JPH08174266A - Composite solder material and its production - Google Patents

Abstract

PURPOSE: To improve the flatness of the height of a solder melt by incorporating a granular material at a specific ratio into the base material for the solder material contg. specific ratios of Sn, Ag, Pb, Ni and Cu. CONSTITUTION: The base material for the solder material contains, by weight %, 0.5 to 10 Sn, 1 to 3 Ag and 0.1 tot 1 Ni or Cu and the balance substantially Pb and the granular material is incorporated at 0.01 to 5wt.% into this material. The granular material is preferably a material having the higher m.p. than the m.p. of the base mateiral for the solder material. If the rate of incorporation is below 0.01%, and effect of improving the horizontal degree of the height of a solder melt is insufficient. Voids are formed and joint strength decreases if the rate exceeds 5%. The voids are less formed if the Ni or Cu is incorporated into the base material. The effect is insufficient if the content of the Sn is below 0.5%. The joint strength degrades if the content exceeds 10%. The effect is insufficient if the content of the Ag is below 1% and the spreadability of the molten solder is no longer stable if the content exceeds 3%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connecting material for a semiconductor chip such as a power transistor, and more particularly to a tape-like or wire-like long composite solder material used for connecting a semiconductor chip to a substrate and a method for producing the same. .

[0002]

2. Description of the Related Art Conventionally, as a connecting material used for connecting a semiconductor chip to a substrate, a pellet is prepared from a tape-shaped or wire-shaped solder material, and an appropriate amount is sandwiched between the semiconductor chip and the substrate. It is known to use by heating and melting. However, in the case of this connecting material, since the solder melt 2 on the substrate 1 flows in an arc shape as shown in FIG. 2, it is difficult to connect the semiconductor chip horizontally on the substrate 1.

Horizontally connecting the semiconductor chip on the substrate is useful in that a predetermined heat-resistant cycle is maintained at the connecting portion and peeling of the semiconductor chip and conduction failure due to temperature change are prevented. Therefore, as a connecting material, by using a pellet made from a long composite solder material in which a granular material having a higher melting point than solder is mixed in a scattered manner in a solder base material manufactured in a tape shape or a wire shape, As shown in 1, hold the thickness (height) of the solder melt 2 substantially horizontally,
It is known that a semiconductor chip set on the solder melt 2 is connected to the substrate 1 substantially horizontally. Further, the applicant of the present invention has invented a method useful for mixing a granular material in the above-mentioned tape-shaped or wire-shaped solder base material, and previously disclosed in Japanese Patent Application No.
11685, Japanese Patent Application No. 6-96571, Japanese Patent Application No. 6-9
Filed as No. 6572.

On the other hand, in recent years, semiconductor devices have been operated at ever higher speeds, and heat cycle conditions for heat generation and cooling have become more severe. For this reason, it is required to prevent the semiconductor chip from peeling off and poor conduction even when the temperature changes more severely.
In response to the demand, when connecting a semiconductor chip to a substrate through a solder material, when heating and melting an appropriate amount of a solder material having a predetermined shape on the substrate, the levelness of the solder melt is set to the conventional level. It has been found that further increase is effective in preventing peeling of the semiconductor chip and conduction failure under more severe temperature change, and a solder material capable of meeting this requirement is required.

In order to meet such demands, a base material as a conventionally known long composite solder material (long composite solder material in which granular materials having a melting point higher than that of solder are mixed in a scattered manner) 48 wt% Sn-2 wt% Ag in the solder material
-If residual Pb alloy is used, the levelness of the height of the solder melt is still insufficient, and it is necessary to further improve the levelness of the height of the solder melt. Further, when 5 wt% In-5 wt% Ag-residual Pb alloy is used for the solder material as the base material, the levelness of the height of the solder melt is improved, but the flow of the molten solder is hindered by the particulate matter. There is a drawback that voids occur and the bonding strength becomes weak. As described above, a long composite solder material as a raw material for pellets, in which the levelness of the height of the solder melt is improved and voids are not generated, has not yet been known.

[0006]

In view of the above-mentioned conventional circumstances, in the present invention, when connecting a semiconductor chip to a substrate through a solder material, a long composite solder material containing a granular material as a solder material is used. By using and heating an appropriate amount of the specified shape on the board to melt it, the levelness of the height of the solder melt is further improved compared to the conventional method, and the specified bonding strength without causing voids. It is an object of the present invention to provide a long composite solder material as a raw material for pellets and a method for manufacturing the same, which can maintain the above.

[0007]

In order to achieve the above object, the long composite solder material of the first invention of the present application is 0.5-10.
A solder material comprising Pb with a balance of Sn, 1 to 3 wt% Ag and the balance excluding unavoidable impurities is used as a base material, and 0.01 to 5 wt% of granular material is mixed therein. To do. The second invention of the present application is characterized in that, in the long composite solder material of the first invention, the solder material base material contains 0.1 to 1% by weight of Ni or Cu.

The method for producing a long composite solder material according to the third aspect of the present invention is 0.5 to 10 wt% Sn, 1 to 3 wt% Ag.
It is characterized in that the solder material base material containing Pb and containing Pb as the balance except for unavoidable impurities is mixed with 0.01 to 5% by weight of a granular material and then subjected to plastic working. The fourth invention of the present application is characterized in that, in the method for producing a long composite solder material of the third invention, the solder material base material contains 0.1 to 1% by weight of Ni or Cu.

[0009]

The present invention will be described in more detail below. First, the solder material as the base material will be described. In the present invention, Pb is 0.5 to 10% by weight as the solder material base material.
It is necessary to contain Sn, 1-3 wt% Ag. It is preferable to further contain 0.1 to 1% by weight of Ni or Cu. Using such a solder material as a base material, a long composite solder material in which 0.01 to 5% by weight of a granular material is mixed inside the base material is prepared, and an appropriate amount of the predetermined shape is heated on a substrate. By the melting, the levelness of the height of the solder melt is further improved as compared with the prior art, and a predetermined bonding strength can be maintained without generating voids.

When the Sn content is less than 0.5% by weight, the effect of improving the variation in the height of the solder melt when the composite solder material having the granules mixed therein is melted is unsatisfactory for this requirement. It is sufficient and the bonding strength is reduced. When the Sn content exceeds 10% by weight, the effect of improving the variation in the height of the solder melt when the composite solder material having the particulate matter mixed therein is melted is insufficient for this requirement, and Bonding strength decreases. Therefore, the Sn content is set to 0.5 to 10% by weight.

When the Ag content is less than 1% by weight, the effect of improving the levelness of the height of the solder melt when the composite solder material having the granular material mixed therein is melted is against this requirement. Not enough. When the Ag content exceeds 3% by weight, the spreadability when the composite solder material with the particulate matter mixed therein is melted is not stable, and the effect of improving the levelness of the height of the solder melt is essential. In addition to being insufficient to meet the requirements, voids are generated and the bonding strength is reduced. It is considered that the reason why the voids are generated is that the spreadability when the composite solder material in which the particulate matter is mixed is melted is deteriorated, and the void is generated in the joint portion by being inhibited by the particulate matter. . Therefore, the Ag content is set to 1 to 3% by weight.

When the solder material base material contains 0.1 to 1% by weight of Ni or Cu, the generation of voids is further reduced.

Next, the granular material mixed in the solder material base material will be described. As the granular material, a material having a higher melting point than the solder material base material is preferable. For example, Cu, W, Mo,
Metals such as Ni, Al ₂ O ₃ , oxides such as glass, Ti
Nitride such as N or AlN is preferably used. The shape of the granular material may be spherical, square or amorphous. Further, the preferred dimension is such that the maximum diagonal dimension is in the range of 20 to 70 μm, and it is properly used depending on the application. A preferable mixing ratio of the granular material in the composite solder material is 0.01 to 5% by weight. If the mixing ratio is less than 0.01% by weight, the improvement effect of improving the levelness of the height of the solder melt when the composite solder material having the granules mixed therein is melted does not meet the present requirement. Is enough. On the other hand, if the mixing ratio exceeds 5% by weight, voids occur and the bonding strength becomes weak.

Thus, by making the composition of the base material of the solder material and the mixing ratio of the granular material as described above, when the composite solder material having the granular material mixed therein is melted, a cavity is formed. The flow of the solder material can be controlled without causing the expansion and the spread can be regulated by the presence of the granular material, the levelness of the height of the solder melt can be further improved as compared with the conventional one, and the void is caused because the void is not generated. It is considered to have an excellent effect that it is possible to prevent a decrease in bonding strength.

The method of manufacturing the long composite solder material according to the present invention will be described in detail below. In the manufacturing method of the present invention, the solder material base material containing 0.5 to 10% by weight of Sn and 1 to 3% by weight of Ag and the balance excluding unavoidable impurities is made of Pb, and 0.01 to 5% by weight of granular material is used. It is necessary to perform plastic working after mixing the substances. Preferably, the solder material base material contains 0.1 to 1% by weight of Ni or Cu. The long composite solder material here means a tape-shaped or wire-shaped composite solder material in which a solder material is used as a base material and granular materials are mechanically mixed therein. Further, the plastic working herein means cold working by two rolling rolls in the case of tape-shaped solder material, and cold working after extrusion processing in the case of wire-shaped solder material. That is, in the production of the tape-shaped composite solder material, as disclosed in Japanese Patent Application No. 5-11685 filed by the applicant of the present invention, two solders are placed between two rolling rolls on the left and right arranged side by side in the horizontal direction. The tape is inserted from above, the part before the joining of the two tapes is expanded to a predetermined angle, the granular material is supplied to the expanded part, and the solder material main body is subjected to cold working (rolling) by winding the rolling roll. A production method in which the above-mentioned granular material is mixed is preferably adopted. Further, in the production of the wire-shaped composite solder material, the methods disclosed in Japanese Patent Application Nos. 6-96571 and 6-96572 filed by the present applicant are preferably adopted. Among them, the solder billet It is preferable to employ a manufacturing method in which the composite solder billet in which the hollow portion provided in the axial direction is filled with the granular material is extruded and then cold working (wire drawing) is performed.

As described above, Sn, Ag, Ni, C are added to Pb.
It is possible to evenly disperse the particles in the obtained long composite solder material by mixing the particles in a predetermined ratio with a solder material base material containing a predetermined amount of u and then performing plastic working. Therefore, the effect of the long composite solder material according to the present invention can be more reliably ensured, and it can be suitably used as a method capable of efficiently reducing the disconnection trouble during the production and efficiently producing the material.

[0017]

EXAMPLES Each example and comparative example shown in Table 1 will be described below. (Example 1) 2 mm thickness containing 0.5% by weight of Sb and 2% by weight of Ag, and the balance being Pb except for unavoidable impurities x
0.4mm by weight of Ni granular powder having a diameter of 30 to 50μm is sandwiched between two 50mm-wide solder tapes, and is inserted between the two rolling rolls as described above to be cold-worked to have a thickness of 0.3mm. A tape-shaped composite solder material having a width of 50 mm was prepared. Using the tape thus obtained as a raw material, press punching is performed, and 0.3 mm thickness x 1.8 mm width x 2.5 mm
Long pellets were obtained. The obtained pellets were placed on an oxygen-free copper plate as a substrate and heated in an oxygen-free atmosphere furnace. For heating, the atmosphere in the furnace was adjusted to 50% N _{2 and} 50% H ₂ , and then the pellets were melted under heating conditions of 350 ° C. × 8 minutes.

Samples were prepared from 10 samples and the height of the solder melt and the occurrence of voids were observed from a scanning electron micrograph magnified 5000 times. As for the height of the solder melt, as shown in the drawing, the height h ₁ at the center position of the pellet before melting and the height h ₂ at a position 1.5 times the length of the pellet before melting were measured. An average of 10 pieces was obtained with (h ₂ / h ₁ ) × 100% as the horizontality. Table 2 shows the results. The presence of voids is observed by scanning electron microscopy when the presence of voids is less than 1% in the cross-sectional area. ◎ When 1% or more and less than 5% ○ When 5% or more and less than 10% △, 10% or more When evaluated as x. Table 2 shows the results. The shear load of the solder melt melted on the substrate was measured using a shear tester, and the average value of 10 pieces was taken as the bonding strength.
Table 2 shows the results.

(Examples 2 to 13 / Comparative Examples 1 to 8) Samples were prepared in the same manner as in Example 1 except that the composition of the solder tape and the mixing ratio of the particulates were as shown in Table 1, and the levelness was measured. , The occurrence of voids and the bonding strength were measured. Table 2 shows the results.

[0020]

[Table 1]

[0021]

[Table 2]

From the measurement results shown in Table 2, Pb contains a predetermined amount of S.
The inventive products (Examples 1 to 5) in which the granular material is mixed in the solder material base material containing n and Ag at a predetermined ratio are heated and melted in an appropriate amount on the substrate, The levelness of the height of the solder melt is 100%, the voids are 1% or more and less than 5% in the cross-sectional area, and the bonding strength is 5.0 to 5.5 g / μm ² . I know there is.

Further, Pb contains a predetermined amount of Sn, Ag, Ni,
The embodiment products of the present invention (Examples 6 to 13) in which the granular material is mixed in the Cu-containing solder material base material at a predetermined ratio are heated and melted in an appropriate amount on the substrate,
The level of the solder melt is 100%, the voids are less than 1% in the cross-sectional area, and the bonding strength is 5.3 to 6.0 g / μm ² , which is even better. I understand.

On the other hand, the composition of the solder base material is 48% by weight.
In the case of Sn-2 wt% Ag-remaining Pb, Comparative Example 1 in which no particulate matter is mixed has a horizontality of about 40%, and it is difficult to connect the semiconductor chip horizontally on the substrate. Further, in Comparative Example 2 in which the particulate matter is mixed within the range of the present invention, the levelness is 80%, which is improved as compared with Comparative Example 1, but the improvement effect required by the present invention (horizontality 100%). However, it is found that the joint strength is inferior and the number of voids is large and the joint strength is poor.

Even if the composition of the solder base material and the content thereof are within the scope of the present invention, in Comparative Example 3 in which no granular material is mixed, the horizontal degree is about 40%, and the semiconductor chip is connected horizontally on the substrate. Is difficult. Further, in Comparative Examples 4 and 5 in which the Sn content is outside the range of the present invention, even if the mixing ratio of the particulate matter is within the range of the present invention, the horizontal degree is 90%, and Comparative Examples 1 to 3
Although it is improved compared to the above, it is not sufficient for the improvement effect (horizontality 100%) required by the present invention, and it is understood that the occurrence of voids is 5 to 10% and the bonding strength is poor.

Further, in Comparative Examples 6 and 7 in which the content of Ag is outside the range of the present invention, even if the mixing ratio of the particulates is within the range of the present invention, the levelness is 80%, which is required by the present invention. It is found that the bonding strength is not sufficient for the improvement effect (horizontality 100%), and that the void strength is 5 to 10%, or 10% or more, the bonding strength is poor. In addition, the composition of the solder base material is 5 wt% In-
In Comparative Example 8 in which 5 wt% Ag-remaining Pb is used, the effect of improving the levelness is satisfied, but it is found that the occurrence of voids is 10% or more and the joint strength is poor. Furthermore, even if the composition of the solder base material is the same as that of the present invention, in Comparative Example 9 in which the particulate matter is mixed beyond the range of the present invention, the effect of improving the horizontality required by the present invention (horizontality It is found that the bonding strength is not sufficient for 100%), and the occurrence of voids is 5 to 10%, resulting in poor bonding strength.

[0027]

As described above, in the long composite solder material of the present invention, Pb contains 0.5 to 10% by weight of Sn and 1 to 3% by weight of Ag in a solder base material with a granular material of 0. Since the composition is mixed with 01 to 5% by weight, when the appropriate amount is placed on the substrate and heated and melted, the levelness of the height of the solder melt is further improved as compared with the conventional one, and the semiconductor chip is It is possible to make horizontal connection on the substrate with extremely high accuracy, and it is possible to maintain a predetermined bonding strength without causing voids. Therefore, it is suitable for use in assembling semiconductor devices that have been operating at ever higher speeds in recent years and the conditions of heat cycles for heat generation and cooling have become more severe, and even if the temperature changes more severely, a predetermined heat-resistant cycle can be maintained at the connection part. Therefore, peeling of the semiconductor chip and conduction failure do not occur, so that it can contribute to the improvement of the reliability of the semiconductor device, which is a great effect.

Further, when the solder base material further contains 0.1 to 1% by weight of Ni or Cu, there is an effect that the generation of voids can be further reduced and the joint strength can be expected to be improved.

Further, according to the manufacturing method of the present invention, S is added to Pb.
Granules are evenly dispersed in the obtained long composite solder material by mixing the granules in a predetermined ratio in a solder material base material containing a predetermined amount of n, Ag, Ni, Cu and then subjecting to plastic working. Can be included. Therefore, the long composite solder material of the present invention, which has many advantages as described above, can be reliably manufactured, the effect thereof can be made more effective, and further, the disconnection trouble during the manufacturing can be greatly reduced and the method can be efficiently manufactured. Can be suitably used as.

[Brief description of drawings]

FIG. 1 is a simplified diagram showing a molten state of a composite solder material according to the present invention on a substrate.

FIG. 2 is a simplified diagram showing a molten state of a conventional solder material on a substrate.

[Explanation of symbols]

 1: Substrate 2: Solder melt

Claims (4)

[Claims] 1. 0.5-10 wt% Sn, 1-3 wt%
A long composite solder for connecting a semiconductor chip, characterized in that a solder material made of Pb containing Ag and the remainder excluding inevitable impurities is used as a base material, and 0.01 to 5% by weight of a granular material is mixed therein. material. 2. The long composite solder material for connecting a semiconductor chip according to claim 1, wherein the solder material base material contains 0.1 to 1% by weight of Ni or Cu. 3. 0.5-10 wt% Sn, 1-3 wt%
For connecting semiconductor chips, characterized in that 0.01 to 5% by weight of a granular material is mixed into a solder material base material made of Pb containing Ag and the balance excluding unavoidable impurities, and then subjected to plastic working. Manufacturing method of long composite solder material. 4. The method for producing a long composite solder material for connecting a semiconductor chip according to claim 3, wherein the solder material base material contains 0.1 to 1% by weight of Ni or Cu.