JP3385549B2 - Composite tungsten ball, probe device and semiconductor package using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a semiconductor element mounted thereon, and a probe device capable of determining a connection state of individual semiconductor elements mounted on a circuit board, and a high density FC (flip chip). The present invention relates to an FC-BGA (ball grid array) having a connecting ball that requires conductivity from a chip to an outer peripheral material in a package, and a ball used for the FC-BGA.

[0002]

2. Description of the Related Art With the progress of higher density and higher integration of a semiconductor device having a semiconductor element mounted thereon, a large-scale and high-speed mounting technology has been particularly advanced.

QFP which is said to be excellent in practical use
(Quad flat package) is usually 25
0 pin, external operating frequency is 50MHz, BGA
If so, it is said that it can cover the area of 370 pins and 155 MHz.

Furthermore, by taking advantage of a ball used as a contact of a chip, it is possible to realize a higher density mounting and at the same time, cost reduction is being promoted.
P (chip size package) -FC-BG for BGA
A is highly expected in terms of high density and reliability.

[0005]

On the other hand, the balls positioned directly under the flip chip are conductive balls having a small diameter and high precision, for example, φ100 μm for high density and high mounting.
In the following, the diameter variation is better within ± 10%, but in order to form a stable connection state, the force to press the ball toward the ball, that is, the pressing force, is applied to the chip and the insulating board located on the opposite side to sandwich the ball. Since it is set over, there are problems such as deformation with soft materials, cracks with some materials, and loss of accuracy during repair.

It is conceivable to use a tungsten sphere for the sphere used in such a BGA.

However, as one of the methods for manufacturing the tungsten sphere, there is a method of cutting a wire / bar and then rolling it with a barrel or the like. However, since the crystalline fiber structure is basically developed, it has a difference in heat conduction. Not only is it anisotropic, but when a force is applied in a certain direction, cracks parallel to the fiber direction tend to occur, which is inconvenient for the above applications.

[0008] In addition, even if a plasma treatment is performed after performing a granulation of a tungsten powder to a desired diameter of a tungsten sphere by a general granulation method, it becomes a sphere, but pores remain in the sphere. This cannot be avoided and causes swelling during plating and variations in electrical conduction, which is also inconvenient.

Furthermore, as another problem, in a package in which chips are mounted on a circuit board, a prober board (probe device) in which probe pins are set at desired positions to determine the electrical connection state of each chip There is.

The above-mentioned high-density and highly-packaged package is called CSP (chip size package) for the polarity, and is one of FC-BGA. In the multi-chip type module in which a plurality of CSPs are mounted, a so-called reliable probe device is necessary and so important in order to reliably determine the so-called connection state of each individual chip.

At this time, since the probe pin usually has a sharp tip, when it comes into contact with the tip or other peripheral material of the tip, it is not only scratched, but also is greatly damaged, and when the connection state is judged tens of thousands of times or more. However, it is difficult to maintain the size and shape of the tip of the needle, which in turn impairs the reliability of the determination accuracy, and this solution has been desired.

[0012] Therefore, a first technical object of the present invention is to provide a reliable composite tungsten sphere capable of high-density and high-density mounting of chips and the like on a substrate without cracking or crushing. It is in.

A second technical object of the present invention is to provide a probe device having a check needle having the composite tungsten sphere at the tip thereof.

Further, a third technical object of the present invention is to provide a semiconductor package using the composite tungsten sphere as an electrical contact.

[0015]

According to the present invention, there is provided a composite tungsten sphere comprising a metal sphere containing at least 95% by weight of elemental tungsten and a conductive coating layer formed on the surface of the metal sphere. , The metal spheres during liquid phase sintering
Coarse Tungsten Powder Produced in Plasma is Passed Through Plasma
Is formed by having a free dense structure of pores,
The composite tungsten sphere has a diameter of 0.05 to 0.2 m.
A composite tungsten sphere is obtained which is characterized in that the diameter variation at m is within ± 10% of the diameter.

Further, according to the present invention, there is provided a probe device used for inspecting electrical characteristics of a circuit board of a semiconductor package, the probe device having a check needle having the composite tungsten sphere at a tip thereof. Is obtained.

Further, according to the present invention, there is obtained a semiconductor package characterized by having the composite tungsten sphere as a ball used for electrical contact of a semiconductor package having a semiconductor chip mounted thereon.

That is, by using the composite tungsten sphere of the present invention, a highly reliable and long-life probe device for checking the electrical characteristics of the package can be obtained. Furthermore, in the BGA, a ball which is particularly FC does not deform, and a semiconductor package having an accurate conductive ball can be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an electron micrograph showing a metal structure of a tungsten sphere used in a composite tungsten sphere according to an embodiment of the present invention. Referring to FIG. 1, a tungsten sphere has no pores in its internal structure and has no directivity in its grain structure, and has a spherical diameter required for a semiconductor package and a probe device for inspecting the characteristics of a semiconductor package. I have it.

The composite tungsten sphere according to the embodiment of the present invention has Au, C on the surface of the tungsten sphere shown in FIG.
A coating layer composed of one layer or two or more layers of u, Ni, Ag, etc. is formed.

Next, a method of manufacturing the composite tungsten sphere according to the embodiment of the present invention will be described.

0.05 to 0.2 required for the above applications
In order to obtain a sphere with a diameter of mm, a spheroidizing treatment is performed using coarse-grained raw powder having a size close to the same size. First, a mixed powder of nickel, iron, copper, cobalt, manganese, and other binding metal powders is mixed with tungsten powder, which is the raw material, and this is liquid-phase sintered to form an alloy. Activates the diffusion of the tungsten particles with each other to coarsen the tungsten particles in the binder phase. At this time, since the particle size of the coarse powder can be controlled by the sintering conditions, the coarsening can be further promoted by sintering at high temperature for a long time. Further, since this coarse-grained powder is obtained by coarsening each powder itself, it becomes a single crystal or a structure close to it, and becomes sufficiently densified.

Next, in order to separate the coarsened tungsten powder, which is dispersed in the binder phase generated when the tungsten powder is coarsened, from the binder phase, a low melting point metal that forms a solid solution with the binder phase, such as Zinc, cadmium, tellurium, etc. are added and heated in a container pressurized with an inert gas to react the binder phase with the low melting point metal to form a melt. Due to this melting, the binder phase is separated from the coarse tungsten powder. After that, only the low-melting metal is evaporated by heating under reduced pressure, and the coarse and coarse tungsten powder that remains is separated from the binder phase alloy that remains as fine particles by sieving and classification to obtain the raw material coarse tungsten powder. To be

Obtained by controlling the sintering conditions,
Coarse tungsten powder having a proper particle size as the raw material coarse powder is processed as follows.

In a device in which an inert gas such as argon gas is used as a medium and a plasma flame is generated from above by a high-frequency coil, the above-mentioned coarse-grained tungsten powder is passed through a plasma by using a trace powder feeder to melt molten tungsten. It is made spherical by the surface tension of and is dropped to the lower part while being rapidly solidified. As a result, it is possible to obtain a tungsten sphere having a high sphericity and having a spherical diameter required for a semiconductor package or the like, which does not have a pore inside as shown in the electron micrograph of FIG.

Then, the spherical tungsten balls are precisely classified by tilt classification or the like to obtain 53 μm (280 me).
sh) to 63 μm (250 mesh) and 63 μm
It is possible to obtain balls having several kinds of diameters, such as (250 mesh) to 75 μm (200 mesh).

As described above, in one of the methods of manufacturing a sphere, a method of cutting from a wire / bar and forming it with a barrel or the like basically has a crystalline fibrous structure, which causes a difference in heat conduction. In addition to being anisotropic, when a force is applied in a certain direction, cracks parallel to the fiber direction easily occur, which is inconvenient. In addition, the one obtained by granulating and plasma-treating the tungsten powder by the general granulation method becomes a sphere, but it is unavoidable that pores remain, and thereafter it causes swelling during plating and variation in electric conduction. This is also inconvenient.

On the other hand, according to the method according to the embodiment of the present invention, since there is no pore, and since the powder is made to grow and spheroidize, anxiety of grain boundary destruction is alleviated. in addition,
95% by weight or more of the main component is tungsten, and the balance is unavoidable impurities other than Ni and Fe. Although Ni and Fe are made as W alloys for coarse-grained powder, the characteristics of the product used by sintering are obtained. Therefore, the thermal and electrical characteristics of tungsten can be substantially expected for the use of the composite tungsten sphere according to the embodiment of the present invention. Not less than 95% pure.

An example of impurities of the obtained bare tungsten sphere is shown in Table 1 below.

[0031]

[Table 1] As shown in Table 1 above, the pure content of the tungsten element was approximately 96 wt%. As for plating, N-type plating is performed by the same process wet plating as general tungsten materials.
i, Cu, Au, Ag, etc. are possible, and stable film formation of the latter two elements is 2 to 8 μm if Ni or Cu is applied to the base.
It is possible to a degree. Thereby, a composite tungsten sphere was obtained.

When a ball made of this composite tungsten sphere is plated with solder (PbSn) and incorporated into an FC-BGA, the outermost skin Au is used, and even when it is used as a probe, the outermost skin Au is used for its wettability and conductivity. The purpose can be achieved without degrading performance such as sex.

Of course, dry plating is also preferable in the case where it is desired to suppress the adhesion rate remarkably.

Most of the BGA solder balls currently used have a diameter of 0.6 to 0.9 mm, and even a small diameter product has a diameter of φ0.
It is 15 to 0.2 mm. For high density and high mounting, at least φ0.2 mm or less, preferably φ0.1 mm or less is required, but it also affects accuracy, but φ0.15 mm or less, particularly φ0.1 mm or less cannot be manufactured. Even with the special steel balls mentioned above, φ0.3 mm is the limit.

Therefore, the balls according to the embodiment of the present invention have a diameter of 0.2 mm or less, and it can be said that the balls can be manufactured according to the embodiment of the present invention.

If the diameter is less than 0.05 mm, classification is not achieved by the present invention alone, and the implementation is difficult, not to mention the level of peripheral technology.

Next, an example of use of the composite tungsten sphere according to the embodiment of the present invention will be specifically described with reference to the drawings.

(Example 1) FIG. 2 shows an example in which the probe pin having the composite tungsten sphere of FIG. 1 at its tip is used as a check needle.

Referring to FIG. 2, the probe device includes a probe pin 1 projecting in a recess of the prober board 10a.
And a probe pin 1 protruding from the prober board 10b. At the tip of this probe pin 1,
A composite tungsten sphere is provided.

The semiconductor chip 21 has a chip holder 22.
The chip holder 22 is connected and fixed to the package substrate 23 by face-down bonding. On the surface of the chip holder 22, a bonding pad 25 connected by a wire bonding 24 and a probing pad 26 connected to the bonding pad 25 are provided. Further, on the back surface of the chip holder 22, lands 27 connected to the probing pad by the internal conductor of the chip holder 22 are arranged in a matrix on the entire back surface. On the surface of the package substrate 23,
The land 28 is directly connected to the land 27, and is connected to the probing land 30 arranged on the back surface via the internal conductor 29.

The probe pins 1 of the probe device are respectively
The state of contacting the probing pad 26 and the land 30 is shown.

The probe pin 1 is obtained by bonding a composite tungsten sphere to the tip of the probe pin 1 so as not to scratch the tip and wiring which are in contact with the tip and wiring far more than a sharp tungsten needle and the like. Since the balls have extremely small diameter variations, a stable and reliable probe device could be obtained.

In addition, when the contact was repeated with the same pressure as in the case of the probe pin and the test was conducted, the wear was less than that of the pin (needle) shape (however, it is better than Kovar due to the fact that it is made of tungsten, etc.). Decisively good),
It was found that a reliable probe device for checking the electrical characteristics of a circuit board was obtained without any damage to the surrounding materials that was touched during operation.

Example 2 FIG. 3 is a sectional view showing an example in which the composite tungsten sphere of FIG. 1 is used as a ball in FC-BGA. Referring to FIG. 3, a plurality of insulating resin layers 58 made of polyimide are formed on a mullite ceramics substrate 60, and conductor patterns 68 made of Al formed on the front and back surfaces of these and penetrating the front and back surfaces thereof and these. A thin film layer 57 is formed by a thin film resistor 59 made of Cr—Si—O provided between them. The mullite ceramics substrate 60 is connected by a through hole 67 penetrating the front and back surfaces, and a conductor is formed on the inner wall of this through hole.

A conductor pattern 68 is formed on the upper surface of the thin film layer 57.
A via hole connected to is formed, and C is formed on the inner surface.
a first metal layer 63 made of an r / Ni-Cu alloy;
A second metal layer 62 made of Ni / Au formed on the metal layer is filled and formed.

The LSI chip 51 has a thin film layer 57 from the conductor pattern 51a provided on the lower surface through the metal balls 2.
Electrically connected to.

On the other hand, the conductor in the through hole on the upper surface of the ceramic substrate and the conductor 61 on the bottom surface of the thin film layer are in direct contact with each other. In addition, an input / output pad 65 made of Ni / Au plating connected to an internal conductor is formed in the through hole portion on the bottom surface of the ceramic substrate 60. The input / output pad has a bump 64 as shown by a broken line. It is connected to a wiring board (not shown) or other circuit components via the.

A cap made of AlN is provided so as to cover the thin film layer 57 and the chip mounted thereon, and is joined to the ceramic substrate 60 by the solder portion 56. In addition, the upper surface of the LSI chip is also
It is joined to the ceiling surface of the cap 66.

The composite tungsten sphere according to the embodiment of the present invention is used for the ball 2.

Here, the size of such a ball determines the distance between the chip package and the circuit board, and if the ball has appropriate performance, the smaller the ball diameter, the higher the density and the higher mounting possible. . Particularly, the balls in the joint portion are preferably 50 to 200 μm.

FIG. 4 is a sectional view showing another example in which the composite tungsten sphere according to the embodiment of the present invention is used as a ball in FC-BGA. Referring to FIG. 4, the back surface of the semiconductor chip and the respective lands (not shown) of ceramic substrate 54 are connected via joint balls 53.
Lands on the front surface of the ceramic substrate and pads 55 on the back surface
Are connected by an internal conductor or wire bonding (not shown). The pad 55 on the back surface is connected to a wiring board (not shown) via the composite tungsten sphere 2.
As the joint ball 53, the composite tungsten sphere according to the embodiment of the present invention can also be used.

As mentioned above, the composite tungsten sphere according to the embodiment of the present invention can withstand even if a force of 5 × 10 ⁻³ gf / μm ² or more is applied, though it is assembled by the pressing and sandwiching process.

After the Au plating, the solder (PbSn) plating is applied and assembled, and the FC ball having conductivity is obtained by utilizing the characteristics of tungsten and plating. The electrical resistivity at this time was approximately 5.5 × 10 ⁻⁶ Ωcm, which was desirable in terms of strength as an FC ball and the above performance.

It should be noted that between the two parallel plates, solder is used so that the setting condition of 50 (in this case solder is tungsten) shown in FIG. 2 is obtained by applying Au plating of 4 μm to a ball of about 100 μm shown in FIG. When the electric resistance was measured, it was about 0.01 mΩ. Generally this value is 2.
Although it is required to be 5 mΩ or less, it is a sufficiently preferable value in terms of electric resistance between connections when FC is connected by balls.

[0055]

As described above, according to the present invention, it is possible to provide a highly reliable composite tungsten sphere capable of high density and high packaging, and free from cracking or crushing.

Further, according to the present invention, it is possible to provide the probe device having the check needle having the composite tungsten ball having the above-mentioned advantages at the tip thereof.

Further, according to the present invention, it is possible to provide a semiconductor package using the composite tungsten sphere having the above-mentioned advantages for electrical contact.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing a metal structure of a composite tungsten sphere according to an embodiment of the present invention.

FIG. 2 is a front view showing an example in which the composite tungsten sphere of FIG. 1 is used as a check needle.

FIG. 3 is a cross-sectional view showing an example in which the composite tungsten sphere of FIG. 1 is used in a semiconductor package.

FIG. 4 is a cross-sectional view showing another example in which the composite tungsten sphere of FIG. 1 is used in a semiconductor package.

[Explanation of symbols]

1 probe pin 2 metal balls 10a prober board 10b prober board 21 semiconductor chips 22 Chip holder 23 Package substrate 24 wire bonding 25 Bonding pad 26 Probing Pad 27 lands 28 lands 29 Inner conductor 30 lands 51 LSI chip 51a Conductor pattern 53 Joint Ball 55 Pad 56 Solder part 57 Thin film layer 58 Insulating resin layer 60 ceramics substrate 61 conductor 62 Second metal layer 63 First metal layer 64 bumps 65 I / O pad 66 cap 67 Through hole 68 conductor pattern

Front page continuation (72) Inventor Yoshinari Amano 1-1-1 Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works (56) Reference JP-A-5-136221 (JP, A) Japanese Patent Laid-Open No. 7-20150 (JP, A) Japanese Patent Laid-Open No. 9-293753 (JP, A) Japanese Patent Laid-Open No. 8-153727 (JP, A) Japanese Patent Laid-Open No. 2-6339 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) B23K 35/40 B22F 1/02 B22F 9/00 H01L 23/12 H01L 21/60 H01L 21/66 G01R 1/073 G01R 31/26

Claims (3)

(57) [Claims] 1. A composite tungsten sphere comprising metal spheres containing at least 95% by weight of elemental tungsten and a conductive coating layer formed on the surface of the metal sphere, the metal sphere being liquid phase sintered. Coarse tungsten powder generated during
It is formed by passing through a plasma and has a dense structure without pores. The composite tungsten sphere has a diameter of 0.05 to 0.2 mm and a diameter variation of ± 1 of the diameter.
A composite tungsten sphere characterized by being within 0%. 2. A probe device used for inspecting the electrical characteristics of a circuit board of a semiconductor package, which has a check needle having the composite tungsten ball according to claim 1 at its tip. 3. A semiconductor package comprising the composite tungsten sphere according to claim 1 as a ball used for electrical contact of a semiconductor package on which a semiconductor chip is mounted.