JP2000200798A - Semiconductor device and its mounting board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the connecting strength of the electrode pad of a semiconductor device to the bump of a mounting board by a method wherein a step part which prevents the progress of a crack is installed at the electrode pad of the semiconductor device, to which the bump is connected. SOLUTION: Every electrode pad 2 of a semiconductor package 1 is constituted in such a way that its cross section is U-shaped, and a nickel-gold plating operation is executed to its surface. The electrode pad 2 is coated with a flux, a bump 3 is mounted so as to be reflow-heated, the electrode pad 2 is connected to the bump 3, and a semiconductor device with the bump is formed. The electrode pad 2 and every electrode pad 2 of the mounting board 5 are constituted of protruding parts 6a, 6b and bottom parts 7a, 7b. A crack which is generated between the U-shaped electrode pad 2 and the U-shaped electrode pad 2 of the mounting board 5 and the bump 3 is first generated along the protruding parts 6a, 6b of the electrode pad 2 and the electrode pad 2 of the mounting board 5. Then, the crack progresses in a direction perpendicular to the protruding parts and then progresses along the bottom parts 7a, 7b. The crack is stopped in the protruding parts 6a, 6b under an ordinary mechanical or thermal load, and the semiconductor package and the mounting board are hard to strip due to the crack.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a mounting board thereof, and more particularly to a connection structure between an electrode pad and a bump of the semiconductor device and a mounting board for a semiconductor device having a bump as an external electrode. The present invention relates to a structure of an electrode pad to which a bump is connected.

[0002]

2. Description of the Related Art BGA, CSP, flip chip, etc.
There is an increasing demand for semiconductor devices having bumps (solder balls) as external electrodes. Semiconductor devices having bumps as external electrodes, such as BGAs, CSPs, and flip chips, are usually plated with nickel-gold (Ni / Au) or vanadium-nickel-gold (Pd / Ni / Au) on the surface of copper (Cu). A flux is applied to the applied electrode pattern, a solder ball is mounted on each electrode, and a bump is formed by reflow heating. In mounting these semiconductor devices, a paste material composed of solder particles and flux is applied in the form of an electrode pattern to a substrate having the same structure as the electrode pattern of the semiconductor device, and the bumps of this semiconductor device and the electrode pattern of the substrate are aligned. Then, the semiconductor device is mounted on the substrate and reflow heating is performed.

However, in recent years, with the demand for smaller and thinner electronic devices, semiconductor devices and substrates have been made smaller and thinner, and the mounting density has been increased. Therefore, when a mechanical or thermal external force is applied to the substrate, the external force applied to the electrode / bump and the bump / substrate connection portion of the semiconductor device is large, and the connection portion cracks in the conventional connection structure. There is concern about peeling.

In order to prevent this, the electrode pads on the surface of the electrode pads of the semiconductor package are roughened into irregularities, a flux is applied to these electrode pads, solder balls are mounted on the electrode pads, and the electrodes are heated by reflow heating. A semiconductor device with bumps in which pads and solder balls are connected is conceivable. Also, the surface of the electrode pad is roughened in an uneven shape on the mounting substrate. After printing the solder paste material on the surface of the roughened electrode pads, the semiconductor device is mounted on the mounting board by reflow heating the semiconductor device and the mounting board by aligning the bumps of the semiconductor device with the electrode pads of the mounting board. It is installed.

[0005]

When a semiconductor device having a bump as an external electrode is mounted on a substrate, the mechanical / thermal load thereafter damages the electrode / bump and the bump / substrate connection of the semiconductor device. And is expected to affect reliability. Recently, the use of a so-called Pb-free solder material that does not contain lead (Pb) is being studied instead of conventional tin-lead (Sn-Pb) eutectic solder for solder balls for environmental reasons. When a semiconductor device on which a bump is formed using a solder ball is mounted on a substrate, there is a concern that the life of the connection portion may be shorter than in the case of the conventional Sn-Pb eutectic solder. Further, even when the surface of the electrode pad is roughened to have irregularities, cracks run along the irregularities, so that the life of the connection portion cannot be maintained too long.

Therefore, by devising the structures of the semiconductor device and the electrode pads of the mounting substrate, not only the strength of the connection between the electrode pads and the bumps of the semiconductor device, but also the connection between the bumps and the electrode pads of the mounting substrate is improved. It is possible to provide a semiconductor device in which, when a crack is generated in the vicinity of a connection interface when a later substrate is subjected to a mechanical or thermal load, the propagation of the crack is prevented.

Accordingly, it is an object of the present invention to provide a semiconductor device and a mounting substrate capable of improving the connection strength between an electrode pad and a bump of the semiconductor device and the mounting substrate. It is another object of the present invention to provide a semiconductor device and a semiconductor device in which a crack generated between an electrode pad and a bump of the mounting substrate is prevented from developing, and a mounting substrate thereof.

[0008]

In order to achieve the object of the present invention, a semiconductor device according to the present invention is a semiconductor device having a bump as an external electrode, wherein an electrode pad of the semiconductor device for connecting the bump is provided. It has a step for preventing the progress of cracks. The electrode pad is provided with a concave portion including a protrusion and a bottom, and prevents a crack from progressing at a step from the protrusion to the bottom. Alternatively, the electrode pad includes a first electrode pad and a second electrode pad provided on the first electrode pad and smaller than the first electrode pad. Cracks are prevented from progressing at the steps between the electrode pads. Further, the electrode pad has a convex portion, and a crack is prevented from progressing at a step between the electrode pad and the convex portion up to the convex portion. Further, the electrode pad has a grid-like electrode pad,
The progress of cracks is prevented by the lattice-shaped steps.

In order to achieve the object of the present invention, a mounting board for mounting a semiconductor device according to the present invention comprises a semiconductor device having a bump as an external electrode, the bump being connected to an electrode pad to mount the semiconductor device. In the mounting board for mounting the semiconductor device, the electrode pad of the mounting board for connecting the bump of the semiconductor device has a step portion for preventing the progress of a crack. The electrode pad is provided with a concave portion including a protrusion and a bottom, and prevents a crack from progressing at a step formed from the protrusion to the bottom. The electrode pad includes a first electrode pad and a second electrode pad provided on the first electrode pad and smaller than the first electrode pad. Cracks are prevented from progressing at the steps between the electrode pads. Further, the electrode pad has a convex portion, and a crack is prevented from progressing at a step between the electrode pad and the convex portion up to the convex portion. The electrode pad has a grid-like electrode pad, and prevents the crack from progressing at the grid-like step. In the above-described semiconductor device, a material containing no lead can be used as a material of the bump. Further, in the above-mentioned mounting board, a material containing no lead can be used in the solder paste material applied to the electrode pads.

In a semiconductor device according to the present invention, in a semiconductor device having a bump as an external electrode, a peripheral portion of an electrode pad of the semiconductor device provided for connecting the bump is higher than a central portion thereof. . In a semiconductor device having a bump as an external electrode, an electrode pad of the semiconductor device provided for connecting the bump is formed in a concave shape. Alternatively, in a semiconductor device having a bump as an external electrode, an electrode pad of the semiconductor device provided for connecting the bump is a second electrode pad smaller than the first electrode pad in the first electrode pad. And a bump is connected to the first and second electrode pads. Furthermore, in a semiconductor device having a bump as an external electrode, an electrode pad of the semiconductor device provided for connecting the bump has a central portion higher than a peripheral portion, and the bump is connected to the electrode pad. ing. In these semiconductor devices, a material containing no lead can be used as the material of the bump.

A mounting board according to the present invention is a mounting board for mounting a semiconductor device having bumps on external electrodes, wherein a peripheral portion of an electrode pad of the mounting board provided for connecting the bump has a central portion. It is higher than. Further, in a mounting board for mounting a semiconductor device having a bump as an external electrode, an electrode pad of the mounting board provided for connecting the bump is formed in a concave shape. Further, in a mounting board for mounting a semiconductor device having a bump as an external electrode, an electrode pad of the mounting board provided for connecting the bump is provided in the first electrode pad in the first electrode pad. Also a small second
Are provided. Furthermore, in a mounting board for mounting a semiconductor device having bumps as external electrodes, the electrode pads of the mounting board provided for connecting the bumps are higher at the center portion than at the peripheral portions.

In these mounting boards, a lead-free material can be used as a paste material applied to the electrode pads to connect the bumps to the electrode pads. In the present invention, the electrode pads of the semiconductor device to which the bumps are connected, the electrode pads of the mounting substrate by configuring the electrode pads as described above, when the substrate after mounting is subjected to mechanical and thermal loads, Since cracks generated from the peripheral portion to the vicinity of the interface of the connection portion can be prevented from being caused by the steps and projections in the electrode pad, the life of the connection portion can be improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the drawings using some examples. FIG. 1 is a partial cross-sectional view showing a first embodiment of a bonding state of a semiconductor device and a mounting board according to the present invention. In the figure, reference numeral 1 denotes a semiconductor package;
Has a concave cross section. The surface of the pad 2 is plated with nickel-gold (Ni / Au). A flux is applied to the electrode pad 2 and the bump 3 is mounted on the electrode pad 2 and then subjected to reflow heating, whereby the electrode pad 2 and the bump 3 are connected, and a semiconductor device with a bump is obtained. The electrode pad 5 of the mounting substrate 4 is also formed with a concave cross section. After printing a solder paste material on the electrode pad 5, the electrode pad 5 is aligned with the semiconductor device with bumps, mounted on the mounting substrate 4, and subjected to reflow heating. Accordingly, the semiconductor device with bumps is mounted on the mounting substrate 4. Copper (Cu) is usually used for the electrode pads 2 and 5, and the surfaces of the electrode pads 2 and 5 are generally plated with gold (Au) via nickel (Ni) base plating. Electrode pad 2,
The concave portion 5 is composed of projecting portions 6a, 6b and bottom portions 7a, 7b. The protruding portions 6a, 6 of the electrode pads 2, 5
b may be connected continuously without interruption, or may be partially interrupted. Further, the shape of the protruding portion viewed from the plane may be various shapes such as a circle, an ellipse, and a polygon. The processing of this electrode pad will be described later with reference to FIG.

In this embodiment, when a crack occurs between the concave electrode pads 2 and 5 and the bump 3, the crack first occurs along the protrusions 6a and 6b of the electrode pads 2 and 5. The crack then travels in a direction perpendicular to it and eventually along the bottoms 7a, 7b, but under normal mechanical or thermal loads, this crack stops at the protrusions 6a, 6b, so Separation hardly occurs. In this way, when only the surface is plated, the strength is 200 g / bump on average, but the electrode pad 2,
The strength is improved by making the surface of No. 5 concave.

FIGS. 2A to 2C are partial cross-sectional views for explaining a process of manufacturing an electrode pad. FIG. 2 (a)
As shown in FIG. 2, after applying a resist 8 to a portion other than the portion where the bottom 7a of the electrode pads 2 and 5 before processing is formed, the resist 8 is immersed in an etching solution to cut the center portion, and as shown in FIG. Form. Thereafter, the resist 8 is removed, and FIG.
The electrode pads 2 and 5 formed in a concave shape as shown in FIG.
Get.

FIG. 3 is a partial sectional view showing a second embodiment of the bonding state of the semiconductor device and the mounting board according to the present invention. In this embodiment, the semiconductor package 1, the mounting substrate 4
Pad 15, on each of the electrode pads 15, 17 of
Electrode pads 16 and 18 smaller than 17 are provided.

An example of a method for manufacturing this electrode structure will be described with reference to FIG. FIGS. 4A to 4C are partial cross-sectional views for explaining a manufacturing process of the electrode pad. As shown in FIG. 4A, a resist 8 is applied to a portion where the electrode pad 18 is not to be formed on the electrode pad 17 formed of copper. Next, as shown in FIG. 4B, copper plating is applied to portions where the resist 8 is not applied. After plating to a desired thickness, as shown in FIG.
And finally nickel-coated electrode pads 17 and 18
Electrode pads 17 and 18 are obtained by applying gold (Ni / Au) plating. The electrode pads 15 and 16 of the semiconductor package 1 can be formed in a similar manner. For example, tin-silver-
When a hard and brittle solder material such as bismuth (Sn-Ag-Bi) is used, if a thermal load is repeatedly applied under the above conditions, cracks enter the interface between the bump 3 and the electrode pad and peel off.

In the electrode pattern structure of this embodiment, cracks occur at the interface with the bumps 3 because other pads 16 and 18 are provided in the electrode pads 15 and 17 and the electrodes are formed in a concave shape. But crack is electrode pad 1
6, 18 and the projections 6a, 6 of the concave electrode pads 2, 5
b once, then small pad 16 in the pad,
Propagation proceeds to the connection portion between the bump 18 and the bump 3. Therefore,
The interface does not peel off simultaneously with the occurrence of cracks.

Also, in many electronic circuit boards, a surface-mounted product in which bumps or leads of a semiconductor device in which external electrodes are formed of bumps or leads are mounted on a mounting board via a solder paste, In many cases, the semiconductor device is composed of both insert-soldered products which are inserted into the through-holes of the substrate and soldered. Normally, after the surface mounting, the connection of the insertion product is performed, so that the connection portion of the surface mounting product receives a thermal history at the time of insertion soldering. Tin-silver-bismuth (Sn-Ag-Bi) based lead (Pb) free (B
i: 0 to 20%) When solder is used, the joints of the surface-mounted products may be damaged and cracks may occur. However, among the semiconductor devices having external electrodes as bumps, the electrode structure of the present invention is not used. No cracks or the like were observed in the connection part after insertion soldering.

FIG. 5 is a partial sectional view showing a third embodiment of the bonding state of the semiconductor device and the mounting board according to the present invention. In the figure, a convex portion 2 is provided at the center of the electrode pads 20 and 21.
2, 23 are provided. In this electrode pad structure as well, cracks are stopped by the protruding portions 22 and 23 for the above-described reason, so that the electrode pads 20 and 21 and the bump 3
Does not peel off.

FIG. 6 is a partial sectional view showing a fourth embodiment of the bonding state of the semiconductor device and the mounting board according to the present invention. FIG. 7 is an enlarged plan view of the grid electrode. In this embodiment, grid-like electrode pads 27 and 28 are provided on the electrode pads 25 and 26. These electrode pads 25,
26 is an electrode pad 27, 28 of the electrode pad 25, 26
Can be obtained by coating a portion other than the portion corresponding to the above with a resist and plating. The electrode pads 27,
As 28, a resist can be used.

Further, when the small pads 27 and 28 made of resist are formed in the electrode pads, the solder does not wet the resist portions and unbonded portions are formed. It is considered that the propagation of the crack does not pass through the resist portion. In such a case, as shown in FIG.
For example, by providing the resist pattern 29, cracks generated from the periphery stop at the resist portion and remain near the center although the number of connection portions is small, which is considered to be effective for improving the life of the product.

For example, 1.27 mm pitch, 4 rows arrangement,
In a 256-pin BGA (outside size 27 mm square: chip size: 14 mm square), bumps are formed using Sn-Ag-Bi balls (φ0.76 mm), which is lead (Pb) -free solder, and further, Sn-Ag- After mounting on a substrate with Bi paste, a temperature cycle was performed at −55 to 125 ° C. to evaluate the life of the connection portion. When comparing the case where the connection part is completely peeled off at the interface, the corner pin is completely peeled off in 200 cycles in the case of only plating on the pattern surface, but by using the pattern structure of the present invention, for example, the electrode pad is made concave. In the case where the electrode pad was formed, the projection was provided at the center of the electrode pad, or the grid pad was provided on the electrode pad, the life could be extended up to 500 cycles.

In the embodiment of the present invention, both the semiconductor package 1 and the mounting substrate 4 are used as the electrode pads of the present invention. However, the mounting substrate 4 on which the semiconductor package 1 having the bumps 3 is mounted is mechanically and thermally. When a heavy load is applied, cracks and peeling mainly occur on the bump and substrate connection portion side. In the case where only the connection portion on the substrate side is cracked, the electrode pad on the semiconductor package 1 side only needs to be formed by conventional plating, that is, it is not necessary to adopt the pad structure of the present invention. Regarding the electrode structure shown in FIGS. 1 and 3, a semiconductor package having bumps formed on conventional electrode pads may be used.

[0025]

As described above, in the electrode pad structure of the present invention, it is possible to improve the connection reliability of a semiconductor device having a bump as an external electrode and a mounting board for mounting the semiconductor device. Further, according to the electrode pad structure of the present invention, even if a lead-free solder material, which is harder than Sn-Pb eutectic solder and is considered to be inferior in connection reliability during mounting, is used for the bumps and pastes, the semiconductor can be used. Equipment and bumps,
Connection reliability between substrates on which the semiconductor device is mounted can be improved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a first embodiment of a bonding state between a semiconductor device and a mounting substrate according to the present invention.

FIG. 2 is a partial cross-sectional view for explaining a manufacturing process of the electrode pad.

FIG. 3 is a partial cross-sectional view showing a second embodiment of a bonding state between a semiconductor device and a mounting board according to the present invention.

FIG. 4 is a partial cross-sectional view for explaining a manufacturing process of the electrode pad.

FIG. 5 is a partial cross-sectional view showing a third embodiment of the bonding state between the semiconductor device and the mounting board according to the present invention.

FIG. 6 is a partial cross-sectional view showing a fourth embodiment of the bonding state of the semiconductor device and the mounting board according to the present invention.

FIG. 7 is an enlarged plan view of a grid electrode pad according to the present invention.

[Explanation of symbols]

1 ... semiconductor package, 2, 5, 15, 16, 17, 1
8, 20, 21, 27, 28 ... electrode pads, 3 ... bumps, 4 ... mounting board. 29 ... Resist pattern.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tasao Soga 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi, Ltd. Production Technology Research Institute (72) Inventor Toshiharu Ishida Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa 292 Hitachi Manufacturing Co., Ltd.Production Technology Research Laboratories (72) Koji Serizawa, Inventor 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Japan Co., Ltd.Production Technology Research Laboratory Hitachi, Ltd. 5-2-1, Honmachi Semiconductor Device Division, Hitachi, Ltd. (72) Inventor Hideo Miura 502, Kandatecho, Tsuchiura-shi, Ibaraki Pref.Mechanical Research Laboratory, Hitachi, Ltd. (72) Ken Takeshi Terasaki Tsuchiura-shi, Ibaraki Pref. 502 Kandatecho Inside Hitachi Machinery Research Laboratory

Claims (22)

[Claims] 1. A semiconductor device having a bump as an external electrode, wherein the electrode pad of the semiconductor device for connecting the bump has a step for preventing the progress of a crack. 2. The semiconductor device according to claim 1, wherein said electrode pad is provided with a concave portion comprising a projecting portion and a bottom portion, and a step from said projecting portion to the bottom portion prevents a crack from advancing. Semiconductor device. 3. The semiconductor device according to claim 1, wherein said electrode pad is provided on said first electrode pad and said second electrode pad is smaller than said first electrode pad.
A semiconductor device, comprising: a first electrode pad and a second electrode pad; 4. The semiconductor device according to claim 1, wherein said electrode pad has a projection, and a crack is prevented from progressing at a step between said electrode pad and said projection until reaching said projection. A semiconductor device characterized by the above-mentioned. 5. The semiconductor device according to claim 1, wherein said electrode pad has a grid-shaped electrode pad, and a crack is prevented from progressing at said grid-shaped step portion. 6. A mounting board for mounting the semiconductor device by connecting the bump to an electrode pad of the semiconductor device having the bump as an external electrode, wherein the electrode pad of the mounting board for connecting the bump of the semiconductor device is provided. Is a mounting board having a step for preventing the progress of cracks. 7. A mounting board according to claim 6, wherein said electrode pad is provided with a concave portion comprising a projecting portion and a bottom portion, and a step formed from said projecting portion to a bottom portion prevents a crack from advancing. Characteristic mounting board. 8. The mounting substrate according to claim 6, wherein said electrode pad is a first electrode pad and a second electrode pad provided on said first electrode pad and smaller than said first electrode pad. A mounting substrate configured to prevent a crack from advancing at a step between a first electrode pad and a second electrode pad. 9. The mounting board according to claim 6, wherein said electrode pad has a convex portion, and a step between said electrode pad and said convex portion up to said convex portion prevents progress of a crack. A mounting board characterized by the above-mentioned. 10. The mounting board according to claim 6, wherein said electrode pad has a grid-like electrode pad, and a crack is prevented from progressing at said grid-like stepped portion. 11. The semiconductor device according to claim 1, wherein a material containing no lead is used as a material of said bump. 12. The mounting substrate according to claim 6, wherein the solder paste material applied to the electrode pad does not contain lead. 13. A semiconductor device having a bump as an external electrode, wherein a peripheral portion of an electrode pad of the semiconductor device provided for connecting the bump is higher than a central portion thereof. Semiconductor device. 14. A semiconductor device having a bump as an external electrode, wherein the electrode pad of the semiconductor device provided for connecting the bump is formed in a concave shape. 15. A semiconductor device having a bump as an external electrode, wherein an electrode pad of the semiconductor device provided for connecting the bump is formed in a first electrode pad of a second electrode smaller than the first electrode pad. And a bump is connected to the first and second electrode pads. 16. In a semiconductor device having a bump as an external electrode, an electrode pad of the semiconductor device provided for connecting the bump has a center portion higher than a peripheral portion, and the bump is formed on the electrode pad. A semiconductor device which is connected. 17. The semiconductor device according to claim 13, 14, 15, or 16, wherein a material containing no lead is used as a material for said bumps. 18. A mounting board for mounting a semiconductor device having a bump as an external electrode, wherein a peripheral portion of an electrode pad of the mounting board provided for connecting the bump is higher than a central portion thereof. A mounting substrate, characterized in that: 19. A mounting board for mounting a semiconductor device having a bump as an external electrode, wherein the electrode pad of the mounting board provided for connecting the bump is formed in a concave shape. Mounting board. 20. A mounting board for mounting a semiconductor device having a bump as an external electrode, wherein an electrode pad of the mounting board provided for connecting the bump is provided in the first electrode pad in the first electrode pad. A mounting substrate provided with a second electrode pad smaller than the electrode pad. 21. A mounting board for mounting a semiconductor device having a bump as an external electrode, wherein a center portion of an electrode pad of the mounting board provided for connecting the bump is higher than a peripheral portion. A mounting board characterized by the above-mentioned. 22. The mounting substrate according to claim 18, wherein the paste material applied to the electrode pad for connecting the bump to the electrode pad does not contain lead. A mounting board characterized by the above-mentioned.