JP2001244622A - Electronic circuit device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Pb-free electronic circuit device having high reliability by realizing a solder hierarchy of Pb-free solder at a plurality of solder connecting parts soldered at different soldering steps. SOLUTION: In a previous step of manufacturing an electronic component 8, an Sn-Sb solder alloy is used as a first Pb-free solder 4. In a following step of mounting such an electric component 8 on a board 9, an Sn-Ag solder alloy is used as a second Pb-free solder 10 having a lower melting point than that of the first solder 4. Thus, in the case of reflow connecting in the following step by realizing the hierarchy of the solders, the first solder 4 is not melted. Here, the first solder contains an Sb of a composition range of 1 to 10 wt.%. The second solder 10 contains the Ag of a composition range of 1.5 to 3.5 wt.%, but trace amounts of Cu, Bi, In are added as needed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit device in which electronic components are connected on a substrate using Pb-free solder, and more particularly to an electronic circuit device using solders having different melting points.

[0002]

2. Description of the Related Art In today's production of electronic circuit devices, a plurality of types of solder alloys having different melting points are often used for mounting electronic components on a substrate. This is because the increase in the number of components and the modularization of the electronic circuit device make it difficult to configure the electronic circuit device by batch connection using one type of solder. Specifically, high-melting-point solder is used in the soldering of electronic components such as ICs (integrated circuits) in the preceding process, and low-melting-point solder is used in the subsequent process of connecting the IC to the board. Soldering is performed by a method such as soldering (providing solder in advance at the soldering portions of the respective parts to be soldered, buttering and melting the solder by heating). This is because when the electronic component and the board that have already been soldered in the previous process are connected by reflow soldering (post-process), the electronic component and the entire board are heated by a heating furnace. This is to prevent the connection portion inside the attached electronic component from being re-melted by heating in the subsequent step, and causing a connection failure such as short circuit or disconnection. Mounting using solders having different melting temperatures in this way is referred to as layering of the solder.

Therefore, conventionally, a high melting point Pb (lead) solder having a melting point of 300 ° C. or more has been used for soldering inside an electronic component, and a Pb—Sn having a melting point of 183 ° C. has been used for connecting an electronic component to a substrate. (Tin) eutectic solders have often been used. However, there is a concern about an environmental problem that Pb is eluted from the discarded electronic devices and contaminates soil and groundwater and has an adverse effect on the human body, and studies have been made on making Pb-free solder.

[0004] Table 1 below summarizes known Pb-free solder alloys.

[0005]

[Table 1] For comparison, Pb-Sn solder is also described.

[0006] In Table 1 above, among the Pb-free solders, Au (gold) -20Sn solder (a solder alloy in which the composition range of Sn is 20 wt (% by weight) and the balance is Au and unavoidable impurities. The same shall apply hereinafter) has the highest melting point of 278 ° C., and the melting point of Sn—Sb (antimony) solder is 2
35-240 ° C, the melting point of Sn-3.5Ag (silver) solder becomes 221 ° C. It can be seen that most Pb-free solders other than Au-20Sn solder have Sn as a main component and a melting point of around 230 ° C. Therefore, these Pb-free solders have melting points close to each other, and it is considered that layering of the solder is difficult. Therefore, the layering technique of the solder has not been sufficiently studied so far.

As described above, it has been considered that it is difficult to form a layer of solder using Pb-free solder because soldering is generally performed at a temperature 20 to 40 ° C. higher than the melting point of solder. Hereinafter, the reason will be described.

[0008] When connection is made by reflow soldering (hereinafter referred to as reflow connection), the temperature in the substrate varies depending on the temperature difference depending on the location in the reflow furnace and the heat capacity of components mounted on the substrate. In a conventional infrared heating furnace, as described later, the temperature difference in the furnace is 2
Since the temperature is 0 ° C. or higher, it has to be heated at a temperature at least 20 ° C. higher than the melting point of the solder used for reflow connection. Thus, the heating temperature for reflow connection is
It is called reflow temperature.

As described above, another reason for setting the reflow temperature several tens of degrees higher than the melting point of the solder is that the higher the temperature, the better the wettability of the solder. Hereinafter, the temperature dependence of the wettability of the solder will be described.

As one of the techniques for evaluating the wettability of solder, there is a meniscograph test. The meniscograph test is a test in which a metal piece sample is fixed to a high-precision load measuring device and a change in load when a part of the sample is immersed in molten solder is measured. When the molten solder is immersed in the molten metal, a force (repulsive force) is generated in the initial stage by which the molten solder liquid tries to push the metal piece out of the liquid. Spreads on the surface of the piece. With the spread of the wetting, a force (drawing force) for drawing the metal piece into the solder is generated. If wetting time is defined as the time from the start of immersion of the metal piece to the time at which the force applied to the metal piece changes from the repulsive force to the pull-in force, the shorter the wetting time, the better the wettability.

FIG. 11 shows P which is the most typical solder alloy.
It is a figure which shows the measurement result of the wetting time with respect to Cu (copper) metal piece of b-Sn eutectic solder. Here, a solution of rosin and alcohol without halogen was used as the flux.

In FIG. 1, the temperature of the molten solder is 210
At ℃, the wetting time is about 9 seconds, but the wetting time decreases as the temperature rises, indicating that the wettability improves. Therefore, better wettability can be obtained by performing reflow connection at a higher temperature.

For the above reasons, it has been considered that the soldering temperature must be higher than the melting point of the solder by 20 to 40 ° C. in order to obtain a good reflow connection over the entire substrate. Has been considered difficult.

[0014]

However, in manufacturing an electronic circuit device using Pb-free solder, a layering technique using Pb-free solder is essential. For this reason, conventionally,
As one of the techniques for realizing this hierarchy, various Pb-free solder alloys having different melting points have been developed.

As one example, Japanese Patent Application Laid-Open No. 10-19316
No. 9 discloses a Sn-Ag Pb-free solder alloy that further lowers the melting point and suppresses the increase in cost, and has both good wettability and good mechanical properties at high temperatures not only at room temperature but also at high temperatures. It has been disclosed. According to this, Cu (0.1 to 2 mass%) and Bi
(Bismuth: 0.1 to 14 mass%) and In (indium: 0.1 to 10 mass%), the melting temperature of the solder alloy becomes 160 to 205 ° C, and Sn-3.5A
g is lower than the eutectic temperature of 221 ° C.

As described above, lowering the melting point of the solder itself by adding an alloy element is an effective method for realizing layering, but In and Bi, which have a large effect of lowering the melting point, are rare metal resources. Yes, In is expensive, and Bi is produced as a by-product of Cu and Pb.
Price fluctuations are expected to be severe. Therefore, when producing a solder having a low melting point, it is very difficult to reduce the cost of the solder and produce it at a stable cost.

The present invention has been made in view of such a problem, and an object of the present invention is to provide an electronic circuit device which realizes a hierarchical structure of solder using a low-cost Pb-free solder alloy and has high connection reliability. It is in.

[0018]

In order to reduce the cost of the required low melting point solder and to use it stably for production,
It is desirable to further reduce the amount of In or Bi added. That is, in order to realize the layering of the solder by the low-cost Pb-free solder suitable for mass production, not only the development of the solder alloy but also the soldering conditions (20 to 40 higher than the melting point of the solder) which have been conventionally accepted as common sense. It is necessary to review the reflow temperature (° C higher) and introduce a soldering method with less variation in temperature.

Here, when the soldering conditions are reviewed, as will be described later, in practice, the melting point is set to be 20 to 40 lower than the melting point.
It was found that there was no need to increase the reflow temperature in ° C.

FIG. 2 is a diagram showing the measurement results of the wetting and spreading ratio of the Sn-3Ag-0.7Cu solder paste. The flux is of the normal RMA type. Sn-3Ag-
The melting point of the 0.7Cu solder paste is 218 ° C,
As is clear from FIG. 2, there is no change in the wetting spread rate between the temperatures of 220 ° C. and 229 ° C.

FIG. 3 shows the above Sn-3Ag-0.7.
Connect Cu pins to the board using Cu solder paste,
FIG. 4 is a diagram showing the result of measuring the pull-out strength. As is apparent from FIG. 3, no difference in strength due to temperature is observed.

From the above, Sn-3Ag-0.7C
In u solder paste, the melting point is slightly higher than its melting point.
It can be said that a soldering temperature of 20 ° C. should be ensured.

Conventionally, soldering has been carried out at a temperature 20 to 40 ° C. higher than the melting point of customarily used solder. However, depending on the type of flux contained in the solder paste, it is slightly higher than this melting point. It has been found that soldering at high temperatures is possible. Therefore, considering the wettability of the solder and the temperature difference inside the board during soldering, if a temperature that is slightly higher than the melting point of the solder can be secured at the lowest temperature part, the amount of the element added to lower the melting point of the solder And the reflow connection can be performed with low-cost Pb-free solder.

Therefore, in order to achieve the above object, the present invention relates to an electronic circuit device having a plurality of solder connection portions soldered in different soldering steps, wherein the electronic circuit device has a plurality of solder connection portions. The solder of the soldered connection portion subjected to the soldering is made of a Sn—Sb solder alloy as a first Pb-free solder, and the solder of the soldered connection portion that has been soldered in the second soldering process is used. The second having a lower melting point than the first Pb-free solder
And a Sn-Ag based solder alloy as a Pb-free solder.

Here, Sb in the first Pb-free solder
Is 1 to 10 wt%, and the rest consists of Sn and unavoidable impurities. At the connection portion between the electronic component and the substrate, the composition range of Ag in the second Pb-free solder is 1.
5 to 3.5 wt%, with the balance consisting of Sn and unavoidable impurities. In this second Pb-free solder, a small amount of Cu, Bi, In is added so as not to affect the cost. This makes it possible to lower the melting point while maintaining good elongation characteristics with temperature. Where Cu
Sn-Ag-Cu solder alloy containing 0 to 0.8 wt% of Ni or a solder alloy containing 0 to 2 wt% of Bi or 0 to 4 wt% of In added to this Sn-Ag-Cu alloy as required I do.

With such a configuration, by using a forced convection type reflow furnace with a small temperature difference in the furnace and setting the reflow temperature of the second Pb-free solder to a temperature closer to the melting point as compared with the prior art, The reflow connection using the second Pb-free solder can be performed while preventing the melting of the first Pb-free solder, and an electronic circuit device having high connection reliability can be provided.

[0027]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of an electronic circuit device according to the present invention and a manufacturing process thereof, wherein 1 is a semiconductor element, 2 is a package substrate, 2A is an inner surface, 2B is an outer surface,
Is metallized, 4 is Sn-Sb solder, 5 is encapsulation metallurgy, 6 is package, 7 is conductor, 8 is electronic component, 9 is substrate, and 10 is Sn-Ag-Cu solder.

The soldering process for this embodiment is divided into a pre-process and a post-process, and FIG. 1A shows an electronic component 8 obtained in the pre-process of the soldering process for the first embodiment. FIG. 1B shows the electronic circuit device of the first embodiment obtained in a post-process of mounting the electronic component 8 and the like on a substrate.

The electronic component 8 shown in FIG. 1A is a package in which the semiconductor element 1 is packaged. The semiconductor element 1 is mounted on a package substrate 2, and the semiconductor element 1 is sealed by a package 6. ing. Package substrate 2
Then, the metallized surface 3 provided on the inner surface 2A and the outer surface 2
B is electrically connected to the metallized 3 provided on the semiconductor element 1 by a conductor 7 filled in a through hole, and the metallized 3 on the inner surface 2A and the metallized 3 provided on the semiconductor element 1 are Pb-free. Sn- which is solder
Solder with Sb solder 4. further,
A sealing metallization 5 is provided on the periphery of the package 6,
Opposite to this, the sealing metallization 5 provided on the inner surface 2A of the package substrate 2 and the Sn-Sb solder 4 are used for soldering.

The melting point of the Sn—Sb solder 4 is 235 to 24.
0 ° C., and the semiconductor element 1 and the package substrate 2 are reflow-connected at a predetermined temperature equal to or higher than the melting point of the Sn—Sb solder 4, for example, 280 ° C. The electronic component 8 is manufactured.

In the post-process shown in FIG.
An electronic component 8 shown in FIG. 1A is placed on a substrate 9 such as mullite or glass ceramic, and metallized 3 (FIG. 1) on the outer surface 2B of the package substrate 2 of the electronic component 8.
(A)) and the metallization 3 of the circuit wiring provided on the surface of the substrate 9 are composed of Sn-Ag-Cu as Pb-free solder.
The electronic circuit device is formed by reflow connection with the solder 10. Note that, in addition to the electronic component 8, components such as a capacitor are mounted on the substrate 9.
Reflow connection is performed using Ag-Cu solder 10.

In the manufacture of the electronic component 8 shown in FIG. 1A, conventionally, a Pb solder having a high melting point of 300 ° C. or more has been used for reflow connection. One of the reasons
First, high melting point Pb solder is used for Pb-S
This is because the melting point is higher by 100 ° C. or more than that of the n solder, and the solder is not melted by soldering in a later process.

Another reason is that the high melting point Pb solder is soft and has an excellent stress relaxation effect.
A semiconductor element 1 made of Si or the like is mounted on a substrate 2 in an electronic component 8.
In the case of reflow connection, the stress generated due to the difference in thermal expansion between the substrate 2 and Si must be reduced by plastic deformation of the solder. This is the operation of the electronic circuit device,
This is because, due to heat generation and cooling caused by the stoppage, distortion due to thermal expansion and contraction is accumulated in the solder connection portion, and sometimes leads to breakage. Focusing only on the melting point of the solder, the high melting point P
As an alternative to b-solder, ie, Pb-free solder, A
u-20Sn solder is most suitable. However, Au-
As is clear from Table 1 above, the 20Sn solder is a very hard solder, and can hardly expect a stress relaxation effect by plastic deformation.

Therefore, although the melting point is considerably lower than that of the high melting point Pb solder, the Sn—Sb solder, which is softer than the Au-20Sn solder, has a higher melting point than the Au-20Sn solder. A promising alternative. The composition of the Sn—Sb solder 4 in this embodiment is, for example, the composition range of Sb is 1 to 10 wt%, and the rest is Sn and inevitable impurities.

Further, in a post-process of the electronic circuit device shown in FIG. 1B, the electronic component 8 is positioned and temporarily mounted on the substrate 9, and is subjected to Sn-Ag-C using a forced convection type reflow furnace.
Reflow connection is performed by u solder 10. Conventionally, Pb-Sn eutectic solder has been often used to connect such an electronic component 8 to the substrate 9. In the first embodiment,
An alternative to Pb-Sn eutectic solder, that is, Sn-Ag based solder is used as Pb-free solder. This is because Sn-Ag based solder has excellent connection reliability and has been used before. And the melting point is lower by 10 to 20 ° C. than that of the Sn—Sb solder.
This is because layering with the n-Sb solder 4 is possible.

In the first embodiment, Sn
-The composition of the Ag-Cu solder 10 is such that the composition range of Ag is 1.5 to 3.5 wt% and the composition range of Cu is 0 to 0.8 w%.
t%, and the remainder is Sn and inevitable impurities. One example is Sn-3Ag-0.7Cu, a Sn-Ag-Cu ternary eutectic alloy with a melting point of 218 [deg.] C.

Next, the reason why the Sn-3Ag-0.7Cu solder 10 and the Sn-Sb solder 4 can be layered will be described.

First, the temperature required for reflow was investigated with the Sn-3Ag-0.7Cu solder paste. FIG. 2 is a diagram showing the results of evaluating the spread rate of wetting with the Sn-3Ag-0.7Cu solder paste obtained by the investigation. The solder paste used here is a normal RMA type, having a flux content of 10 to 11% and a halogen content of about 0.05%. When comparing the wetting spread ratio, almost no change was observed between 220 ° C and 229 ° C.

FIG. 3 is a diagram showing the results of measuring the pull-out strength of the pins by reflow-connecting the pins obtained by plating Cu with Ni / Au to the substrate with Sn-3Ag-0.7Cu solder paste. As is clear from the results, no change was observed in the pull-out strength between 220 ° C. and 229 ° C. under the reflow condition.

From the above, Sn-3Ag-0.7C
When reflowing the u solder paste, it was found that the minimum temperature in the substrate should be set to 220 ° C. or higher.

Next, the influence of temperature unevenness in the reflow furnace for ensuring the minimum temperature in the substrate of 220 ° C. or more during reflow connection was investigated. Fig. 4 is 300mm x 300mm
A thermocouple is installed at the center and the end of the substrate, and the results of measuring the temperature unevenness in the substrate in a conventionally used infrared heating furnace and a forced convection type reflow furnace are shown. A2 indicates the temperature at the center of the substrate, ΔA indicates the temperature difference between the edge and the center of the substrate, and B1 indicates the forced convection. B2 indicates the temperature at the center of the substrate in the mold reflow furnace, B2 indicates the temperature at the center of the substrate, and ΔB indicates the temperature difference between the edge and the center of the substrate.

In FIG. 4, the temperature difference ΔA in the substrate when the infrared heating furnace is used is 25 to 35 ° C. at the maximum. On the other hand, in the forced convection type reflow furnace used in the production of this embodiment, the temperature difference ΔB in the substrate of the same size as described above is 10 to 15 ° C., which is set higher than the infrared heating furnace used conventionally. It has been found that the temperature can be lowered.

That is, in the post-process shown in FIG. 1B, by using a forced convection type reflow furnace and setting the reflow temperature at 235 ° C., the temperature of 220 ° C. can be maintained even at the lowest temperature in the substrate 9. Melting point of 218
Good reflow connection becomes possible with the Sn-3Ag-0.7Cu solder 10 at a temperature of. In addition, since the melting point of the Sn—Sb solder 4 is 235 to 240 ° C., it does not re-melt in the reflow soldering step in the subsequent step.

As described above, it is possible to perform reflow connection with the Sn-Ag-Cu solder 10 without re-melting the connection portion of the Sn-Sb solder 4, and it is possible to layer the solder.

When the heat capacity of the components connected to the substrate is large and the temperature difference within the substrate is 10 to 15 ° C. or more, it is necessary to use solder having a lower melting point.
However, in such a case, Sn-3Ag-0.7C
By adding a small amount of Bi or In to u, the melting point of the solder can be lowered.

FIG. 5A shows the case where Bi is added to Sn-3Ag-0.7Cu, and FIG. 5B shows the case where Sn-3Ag-0.7Cu is added.
It is a figure which shows the result of having investigated change of the melting point of each solder alloy when In is added to -0.7Cu.

As is clear from FIGS. 5A and 5B,
In the case of Bi, the addition of 2% lowers the liquidus temperature to 216 ° C, and the addition of 4% lowers the liquidus temperature to 214 ° C. As described above, by suppressing the addition amounts of Bi and In to about several percent, the melting point of the solder is reduced, the solder is completely melted, and a sound reflow connection can be obtained. Although the addition of In and Bi may cause an increase in the cost of the solder, the increase in the cost of the solder can be suppressed to a small value by adding about several percent as in this embodiment.

On the other hand, if the heat capacity of the components connected to the board is small and the temperature difference in the board can be suppressed to about 10 ° C., the Ag as the Pb-free solder 10 is set to 3.
Layering of Sn-3.5Ag solder containing 5 wt% and Sn-Sb solder as Pb-free solder 4 is also possible. This is because the eutectic temperature of the Sn-3.5Ag solder is 22
If the reflow temperature is 1 ° C. and the reflow temperature is 235 ° C., 225 ° C. can be secured even at the lowest temperature portion, and the Sn−
This is because 3.5 Ag solder can be melted.

Effect of Bi, In on reliability of solder joint
Can be evaluated from the elongation of the solder alloy which has the greatest influence on the reliability. This is because stress is generated in the solder connection part due to expansion and contraction of the member due to heat generation and cooling of the electronic circuit device, but this stress is relaxed by plastic deformation of the solder alloy. is there.

FIG. 6A shows the case where Bi is added to Sn-3Ag-0.7Cu at an ambient temperature of 20 ° C. FIG. 6B shows the case where Sn-3Ag-0.7C
It is a figure which shows the result of having investigated elongation of each solder alloy when In is added to u.

As is clear from FIGS. 6A and 6B,
In the case of Bi, no decrease in the elongation of the solder alloy is observed until the addition amount is 2%. In the case of In, the elongation when not added is 25%. 2
There was a 3% growth. Therefore, even if Bi is added up to 2% or In is added up to 4%, the connection reliability is not impaired. Further, both elements of Bi and In are each 2%,
Even if added by 4%, the mechanical properties are the same as those of the solder alloy to which Bi is added by 2%, and the melting point of the solder alloy can be lowered by the addition of In.

From the above, the second Pb of Bi, In
As the amount of addition to the free solder, Bi is 0 to
2% and In are set to 0 to 4%. In this range, the melting point can be lowered while maintaining good mechanical properties.

As described above, it is possible to realize the layering of the solder by the low-cost Pb-free solder without deteriorating the connection reliability of the soldered portion, and to provide a highly reliable electronic circuit device.

The Pb-free solder alloy contains impurities mixed from a crucible or the like at the time of preparing the solder alloy, impurities in a mother alloy used at the time of preparing the solder alloy, oxygen mixed by oxidizing the surface of the solder, and adsorption. Elements such as C, N, H, etc., mixed as a result are included as unavoidable impurities. The above is the same for the other embodiments.

FIG. 7 is a block diagram showing a second embodiment of the electronic circuit device according to the present invention, wherein 11 is an electronic component,
Is a lead, 13 is an electronic component, 14 is a board, 15 is a composite electronic component, 16 is Sn-Sb solder, 17 is a lead, 18
Is an electronic component, 19 is a lead, and 20 is a substrate. The same reference numerals are given to portions corresponding to those in FIG.

Also in this embodiment, the soldering process is divided into a pre-process and a post-process. FIG. 7B shows the electronic circuit device of this embodiment and the post-process of soldering. 7A shows a composite electronic component 15 to be mounted on the electronic circuit device shown in FIG. 7B and a soldering process thereof (previous process).
It shows.

First, in FIG. 7A, as the composite electronic component 15, an electronic component 11 such as an LSI or an electronic component 13 such as an LSI is mounted on a substrate 14 made of ceramic or a heat-resistant organic material. It is a thing. Wiring is provided on the substrate 14, and the metallization 3 of the wiring corresponds to the lead 12 of the electronic component 11 and the Sn
-Connected by Sb solder 4 and electronic component 13
Are connected to each other by a Sn-Sb solder 4. Such a connection is made by reflow soldering.

In the post-process shown in FIG. 7B, first, the composite electronic component 15 obtained in the preceding process is connected to the lead 17 with a Sn-Sb solder 16 using a laser or the like. The lead 17 to which the electronic component 15 is connected is connected to the substrate 2
0 at a predetermined position on the metallized 3
The lead 19 of an electronic component 18 such as, for example, a single LSI is mounted on another portion of the substrate 20 via the g-Cu solder 10 and the Sn-Ag
-Mounted via Cu solder 10 and connected by reflow using a forced convection type reflow furnace. Thereby, the illustrated electronic circuit device is obtained.

Here, Sn-Sb solder 4 or Sn-Ag
The composition of the -Cu solder 10 is the same as that of the first embodiment shown in FIG. 1, and the Sn-Ag-Cu
Bi or In may be added to the solder 10 within the above range as necessary to lower the reflow temperature. For example, as an example, the Sn-Ag-Cu solder 10 may be made of Sn-3Ag-0. 7Cu-1Bi-2In.

FIG. 8 is a block diagram showing a third embodiment of the electronic circuit device according to the present invention.
2 is a Mo (molybdenum) substrate, 23 is an alumina substrate, 2
4 is Sn-Ag solder, 25 is Cu water cooling jacket, 2
Reference numeral 6 denotes metallization, reference numeral 27 denotes a wire, and reference numeral 4 denotes Sn-Sb solder similar to that of the previous embodiment. This embodiment is an example of an electronic circuit device called a power module.

In the figure, as a pre-process, a Si semiconductor element 21 and a Mo substrate 22 as a stress relieving material are
Reflow connection with Sb solder 4 and then as a post process
The Mo substrate 22 and the alumina substrate 23 to which the Si semiconductor element 21 is connected, and the alumina substrate 23 and the Cu water cooling jacket 25 plated with Ni or the like are reflow-connected by Sn-Ag solder 24, respectively. And S
The metallization 26 provided on the i-semiconductor element 21 and the metallization 26 provided on the Cu water cooling jacket 25 are bonded by wires 27.

Here, the Sn—Sb solder 4 and the Sn—Ag
Although the composition of the solder 24 is the same as that of the previous embodiment, Cu, Bi, and In are added to the Sn-Ag solder 24 as necessary within the same range as in the previous embodiment. The melting point can be lowered.

In the third embodiment having such a structure, the residual stress generated due to the difference in the coefficient of thermal expansion between the Si semiconductor element 21 and the Cu water cooling jacket 25 can be reduced, and the Si semiconductor element 21 having a large calorific value and Mo can be used. By using the high melting point Sn—Sb solder 4 for the connection with the substrate 22, a power module having excellent heat resistance and connection reliability can be obtained.

FIG. 9 is a block diagram showing a fourth embodiment of the electronic circuit device according to the present invention.
Is a lead, 30 is Sn-Ag solder, 31 is Sn-Sb
The portions corresponding to those in FIG. 7 are denoted by the same reference numerals, and redundant description will be omitted.

In each of the above embodiments, Sn-Sb
Perform solder reflow connection, and use S
n-Ag solder (If necessary, Cu, B
Although the soldering step by the reflow reflow process for performing the reflow connection (i, In is added) is employed, the fourth embodiment is not limited to the reflow reflow process. That is, it is also possible to apply a flow process (a process in which a soldered portion is brought into contact with or immersed in molten solder to perform soldering) for connection using Sn-Ag solder as a post-process. In the embodiment, the post-process Sn-
The connection by Ag solder is flow connection (connection by flow soldering).

In FIG. 9, the leads 19 of the electronic component 18 such as an LSI and the metallized 3
Are connected by reflow soldering with Sn-Sb solder 31, and then, as a later step, the leads 29 of another electronic component 28 are connected to the substrate 20.
The lead 29 is inserted from the back surface of the substrate 20 with the Sn-Ag solder 30 into the substrate 2.
0 is to be flow-connected to the metallization 3 on the back surface.

In such a flow process, a jet of Sn—Ag solder 30 is sprayed onto the substrate 20 from the back side of the substrate 20, so that this solder 30
Flows, and the leads 29 and the substrate 20 are connected. At this time, since the substrate 20 has a thickness, a temperature difference occurs between the back surface and the front surface. Therefore, the electronic component 18 reflow-connected to the front side and the solder 31
Since the temperature at and is lower than the temperature of the jet solder,
The flow connection can be performed without re-melting the connection portion by the n-Sb solder 31.

In this embodiment, Sn-S
The compositions of the b solder 31 and the Sn-Ag solder 30 are the same as in the previous embodiment.

FIG. 10 shows a fifth embodiment of the electronic circuit device according to the present invention.
It is a block diagram showing an embodiment of the present invention, 32 is a substrate, 33 is a plug pin, 34 is a high melting point solder, 35 is a composite electronic component,
Reference numeral 36 denotes a printed circuit board, and 37 denotes Sn-Ag-Bi solder. Portions corresponding to the above-described drawings are denoted by the same reference numerals, and redundant description will be omitted.

In the fifth embodiment, the electronic circuit device of each of the first and second embodiments using the first and second Pb-free solders in the first and second steps (the pre-step and the post-step), further,
The present invention relates to an electronic circuit device formed using a third Pb-free solder. Here, FIG.
, FIG. 10B is a second step, and FIG. 10C is a third step, and three steps are shown.

The first step shown in FIG.
The semiconductor device 1 and the package 6 are reflow-connected to the package substrate 2 using Sn—Sb solder 4 as a first Pb-free solder, and the semiconductor device is packaged. The electronic component 8 sealed therein is formed.

The second step shown in FIG. 10B is a step of mounting the electronic component 8 and the like formed in the first step on the substrate 32. The substrate 32 is formed with through holes filled with a predetermined number of conductors 7 in advance, and one end of each of the conductors 7 is connected to the metallization 3 provided on the surface 32A of the substrate 32. The other end of the conductor 7 is connected to the metallization 3 provided on the back surface 32B of the substrate 32, and the insertion pin 33 is connected to the metallization 3 on the back surface 32B side with a high melting point solder such as Au-20Sn or Ag solder. The connection is fixed at 34. The metallization 3 on the surface 32A side of the substrate 32 having such a configuration and the metallization 3 on the outer surface 2B side of the package substrate 2 of the electronic component 8
Are reflow-connected using the Sn-Ag-Cu solder 10 as the second Pb-free solder in the same manner as in the subsequent step of FIG. 1B. Thus, the composite electronic component 35 having the structure shown in the drawing is obtained.

The third step shown in FIG.
The composite electronic component 35 shown in FIG.
6 is implemented. The printed circuit board 36 is provided with through holes in advance.
The metallization 3 is provided around the through-hole on the back surface 36B of the metal plate 6. When mounting the composite electronic component 35 on the printed circuit board 36, the insertion pins 33 of the composite electronic component 35 are inserted into the through holes of the printed circuit board 36 from the front surface 36A side, and the metallized 3 is inserted from the rear surface 36B side. A jet of Sn-Ag-Bi solder 37, which is a third Pb-free solder, is sprayed on the provided portion. As a result, the Sn-Ag-Bi solder 37 flows into the through holes, and the insertion pins 33 are flow-connected to the printed circuit board 36.

The Sn-Ag of the third Pb-free solder
-The composition of the Bi solder 37 has a Bi range of 4
The composition range of 0 to 60 wt% and Ag is 0.1 to 3 wt%, and the rest is Sn and inevitable impurities. For example, if the composition is Sn-1Ag-57Bi, the melting point is 137 to 138 ° C. Yes, it has a lower melting point than the first and second Pb-free solders. Therefore, Sn-Ag
In the flow process using the Bi solder 37,
Soldering can be performed without remelting the second Pb-free solder.

The Sn-Sb solder 4 and the Sn-Ag-
The composition of the Cu solder 10 is the same as in the previous embodiment.

In the fifth embodiment, the electronic component mounted on the board 32 of the composite electronic component 35 is the same as that shown in FIG.
Although the electronic component 8 shown in FIG. 7 is used, any electronic component shown in FIGS. 7A, 8, and 9 may be used as long as the electronic component has a configuration in which a conductor is guided through a through hole to the metallization on the back surface side of the substrate. Good.

[0077]

As described above, according to the present invention,
Sn-Sb solder, which is a high melting point Pb-free solder, and Sn-Ag having a lower melting point (Cu, B if necessary)
Using i) and (indium) solder makes it possible to form a layer of solder, and to provide an electronic circuit device having high connection reliability. In addition, Sn-Ag-B
The use of i-solder makes it possible to form a three-stage solder hierarchy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an electronic circuit device according to the present invention.

FIG. 2 is a view showing a result of measuring a wet spread rate of a Sn-3Ag-0.7Cu solder paste.

FIG. 3 is a diagram showing the results of measuring the pull-out strength of Ni / Au-plated Cu pins reflow-connected with Sn-3Ag-0.7Cu solder paste.

FIG. 4 is a diagram showing the results of an investigation of temperature variations in a substrate between a conventional infrared heating furnace and a forced convection heating furnace.

FIG. 5 is a graph showing changes in liquidus temperature and solidus temperature (° C.) with respect to the amount of Bi or In added to Sn-3Ag-0.7Cu solder.

FIG. 6 is a diagram showing a change in elongation (%) at 20 ° C. with respect to the amount of Bi or In added to a Sn-3Ag-0.7Cu solder.

FIG. 7 is a configuration diagram showing a second embodiment of the electronic circuit device according to the present invention.

FIG. 8 is a configuration diagram showing a third embodiment of the electronic circuit device according to the present invention.

FIG. 9 is a configuration diagram showing a fourth embodiment of the electronic circuit device according to the present invention.

FIG. 10 is a configuration diagram showing a fifth embodiment of the electronic circuit device according to the present invention.

FIG. 11 is a view showing the result of evaluating the wettability of a Pb-Sn eutectic solder at a melting point or higher.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 semiconductor element 2 package substrate 3 metallization 4 Sn-Sb solder (first Pb-free solder) 5 package and substrate sealing metallization 6 package 7 conductor 8 electronic component 9 substrate 10 Sn-Ag-Cu solder (second Pb 11 electronic component 12 lead 13 electronic component 14 substrate 15 composite electronic component 16 Sn-Sb solder 17 lead 18 electronic component 19 lead 20 substrate 21 Si semiconductor element 22 MO substrate 23 substrate such as alumina 24 Sn-Ag solder 25 Cu Water cooling jacket 26 Metallized 27 Bonded wire 28 Electronic component 29 Lead 30 Sn-Ag solder 31 Sn-Sb solder 32 Substrate 33 Plug-in pin 34 High melting point solder such as Au-20Sn solder or Ag solder 35 Composite electronics Article 36 PCB 37 Sn-Ag-Bi solder (Third Pb-free solder)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidee Shimokawa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture In-house Research Laboratory of Hitachi, Ltd. (72) Inventor Toshitaka Murakawa 1-Horiyamashita, Hadano-shi, Kanagawa Hitachi Server Enterprise Server Division (72) Inventor Koji Serizawa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi, Ltd. Production Technology Research Laboratory F-term (reference) 5E319 AA03 AA07 AB06 BB01 BB07

Claims (8)

[Claims] 1. An electronic circuit device having a plurality of solder joints soldered in different soldering steps, wherein the solder of the solder joints soldered in the preceding first soldering step is the second solder joint. (1) a solder alloy comprising Sn, Sb and unavoidable impurities as Pb-free solder, wherein the solder of the solder connection portion soldered in the second soldering step following the first soldering step is: First
Composed of Sn, Ag, and unavoidable impurities as a second Pb-free solder having a lower melting point than that of the Pb-free solder.
An electronic circuit device comprising an n-Ag solder alloy. 2. The electronic circuit device according to claim 1, wherein the first Pb-free solder is a solder alloy having a composition range of Sb of 1 to 10 wt%. 3. The electronic circuit device according to claim 1, wherein the composition ratio of the Ag in the second Pb-free solder is 1.5 to 3.5 wt%. 4. The electronic circuit device according to claim 1, wherein Cu is added to the second Pb-free solder in a range of 0 to 0.8 wt%. 5. The electronic circuit device according to claim 1, wherein the second Pb-free solder is a solder alloy to which In or Bi is added. 6. The electronic circuit device according to claim 5, wherein the composition range of Bi is 0 to 2 wt%, and the composition range of In is 0 to 4 wt%. 7. The solder according to claim 1, wherein the solder of the solder connection portion soldered in the third soldering step subsequent to the second soldering step is:
An electronic circuit device comprising a third Pb-free solder as a solder alloy comprising Sn, Bi, Ag and unavoidable impurities. 8. The composition according to claim 7, wherein the composition range of the Bi in the third Pb-free solder is 40-60 wt%, and the composition range of the Ag in the third Pb-free solder is 0.1-6.0. An electronic circuit device comprising 3 wt%.