JP2003200288A - Pb-FREE SOLDER MATERIAL AND ELECTRONIC APPARATUS USING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide Pb-free solder having the characteristics approximately the same as those of the conventional solder containing Pb and packaged parts using the same. <P>SOLUTION: The purposes can be achieved by the Sn-Ag-Bi-base solder composed of 10 to 25 wt.% Bi, 1.5 to 3 wt.% Ag and the balance Sn and inevitable impurities or the Sn-Ag-Bi-Cu-base solder alloy containing ≤1 wt.% Cu in this solder alloy, and further preferably Sn-Ag-Bi-Cu-base solder alloy containing ≤0.1 wt.% Cu. The ternary eutectic amount to melt the solder alloy of the above ranges at a low temperature is ≤20%. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention
Related to free solder alloys and mounted products using the same
It is. This solder alloy is applied to circuit boards such as organic substrates.
It can be applied to the connection of electronic parts such as LSI,
Pb-Sn used for soldering at 230 ° C
It is a substitute for crystal solder. 2. Description of the Related Art Conventionally, an LSI or the like is mounted on a circuit board such as an organic board.
In order to connect electronic components and manufacture an electronic circuit board, S
n-Pb eutectic solder and near Sn-Pb eutectic solder
Beside, Sn-Pb solder with similar melting point or these
Alloys with a small amount of Bi or Ag added to
I have. [0003] These solders contain about 40% by weight of Pb.
include. Each solder alloy has a melting point of almost 18
3 ℃, soldering at 220-230 ℃ is possible
there were. It also guarantees reliability at high temperatures of about 150 ° C.
I was able to. [0004] However, the above Sn-
Pb contained in Pb eutectic solder is toxic heavy
By discarding products containing Pb
Pollution of the global environment and adverse effects on living organisms have become problems.
This pollution of the global environment includes Pb left undisturbed.
Pb elutes from electrical products due to rain, etc.
It happens. Pb elution accelerated by recent acid rain
Tend to be. Therefore, to reduce environmental pollution
The Sn-Pb eutectic system used in large quantities
Low toxicity solder alloy containing no Pb as an alternative material
is necessary. [0005] As an alternative material to the Sn-Pb eutectic solder,
All Pb-free solder alloys have the following characteristics
There must be. First, as with the conventional Sn-Pb eutectic solder,
Must be solderable at temperatures between 220 and 230 ° C
I have to. This is for electronic components such as LSI and organic
Due to the heat resistance of circuit boards such as boards,
This is because it is difficult to attach. For this, solder alloy
Must be approximately 210 ° C. or less. The wettability of this solder alloy is based on Sn-
Pb eutectic solder or Sn-
Ag eutectic solder (3.5% by weight of Ag, remaining Sn
Must be approximately equivalent to If this Pb-free
Compared to conventional solder, solder is not
If the wettability is extremely poor, the soldering atmosphere will be improved,
Flux, cleaning material and cleaning method suitable for solder material
Development of materials for electrode parts to be soldered
Challenges arise. [0008] In terms of the solder structure, the crack
Large crystals with high aspect ratio such as needles
It is important that they do not exist. These needle-like crystals
Grows from the solder surface, causing an electrical short
It can be lost. Further, the temperature is as high as possible, ie, 150 ° C.
Must be reliable at least at 125 ° C
Absent. This means that when using electrical products, the parts themselves
Due to heat or high temperature,
This is because the temperature of the connecting portion may increase. [0010] Also, the elongation of the solder alloy depends on the electronic parts and the circuit.
Important for application to thermal expansion mismatch between circuit boards
You. Therefore, a Pb-free solder having the above characteristics
I need money. However, such a Pb-free solder alloy is
Until now not offered. Sn-Ag which is a binary alloy
Pb-free is not used for eutectic solder or Sn-Bi eutectic solder
It is used as a solder for hierarchical connection
However, the melting points are 221 ° C and 138 ° C, respectively.
A soldering temperature of about 240 ° C is required.
Are difficult to ensure reliability at high temperatures. Also, S
The melting point of the Sn-Zn eutectic solder is 19 for the n-Zn based solder.
Since the temperature is 9 ° C, the melting point of Sn-Pb eutectic solder is
Although it is a promising alternative material, it is not
It was difficult to ensure sufficient wettability inside. Further, Japanese Patent Application Laid-Open No. 7-1179 or
Pb as described in JP-A-7-88680
There is also a free solder alloy, but the former has a melting point of about 138 ° C
The latter is difficult to solder at 220-230 ° C.
Both are difficult alternatives to Sn-Pb eutectic solder
Could not be. Therefore, an object of the present invention is to satisfy the above-mentioned conditions.
Provided Pb-free solder and mounted products using it
Is to do. [0014] The above object is attained by providing 10% by weight.
~ 25 wt% Bi, 1.5 wt% -3 wt% Ag,
The remaining Sn and Sn-Ag- composed of unavoidable impurities
1 weight of Cu in Bi-based solder or this solder alloy
% Sn-Ag-Bi-Cu based solder alloy,
Preferably contains less than 0.1% by weight of Cu.
-Can be achieved by Bi-Cu based solder alloy
You. The ternary melting of solder alloys in these ranges at low temperatures
The crystallization amount is 20% or less. The following is a description of the process for selecting the solder alloy of the present invention.
Explain why. Bi is 0 to 60% by weight, and Ag is 0 to 5% by weight.
%, Sn-Ag-Bi solder in the range of the remaining Sn
Thus, the melting characteristics were examined in detail. As an example of this study
2% by weight of Ag, 13% by weight of Bi, and the remaining Sn
(A) 2% by weight of Ag, 15% by weight of Bi and the rest
Sn solder (b), 2 wt% Ag, 22 wt% B
i, the melting characteristics of the remaining Sn solder (c)
1 is shown. These are the same amount of solder alloy of each composition
Weigh out, melt and solidify using reflow oven, differential
The melting characteristics were examined by thermal analysis. Reflow furnace
The sample was melted and solidified using a cooling rate of
This is for the same purpose as when soldering. Differential thermal analysis
The test was performed at a heating rate of 2 ° C./min. Such a detailed examination
As a result of performing the composition within the above range, 220 to 230
For soldering at ℃, the liquidus temperature must be at least
Must be 210 ° C. or less, and the amount of Bi is at least
It was found that 10% by weight or more was necessary. FIG. 2 shows that 10% by weight of Bi and 2% by weight of A
g, remaining Sn solder (d), 10 wt% Bi, triple
% Ag, the remaining Sn solder (e), and 10% by weight
Of Bi, 4% by weight of Ag, and the remaining Sn of solder (f) 3
The structure of the various solder alloys is shown. This is
After melting the solder alloy at 240 ° C for 30 seconds, 80 ° C /
After cooling in minutes, the tissue is polished in cross section and examined with a metallurgical microscope.
Observed. From now on, Sn of (d) and (e)
-Ag-Bi solder has a spherical shape between Sn round crystals.
Bi crystals and small crystals of Ag3Sn were observed.
-In Ag-Bi-based solder (f), large Ag3Sn
It was found that fine needle crystals were crystallized. As a result
Is the organizational view of other Bi contents by changing the Ag content in the same manner.
As a result, the Sn-Ag binary eutectic line was similarly observed.
Is exceeded in the direction of increasing the Ag concentration, the primary crystal of Ag3Sn
Was precipitated. For this reason, do not cross this line
Shows that the amount of Ag must be less than 3% by weight
Was. Ag is used to improve the mechanical properties of solder.
The effect is less than 1.5% by weight.
I couldn't see it. Also, when the amount of Ag decreases, the liquidus line
The temperature rises and the difference between the liquidus temperature and the solidus temperature
Turned out to be large. Therefore, the amount of Ag
Must be at least 1.5% by weight. Next, the signal at 150 ° C. and at least 125 ° C.
The conditions for ensuring reliability are described below. Such high
To ensure reliability at high temperatures, the solidus temperature of the solder
is important. Detailed solder melting characteristics as shown in Figure 1
From the study of the sex, in this Sn-Ag-Bi system, Bi
If it becomes 10% by weight or more, the part melting around 138 ° C
Was found to occur. This is the cooling during preparation of the measurement sample
Influenced by the speed, if the cooling rate is fast Bi
Below 18% by weight, this melting peak does not appear
But cooled by the normal cooling rate during soldering
In the sample, Bi is in the range of 10% by weight to 18% by weight.
Was also found to melt. Melt at 138 ° C
Is the part of the ternary eutectic composition of Sn-Ag-Bi.
You. Therefore, on the Sn-Ag binary eutectic line, the amount of Bi is
Change the proportion of the portion that melts at 138 ° C
Original eutectic composition (1 wt% Ag, 57 wt% Bi, balance
Sn) by comparing with the peak calorific value of the solder.
FIG. From this, the rate of melting at 138 ° C
Was found to change smoothly with the amount of Bi. Three
There is no practical problem if the ratio of the eutectic is small
It can be said. Therefore, various temperature cycle tests are performed
As a result of discussion, the ternary eutectic ratio must be less than about 20%.
Bi must be 25% by weight or less
I understand. To ensure reliability at this high temperature
Bi content can be confirmed by tensile test at high temperature.
did it. FIG. 4 shows that at 150 ° C. when the amount of Bi was changed.
The tensile strength was indicated. This is because the strength at 150 ° C
This is because it is a measure of reliability. Tensile test is 0.1m
The test was performed at a pulling speed of m / min. 0.1mm / min tensile speed
The reason was that the sample was not
Equivalent conversion to tensile speed to reproduce the maximum strain rate experienced
It depends. From now on, if Bi is 25% by weight or less
If it has, it has a tensile strength at 150 ° C and can be used at high temperatures
I found it to be tolerable. Some ternary eutectic exists
However, the reason why the strength is guaranteed at 150 ° C is that the ternary eutectic
Based on generation mechanism. That is, when the amount of Bi is increased,
Crystals are generated, but are scattered in the gaps of the Sn crystals having a high melting point.
Have strength for your situation. When Bi further increases, S
The amount of Bi in the n crystal increases, the melting point of the Sn crystal itself decreases, and
The amount of ternary eutectic in the gap between the Sn crystals also increases, so the strength is increased.
It becomes. Here, Bi is 25% by weight and ternary eutectic is 20%.
%, The ternary eutectic completely fills the Sn crystal gap
In order not to run out, it will have strength at 150 ° C.
You. Similarly, conduct a tensile test at 125 ° C to measure the tensile strength.
And Bi is 25% by weight or more as shown in FIG.
And the tensile strength will be 5 MPa or less,
If it is 25% by weight or less, the tensile force increases as Bi decreases.
It turns out that strength is increased and reliability at high temperatures can be secured.
Was. Cu was added for improving the structure.
Cu is usually Cu-Sn in Sn-Ag-Bi solder.
Exists as a compound of Cu-Sn compound has Cu content
If it is a trace amount, it is a small sphere, so it is dispersed between Sn
It becomes a dispersion strengthened alloy. This is because a small amount of Sn-Cu
It is effective only by the presence of the compound. Cu in Sn
Cu-Sn compound because it dissolves up to 0.006% by weight
In order to produce, the content of Cu of 0.006% by weight or more
Addition is required. However, the Cu content is 0.1% by weight or more.
Then, the solder starts to be embrittled. Cu-Sn compound
The compound is large and hard to deform due to its hardness.
This is because the flexibility of the entire joint is exposed. this
Is a solder ball with a lead-free structure.
Soldering due to increased mounting density
The effect of heat generation in electronic circuits due to the smaller gripper
And the strain on the connection increases
Is particularly important for connections that require solder flexibility.
Eyes. Further, when the Cu content is 1% by weight or more, another item
Deterioration by eyes is seen. First, the wettability is shown in FIG.
15% by weight of Bi, 2.5% by weight of Ag, and the remaining Sn
This indicates the spread of solder when Cu is added.
However, when the Cu content is 0.5% by weight, the wet spread is the highest.
If the Cu concentration is higher than that, the Cu
When the spread was reduced and Cu was not added at 2% by weight.
It was found that the wettability was deteriorated as compared with the case. Ma
In addition, when the amount of Cu increases, Sn in the solder changes to Cu.
Since it is consumed for compound production, the amount of Ag increases relatively,
Ag3Sn crystals having a large shape are easily formed. 15 layers
% Bi, 2.8% Ag by weight, the remaining Sn
0.5% by weight, 1% by weight and 2% by weight of Cu
The structure of the solder was observed.
To increase the amount of Cu-Sn compound and increase the content of C by 1% by weight or more.
When u is added, a large Ag3Sn crystal is formed.
I found out. This large Ag3Sn crystal
It can be a trigger for rack development. Therefore, prevent this
It is conceivable to reduce the amount of Ag in advance in order to
, The liquidus temperature rises. From the above, Cu
Is 1% by weight or less, preferably 0.1% by weight or less.
The wettability of solder alloys in the above composition range is determined by S
It is almost at the same level as n-Ag eutectic solder.
And electrode material can be used as it is. FIG. 7 shows the Bi content on the binary eutectic line.
The elongation at room temperature was shown when the temperature was changed.
The elongation of the solder alloy in the box is 17% or more at room temperature. Real
There is no problem in use. Further, solderability at 220 to 230 ° C.,
And to improve reliability at high temperatures,
13% to 20% by weight of B in the selected composition
i, 2% to 3% by weight of Ag, remaining Sn, and inevitable
Sn-Ag-Bi based solder composed of impurities, or
Describes that Sn- containing less than 1% by weight of Cu in this solder alloy.
Ag-Bi-Cu-based solder alloy, and the above ternary solder
Sn-Ag-Bi containing less than 0.1% by weight of Cu in alloy
-A Cu-based solder alloy is desirable. This is Bi 13
If the amount is more than 10% by weight, the liquid phase is more than that in the case where Bi is 10% by weight.
The line temperature drops and even parts with a large heat capacity can reach 220-
This is because soldering at 230 ° C. can be facilitated.
Also, Ag has a smaller Ag content than the Sn-Ag binary eutectic line.
In the region where there is not, it has the effect of lowering the liquidus temperature and the amount of Ag
Is 2% by weight or more, the reflow property is further improved,
This is because the mechanical properties are further improved. In addition, Bi amount is 20
% By weight, the ternary eutectic melt at around 138 ° C.
And the tensile strength at 150 ° C.
Degree is more than 5MPa, tensile strength at 125 ℃ is 15M
High strength and creep at high temperature
Improved reliability of characteristics, vibration, shock, etc., used at high temperature
The reliability margin for electrical products
Wear. As shown above, Sn-Ag-Bi
The effective range of the alloy was selected. DESCRIPTION OF THE PREFERRED EMBODIMENTS Solders having six compositions shown in Table 1 were prepared.
The results of examining the properties are described below. [Table 1] (Embodiment 1) As an example of the present invention, 1
5% by weight of Bi, 2% by weight of Ag, and the remaining Sn alloy
Done. The liquidus temperature of this alloy is 207 ° C, the solidus temperature
Is 156 ° C, but the ternary eutectic melts around 138 ° C.
The ratio is 5%, and there is no practical problem.
No. Tensile strength at room temperature is 77MPa, tensile at 150 ℃
Strength is 11MPa, tensile strength at 125 ℃ is 22MP
a, The elongation at room temperature was 19%. Also in the atmosphere
Has a wettability of 91% of the Sn-Ag eutectic,
g It can be said to be about the same as eutectic solder. This solder alloy is powdered
And knead with flux components to create solder paste
did. Using this solder paste, a 0.5 mm
H, 208-pin QFP (Quad Flat Package)-LSI
Is soldered to a glass epoxy board, -55 ° C for 30 minutes
Temperature cycle of ~ 125 ° C for 30 minutes (1 hour / 1 cycle)
Test. The lead of QFP-LSI is Sn plating
Have been. The maximum temperature during soldering is 220 ° C
Met. The corner pin flange where the stress acts the most
From the beginning to 1000 cycles
Was followed up with an electron microscope.
Cracks that can lead to disconnection
Not as good as Sn-Pb eutectic solder
Was. The cross section of this corner pin was polished and observed.
It was confirmed that no rack had occurred. Therefore,
The composition of the solder alloy is an alternative material to Sn-Pb eutectic solder
Can be used as About this solder alloy
Are BGA (Ball Grid Array), CSP (Chip Size P)
ackage) etc.
Can be. Also, since the surface oxidation is low, flow
It can also be used as a soldering material for soldering. Change
Used as a solder foil for chip die bonding,
It is also applicable for joule mounting and sealing. (Embodiment 2) Similarly, an example of the present invention
Then, 15% by weight of Bi, 2.5% by weight of Ag, and the remaining S
n was prepared. The liquidus temperature of this alloy is 204
℃, solidus temperature is 155 ℃, around 138 ℃ ternary eutectic
The rate of melting was 5%. Room temperature tensile strength is 78
MPa, tensile strength at 150 ° C. is 10 MPa, at room temperature
The elongation was 20%. Also, the wettability in the atmosphere is
It was 92% of the Sn-Ag eutectic. This solder alloy
And the same temperature cycle test as in Example 1 was performed.
went. As a result, the corner where the stress acts the most
Part of the solder fillet surface, up to 1000 cycles,
Similar to the result of Example 1, a slight change in the surface occurs
As a result, no crack leading to disconnection occurred. Therefore,
The solder alloy of Example 2 is a substitute for Sn-Pb eutectic solder
It is effective as a fee. (Embodiment 3) Similarly, one example of the present invention
Then, 20% by weight of Bi, 2.5% by weight of Ag, and the remaining S
n was prepared. The liquidus temperature of this alloy is 200
℃, solidus temperature is 138 ℃, ternary eutectic around 138 ℃
The rate of melting was 10%. Tensile strength at room temperature is 7
5MPa, tensile strength at 150 ° C is 5MPa, room temperature
The elongation was 25%. Also, the wettability in the atmosphere is
It was 87% of the Sn-Ag eutectic. This solder alloy
And the same temperature cycle test as in Example 1 was performed.
went. As a result, the corner where the stress acts the most
Part of the solder fillet surface, up to 1000 cycles,
Similar to the result of Example 1, a slight change in the surface occurs
As a result, cracks such as disconnection did not occur, and both Sn-Pb
There was no inferiority to the crystal solder. Therefore, Example 3
Is a substitute for Sn-Pb eutectic solder
Effective. (Embodiment 4) Similarly, one example of the present invention
15% Bi, 2.8% Ag, 0.5%
An alloy of weight% of Cu and the remaining Sn was prepared. Of this alloy
Liquidus temperature is 204 ℃, solidus temperature is 157 ℃, ternary
The melting ratio of the crystals was 5%. The tensile strength at room temperature is
83 MPa, tensile strength at 150 ° C. is 11 MPa, room temperature
Was 21%. In addition, wettability in the atmosphere
Was 90% of the Sn-Ag eutectic. This solder alloy
Into a solder paste, and TSOP (Thin Small Outline)
Package), soldering chip components to glass epoxy board
Temperature cycle test under the same conditions as in Example 1.
Was. TSOP and chip parts have short leads
Is a leadless component, so the difference in thermal expansion
QFP-LS with long lead that must be applied
This is a stricter connection than I. Such a temperature cycle
Solder fillet at corner of TSOP tested
The surface was observed up to 1000 cycles.
As a result, although some deterioration is observed,
No cracks were found. Also, chip parts
But there is no big change
It can be confirmed that it has not occurred, and compared with Sn-Pb eutectic.
There was no inferiority. Also soldered like this
A shear test was performed on the chip component.
After the high temperature storage test in the above, and the above temperature cycle test 1
Even after 000 cycles, the shear strength deteriorates compared to the initial
Was not seen. In addition, the conventionally used Sn-P
It had almost the same shear strength as b eutectic. Also electrical
There was no problem in the continuity test. (Embodiment 5) 18% by weight of Bi, double
Amount of Ag, the remaining Sn alloy was used for BGA connection.
Here is an example. As shown in FIG. 8, the above-described composition
The solder ball 2 was soldered. The solder ball diameter is 0.
The soldering temperature was 225 ° C. This
Of the same composition on the printed circuit board 4 side
Solder paste 5 under the same conditions
Was. By going through the above process, using Pb
No low toxicity BGA connections can be made. This pre
BGA connected to the printed circuit board as in Example 1.
Temperature cycle test, but no problem in practice
all right. Further, the solder connected to the BGA body
The ball 2 has a high melting point solder, for example, a Sn-Ag eutectic solder.
The solder used on the printed circuit board side
Use of bright solder allows connection at 220-230 ° C
Noh. Thus, the solder of the present invention is used for
It can also be used for connection using a ball. (Embodiment 6) 15% by weight of Bi, 2.
5% by weight of Ag, 0.08% by weight of Cu and the balance of Sn
Manufacturing method of electronic circuit board for 8mm video using gold
Show. First, the size of this solder alloy is 25-45 μm.
Powder and knead it with flux components
Paste created. 0.15m of this solder paste
using a metal mask with a thickness of m
Separately supplied. Print to which this solder paste was supplied
Various electronic components are mounted on the board using a component mounting machine,
Soldering was performed through an elementary reflow furnace. Nitrogen reflow
-The oxygen concentration in the furnace was 100 ppm. Soldering temperature
The degree differs even on the same substrate due to the difference in heat capacity of various parts.
However, the preheating is almost 150 ° C, and the highest temperature is the highest
The temperature was set to 230 ° C. even at the raised position. After this,
Print the solder paste on the back side as well, various parts
And heating by nitrogen reflow. This electronic times
The circuit board includes a 0.4 mm pitch QFP-LSI,
It is 1.0mm long and 0.5mm wide called 05
Chip components and the like are included. Cleaning after soldering
I didn't know. After soldering in this way,
The appearance of the soldered part was inspected using a visual inspection device.
As a result, compared to the conventional Sn-Pb eutectic,
Has a low false alarm rate due to the low gloss. Also,
Solderability using conventional Sn-Pb eutectic
Compared with the printed board, but the Cu pad on the printed board
Spreads slightly to the surface, but at a level sufficient for practical use.
Was. Among them, due to the displacement at the time of component mounting,
Several chip components were seen missing, but this
It could be easily corrected with a trowel. The electronic circuit for 8 mm video produced in this way.
Circuit board is incorporated into the actual 8mm video body,
Perform product inspections such as checks, vibration tests, and high-temperature / high-humidity tests
However, there were no particular problems. Thus, Pb is not included
Using low-toxic Sn-Ag-Bi-Cu solder,
By setting the soldering temperature up to 230 ° C
To produce electronic circuit boards with low environmental and biological toxicity
I was able to. (Embodiment 7) 15% by weight of Bi;
8% by weight of Ag and the rest of the alloy of Sn
Soldered to QFP-LSI and TSOP. Han
The maximum soldering temperature was 230 ° C. These electrons
Conventionally, the lead electrode of the component is 90% by weight in 42 alloy.
Sn, solder plating having a composition of 10% by weight of Pb (hereinafter, referred to as “Pb”)
Sn-10Pb) is used.
You. However, since these also contain toxic Pb,
It is also necessary that the gate electrode be Pb-free. Therefore, this implementation
In the embodiment, Cu alloy is plated on 42 alloy and then 8
Wt% Bi and the remaining Sn composition solder plating (hereinafter, referred to as
Sn-8Bi). Cu plating thickness
Is 5 μm, and the thickness of Sn-8Bi plating is 10 μm.
Was. An embodiment of the above soldered board
Performed the same temperature cycle test as in 1, but with sufficient reliability
Obtained. The reason why the lead electrode is configured as described above.
Is the work on the split board after soldering or the probing
The board warps at the time of a strike, or is connected by handling etc.
Large stress is applied to the solder connection part of LSI etc.
Without securing the strength of the solder joints that can withstand it
Because it must not. Therefore, it has sufficient connection strength.
In order to obtain a configuration, the solder alloy of the present invention and various types of
I checked the connection strength with lead using Pb-free material.
A description will be given below. Various solder plating, Pd plating, etc. on the surface
A model lead was prepared. Model lead material
Is 42 alloy, and Cu is used as a base for plating on the surface.
Consider 3 types of plating, Ni plating, or no base
Was. The model lead width is 3mm and the length of the soldered part
Bend at a 90 ° angle so that the
You. These soldering methods can be used to
On a 3.5 mm, 25 mm long Cu pad,
Place the same size solder foil according to the composition of the present invention,
Put the above model lead on top, and in air, at maximum temperature
Soldered at 220 ° C. At this time, the chlorine amount is 0.2
% Flux was used. After washing this,
At a speed of 5 mm / min to perform a peel test.
The strength of the fillet portion at which the strength was greatest was determined. Pea
The initial test after soldering and the change over time after soldering
After soldering, 125
After leaving at ℃ for 168 hours, the wettability of the lead electrode is poor.
Model lead at 150 ° C to 16
After soldering for 8 hours, and after 3 types
Was. The solder composition, Bi amount, Ag amount, within the scope of the invention
The study was conducted by changing the amount of Cu. As a result, this solder composition range
The same tendency is seen in the box, and the C
Improved connection strength when u-plated
all right. This is low reactivity between Bi and 42 alloy
Therefore, compared with the conventional Sn-Pb eutectic, sufficient compound
Is not generated and strength cannot be obtained. Presence of Cu
42 alloy lead
Not enough connection using Cu-based lead frame
Strength is obtained. The composition of the surface is such that Bi is 25% by weight.
% In the case of Sn-Bi composition containing up to about
It was found that strength was obtained. Of these results,
15% by weight of Bi, 2.8% by weight of Ag, and the remaining Sn
After that, Sn-8Bi plating on 42 alloy was 10 μm.
, 42 undercoat with 5μm Cu undercoating
With a model lead with Sn-8Bi plating of 10 μm
FIG. 9 shows the fillet strength. Figure 9 shows the conventional
Fillet in the case of a combination containing Pb
The cut portion strength is similarly shown. From now on, 42 alloys
Cu base plating and Sn-8Bi plating on top
In the configuration, the Sn-8Bi plating was directly applied on the 42 alloy.
Connection strength is higher than when
Used Sn-Pb eutectic solder and Sn-10Pb
Connection strength higher than the configuration with the plating lead can be obtained
all right. Thus, the solder alloy of the present invention
Or use Cu-based lead frame
Then, a surface treatment such as Sn-8Bi plating should be performed thereon.
Thereby, a connection portion having sufficient strength can be obtained. As described above, according to the present invention,
For gold, Sn-Pb eutectic which has been used in large quantities
Low toxicity Pb-free solder as an alternative to solder
Can be provided. This solder alloy is subject to soldering temperature
And the wettability has been improved.
-Flux, electrode material because of the same level as Ag eutectic solder
No special development of fees is required. Also melts at low temperatures
Since the ternary eutectic amount is also 20% or less, reliability at high temperatures is improved.
Electronic components to the circuit board with high reliability.
You can continue.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows melting characteristics of three types of Sn-Ag-Bi solders. FIG. 2 is a photograph showing the structure of three types of Sn—Ag—Bi solders. FIG. 3 shows the ternary eutectic ratio when the amount of Bi near the Sn—Ag binary eutectic line is changed. FIG. 4 shows tensile strength at 150 ° C. when the amount of Bi was changed. FIG. 5 shows tensile strength at 125 ° C. when the amount of Bi was changed. FIG. 6 shows the wetting characteristics when the amount of Cu in the Sn—Ag—Bi solder is changed. FIG. 7 shows the elongation characteristics at room temperature when the amount of Bi is changed. FIG. 8 shows an example in which the present invention is applied to a BGA. FIG. 9 shows the connection strength between the solder of the present invention and a lead. [Explanation of reference numerals] 1. BGA body 2. solder balls BGA 4. 4. Printed circuit board Solder paste

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Tetsuya Nakatsuka             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd. Production Technology Laboratory (72) Inventor Toshiharu Ishida             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd. Production Technology Laboratory (72) Inventor Masahide Harada             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd. Production Technology Laboratory (72) Inventor Megumi Hamano             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd. Production Technology Laboratory (72) Inventor Kenichi Yamamoto             5-20-1, Stock, Honcho, Kosui, Tokyo             Hitachi Semiconductor Co., Ltd. F term (reference) 5E319 AA03 AB05 AC01 AC04 BB08                       CC33 GG03

Claims (1)

Claims: 1. An electronic apparatus comprising: a circuit board on which a predetermined wiring pattern is formed; and an electronic component having an electrode connected to the wiring pattern. The electrodes of the electronic component are
Wt% to 25 wt% Bi, 1.5 wt% to 3 wt% Ag, the balance being Sn and Sn composed of unavoidable impurities
-An electronic device characterized by being connected by an Ag-Bi solder.