JP2003290974A - Joining structure of electronic circuit device and electronic parts used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joining structure of an electronic circuit device having a high effect of suppressing the diffusion of an Ni electrode material formed by an electroless plating process, capable of assuring the reliability of joining and permitting joining at a low temperature as well. <P>SOLUTION: The junctions of the joining structure of the electronic circuit device in which connecting electrodes on a circuit board and connecting terminal electrodes on the electronic parts packaged to the board are electrically connected by Sn solder are formed of the solder containing 30 to 60 wt.% Bi, 0.5 to 2 wt.% Cu, and 0.1 to 2 wt.% Zn in addition to Sn. The solder can further contain 0.5 to 3 wt.% Ag as well. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint structure in an electronic circuit device in which a connection electrode on a circuit board and a connection terminal electrode on an electronic component such as a semiconductor chip are electrically connected by Sn-based solder.

[0002]

2. Description of the Related Art Conventionally, Sn-Pb eutectic solder (Sn-3) has been used for electrical and mechanical joining of electronic parts such as semiconductor elements.
7Pb, melting point 183 ° C) has been commonly used. Further, although Cu has been mainly used as an electrode material for a circuit board or the like to be bonded to these electronic components, in order to suppress deterioration of the reliability of the bonding portion due to diffusion of the electrode material, N is deposited on the Cu electrode surface.
The i-type barrier layer is mainly used. Sn
With this combination of the -Pb eutectic solder and the Cu electrode provided with the Ni barrier layer, a joint having high electrical and mechanical reliability is formed.

In recent years, it has been required to use Pb-free solder (Pb-free solder) from the viewpoint of environmental impact. Since the composition of Pb-free solder is mostly Sn, and therefore the amount of Sn is large, the diffusion amount of the electrode material such as Cu to the solder side is large compared to the Sn-Pb eutectic solder. Has become apparent. Further, recently, with respect to Ni of the barrier layer, electroless plating has been often used mainly for cost reduction. Since Ni formed by electroless plating is more likely to diffuse than Ni formed by conventional electrolytic plating, it is necessary to suppress diffusion during solder melting.

Further, the Sn-Bi alloy solder having a melting point lower than that of the Sn-Pb eutectic solder has a melting point of 13 when adding 58% by weight of Bi by adding Bi to Sn.
The temperature is lowered to 7 ° C, and it becomes possible to join at low soldering temperature. Therefore, by using it for mounting a component having a large heat capacity, which is simultaneously mounted, it becomes possible to mount a component having low heat resistance without causing thermal damage.

The characteristics of the solder containing Bi are that it is hard and does not easily undergo creep deformation and that the solder has a small allowable amount of absorbing stress. However, primary mounting for mounting electronic components such as semiconductor chips on a package substrate. Then, the technique of filling the underfill resin between the electronic component and the substrate is used, and the problem is reduced. However, such a solder material having a large amount of Bi has a low melting point,
Mount the package that has undergone the primary mounting onto the circuit board. 2
At the time of the next mounting, the joint portion on the primary mounting side is melted, so that there is a concern that the reliability may be deteriorated due to the diffusion of the electrode material, and it was actually difficult to use for the primary mounting. Further, when used in the secondary mounting, since the creep deformation is small, the reliability in the heat cycle test is higher than that of the conventional Sn-Pb. However, since the bonding interface strength decreases due to the problem of the diffusion of the electrode material, it is necessary to suppress the diffusion of the electrode material.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to an electrode material,
In particular, it is an object of the present invention to provide a bonding structure for an electronic circuit device, which has a high effect of suppressing diffusion of a Ni electrode material formed by an electroless plating method, can secure bonding reliability, and enables bonding at a low temperature.

[0007]

The inventor of the present invention is effective in forming a Zn-Ni barrier layer by adding Zn through various attempts to suppress liquid layer diffusion (corrosion) of an electroless Ni electrode. It was also found that the electrode diffusion suppressing effect is exhibited from the Zn addition amount of about 1 wt%. But,
It was also found that when 1 wt% or more was added, a Zn-Ni layer was formed at the interface, but the layer was non-uniform and excessive Zn that did not react at the interface was deposited in the solder in the form of needles. . Therefore, paying attention to the fact that Zn has a high reactivity with Cu, when adding Zn to Sn-Bi solder, Ni is added.
By simultaneously adding Cu capable of forming a SnCuNi compound to the electrode interface to the solder material, Z
Since n exists in the form of a compound with Cu, stable ZnNiCu (S
The present invention was completed by finding out that the n) layer was formed.

That is, in the junction structure of the electronic circuit device provided by the present invention, the connection electrode on the circuit board and the connection terminal electrode on the electronic component mounted on this board are electrically connected by Sn-based solder. In the joint structure of an electronic circuit device, the solder composition forming the joint is B in addition to Sn.
i is 30 to 60 wt%, Cu is 0.5 to 2 wt%, and Zn is 0.1 to 2 wt%. The solder composition of the joint portion may further contain Ag in an amount of 0.5 to 3 wt%.

According to the present invention, there is provided an electronic component which can be used for forming the above-mentioned joint structure, and is an Sn-based solder formed from, for example, a solder ball on a connection terminal electrode for connection to a circuit board or the like. Of the connection terminal electrode, at least the surface layer of which is made of Ni, and the Sn-based solder contains B in addition to Sn.
An electronic component is also provided, which is a solder containing i of 30 to 60 wt%, Cu of 0.5 to 2 wt%, and Zn of 0.1 to 2 wt%.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The joining structure of an electronic circuit device according to the present invention is one in which the connecting terminal electrodes of an electronic component and the connecting electrodes of a circuit board are electrically connected via a solder material. Typical examples of electronic components include semiconductor chips as well as package types known as BGA (ball grid array) or CSP (chip scale package). A typical example of the circuit board is a printed wiring board.

At least one of the connection terminal electrode of the electronic component and the connection electrode of the circuit board may be an electrode entirely made of a Ni material, or the surface layer may be made of Ni and below the surface layer, for example, Cu or the like may be used. It may be a multi-layered electrode having a lower layer formed, and it is common to form an Au layer on the Ni electrode for improving soldering. In the following description, these may be collectively referred to as Ni electrodes.
The present invention, when the Ni electrode or the surface layer of Ni is less dense than that formed by the electrolytic plating method, and therefore is more likely to diffuse during solder melting, is formed by the electroless plating method, Especially effective.

The joint between the connection terminal electrode of the electronic component and the connection electrode of the circuit board in the joint structure of the present invention is formed of a solder containing Sn, and the solder composition of this joint is Sn in addition to Sn. Bi of 30 to 60 wt%, Cu
Of 0.5 to 2 wt% and Zn of 0.1 to 2 wt%. When Bi is less than 30 wt%, the liquidus temperature of the solder becomes high and the melting point rises, which is not preferable. B
If the i concentration exceeds 60 wt%, the solder becomes hard and the reliability after joining deteriorates. If Cu is less than 0.5 wt%, the effect of suppressing the diffusion of Ni by the addition of Cu cannot be secured, and if it exceeds 2 wt%, the melting point of the solder increases, which is not preferable. Even when Zn is 0.1 wt%, the effect of suppressing the diffusion of Ni by the addition of Zn cannot be ensured, and the Zn content is 2%.
When the content exceeds wt%, the Zn component which is easily oxidized becomes a base causing a problem of oxidation of the solder surface, which is not preferable. In addition to these essential components, this solder composition may contain inevitable impurities derived from the manufacturing raw materials and manufacturing processes.

The solder composition of the joint may contain 0.5 to 3 wt% of Ag in addition to the above essential components. The solder with an appropriate amount of Ag has improved ductility, and Ag is
By acting as a Zn trap that reacts with excess Zn, it is possible to prevent Zn from moving to the solder surface, which may cause oxidation. If the Ag addition amount is less than 0.5 wt%, the effect of the addition does not appear, and if it exceeds 3 wt%, the melting point of the solder rises, and a coarse Ag-Zn compound or Ag-Sn compound is formed to improve the solder characteristics. It is not preferable because it lowers.

As described above, the joint portion in the joint structure of the present invention is made of the solder material mainly composed of Sn and Bi, and is made of Z
n and Cu are added to suppress the diffusion of the Ni electrode, especially the Ni electrode formed by the electroless plating method. At the same time as the addition of Zn that reacts with the Ni material of the electrode to form a Zn-Ni barrier layer, an effective amount of Cu is added to form a stable diffusion suppressing barrier layer at the Ni electrode interface, thereby diffusing the electrode material. Can be reduced.

This joint can be formed by using the solder having the above composition. In this case, at the time of joining, that is, when melting the solder, CuZnNi is formed
A layer is formed. This layer is mainly formed by the reaction between the Zn and Cu components in the solder and the Ni of the electrode, but some Sn components in the solder may be found. Therefore, in this specification, the diffusion suppressing layer (barrier layer) at the interface between the solder and the electrode after joining is defined as CuZnNi.
It may be referred to as a (Sn) layer.

The joint portion in the connection structure of the present invention is Z
A small amount of Sn-Bi solder material containing n and Cu is previously supplied to the surface of the electrode by, for example, a printing method, and then a thin CuZnNi (Sn) layer is formed on the electrode by heating, and then on this electrode. It can also be formed by using the formed Sn—Bi solder balls (the composition of which may be the same as or different from that used to form the CuZnNi (Sn) layer). is there. In this case, the Zn concentration in the solder can be suppressed to a lower value while the diffusion suppressing effect of the CuZnNi (Sn) layer is ensured, thereby ensuring the wettability at the time of joining.

[0017]

EXAMPLES Next, the present invention will be further described with reference to examples, but the present invention is not limited to these examples.

(Example 1) Glass epoxy substrate (FR-
4 equivalent) diameter 0.7 formed by electroless Ni plating method
mm-electrode, Sn-57Bi- with a diameter of 0.76 mm
1Zn-0.5Cu solder balls were mounted and the substrate was held on a 200 ° C. hot plate for 15 minutes.
After cooling the substrate to room temperature, the junction between the electrode and the solder ball was examined with a scanning electron microscope (SEM) and electron probe microanalyzer (EPMA), and a good junction with almost no diffusion of electroless Ni in the electrode was obtained. It was confirmed that was obtained.

0.8 mm pitch BGA with 0.45 mm diameter solder balls having the above composition was mounted on an FR-4 glass epoxy substrate, and a temperature cycle test from -25 ° C to 125 ° C was conducted up to 1000 cycles. However, no joint failure occurred.

Example 2 A Sn-57Bi-1Zn- having a diameter of 0.76 mm was formed on an electrode having a diameter of 0.7 mm formed on a FR-4 glass epoxy substrate by an electroless Ni plating method.
A 0.5Cu-1Ag solder ball was mounted and the substrate was held on a hot plate at 200 ° C. for 15 minutes. After the substrate was cooled to room temperature, it was examined by SEM and EPMA, and it was confirmed that a good bonded portion with almost no diffusion of electroless Ni of the electrode was obtained.

A 0.8 mm pitch BGA with a solder ball of 0.45 mm diameter having the above composition was mounted on an FR-4 glass epoxy substrate, and a temperature cycle test from -25 ° C to 125 ° C was conducted up to 1000 cycles. However, no joint failure occurred.

Example 3 An Sn-50Bi-1Zn-having a diameter of 0.76 mm was formed on an electrode having a diameter of 0.7 mm formed on a FR-4 glass epoxy substrate by electroless Ni plating.
200 with 0.7Cu-0.5Ag solder balls
The substrate was held on a hot plate at ℃ for 15 minutes. After the substrate was cooled to room temperature, it was examined by SEM and EPMA, and it was confirmed that a good bonded portion with almost no diffusion of electroless Ni of the electrode was obtained.

A BGA having a diameter of 0.45 mm and a solder ball having the above composition and having a pitch of 0.8 mm was mounted on an FR-4 substrate, and a temperature cycle test from −25 ° C. to 125 ° C. was conducted up to 1000 cycles. No joint failure occurred.

(Embodiment 4) An electrode having a diameter of 0.7 mm formed on a FR-4 glass epoxy substrate by an electroless Ni plating method and Sn-50Bi-1Zn- having a diameter of 0.76 mm were used.
200 with 0.5Cu-0.5Ag solder balls
The substrate was held on a hot plate at ℃ for 15 minutes. After the substrate was cooled to room temperature, it was examined by SEM and EPMA, and it was confirmed that a good bonded portion with almost no diffusion of electroless Ni of the electrode was obtained.

A BGA having a diameter of 0.45 mm and a solder ball of the above composition and having a pitch of 0.8 mm was mounted on an FR-4 substrate, and a temperature cycle test from -25 ° C. to 125 ° C. was conducted up to 1000 cycles. No joint failure occurred.

As summarized in Table 1, Examples 1 to 4
The result of the temperature cycle test in
The result was the same as the temperature cycle test result of 37Pb eutectic solder.

[0027]

[Table 1]

Example 5 With respect to various solders having the compositions shown in Table 2, the reliability of the joint was evaluated by measuring the electrode reduced film thickness due to the liquid phase diffusion of electroless Ni of the electrode material.

[0029]

[Table 2]

Therefore, a diameter of 0.7 mm formed by an electroless Ni plating method similar to those manufactured in Examples 1 to 4
For the FR-4 glass epoxy substrate in which solder balls having a diameter of 0.76 mm were mounted on the electrode of No. 3, the relationship between the holding time on a hot plate at 250 ° C. and the Ni-decreased film thickness of the electrode was investigated. The result is shown in FIG.

As is apparent from the graph of FIG. 1, the SBACZ solder having the same composition as in Example 2 has the smallest reduction in film thickness. For example, when the holding time is 10 minutes, the conventional Sn-37Pb solder is used. Compared with the case of using (eutectic solder), the decrease in the Ni electrode film thickness was suppressed by about 30%, and it was shown that the reliability of the joint was improved accordingly.

The present invention is as described above,
The features will be described below together with various aspects. (Supplementary Note 1) A joint structure of an electronic circuit device in which a connection electrode on a circuit board and a connection terminal electrode of an electronic component mounted on this board are electrically connected by Sn-based solder, and a joint portion is formed. In addition to Sn, the solder composition contains Bi of 3
0-60wt%, Cu 0.5-2wt%, and Zn
0.1% to 2% by weight of the junction structure of the electronic circuit device. (1) (Appendix 2) The joint structure of the electronic circuit device according to Appendix 1, wherein the solder composition further contains Ag in an amount of 0.5 to 3 wt%. (2) (Supplementary note 3) Supplementary note 1 or 2 wherein at least one of the connection terminal electrode of the electronic component and the connection electrode of the circuit board is an electrode having at least its surface layer formed of Ni.
A junction structure for the electronic circuit device described. (Supplementary Note 4) The joining structure of the electronic circuit device according to Supplementary Note 3, wherein Ni in the surface layer is formed by an electroless plating method. (Supplementary note 5) The joint structure of the electronic circuit device according to supplementary note 3 or 4, wherein the joint portion is formed by using the solder having the composition. (Supplementary note 6) The joint structure of the electronic circuit device according to supplementary note 3 or 4, wherein the joint portion is formed by using a solder having the above composition on a CuNiZn layer formed in advance on Ni of the surface layer of the electrode. . (Supplementary note 7) The junction structure of the electronic circuit device according to any one of supplementary notes 1 to 6, wherein the electronic component is a semiconductor chip, a BGA (ball grid array) or a CSP (chip scale package). (Supplementary note 8) An electronic component, comprising an Sn-based solder protrusion formed on a connection terminal electrode for connection to a circuit board or the like, wherein at least the surface layer of the connection terminal electrode is formed of Ni, and the Sn is In addition to Sn, Bi-based solder
Is a solder containing 30 to 60 wt% of Cu, 0.5 to 2 wt% of Cu, and 0.1 to 2 wt% of Zn. (3) (Supplementary note 9) The electronic component according to supplementary note 8, wherein the solder further contains 0.5 to 3 wt% of Ag. (4) (Supplementary Note 10) Ni of the surface layer is formed by an electroless plating method, and the protrusion of the Sn-based solder is N of the surface layer.
10. The electronic component according to appendix 8 or 9, which is formed from a solder having the above composition on a CuNiZn layer previously formed on i. (Supplementary note 11) The electronic component according to any one of supplementary notes 8 to 10, wherein the electronic component is a semiconductor chip, a BGA (ball grid array) or a CSP (chip scale package). (5)

[0033]

As described above, according to the present invention,
Corrosion of electroless Ni, which is a concern in Sn-based solder, can be made equal to or less than that in the case of using a conventional Sn-Pb eutectic solder, and the joint reliability can be equally ensured. In this way, it is possible to use electroless Ni, which is advantageous in terms of cost, and it is also possible to perform low temperature bonding by suppressing the corrosion, which is also a disadvantage of the Sn-Bi alloy having a low melting point.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the substrate holding time on a hot plate and the Ni-decreased film thickness of electrodes investigated for various solder materials.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H01L 23/12 501 H01L 21/92 603B

Claims (5)

[Claims] 1. A joint structure of an electronic circuit device, wherein a connection electrode on a circuit board and a connection terminal electrode of an electronic component mounted on this board are electrically connected by Sn-based solder, and a joint portion is formed. In addition to Sn, the solder composition
A junction structure of an electronic circuit device, characterized in that i is contained in an amount of 30 to 60 wt%, Cu is included in an amount of 0.5 to 2 wt%, and Zn is included in an amount of 0.1 to 2 wt%. 2. The solder composition contains Ag of 0.5 to 3 wt.
%, The junction structure for an electronic circuit device according to claim 1, further comprising: 3. An electronic component comprising a Sn-based solder protrusion formed on a connection terminal electrode for connection to a circuit board, wherein at least the surface layer of the connection terminal electrode is formed of Ni, and the Sn is formed. In addition to Sn, Bi-based solder
Is a solder containing 30 to 60 wt% of Cu, 0.5 to 2 wt% of Cu, and 0.1 to 2 wt% of Zn. 4. The electronic component according to claim 3, wherein the solder further contains Ag in an amount of 0.5 to 3 wt%. 5. The electronic component is a semiconductor chip, a ball grid array, or a chip scale package,
The electronic component according to claim 3 or 4.