was set at a high temperature. After the set heater temperature was stabilized, a Cu substrate (plate thickness: about 0.70 mm) was set in the heater section and heated for 25 seconds.

  Next, the solder alloy of each sample was placed on a Cu substrate and heated for 25 seconds. After the heating was completed, the Cu substrate was taken up from the heater part, and once installed in a place where the nitrogen atmosphere next to it was kept, it was cooled. After sufficiently cooling, it was taken out into the atmosphere and a joint portion was confirmed. The joint between the solder alloy of each sample and the Cu substrate is visually checked, and “X” indicates that the bonding cannot be performed, “△” indicates that the bonding is successful but the wetting spread is poor (the solder does not spread), A case where bonding was possible and wetting and spreading was good (a state where the solder was thin and spreading) was evaluated as “◯”. The obtained evaluation results are shown in Table 2 below.

<Heat cycle test>
A heat cycle test was conducted to evaluate the reliability of solder joints. This test was performed using two samples each having a solder alloy bonded to a Cu substrate in the above-described wettability evaluation (samples having a wettability evaluation of ◯ or Δ). That is, for one of the two Cu substrates to which the solder alloy of each sample is bonded, 500 cycles are used for confirmation during the heat cycle test in which cooling at −55 ° C. and heating at + 125 ° C. are performed as one cycle. Repeat until. For the remaining one, the same heat cycle test was repeated up to 1000 cycles.

  Then, about each sample which performed the heat cycle test of 500 cycles and 1000 cycles, the Cu board | substrate with which the solder alloy was joined was embedded in resin, cross-section grinding | polishing was performed, and SEM (device name: HITACHI S-4800) performed the joining surface. Observations were made. As a result of this observation, the case where the joint surface peeled or the solder 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 indicated as “◯”. . The obtained evaluation results are shown in Table 2 below.

  As can be seen from Table 2 above, each of the Pb-free In-based solder alloys of Samples 1 to 11 according to the present invention exhibits good characteristics in all evaluation items of workability, wettability, and reliability. That is, even when processed into a sheet shape, there was no generation of scratches, cracks or deflection, the sheet thickness could be processed uniformly, and wettability and reliability were also good. Particularly good results in wettability are considered to be that the effect of Ag or Sn is great, and as a result of suppressing the oxidation of the solder surface, the solder alloy spreads on the substrate at the moment of contact with the Cu substrate.

  Further, each of the solder alloys of Samples 1 to 11 does not generate cracks or the like in the heat cycle test, despite severe conditions such as 1000 cycles, and exhibits good bondability and reliability. It is considered that the stress relaxation property due to the properties was sufficiently exhibited. Further, the Vickers hardness is 1.1 or more, which is higher than that of In alone (sample 18), indicating that the hardness is appropriate. The Pb-free In-based solder alloy of the present invention that functions satisfactorily even under such severe conditions can sufficiently withstand applications where thermal stress is frequently applied and even higher reliability is required.

  On the other hand, each of the solder alloys of Samples 12 to 18 as a comparative example has an unfavorable result in two or more evaluations because the content of any of Sn, Ag, Cu, Zn, and P is not appropriate. It was. For example, sample 18 which is an In simple substance has a Vickers hardness of 0.78 and is too soft to stick to a roll during rolling, and cannot be rolled to a thickness of 100 μm. There wasn't. Sample 14 had many cracks. Regarding the wettability, except for Samples 12 and 17, unfavorable results were obtained. In particular, in the heat cycle test, defects occurred up to 1000 times in all the samples (excluding Samples 13, 14, 16, and 18 that could not be joined).

[Example 2]
The Pb-free In-based solder alloys of Samples 1 to 11 according to the present invention manufactured in Example 1 were evaluated in a pseudo manner assuming that they were mounted on a semiconductor device. That is, a sheet-like solder having a length and width of 25 mm × 25 mm and a thickness of 100 ± 3 μm is prepared from each solder alloy of Samples 1 to 11, and a dummy chip (25 mm × 25 mm) and an Ag plating layer are prepared using each of the sheet-like solders. The Cu substrate on which was formed was bonded.

  Thereafter, the Cu substrate to which the dummy chip is bonded is resin-sealed, a temperature cycle test in which cooling at −50 ° C. and heating at + 150 ° C. is repeated 1000 cycles, and a constant temperature that is maintained at a temperature of 80 ° C. and a humidity of 80% for 1000 hours. A constant humidity test was performed. After these tests, the resin was unsealed, and solder bleeding, void generation at the solder joint, crack generation at the dummy chip or solder joint, and the like were observed. As a result, no defects occurred in all the samples, and good reliability was confirmed even when mounted.

Claims (7)

Free of Pb, a Pb-free In-based solder alloy mainly containing In, Sn content is less 3.9 wt% or more 11.00 wt%, the remaining part of In and inevitable impurities A Pb-free In-based solder alloy. It further contains at least one of Cu and Zn. When Cu is contained, the content is 0.01 mass% or more and 0.90 mass% or less, and when Zn is contained, the content is 0.01 mass%. The Pb-free In-based solder alloy according to claim 1, wherein the Pb-free In-based solder alloy is at least 3.00% by mass. A Pb-free In-based solder alloy not containing Pb and containing In as a main component, the Sn content is 0.01 mass% or more and 11.00 mass% or less, and the Ag content is 0.01 mass% % Pb-free In, characterized in that the Cu content is 0.01 mass% or more and 0.90 mass% or less, and the balance is In and inevitable impurities. Solder alloy. The Pb-free In-based solder alloy according to claim 3, further comprising Zn and having a content of 0.01% by mass to 3.00% by mass. The Pb-free In-based solder alloy according to any one of claims 1 to 4, wherein the Pb-containing In-based solder alloy contains P and has a content of 0.5% by mass or less. The Pb-free In solder alloy according to any one of claims 1 to 5 , wherein the Vickers hardness (Hv) is 0.80 or more. Electronic components are bonded using a Pb-free In-based solder alloy according to any one of claims 1-6.