JP3460438B2 - Lead-free solder and mounted products using it - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of soldering at a soldering temperature of 220 to 230 [deg.] C. as an alternative to the conventional Pb-Sn eutectic solder for connecting LSIs, parts, etc. to a substrate. The present invention also relates to a Pb-free solder composition having mechanical strength equivalent to that of a Pb-Sn eutectic crystal and a mounted product using the same.

[0002]

2. Description of the Related Art Most of the commonly used printed circuit board materials are made of glass epoxy. The heat resistant temperature of the glass epoxy substrate is up to 220 ~ when using a reflow furnace.
It is 230 ° C. The connecting solder used for this is Pb
-63 wt% Sn eutectic solder (melting point: 183 ° C), or a solder composition with a similar melting point near the eutectic is used, and within the heat-resistant temperature (230 ° C) of a widely used glass epoxy substrate. Was enough connection. The reliability at high temperature depends on the product, but the maximum is 150.
I was able to guarantee up to ℃. Hereinafter, all weight% are shown as%.

Recently, in the United States, lead (hereinafter referred to as Pb) contained in solder from electrical products left unattended
It has been publicly announced that is dissolved in groundwater by being dissolved by acid rain, etc., and that these groundwaters have an adverse effect on the human body when used as drinking water. Therefore, Pb-free solder alloys that do not contain Pb have been focused on so that they are less toxic to the environment and the human body. Already S for binary solder
n-3.5% Ag (melting point 221 ° C.) and Sn-5% Sb (melting point 240 ° C.) have been used as Pb-free solders. However, its melting point is too high to be used for soldering glass epoxy substrates. Sn-9% Zn (melting point 1
Although the melting point of eutectic crystals at 99 ° C) is lowered, electronic parts are mounted on a commonly used glass epoxy substrate at 220 to 230 ° C.
I cannot reflow in the atmosphere. That is, the surface is easily oxidized, and the wettability to Cu or Ni is Sn.
Compared to -Ag type and Sn-Sb type, even when using the rosin type flux (containing 0.2% chlorine) that is commonly used, at a normal reflow temperature of 230 ° C, it is compared to the base metal in the atmosphere. It has proven to be almost wet and difficult to solder.

On the other hand, Sn-Bi type solder (representative composition Sn
Although there are -58% Bi; melting point 138 ° C) and Sn-In based solder (representative composition Sn-52% In; melting point 117 ° C), the melting point is too low to guarantee high temperature strength comparable to Pb-Sn. Therefore, these compositions cannot be said to be solders for substitution of Pb-63% Sn eutectic solder. Therefore, there is a demand for the development of new solder materials that meet the demands of new combinations.

On the other hand, as a material focused on mechanical properties,
A lead-free solder material obtained by adding Zn to Sn and Ag as main components is described in Japanese Patent Laid-Open No. 6-238479.
This solder contains Zn in order to improve mechanical strength and creep characteristics while maintaining excellent solder wettability of Sn-Ag solder. But S
The n-3.5% Ag-1% Zn ternary alloy has a melting point of about 215 [deg.] C. as described in that publication, and the conventional Sn-
As a substitute material for Pb eutectic solder, it cannot be used as it is for soldering a glass epoxy substrate.

As described above, there is no alternative material for the Pb-Sn eutectic solder that can achieve both soldering temperature and strength reliability.

[0007]

SUMMARY OF THE INVENTION The present invention is capable of reflowing or flowing at 230 ° C. or lower and is used for mounting electronic parts such as LSI and parts on an organic substrate centering on a conventional glass epoxy substrate with high reliability. Supply Pb-Sn eutectic solder substitute solder that does not use Pb and can secure sufficient wettability on the Cu conductor and Sn-based solder-plated terminals of parts with a general flux with a proven track record. It is an object.

That is, the object of the present invention is to have a solid phase temperature of at least 150 ° C. or higher, preferably 155 ° C. or higher in order to withstand use at a high temperature with a melting point of about 150 ° C., a substrate,
The liquidus temperature is set to 195 ° C. or lower at the maximum in order to reduce the thermal effect on the parts.

[0009]

In order to achieve the above object, as a Pb-free solder, there is little influence on the environment,
Sn-Zn that has low toxicity to human body, has no problem of resource depletion, has a target melting temperature range, and can secure wettability
A solder composition based on a quaternary solder of -Bi-In was examined. The melting point of this quaternary solder is unknown. Therefore, it is necessary to clarify the relationship between the composition and the melting point (solid phase temperature, liquid phase temperature), the composition and the wettability, the physical properties, the mechanical properties, and the like. The solder of the present invention has a Zn content of 3 to 3.
9%, Bi 1-16%, In 1-10%, balance S
Sn-Zn-B with n and Zn + Bi ≧ 9%
An alloy based on i-In system, preferably Zn is 4 to
7%, Bi is 5 to 13%, In is 1 to 7%, the balance is Sn, or these alloys have Ag of 1 to 3% and S
The wettability and mechanical properties are improved by adding one or more of b of 1 to 3% and Cu of 1 to 3%. Furthermore, Sn or Sn alloy is 1 to 10 μm or Au is 0.2 μm on the solder surface.
The following are covered.

The reason why the solder composition is limited to the above is as follows. Among the binary eutectic solders based on Sn, Sn-P is used as a substitute material for the Sn-Pb eutectic solder.
b The closest melting point of eutectic solder to 183 ° C is Sn-9%
It is a Zn alloy. However, even this alloy has a melting point of 199 ° C.
In addition, there is a problem of surface oxidation of Zn, and as described above, it is difficult to perform reflow at 220 ° C. to 230 ° C. in the conventional atmosphere. Therefore, this problem is solved by adding Bi and In, which are materials that are considered to be capable of lowering the melting point of this Sn-Zn-based alloy and which are comprehensively excellent in terms of environment, performance, and cost. It was to be.

First, with respect to In, when In exceeds 10%, there arises a problem in corrosion resistance to the environment. Also In
If the amount is large, the cost of the solder is high and it is not practical.
Therefore, the added amount of In must be 10% or less, preferably 7% or less. Further, if it is 1% or less, a predetermined effect cannot be obtained.

With respect to the amount of Bi, if Bi exceeds 17%, the solid phase temperature will drop below 150 ° C. when In is added. Furthermore, when a large amount of Bi is added, embrittlement of the solder is caused. Therefore, Bi is set to 16% or less, preferably 13% or less. That is, if Bi is 16% or less, the solid phase temperature is 1
Solid phase temperature 1 if 50 ° C or higher can be secured and 13% or lower
This is because a temperature of 55 ° C or higher can be secured. This solid phase temperature 15
The reason why 0 ° C. is used is to ensure reliability in a usage state of about 150 ° C. Therefore, the solid phase temperature should be 15
By setting the temperature to 5 ° C. or higher, the reliability in the use condition of about 150 ° C. can be further improved. Further, Bi is set to 1% or more, preferably 5% or more, because if it is less than that, the liquidus temperature rises too much. That is, when Bi or In is added, the overall liquidus temperature drops, but if Bi is less than 5% (particularly less than 1%), the liquidus temperature expected by the present invention: 195 ° C. or lower cannot be realized. is there.

Zn is easily oxidized and the oxide film is strong, which causes deterioration of wettability. Therefore, it is necessary to reduce the amount of Zn added as much as possible. If Zn is 9% or less, the wettability can be secured in the conventional rosin-based flux (containing halogen) and N2 atmosphere. Therefore Z
The amount of n was 9% or less, preferably 7% or less. If the Zn content is 9% or less, the wettability necessary when O2 is 100 ppm can be secured, and if it is 7% or less, O2 is 1000 ppm.
This is because the necessary wettability can be secured in this case (see FIG. 6: FIG. 6 will be described later). The Zn content is set to 3% or more, preferably 4% or more. If it is less than that, the liquidus temperature rises too much, and even if Bi or In is added, the liquidus temperature expected by the present invention is: This is because it is not possible to achieve 195 ° C. or lower and solid phase temperature: 150 ° C. or higher.

As described above, S containing a small amount of Zn, Bi and In
In the n-rich region, the melting point (liquidus temperature) becomes high, so In and Bi are added to the Sn—Zn-based alloy,
To enter the desired melting point range (liquidus temperature: 195 ° C or lower),
It is necessary that Zn is 3% or more, Bi is 1% or more, Zn + Bi is 9% or more, preferably Zn is 4% or more and Bi is 5% or more. Here, Zn + Bi is set to 9% or more because if Zn + Bi is less than 9%, the overall liquidus temperature is 205 ° C. or higher, and even if In is added, the liquidus temperature expected by the present invention is 195 ° C. or lower. Because it cannot be realized.

From the above, since the solder alloy having such a composition does not contain Pb, it is less toxic to the environment and the human body, can reflow at a melting point of 220 to 230 ° C., and has a melting point of around 150 ° C. The connection reliability can be assured, and a solder alloy excellent in wettability, mechanical strength, and cost can be supplied.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.

FIG. 1 is a known state diagram of a Sn-Zn-Bi ternary solder [International Critical Tables, 2 (192
7), 418]. Although the overall temperature distribution of the melting point (liquidus temperature) is known, the detailed distribution and clear temperature are not known. Further, the relationship between the liquidus temperature and the solidus temperature is unknown. Furthermore, these Sn-Zn-Bi 3
Even the liquidus temperature is not known for the quaternary solder in which In is added to the original alloy. Therefore, first, Sn-Zn-
The results of measuring the solid phase temperature of the Bi ternary system are shown in FIG. To make alloys, weigh each material accurately and
Heated in a crucible in 2 atmosphere, stirred sufficiently, and then rapidly cooled. The melting point is measured by DSC (Differential Scannin).
g Calorimetry) at a heating rate of 2 ° C./min. FIG. 2 shows the solid phase temperature when the amount of Bi is changed when Zn is 3, 5, 7, 9%. From this result, Zn is 3 to
In the range of 9%, the solid phase temperature does not change depending on the amount of Zn,
It was found that the solid phase temperature was determined by the amount of Bi. When the Bi content exceeds 17%, the solid phase temperature is 150
It goes below ℃. Therefore, in order to secure the reliability at 150 ° C., considering that In is further added by 1% or more, the Bi amount is 16% or less, preferably the solid phase temperature is 1% or less.
It must be 13% or less so that the temperature becomes 55 ° C or higher.

Next, the effect of adding In will be described. Bi 10
%, Zn 5% and the rest Sn mixed alloy (Sn-10%
FIG. 3 shows the melting points when 2.5% of In was added to Bi-5% Zn). Since the liquid phase temperature of Sn-10% Bi-5% Zn alloy is as high as 202 ° C, it is difficult to reflow-solder electronic components at 220 to 230 ° C on a glass epoxy substrate. However, this solder alloy
When n is added, both the solid phase temperature and the liquid phase temperature decrease as shown in FIG. 3, and when 5% In is added, the liquid phase temperature is 189
It was found that the solid phase temperature was 150 ° C. and the melting point was 150 ° C. As described above, it was found that when In was added to the Sn-Zn-Bi ternary alloy, both the solid phase temperature and the liquidus temperature were lowered and the solder alloy in the target melting point region was obtained. This result is the same for Sn-Zn-Bi alloys having other compositions, and the melting point is lowered by adding In.

In addition, In acts to improve the wettability of the solder. An alloy (Sn-15% Bi-5% Zn) in which Bi is 15%, Zn is 5%, and the rest is Sn is mixed with In of 1,
The wettability of solder was measured for the alloys added with 3, 5%. The measurement was performed using a solder ball of each composition having a diameter of 1 mm by C
It was placed on a u plate, coated with flux, and heated on a hot plate at a temperature of 100 ° C./minute to a temperature higher by 50 ° C. than the liquidus temperature, and the spread area after solidification was measured. The atmosphere was air. As a result, when the spread area of the alloy containing no In was 100%, the spread areas of the alloys containing 1, 3, and 5% were 103%, 110%, and 113%, respectively. That is, the addition of In improves the wettability of the solder.

Next, a region containing a small amount of Zn and Bi will be described. FIG. 4 shows the liquidus temperature when the amount of Bi is changed within the range of Zn of 5% or less. From this, it was found that when the amount of Bi was constant, the liquid phase temperature increased when the amount of Zn decreased, and when the amount of Zn was constant, the liquid phase temperature increased when the amount of Bi decreased. Further, FIG. 5 shows the temperature difference between the liquidus temperature and the solidus temperature when the Bi content is fixed at 10%.
As the temperature decreases, the temperature difference increases. Therefore, In is 1 to
In order to obtain a solder alloy having a desired melting point region by adding 10%, Zn is 3% or more, Bi is 1% or more, and Bi + Z in consideration that the melting point is lowered by adding In.
n is 9% or more, preferably Zn is 4% or more, Bi is 5%
It must be above.

Next, the effect of the Zn content on the wetting will be described.
FIG. 6 shows the spread area of the solder when Zn was added to Sn-10% Bi-2% In. In the experiment, a solder ball having a different composition was placed on a Cu plate, flux was applied, and the temperature was 5 ° C from the liquidus temperature at 100 ° C / min on a hot plate.
It was heated to a temperature higher by 0 ° C. and the spread area was measured. The atmosphere contains less than 100 ppm oxygen and 1000 ppm
It was conducted in nitrogen containing the above. The size of the solder ball is 1 mm in diameter, and the flux is rosin-based and contains 0.2 chlorine.
% Contained. From this result, oxygen is 100
It was found that when the content is less than ppm, the wettability deteriorates only slightly at 9% of Zn, but when the content of oxygen exceeds 1000 ppm, the wettability deteriorates at 7% of Zn. Considering the use of the current nitrogen reflow furnace, Zn must be 9% or less, preferably 7% or less.

Sn-Zn having the above-defined composition
The solderability, strength, etc. of alloys of several compositions among the alloys of -Bi-In will be described.

Example 1 Sn-10% Bi-5% Zn
Since the -5% In solder is in the target melting point range as described above, it is used as an electronic component and 220 to 2 with respect to the glass epoxy substrate.
Soldering is possible at 30 ° C., and reliability at high temperatures can be secured. This Sn-10% Bi-
A 5% Zn-5% In alloy was made into a powder having a particle size of about 40 to 50 μm, and a flux component was mixed with this powder in an amount of about 10% to prepare a solder paste. Flux components are solvents, rosins, activators, organic halogens, thickeners and the like.
The viscosity of the solder was adjusted to about 500,000 cps. The amount of chlorine contained in the organic halogen was set to about 0.15%. This solder paste is printed on a glass epoxy board to a thickness of about 150 μm and printed with a 0.5 mm pitch QFP (Quad F
It was reflowed in an N2 atmosphere with an oxygen concentration of 100 ppm by mounting a lat package). The lead of the 0.5 mm pitch QFP has a Sn alloy plating of about 7 μm on 42 alloy. The reflow temperature was 140 ° C. for about 30 seconds for preheating, 220 ° C. for 30 seconds for main heating, and the maximum temperature was 230 ° C. As described above, in the lead portion of the QFP soldered with the above solder alloy, the fillet portion is not sufficiently formed as compared with the case where the conventional Sn-Pb eutectic solder paste is used, but in the range where there is no practical problem. is there. In addition, the proper wettability ensures sufficient wettability.

In order to confirm the reliability of the soldered QFP, -55 ° C. for 30 minutes, 125 ° C. for 30 minutes
A temperature cycle test is performed as a cycle, and SEM (Scan
ningElectron Microscopy) was observed for cracks in the solder fillet. As a result, even after 500 cycles, only a few cracks are generated, and the life is not affected as in the Sn-Pb eutectic solder. In addition, the substrate on which QFP was soldered with the above solder paste was washed with a hydrocarbon-based organic solvent and the insulation resistance was measured, but the same insulation resistance as when using the Sn-Pb eutectic solder paste was obtained. . Thus, Sn-10% Bi-
It was confirmed that by using the alloy of 5% Zn-5% In, it is possible to perform soldering similarly to the conventional Sn-Pb eutectic solder without containing Pb.

[Embodiment 2] As in Embodiment 1, Bi is 13
%, Zn 5%, the remaining Sn (Sn-13% Bi-5% Z
n) An example in which In is added to the alloy is shown. Sn-13
In the% Bi-5% Zn alloy, the liquidus temperature was 194 ° C. and the solidus temperature was 157 ° C., which had almost the desired melting point, but 3% In was added to further lower the liquidus temperature. This S
In the n-13% Bi-5% Zn-3% In alloy,
The liquidus temperature is 189 ° C and the solidus temperature is 151 ° C.
Reflow soldering at 0 to 230 ° C is possible. This solder alloy was mixed with a flux component in the same manner as in Example 1 to make a trial solder paste. As a result of soldering a QFP lead having a solderability of 0.5 mm pitch by vapor reflow, the same result as the Sn-Pb eutectic crystal was obtained. Vapor reflow is similar to N2 reflow,
It is possible to prevent a significant decrease in wetting due to the oxidation of solder.

Example 3 Bi = 15%, Zn = 5%,
In was added to the Sn-15% Bi-5% Zn alloy which is the remaining Sn to prepare a solder alloy, and the strength of the alloy was measured. Samples are each alloy 1 (t) x 2 (w) mm x
It processed into the test piece of parallel part 10mm.

The tensile strength at a tensile speed of 0.05 mm / min is shown in FIG. It was found that the addition of In lowers the melting point and improves the strength. This alloy was left to stand at a high temperature of 125 ° C. for 200 hours and the tensile strength was measured under the same conditions, but no deterioration of the strength due to the high temperature was observed.

Further, the results of measuring the elongation percentages at room temperature and high temperature of a solder alloy obtained by adding In to a Sn-13% Bi-5% Zn alloy in which Bi is 13%, Zn is 5%, and the balance is Sn Is shown in FIG. The elongation at high temperature was measured for each composition when it was left in a high temperature bath at 100 ° C., 125 ° C., and 150 ° C. and reached sufficient equilibrium. As a result, it was found that the addition of In increases the elongation at high temperature. Therefore, it can be said that the addition of In can alleviate the stress caused by the difference in thermal expansion between the materials at the time of connection and improve the reliability of the product.

As described above, the solder having good elongation at high temperature has a lead-free structure, that is, a structure using solder bumps such as die bonding of Si chip, BGA (Ball Grid Array) and flip chip mounting, Further, it is particularly effective in module joining using solder foil. This is because in a structure that is soldered using leads such as QFP, the stress generated by the difference in thermal expansion between components and substrate materials is absorbed by the deformation of the leads, which affects solder. Can be made smaller. Further, the repeated stress during actual operation can be absorbed by the deformation of the lead. Therefore, even solder with poor elongation can be used in a wide range. However, in the structure including only the solder having no lead, the solder must absorb all the stress generated by the difference in thermal expansion. For this reason, a hard solder material having poor elongation cannot absorb the stress, stress concentrates on the interface, and cracks occur, resulting in destruction at the soldering interface. However, the addition of In improves the elongation at high temperature and makes it soft, so that the stress applied to the solder can be absorbed by the deformation in the solder. Further, when the Si chip is die-bonded, soft bonding can be performed, so that the Si chip can be prevented from being broken. Therefore, it is possible to contribute particularly to the improvement of reliability of the mounting structure using the solder bumps and the structure for bonding the Si chip.

Example 4 Zn 7%, Bi 8%, I
Alloy consisting of 5% n and the rest Sn (Sn-7% Zn-8%
Bi-5% In alloy) was used to prepare solder balls of about 100 μm. This solder alloy has a desired melting point region. 2μm Sn plating, Sn on this solder ball
-Bi plating and Sn-In plating and three types of surface treatments were performed. As a pretreatment for the surface treatment, Sn-7% Zn
The -8% Bi-5% In alloy was dipped in a solution containing sulfuric acid to completely remove the oxide film on the surface. The plating was barrel plating. When the surface treatment is carried out in this way, the surface is covered with Sn or Sn—Bi plating or Sn—In plating, so that it is difficult to oxidize Zn when melting, which causes wetting, and therefore the surface is not covered. Compared with solder balls, it is possible to secure the wettability on board pads and terminals of components. Therefore, it is possible to perform air reflow at a temperature of up to 230 ° C. using a normal flux with weak activity. At this time, Sn or Sn-B coated on the solder
Since the amount of i or Sn-In is smaller than the amount of solder in the paste, the components hardly change. Therefore, the melting point of the final solder composition was almost the same as the melting point of the original solder. The wet spread area on the Cu plate at 230 ° C. was measured for the solder ball subjected to this surface treatment. The flux used was an isopropyl alcohol solution to which rosin and organic halogen were added so that chlorine was 0.15%. According to this, the spread area of the solder balls plated with Sn, Sn-Bi or Sn-In is 1 Sn-Pb eutectic solder.
When it is set to 00%, the wettability is 75%, 74% and 78%, respectively, which can be practically used, and the wettability is improved from 68% of the uncoated solder ball.

Au plating was applied to the same solder alloy to 0.1
Although a μm-coated solder ball was prepared in the same manner, it was confirmed that this solder ball was improved in wettability as compared with an uncoated solder ball.

[Embodiment 5] FIG. 9 shows an example in which the solder of the present invention is applied to power module mounting. 9A shows an example using an Al2O3 substrate, and FIG. 9B shows an example using a Cu substrate.

1) Zn 8%, Bi 8%, In 10%, rest Sn 2) Zn 8%, Bi 5%, In 10%, rest Sn 3) Zn 8%, Bi 4%, In 10%, Ag 1%, rest Sn The solder foil (t = 0.1 to 0.15 mm thickness) 1 and metallized 2 by vapor deposition, electronic beam, etc. 10 m
The m-sided Si chip 3 is a thick-film metallized Al
Soldered to a 2O3 substrate 4, a Cu substrate 5 and the like. The Si chip 3 has Cr (0.1 μm thickness) -Ni (1.5 μm)
Thickness) -Au (0.1 μm thickness) metallized 2
The 1 2 O 3 substrate 4 was subjected to W-Ni plating-Au plating metallization 6 and the Cu substrate 5 was subjected to Ni plating 7. Soldering was performed in a nitrogen atmosphere after cleaning the surface of the solder foil and applying an antioxidant film that was stable up to high temperatures. In the temperature cycle test after bonding (-55 to 125 ° C), the characteristic deterioration after 1000 cycles was small even in the case of the Cu substrate having a large difference in thermal expansion coefficient.

By adding 10% In, the hardness of the solder itself can be reduced and the elongation at high temperature can be improved. For this reason, the stress load on the Si chip is small, and even a large chip can be die-bonded. As a solder supply method, a solder paste may be used instead of the solder foil. The particle size of the solder paste was set to 30 to 50 μm, and in order to improve the pot life of the paste, the surface of the particles was treated so as not to come into direct contact with the rosin, and the particles were melted and joined at the time of connection.

[0035]

As described above, the Sn-Zn-B of the present invention is used.
Since the i-In-based solder does not contain Pb, it is not harmful to the environment and human body, can be stably supplied as a resource, has no problem of depletion, does not have a high cost, and has a conventional Pb-content.
The same reflow device can be used for soldering to a glass epoxy substrate that has been conventionally used at a reflow temperature equivalent to that of Sn eutectic solder. This solder has high strength, especially at high temperatures and excellent creep resistance. Also as a joint for electronic parts, it has the same reliability as the conventional Pb-Sn eutectic. Although glass epoxy was used as the organic substrate, composite substrates, paper phenol substrates, paper epoxy substrates, Kepler epoxy substrates, etc. are applicable because their heat resistance temperatures are almost the same as those of glass epoxy substrates. Since glass polyimide, Kepler polyimide, ceramic substrate and the like have high heat resistance, there is no temperature limitation even if these solders are used.

[Brief description of drawings]

FIG. 1 shows a known Sn—Zn—Bi ternary phase diagram (liquidus temperature).

FIG. 2: Zn: 3-9%, Bi: 0-3 by thermal analysis
The solid phase temperature within the range of 0% and the remaining Sn is shown.

FIG. 3: Thermal analysis of Zn: 5%, Bi: 10%, I
n: 2 to 5%, the liquid phase and solid phase temperature within the range of the remaining Sn are shown.

FIG. 4 shows Zn: 0 for solder alloys with different Bi contents.
Liquid phase temperature in the range of ˜5%.

FIG. 5: By thermal analysis, Bi: 10%, Zn: 0-5
%, The solid phase and liquid phase temperature difference within the range of the remaining Sn are shown.

[FIG. 6] Bi: 10%, In: 2%, when the remaining Sn, Z
The effect of n amount on wettability is shown.

FIG. 7: Zn: 5%, Bi: 15%, In: 0-5%,
The tensile strength within the range of the remaining Sn is shown.

FIG. 8: Zn: 5%, Bi: 13%, In: 0-2%,
It shows room temperature and high temperature elongation within the range of the remaining Sn.

FIG. 9 shows an example in which the solder of the present invention is applied to power module mounting.

[Explanation of symbols]

1: Solder foil 2: Cr-Ni-Au 3: Si chip 4: Al2O3 substrate 5: Cu substrate 6: W-Ni plating-Au plating 7: Ni plating

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiharu Ishida 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Inside the Institute of Industrial Science, Hitachi, Ltd. (56) Reference Japanese Patent Laid-Open No. 7-155984 (JP, A) Kaihei 6-344181 (JP, A) JP-A-6-238479 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 35/00-35/26

Claims (6)

(57) [Claims] 1. A mounted product having an electronic component and a substrate on which the electronic component is mounted, wherein the electronic component and the substrate are: Zn: 3 to 9% by weight, Bi: 1 to 16% by weight, In : 1
10% by weight, balance of Sn, Zn + Bi ≧
A mounted product, which is formed of 9 wt% lead-free solder and is connected by a solder ball whose surface is covered with Sn or an alloy containing Sn. 2. A mounted product having an electronic component and a substrate for mounting the electronic component, wherein the electronic component and the substrate are: Zn: 4 to 7% by weight, Bi: 5 to 13% by weight, In : 1
A mounted product, characterized in that the solder ball is formed of lead-free solder whose content is ˜7% by weight and the balance is Sn, and whose surface is covered with Sn or an alloy containing Sn. 3. The mounted product according to claim 1 or 2, wherein the Sn or the alloy containing Sn has a thickness of 1 to 10 μm. 4. A mounted product having an electronic component and a substrate on which the electronic component is mounted, wherein the electronic component and the substrate are: Zn: 3 to 9% by weight, Bi: 1 to 16% by weight, In : 1
-10% by weight, balance of Sn, Zn + Bi ≧
A mounted product, which is formed of 9 wt% lead-free solder and is connected by a solder ball whose surface is covered with Au or an alloy containing Au. 5. A mounting product having an electronic component and a substrate for mounting the electronic component, wherein the electronic component and the substrate are: Zn: 4 to 7% by weight, Bi: 5 to 13% by weight, In : 1
A mounted product, characterized in that the solder ball is formed of lead-free solder whose content is ˜7% by weight and the balance is Sn, and whose surface is covered with Au or an alloy containing Au. 6. The mounted product according to claim 4 or 5, wherein the Au or an alloy containing Au has a thickness of 0.2 μm or less.