JP3479898B2 - Semiconductor package - 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 package and a manufacturing method thereof, and more particularly to an area array terminal type semiconductor package represented by a ball grid array (BGA) and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, the trend toward higher performance and higher density of electronic information devices, that is, portable devices has become more rapid. As a key technology to support this, surface mounting of electronic parts and semiconductor chips is becoming more important.

Conventional quad flat package (QF
The shift from P) to the area array terminal type package represented by BGA is rapid. Moreover, in the same flow,
Practical application in tip size package (CSP) has also made great progress.

Internal electrodes, that is, a chip and a substrate (eg,
The connection terminal of the interposer) is currently formed as a flip-chip (hereinafter referred to as FC) connection by welding or cutting a wire material of solder, gold or gold alloy. Furthermore, more traditionally, wire bonding (hereinafter WB
However, the demand for higher packaging density is becoming severely limited.

By the way, it is known that the FC connection has advantages such as an increase in the number of I / Os and a low inductance as compared with the WB. However, on the other hand, various reliability problems are confronted. In practical terms, the electrical performance as a connection terminal is secured, and in addition, a semiconductor package that is reliable against the heat cycle during mounting is constructed. Is required to do.

In the BGA CSP, 200 to 37
It covers almost the range of 0 pin and external operating frequency of 60 to 155 MHz.

[0007]

[Problems to be Solved by the Invention] However, the above-mentioned problems are inherent, and with further miniaturization of the device itself in the future, higher packing density will be required and further countermeasures against signal delay and noise will be lacking. I can't do it.

In the conventional display method, the connection of the internal electrodes at 800 to 1000 pins or more and the external operating frequency of 250 to 300 MHz or more is not sufficient in the conventional FC connection.

C4 with the most reliable ball bump
Connection (Controlled Collapse Chip Connection)
Since most of them are made of solder, the connection length cannot be maintained with high precision, and it is said that there is a variation of substantially 5 to 15 μm. Moreover, cracking or peeling of the solder during the heat cycle is not sufficient due to embrittlement due to the alloying reaction with the pad or core ball on the element side.

On the other hand, in the method using gold or a gold alloy, the connection length cannot be maintained with high precision, and the plating performed to secure the connection or welding of the pad and the periphery is rather fragile as described above. In many cases, an alloying reaction that causes

However, the properties required for the core ball are
It is a highly accurate core ball, and the connection between the element and the board can use the existing mounting machine and system, so that the outermost skin is at least a solder layer, and the alloying reaction with the core ball and the pad It is required to be a constituent material that is hard to get up, to have rolling properties, and to have little adhesion between balls. Moreover, it is essential to develop a reliable and mass-producible coating method.

In addition, the coating layer having the solder layer on the core ball has a thickness (with a thickness of 5 μm or less, which is stable when assembled into a package, because of the material constituting the coating layer, the connection is easy and the mass production stability is maintained. I am a little worried about the connection itself,
Further, the amount of the coating layer material that is sufficiently stable is preferably 10 μm or more, and of course, when it is 25 μm or more, the connection pitch interval in high-density mounting is not stable and it is practically meaningless). Precision is essential.

This cannot be handled as it is with the conventional method of using the BGA ball size (300 to 800 μm) for the external electrode, and the plating technique is also extremely difficult. If you stick to such simple process, it will never be solved.

Therefore, a technical object of the present invention is to provide a composite ball which can be used as an FC ball without using a conventional mounting machine and system without major modification, and which is provided with an electrically and thermally consistent coating layer. You can get the compound ball,
It is an object of the present invention to provide a semiconductor package which is reliable against heat cycles and a method for manufacturing the same by using it as a semiconductor element or the like and a bonding terminal, especially as an internal electrode.

[0015]

According to the present invention, a semiconductor package having a semiconductor element mounted thereon has a diameter of 0.
It is composed of a composite ball having a solder layer on the outermost skin of a core ball made of copper with a diameter variation of 04 to 0.1 mm and within ± 5% of the diameter, and a coating layer having a total coating layer thickness of 6 μm or more. And the coating layer is formed on the core ball side.
The first layer is a base layer, and the second layer on the base layer is tin or tin.
And an alloy plating layer mainly containing
It is possible to obtain a semiconductor package characterized in that it has a structure having three solder layers .

Further, according to the present invention, in the semiconductor package, the semiconductor package is obtained in which the thickness of the entire covering layer is 10 μm or more.

[0017]

Further, according to the present invention, there is obtained a semiconductor package characterized in that in the semiconductor package, a ratio of the diameters of the composite ball having the coating layer and the core ball is 1.1 or more. To be

According to the invention, in the semiconductor package, the solder forming the solder layer is PbS.
n, CuSn, AgSn, SnZn, SnBi, Sn,
A semiconductor package characterized by comprising at least one of B and Bi is obtained.

[0020]

Specifically, in the present invention, first of all, the coating layer of the core ball made of copper (hereinafter referred to as a copper core ball) is made of nickel as an underlayer in order to suppress the reactivity of copper, which is the core ball. 1 to 3 micron electroplating.

Secondly, the desired coating layer thickness of about 2 to 10 μm is obtained by electroless tin plating, which has been the second prior art.
Thick plating. Electroless tin plating (Patent No. 16238
No. 69, reference) reduces the adhesion of copper core balls to each other due to electric solder plating, and solves the consistency of the entire plating process, which is important for ensuring the thickness of the entire coating layer.

Further, the third solder plating is 2 to 5 μm.
The total thickness is 6 μm or more, more preferably 10 μm or more, which enables more stable and easy joining. The coating layer thus obtained has good rolling properties because it can provide a composite ball having a stable film formation that is electrically and thermally consistent and can be put to practical use.

Here, the solder of the present invention may be selected from practically possible materials in view of melting point, reactivity, etc.
Main component is PbSn, CuSn, AgSn, SnZn, S
One of at least one of nBi, Sn, and Bi solders is used, and plating is performed by this.

[0025]

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

FIG. 1 is a sectional view showing a semiconductor package according to an embodiment of the present invention. Referring to FIG. 1, a semiconductor package 1 includes a semiconductor chip 5 mounted on a base 2 via flip chip (FC) balls 2 composed of compound balls, and an FC between the base 2 and the semiconductor chip 5. The resin 4 to be filled including the ball 2 and the base 2 are, for example,
A ball grid array (BGA) ball 6 for mounting on a printed wiring board.

In the embodiment of the present invention, the core ball used for the FC ball 2 or the like is basically preferably copper because of its good thermal conductivity, and even if the skin is plated, it can be mass-produced at low cost. From the physical properties, tungsten (which is not preferable for heat conduction lower than this) is sufficiently conceivable, but there are not many other options.

In order to manufacture a core ball made of copper (hereinafter, referred to as a copper core ball) according to the embodiment of the present invention, an elementary ball obtained by a rotary plasma electrode method or an atomizing method by high pressure injection is subjected to precision sieving. And the defective spheres are removed by the image processing system.

In the above semiconductor package, the FC ball has a diameter of 40 because of the resin inflow property at the time of FC connection.
If it is less than μm, it is difficult to assemble due to the adhesion and various characteristics, and 100 μm or less is required from the mounting level according to the embodiment of the present invention.
Desirably, the thickness is 60 μm or less. Further, if the outermost skin of this core ball is provided with a solder layer of 2 to 5 μm, the connection of the pad and the periphery or welding can be performed by the conventional device or method.

The FC ball 2 shown in FIG. 1 has a diameter of 40-100.
An underlayer of 1 μm Ni plating is formed on a copper core ball of μm, and a 7
〜20μm electroless Sn plating is applied, and PbS on it
Solder plating of n, AgSn, ZnSn or the like is applied.

FIG. 2 is a diagram showing a schematic configuration of a solder plating apparatus for producing a solder coating layer of the FC ball 2 of FIG.
Referring to FIG. 2, about 80 liters of plating solution 19 is stored in a plating tank 11, and a pair of anodes 12 and a plating jig 13 are arranged between them. Plating jig 13
A plating basket 15 made of resin is provided at the lower end of the plating basket 15, and the bottom of the plating basket 15 serves as the cathode 14. A three-dimensional vibration motor 17 for applying three-dimensional vibration to the resin-made plating basket 15 is provided at the upper end of the plating jig 13. Plating basket 15
A copper core ball work is inserted inside. The cathode 14 and the anode 12 are electrically connected to a rectifier 18, respectively,
It is configured to pass an electric current.

In the embodiment of the present invention, the most important point is a technique of forming a solder coating layer on a copper core ball by plating, which is obtained as a result of trial and error of various tests and combinations of materials. Is. Naturally, since the coating layer obtained by the embodiment of the present invention is much thicker than the layer thickness obtained by ordinary plating, it is difficult to use the dry method or the like, and it is practically impossible in terms of cost.

In the solder plating, not only the adhesion of the microspheres to each other occurs even if the plating thickness is 5 μm or less during the growth process of the plating layer, but also because the growth rate becomes uneven, it becomes a messy layer. It becomes an aspherical shape that does not roll. Generally, the film is formed by particle suspension using an inflator (stirring blade with blade) or a vibrating plate. With this method, the above-mentioned drawback of non-spherical shape was not avoided.

In the embodiment of the present invention, the problem of non-spherical copper core balls is solved by using a plating apparatus using a plating jig 13 equipped with a three-dimensional vibration motor that moves three-dimensionally during plating. did.

Moreover, stable film formation could be obtained by making the number (concentration) of the copper core balls in the predetermined liquid volume extremely higher than the conventional one.

The composite ball, which is obtained by the above-mentioned method and is made of copper core balls having a solder coating layer on the surface according to the embodiment of the present invention, is the FC ball 2 shown in FIG. Can be used without major changes, and it is possible to obtain a coated ball that is provided with a coating layer that is electrically and thermally compatible. Moreover, the composite ball can be used as a semiconductor element and other bonding terminals, especially as internal electrodes. It can be assembled into a semiconductor package that is reliable against heat cycles. This package can be a CSP,
Package compatibility, ease of implementation, KGD (Kn
It has the characteristic of being "own good die", and has the advantage that it can be used for devices in the general consumer field and can be expected to be put into practical use.

A specific example of manufacturing a semiconductor package according to the embodiment of the present invention will be described below.

(First Embodiment) About 5 million spheres of precisely classified copper core balls (49 to 53 μm) were pretreated,
Using the Watt bath, the underlying Ni plating was performed at 0.5 A for 120 minutes with the apparatus shown in FIG. Plating thickness is 0.5 to 1.5
was μm. Next, a commercially available organic acid solder plating bath was used for electric solder plating at 0.5 A for 400 minutes. The plating thickness was 9 to 13 μm. However, about 10% of the balls adhered to each other, and the desired composite ball was obtained by classification. It was confirmed that almost the entire amount rolled constantly with a slight inclined plate.

(Second Embodiment) By the same treatment as in the first embodiment, after Ni undercoating and dipping in an electroless tin plating bath, 0.1 A, 60 seconds is used using the apparatus of FIG. After electrolysis (forming tin nuclei), turn off the current at 70 ℃
Electroless plating was performed for 3 hours. Plating thickness is 4 ~
It was 6 μm. Next, with an electric solder plating solution, 0.5
Solder plating was performed at A for 150 minutes using the same apparatus. The total plating thickness of electroless tin plating and solder plating is 7
Plating of ˜11 μm was obtained, and each composite ball had no adhesion and no abnormal shape was observed. The rolling performance similar to that of the first embodiment was also obtained in the second embodiment.

(Third Embodiment) A copper core ball having a diameter of 83 to 88 μm, which is the same as that of the first embodiment, is shown in FIG.
Ni plating was performed at 0.5 A for 60 minutes with the above apparatus. The plating thickness was 0.8 to 1.0 μm. Then, using a commercially available organic acid solder plating bath, electric solder plating (1.8A, 110
Minutes). The plating thickness was 3-4 microns.
Finally, an electric Bi plating solution was used to carry out Bi plating for about 30 minutes at 1 A for about 1.2 to 1.8 μm, and the total plating thickness (thickness of all coating layers) was set to about 6 μm. No composite balls were attached to each other. In this case, there is a demand for a sealing resin having a higher melting point than that used in the above-mentioned embodiment, etc. Further, since it is desired to make it smaller against expansion, a Bi skin is used and the solder is tin rich.

The third embodiment is the same as the first embodiment.
The rolling performance similar to that of the second embodiment was obtained, and the assembly could be performed without any inconvenience.

The material of the solder is not limited to the above-mentioned embodiment, although brittleness and the like due to alloy formation are taken into consideration.
If the ball has a low concentration with respect to the liquid, the film formation is rather uneven, which is not good. The heat cycle was judged by repeating heating / cooling by energization / driving ON / OFF in order to inspect the performance of the element by sealing these with a resin after joining the composite balls by heating or the like.

[0043]

INDUSTRIAL APPLICABILITY As described above, the composite ball of the present invention can be used as an FC ball without using a conventional mounting machine and system without major modification, and is a coated ball provided with a coating layer having electrical and thermal compatibility. Can be obtained. Moreover, the composite ball can be assembled into a semiconductor package that is reliable against heat cycles by using it as a semiconductor element and other bonding terminals, especially as internal electrodes.

This semiconductor package can be formed as a CSP and has compatibility as a package, ease of mounting, and KGD.
It has the feature of (Known Good Die), and has the advantage that it can be used for devices in the general consumer field and can be expected to be put into practical use.

[Brief description of drawings]

FIG. 1 is a sectional view showing a semiconductor package according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a solder plating apparatus for manufacturing the composite ball of the semiconductor package of FIG.

[Explanation of symbols]

1 Semiconductor package 2 foundation 3 FC balls 4 resin 5 semiconductor chips 6 BGA balls 10 Solder plating device 11 plating tank 12 Anode 13 Plating jig 14 cathode 15 Plating basket 16 work 17 Three-dimensional vibration motor 18 Rectifier 19 Plating solution

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiko Doi 5-24-8 Higashi-Ueno, Taito-ku, Tokyo Within Tokyo Tungsten Co., Ltd. (72) Inventor Koyano ▲ UK ▼ Matsu 2 13-7 Totec Co., Ltd. (56) Reference JP-A-8-139097 (JP, A) JP-A-9-82756 (JP, A) JP-A-8-236529 (JP, A) JP-A-62 -266842 (JP, A) JP-A-8-191073 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/60 H01L 23/12

Claims (4)

(57) [Claims] 1. A semiconductor package having a semiconductor element mounted thereon, wherein a solder layer is provided on an outermost skin of a core ball made of copper having a diameter of 0.04 to 0.1 mm and a diameter variation of ± 5% or less of the diameter. the thickness of the total coating layer is formed with a composite ball having a coating layer is 6μm or more, the coating layer
Is an underlayer on the first layer on the core ball side, on the underlayer
2nd layer of tin or an alloy plating layer containing tin as a main component
And a structure having a solder layer on the third layer on the second layer.
Semiconductor package, characterized in that Eteiru. 2. The semiconductor package according to claim 1, wherein the thickness of the entire covering layer is 10 μm or more. 3. The semiconductor package according to claim 1 , wherein a diameter ratio of the composite ball having the coating layer and the core ball is 1.1 or more. 4. The semiconductor package according to claim 1, wherein the solder forming the solder layer is PbSn, CuS.
A semiconductor package comprising at least one of n, AgSn, SnZn, SnBi, Sn, and Bi.