JP2013052433A - SOLDER ALLOY OF Pb-FREE Zn SYSTEM - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder alloy of Pb-free Zn system for high temperatures having a melting point at about 300-400°C suitable for the assembling or the like of a semiconductor device capable of improving and progressing workability and stress relieving largely and excellent in wettability and reliability.SOLUTION: The solder alloy of the Pb-free Zn system which uses Zn as a main ingredient and does not include Pb contains Al 1.0 mass% or more and 9.0 mass% or less, and contains Cu by 0.001 mass% or more and 3.000 mass% or less, and of which the rest is composed of Zn and inevitable impurities. The solder alloy in the Pb-free Zn system can contain Ag 4.0 mass% or less and/or P by 0.500 mass% or less in order to further progress the wettability or the like.

Description

  The present invention relates to a Pb-free solder alloy containing no Pb, and more particularly to a Pb-free solder alloy mainly composed of Zn suitable for high temperatures.

  High-temperature soldering is performed in soldering in the assembly process of various semiconductor devices including die bonding of power transistors, and a high-temperature solder alloy having a relatively high melting point of about 300 to 400 ° C. is used. . As such a high-temperature solder alloy, a Pb-based solder alloy represented by a Pb-5 mass% Sn alloy has been mainly used conventionally.

  However, in recent years, there has been a strong movement to limit the use of Pb from the viewpoint of environmental pollution. For example, Pb is a regulated substance in the RoHS directive. Corresponding to these movements, in the field of assembling semiconductor devices and the like, it is required to provide a solder alloy that does not contain Pb, that is, a Pb-free solder alloy.

  As for a solder alloy for medium and low temperatures (about 140 to 230 ° C.), a Pb-free solder alloy containing Sn as a main component has already been put into practical use. For example, in Patent Document 1, Sn is the main component, Ag is 1.0 to 4.0 mass%, Cu is 2.0 mass% or less, Ni is 1.0 mass% or less, and P is 0.2 mass%. Pb-free solder alloys containing up to 10% are described. Patent Document 2 describes a Pb-free solder alloy containing 0.5 to 3.5% by mass of Ag, 0.5 to 2.0% by mass of Cu, and the balance being Sn.

  On the other hand, with respect to high temperature solder alloys, Bi-based solder alloys and Zn-based solder alloys have been studied in order to realize Pb-free. For example, for a Bi solder alloy, Patent Document 3 describes a Bi / Ag brazing material containing 30 to 80% by mass of Bi and having a melting temperature of 350 to 500 ° C. In addition, Patent Document 4 describes adjustment of liquidus temperature and reduction of dispersion by adding a binary eutectic alloy having a different eutectic point temperature to a eutectic alloy containing Bi and further adding an additive element such as Pd. A method for producing a high-temperature solder material capable of achieving the above is disclosed.

  As for the Zn-based solder alloy, for example, Patent Document 5 describes a high-temperature Zn-based solder alloy based on a Zn—Al alloy in which Al is added to lower the melting point of Zn, and Ge or Mg is added thereto. Has been. Patent Document 5 also describes that the addition of Sn or In has an effect of further lowering the melting point.

  Specifically, in Patent Document 5, a Zn alloy containing 1 to 9% by mass of Al and 0.05 to 1% by mass of Ge, with the balance being Zn and inevitable impurities; 5 to 9% by mass of Al, Zn alloy containing 0.01 to 0.5% by mass of Mg, the balance being Zn and inevitable impurities; 1 to 9% by mass of Al, 0.05 to 1% by mass of Ge, and 0.01 to 0.5% of Mg. Zn alloy containing 5% by mass, the balance being Zn and inevitable impurities; 1-9% by mass of Al, 0.05-1% by mass of Ge, 0.1-25% by mass of Sn and / or In, and the balance Zn alloy consisting of Zn and inevitable impurities; Al 1-9 mass%, Mg 0.01-0.5 mass%, In and / or n 0.1-25 mass%, the balance Zn and inevitable Zn alloy composed of impurities; Al 1-9 mass%, Ge 0.05-1 mass%, Mg 0.01-0. Mass%, the Sn and / or In includes 0.1 to 25 wt%, and the balance are described Zn alloy consisting of Zn and unavoidable impurities.

Japanese Patent Application Laid-Open No. 11-077366 Japanese Patent Laid-Open No. 08-215880 JP 2002-160089 A JP 2006-167790 A Japanese Patent No. 3850135

  In the conventional Pb-free high-temperature solder alloy, the Bi / Ag brazing material of Patent Document 3 has a high liquidus temperature of 400 to 700 ° C., so that the working temperature at the time of joining is 400 to 700 ° C. or higher. It is presumed that the temperature exceeds the temperature that the semiconductor element or the substrate can withstand. In addition, the method of Patent Document 4 becomes a quaternary or higher multi-component solder alloy only by adjusting the temperature of the liquidus, and Bi is not effectively improved in terms of brittle mechanical properties.

  Furthermore, the Zn-based solder alloy disclosed in Patent Document 5 often has insufficient wettability within the composition range. That is, Zn, which is the main component, has a strong reducibility and is likely to be oxidized by itself. Moreover, since Al is more reducible than Zn, for example, when 1% by mass or more is added, the wettability may be lowered. Further, it is considered that these oxidized Zn and Al cannot be reduced even if Ge or Sn is added in terms of thermodynamic equilibrium, and the wettability cannot be improved. However, when melting and solidification are performed in a very short time as in the case of soldering, the metal reaction is often dominated by a non-equilibrium reaction, and not all can be explained by equilibrium theory.

  In addition, the Zn-based solder alloy disclosed in Patent Document 5 has problems with workability and stress relaxation as more important problems in solder bonding, in addition to the above-described problem of wettability. That is, Zn and Al are eutectic alloys and are soft alloys having a certain degree of flexibility. However, since the bonding temperature is relatively high (eutectic temperature of Zn—Al alloy: 381 ° C.), the semiconductor element (main component: Si) and the substrate (main component: Cu) are cooled to room temperature after bonding. A large stress is generated due to a large temperature difference and a difference in shrinkage rate during cooling of Si and Cu. Therefore, as compared with the medium / low temperature solder, the high temperature solder is required to have more excellent stress relaxation because of the large temperature difference.

  Moreover, although the said Zn-Al type alloy exists in a preferable range with about 300-400 degreeC (Zn-Al eutectic temperature: 381 degreeC) about melting | fusing point, it is not necessarily an optimal alloy from viewpoints of workability. Further, when Mg or the like is added to the Zn—Al alloy, an intermetallic compound is generated and becomes extremely hard, and there are cases where good workability and stress relaxation properties cannot be obtained. For example, when Mg is contained in an amount of 5% by mass or more, it cannot be substantially processed into a wire shape or a sheet shape.

  As described above, the actual situation is that a high-temperature Pb-free solder alloy that can replace a Pb-based solder alloy represented by a conventional Pb-5 mass% Sn alloy has not yet been put into practical use. In particular, for Pb-free solder alloys containing Zn as a main component, improving workability and stress relaxation properties while maintaining a balance with various properties such as wettability is a major issue. It has not been solved yet.

  The present invention has been made in view of such conventional circumstances, has a melting point of about 300 to 400 ° C. suitable for use in assembling semiconductor devices, and greatly improves workability and stress relaxation properties. An object is to provide a high-temperature Pb-free Zn-based solder alloy that can be improved and improved, and has excellent wettability and reliability.

  In order to achieve the above object, the first Pb-free Zn-based solder alloy provided by the present invention contains Zn as a main component and does not contain Pb, and contains Al in an amount of 1.0% by mass to 9.0% by mass. Cu is contained in an amount of 0.001% to 3.000% by mass, and the balance is made of Zn and inevitable impurities.

  In the first Pb-free Zn solder alloy according to the present invention, Al is contained in an amount of 3.0% to 7.0% by mass and Cu is contained in an amount of 0.003% to 1.000% by mass. Is preferred.

  Further, the second Pb-free Zn-based solder alloy provided by the present invention contains Zn as a main component and does not contain Pb, contains Al in an amount of 1.0% to 9.0% by mass, and contains Cu in an amount of 0.0%. In addition to being contained in an amount of 001 mass% to 3.000 mass%, Ag is contained in an amount of 4.0 mass% or less and / or P is contained in an amount of 0.500 mass% or less, with the balance being Zn and inevitable impurities.

  In the second Pb-free Zn-based solder alloy according to the present invention, Al is contained in an amount of 3.0% by mass to 7.0% by mass and Cu is contained in an amount of 0.003% by mass to 1.000% by mass. , Ag is contained in an amount of 3.0% by mass or less and / or P is contained in an amount of 0.30% by mass or less.

  According to the present invention, it is particularly excellent in workability and stress relaxation properties, is excellent in wettability, bondability, reliability, etc., and can sufficiently withstand a reflow temperature of about 300 ° C. A high-temperature Pb-free Zn-based solder alloy suitable for soldering in an assembly process such as die bonding can be provided.

  The first Pb-free Zn-based solder alloy according to the present invention is composed of an impurity element that does not contain Pb, contains Al and Cu, and the balance is inevitably contained in the manufacturing process. Zn which is the main component has a melting point of 419 ° C., which is disadvantageous in that it is too high for 300 to 400 ° C. which is the junction temperature of the semiconductor element. In order to cope with such defects of Zn, in the present invention, by adding Al as an essential element, a eutectic alloy with Zn is formed, and the melting point is lowered to a temperature that is easy to use as a solder of about 400 ° C. or less. ing. Further, by containing Al, it is possible to obtain an effect of making the crystal finer and improving workability.

  However, as described above, Zn—Al alloys to which Al is added have insufficient stress relaxation properties and workability as high temperature solders that require higher stress relaxation properties than medium / low temperature solders. Therefore, in the present invention, Cu is further added as an indispensable element in order to improve the stress relaxation property and workability of the Zn—Al alloy and to make the material easy to use. That is, when Cu is contained, before melting and solidifying after the solder is melted, Cu having a high melting point is first precipitated, and a crystal is formed using it as a nucleus. To improve. In addition, Cu itself being a soft metal also contributes to improving the flexibility of the Zn-Al alloy. As a result, sufficient stress relaxation and workability can be obtained as a high-temperature solder.

  Further, the second Pb-free Zn-based solder alloy according to the present invention includes at least one of Ag and P in addition to the first Pb-free Zn-based solder alloy containing Zn as a main component and Al and Cu as essential components. It is added and contained. In this second Pb-free Zn-based solder alloy, by adding at least one of Ag and P, wettability, bonding strength, etc. can be appropriately adjusted according to the purpose, and reliability as a high-temperature solder Can be further increased.

  The essential elements in the first and second Pb-free Zn-based solder alloys according to the present invention described above and the elements to be added according to the situation will be described in detail below.

<Al>
Al is an essential element that plays an important role in the Pb-free Zn-based solder alloy of the present invention. The effect of adding Al to the Zn-based solder alloy of the present invention is to adjust the melting point as described above, that is, to lower the melting point to 381 ° C. of the solidus temperature as a Zn—Al alloy. Further, since the Zn—Al alloy is a eutectic alloy, the metal becomes soft, and the workability and stress relaxation properties are improved. However, since the high temperature solder is required to have high stress relaxation properties, it is essential to simultaneously contain Cu described below.

  The Al content is 1.0 mass% or more and 9.0 mass% or less. When the Al content is less than 1.0% by mass, even if other elements are added, the melting point is not sufficiently lowered, so that the bondability is lowered. On the other hand, if the Al content exceeds 9.0% by mass, the liquidus temperature of the Zn-Al alloy becomes too high, and the actual joining temperature of electronic parts and the like does not melt sufficiently, resulting in a void generation rate. Since it becomes too high or alloying of the joint portion becomes insufficient, joining that can withstand practical use cannot be performed.

  A more preferable Al content is 3.0% by mass or more and 7.0% by mass or less. The reason is that if the Al content is in the range of 3.0 to 7.0% by mass, the eutectic composition of the Zn-Al binary alloy (Zn = 95% by mass, Al = 5% by mass). This is because the melting point is lowered and the crystal becomes finer and the workability is improved, so that the solder becomes easier to use.

<Cu>
Cu is an essential element that plays an important role in improving the stress relaxation property and workability in the Pb-free Zn-based solder alloy of the present invention. Cu has a higher melting point than Zn and Al (Zn melting point: 419 ° C., Al melting point: 660 ° C., Cu melting point: 1084 ° C.), and has a high melting point when solidified in the cooling process after melting of the solder alloy. Since Cu first precipitates and forms crystals as nuclei, the crystal of the solder alloy is refined. By making the crystal finer, it becomes possible to obtain a soft solder in which cracks are difficult to progress.

  A solder alloy having such a flexible property exhibits very excellent properties in workability and stress relaxation properties. That is, when processing into wires and sheets, the solder is soft, so cracks and chips are not likely to occur, and various processing speeds such as the extrusion speed to the wire and the rolling speed to the sheet can be increased compared to hard solder materials. , Productivity is excellent, defective products are not generated, and the yield can be increased. Furthermore, when processing into a preform material, etc., it is easy to process with little burr and warpage, and the quality inspection cost per unit amount can be reduced. Since such a soft solder alloy can be easily deformed, there is little warping of the solder at the time of joining the semiconductor elements, and the substantial contact area is increased, so that the wettability and the joining property are very excellent.

  Moreover, Cu is a very soft metal among metals, and naturally, it is softer than Zn, and the softness of Cu itself is also exhibited in a Zn-Al alloy. And, since solder bonding is performed in a very short time and a non-equilibrium phenomenon occurs, even if the Cu content is much less than Zn or Al, a Cu rich phase is generated depending on the solder composition and bonding conditions. The As can be seen from each of the binary phase diagrams of Cu-Zn and Cu-Al, Cu has a large amount of Al and Zn, so the Cu-rich phase contains some Zn and Al. Therefore, the stress applied to the solder can be absorbed even in the Cu-rich phase, and the solder alloy is further softened.

  And it is stress relaxation that the flexible property of the solder alloy of the present invention appears most remarkably. In other words, electronic components soldered with semiconductor elements are mounted on automobiles, home appliances, and various devices, but when they are used, current flows through the electronic components and heat is applied, or thermal stress is applied due to changes in the outside temperature. . Electronic components assembled with a substrate based on Cu and a semiconductor element based on Si differ in thermal expansion coefficient by about five times, and the thermal stress applied repeatedly is large. The solder alloy of the present invention is excellent in stress relaxation property that absorbs this large thermal stress, and enables long-term use of electronic components under severe environments.

  The Cu content is 0.001 mass% or more and 3.000 mass% or less. The effect of the addition of Cu is an improvement in workability, flexibility, etc. due to the refinement of the solder alloy and the formation of a Cu rich phase. Therefore, when giving priority to the effect of miniaturization, the Cu content may be very small, and the lower limit of 0.001% by mass is sufficient. On the other hand, when giving priority to the effect of Cu-rich phase generation, the higher the Cu content, the better. However, if the limit is exceeded, the liquidus temperature becomes too high and good bonding cannot be achieved, so the upper limit is 3.000. Mass%. Furthermore, it is preferable that the Cu content is 0.003 mass% or more and 1.000 mass% or less because the above-described effect is more likely to appear.

<Ag>
Ag is an element that is added as appropriate when adjusting the various characteristics of the Pb-free Zn-based solder alloy of the present invention in accordance with the purpose, and the main effect of the addition is to improve wettability. In other words, as can be seen from the fact that Ag is used for the uppermost layer of the metallization of the substrate or semiconductor element, the effect of improving the wettability is great. This is because Ag is difficult to oxidize. In addition, when the Ag content is increased on the Zn-rich side in the Zn-Ag alloy, the liquidus temperature increases monotonically, so Ag affects the melting point of the solder alloy of the present invention.

  As described above, it is better to increase the amount of Ag in terms of improving wettability, but it is preferable to reduce the amount of Ag in view of the melting point. Accordingly, Ag is contained in consideration of the balance between the melting point and wettability. However, if Ag exceeds 4.0% by mass, the liquidus temperature becomes too high even if Al is contained. Since it becomes difficult to obtain bonding, the Ag content is 4.0 mass% or less, preferably 3.0 mass% or less.

<P>
P is an element that is appropriately contained when adjusting the various characteristics of the Pb-free Zn-based solder alloy of the present invention in accordance with the purpose as in the case of Ag, and the main effect of the addition is wettability as in the case of Ag. It is in improvement. That is, P is highly reducing and suppresses oxidation of the solder alloy surface by oxidizing itself. In particular, in the present invention, Zn that is easily oxidized is a main component, and Al that is more easily oxidized than Zn is contained. Therefore, when wettability is insufficient, the role of improving wettability by containing P is large.

  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 easily oxidizes itself, oxidation proceeds preferentially over Zn and Al, which are the main components 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 bonding surface of the semiconductor element or the substrate to ensure wettability. At the time of this joining, the oxide on the soldering surface and the joining surface of the semiconductor element, etc. disappears, so that voids formed by the oxide film are less likely to occur, and the joining property and reliability are improved. Can do.

  As described above, P is not left on the surface of the solder, the substrate or the like because it vaporizes and flows into the atmospheric gas when the joint surface such as the solder alloy or the substrate is reduced to an oxide as described above. 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 additive element.

  Content of P shall be 0.500 mass% or less. Since P is very reducible, the effect of improving the wettability can be obtained if a trace amount is contained, but the effect of improving the wettability does not change so much even if contained in excess of 0.5% by mass. Inclusion of a large amount of P or P oxide gas increases the generation rate of voids, segregates by forming a fragile phase of P, or embrittles solder joints, reducing reliability. There is a risk that. In particular, it has been confirmed that when processing into a shape such as a wire, it is likely to cause disconnection. Further, if the content of P is 0.300% by weight or less, it is more preferable because the reduction effect is exhibited and the possibility of generating a brittle P compound is reduced.

  As raw materials, Zn, Al, Cu, Ag and P having a purity of 99.99% by weight or more were prepared. Large flakes and bulk-shaped raw materials were finely cut to a size of 3 mm or less by cutting and pulverizing while paying attention to the uniformity of the composition of the alloy after melting without variation in 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 metal began to melt, it was stirred well with a mixing rod and mixed uniformly so as not to cause local compositional variations. After confirming that all the raw materials were sufficiently melted, 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.

  In this way, Pb-free Zn-based solder mother alloys of Samples 1 to 19 were produced by changing the mixing ratio of the respective raw materials. About the obtained samples 1-19, the composition of each Zn type | system | group solder mother alloy was analyzed using the ICP emission-spectral-analyzer (SHIMAZU S-8100). The obtained analysis results are shown in Table 1 below as the solder composition.

  Next, each Zn-based solder mother alloy of Samples 1 to 19 was processed into a sheet shape with a rolling mill as described below, and the workability of the Pb-free Zn-based solder alloy was evaluated. In addition, mechanical properties (tensile strength, elongation) were measured using a tensile tester (Tensilon universal tester). Further, for each solder alloy processed into a sheet shape, wettability (joinability) was evaluated by the following method and reliability was evaluated by a 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 5 mm) of Samples 1 to 19 shown in Table 1 was rolled to a thickness of 0.05 mm using a rolling mill. At that time, rolling was performed while adjusting the feed speed of the ingot, and then it was cut into a width of 25 mm by slitting.

  After processing into a sheet shape in this way, the obtained sheet-like Zn-based solder alloy was observed, and when there were no scratches or cracks, “◯”, cracks and cracks per 10 m of sheet length were 1 to 3 The evaluation results are shown in Table 2 below, where “Δ” indicates that there are places, and “×” indicates that there are four or more places.

<Evaluation of mechanical properties>
In order to evaluate mechanical properties, the sheet-like Zn-based solder alloys of Samples 1 to 19 rolled to a thickness of 0.05 mm as described above were processed into a width of 3 mm with a slitter, and the length was cut to about 15 cm. . Samples for measuring mechanical properties were prepared as described above, and tensile strength and elongation were measured with a tensile tester. Both the tensile strength and elongation were evaluated relative to the measured value of Sample 1 as 100%, and the evaluation results are shown in Table 2 below. The measured values of Sample 1 were a tensile strength of 135 MPa and an elongation rate of 110%.

<Evaluation of wettability (bondability)>
Each solder alloy of Samples 1-19 processed into a sheet as described above was evaluated using a wettability tester (device name: atmosphere control type wettability tester). In other words, a double cover is applied to the heater section of the wettability tester, and the heater set temperature is about 10 ° C. higher than the melting point of each sample while flowing nitrogen from four locations around the heater section at a flow rate of 12 liters / minute. Heated to set 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), When bonding was possible and wetting spread was good (a state where the solder was thinly spreading), the evaluation was “◯”, and the 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 of which the solder alloy could be bonded to the Cu substrate in the above-described evaluation of wettability (samples with 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, 300 cycles are required for confirming the heat cycle test in which one cycle includes cooling at −40 ° C. and heating at + 150 ° C. The same heat cycle test was repeated up to 500 cycles for the remaining one.

  Then, about each sample which performed the heat cycle test of 300 cycles and 500 cycles, Cu board | substrate with which the solder alloy was joined was embedded in resin, cross-section grinding | polishing was performed, and the joining surface was carried out by SEM (device name: HITACHI S-4800). Observed. 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 evaluation results are shown in Table 2 below.

  As can be seen from Tables 1 and 2 above, each of the Zn-based solder alloys of Samples 1 to 13, which are examples of the present invention, exhibits good characteristics in all evaluation items. That is, there was no generation of scratches or cracks even when processed into a sheet, the tensile strength and elongation showed good values, and wettability and reliability were also good.

  The reason why the workability and wettability in each of the Zn-based solder alloys of Samples 1 to 13 are good is that the Cu-containing Zn-Al alloy increases the flexibility of the solder alloy and cracks even when rolled. As a result, the workability has been improved, and further, since such flexibility, solder warpage and burrs do not occur at the time of joining the solder and the substrate, and the substantial joint area is wide. It is considered that the wettability has been improved by the removal.

  Furthermore, in the heat cycle test, each Zn-based solder alloy of Samples 1 to 13 did not generate cracks up to 500 times, and showed good bondability and reliability. The reason for this is considered to be that the effect of addition of Cu is large and the thermal stress repeatedly applied by the Zn-based solder alloy with increased softness is absorbed and relaxed.

  On the other hand, each of the Zn-based solder alloys of Samples 14 to 19 as the comparative example had an unfavorable evaluation result because the content of any of Al, Cu, Ag, and P was not appropriate. Specifically, in the evaluation of workability, scratches and cracks occurred in all samples, the tensile strength and elongation were not high, and all the samples were unfavorable in terms of wettability. In the samples (excluding samples 14 and 15 that could not be joined), defects occurred up to 300 times.

Claims (4)

  Zn as a main component and not containing Pb, Al is contained in an amount of 1.0% to 9.0% by mass, Cu is contained in an amount of 0.001% to 3.000% by mass, and the balance is Zn and inevitable. A Pb-free Zn-based solder alloy comprising impurities.   2. The Pb-free Zn-based solder according to claim 1, wherein Al is contained in an amount of 3.0% to 7.0% by mass and Cu is contained in an amount of 0.003% to 1,000% by mass. alloy.   It contains Zn as a main component and does not contain Pb, Al is contained in an amount of 1.0% to 9.0% by mass, Cu is contained in an amount of 0.001% to 3.000% by mass, and Ag is 4. A Pb-free Zn-based solder alloy comprising 0% by mass or less and / or 0.5% by mass or less of P, the balance being made of Zn and inevitable impurities.   Al is contained in an amount of 3.0% by mass or more and 7.0% by mass or less, Cu is contained in an amount of 0.003% by mass or more and 1.000% by mass or less, Ag is 3.0% by mass or less, and / or P is 0.0% by mass. The Pb-free Zn-based solder alloy according to claim 3, which is contained in an amount of 300% by mass or less.