JPH08172158A - Printed wiring board - Google Patents

Abstract

PURPOSE: To make electric noise hard to be generated, and make short-circuit between wires and printed wirings hard to be generated, by a method wherein at least one out of wirings electrically connected with the power supply electrode or the ground electrode of a mounted semiconductor chip is led out form a chip connection electrode toward the inside direction and the others are led out toward the outside direction. CONSTITUTION: Connection electrodes 14 are formed in the peripheral part of a semiconductor chip mounting part 16. Wirings 10, 17 to be connected with a power supply electrode 20 and a ground electrode 19 out of the connection electrodes 14 are led out from the chip connection electrodes 14 toward the inside direction, and the other wirings 15 are led out toward the outside. Thereby influence between the wirings can be reduced, so that impedance matching with the external circuit is facilitated, electric noise is made hard to be generated, and electric short-circuit can be made hard to be generated when wire bonding is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board in which a semiconductor chip is directly mounted on the printed wiring board and is wire-bonded to electrodes on the printed wiring board.

[0002]

2. Description of the Related Art A semiconductor chip is directly mounted on a printed wiring board, and a bonding wire is used to connect the electrodes of the semiconductor chip.
A technology for electrically connecting electrodes for connecting a semiconductor chip on a printed wiring board is COB (Chip on boar).
Conventionally known as d). This technique does not require components such as lead frames, and directly mounts semiconductor chips and connects them with bonding wires, so that the packaging density of components can be improved. In addition, a single or a plurality of semiconductor chips are mounted on a small printed wiring board, electrodes for external connection are provided on the periphery, side surfaces or back surface of the printed wiring board, and electrodes of the semiconductor chip,
It is also known in the related art to electrically connect external connection electrodes with wiring provided on a printed wiring board to form a semiconductor module.

In such a printed wiring board used for a COB or a semiconductor module, an electrode for connecting a semiconductor chip is provided around the semiconductor chip mounting portion, and the electrode is directed from the electrode to the side opposite to the semiconductor chip mounting portion. Wiring is drawn out and electrically connected to other component connection electrodes and external connection electrodes. As an example of the printed wiring board as described above, the case of the semiconductor module is the case of the single semiconductor chip.
No. 172758.

[0004]

By the way, in recent years, cost reduction of semiconductor chips, downsizing for higher performance, higher pin count, and further, the bonding wire length for connecting between the semiconductor chip and the electrodes of the printed wiring board is Shortening is desirable in order to reduce the cost and improve the connection reliability by saving the material of the bonding wire such as gold and aluminum. Along with this, the number of electrodes for connecting the semiconductor chip is increased and the electrodes for connecting the semiconductor chip are narrowed around the semiconductor chip mounting part. Pitching is progressing. Along with this, the wirings drawn from the electrodes are also closely arranged with a very narrow distance between the respective wirings. Furthermore, it is very important to stabilize the power supply and ground potential of the semiconductor chip in order to prevent electrical noise, malfunctions, etc. as the density of semiconductor chips increases and the speed of signals increases. , The ratio of power source and ground electrode is increasing, and in many cases, it is 1/2
Some occupy the above.

In this specification, the "power supply potential" means the potential of the operating power supply of the semiconductor chip.

Under the above background, as in the conventional case,
In the structure in which electrodes for connecting semiconductor chips are provided around the semiconductor chip mounting portion, and wiring is drawn from the electrodes toward the periphery, a printed wiring board is used as the substrate of the COB or the semiconductor module. In such a case, among the wirings, the wirings having the power supply and the ground potential increase. Therefore, in the wirings other than the wirings having the power supply and the ground potential, that is, the general signal wirings, many signal wirings are adjacent to or sandwiched between the power supply and the ground potential. On the other hand, there is also a portion where a plurality of signal wirings are adjacent to each other.
In that case, when the COB or the semiconductor module is considered from the side of the external printed wiring board or the electronic circuit to which they are connected, the characteristic impedance varies from wiring to wiring.

When the characteristic impedance is considered by paying attention to a certain wiring, the characteristic impedance greatly differs depending on what kind of potential wiring exists around the wiring and the distance from the surrounding wiring. . That is, if there is a wiring having a power supply potential or a ground potential in the surroundings, the characteristic impedance of the wiring decreases, and if the distance to the wiring having the power supply potential or the ground potential is close, the characteristic impedance of the wiring decreases. To do. Characteristic impedance when the COB or the semiconductor module is considered from the side of the external printed wiring board or the electronic circuit to which they are connected, and conversely, the external printed wiring board or the electronic circuit is considered from the side of the COB or the semiconductor module. If they do not match the characteristic impedance in the case of the above, electrical signals will be reflected at the junction, causing electrical noise.

As described above, when the COB or the semiconductor module is considered from the side of the external printed wiring board or the electronic circuit to which they are connected, the characteristic impedance varies from wiring to wiring. There is a problem that it is difficult to match the characteristic impedances. Therefore, as a result, electrical noise increases and the reliability of the electronic device using the COB or the semiconductor module decreases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a printed wiring board which makes it easy to match the characteristic impedance with an external circuit and to obtain an electric device in which electrical noise is unlikely to occur.

It is another object of the present invention to provide a printed wiring board on which a semiconductor chip is mounted and when wire bonding is performed, an electrical short circuit is unlikely to occur between the bonding wire and the printed wiring board.

[0011]

In order to solve the above problems, according to the invention of claim 1, a semiconductor chip mounting portion is formed on an insulating substrate, and a semiconductor chip connecting portion is formed around the semiconductor chip mounting portion. Of the wiring, a wiring electrically connected to the electrode, and a protective layer for protecting the surface of the wiring, in the wiring, a power electrode or a ground electrode of a semiconductor chip to be mounted. At least one of the electrically connected wirings is drawn inward from the electrode for semiconductor chip connection, and the other wiring is drawn out in the outward direction from the electrode for semiconductor chip connection. .

In this structure, the material used in the conventional printed wiring board can be applied as the insulating base material. For example, a glass-epoxy base material, a glass-polyimide base material, a glass-bismaleimide triazine base material, a ceramic base material and the like can be exemplified. Further, examples of the wiring material include copper, aluminum, gold and the like. The semiconductor chip connecting electrode may be made of the same material as the wiring, or may be further plated with nickel, gold or the like. The semiconductor chip mounting portion may have the insulating base material exposed or covered with a protective layer.
Further, a metal layer may be provided in order to reduce noise, improve electric characteristics, or efficiently dissipate heat generated from the semiconductor chip. Further, the wiring drawn inward from the electrode for connecting the semiconductor chip is at least one of a power electrode and a ground electrode, and both the power electrode and the ground electrode are drawn inward from the electrode for connecting the semiconductor chip. This is more preferable in order to enhance the effect of the present invention described later.

By the way, when the above-mentioned structure is adopted, the wiring electrically connected to the power supply electrode or the ground electrode of the mounted semiconductor chip is drawn inward from the electrode for connecting the semiconductor chip. Therefore, when the electrode for connecting the semiconductor chip and the electrode of the semiconductor chip are connected by wire bonding, the wire bonding is performed so as to straddle the wiring electrically connected to the power supply electrode or the ground electrode. Therefore, the insulation between the wiring and the bonding wire may become insufficient, or even contact may occur in an extreme case. Therefore, there has been a demand for a printed wiring board in which the insulation between the wiring pulled out inward from the electrode for connecting a semiconductor chip and the bonding wire is not deteriorated.

The invention according to claim 2 is based on such a demand. That is, the invention of claim 2 is characterized in that, in the invention of claim 1, the protective layer is formed at least at a portion between the semiconductor chip mounting portion and the semiconductor chip connecting electrode. As such a protective layer, a material used as a surface protective layer of a general printed wiring board may be used. That is,
An epoxy resin or the like.

[0015]

According to the present invention, at least one of the wirings electrically connected to the power supply electrode or the ground electrode of the mounted semiconductor chip is an electrode for connecting the semiconductor chip. From the electrode for connecting the semiconductor chip to the outer side, the characteristic impedance of the other wiring is electrically connected to the power supply electrode or the ground electrode. Not affected by. Further, the influence of the characteristic impedances of the other wirings on the other wirings can be reduced by increasing the distance between the wirings of the wirings drawn outward from the electrodes for connecting the semiconductor chip.

According to the second aspect of the invention, since the protective layer is formed at least at a portion between the semiconductor chip mounting portion and the semiconductor chip connecting electrode, a semiconductor chip is mounted, When wire bonding is performed, it is possible to improve the insulation between the wiring and the bonding wire.

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples.

[Embodiment 1] FIG. 1 is a top view of a printed wiring board according to an embodiment of the present invention. FIG. 2 is a bottom view of the printed wiring board according to the embodiment of the present invention. On the insulating substrate 11 made of a base material such as glass-epoxy, the wiring 15 made of copper and the through holes 12 and 13 are formed by the subtractive method. The manufacturing method is not limited to the subtractive method, and an additive method or a transfer method may be used. In this embodiment, the semiconductor chip mounting portion 16 is left without etching the copper foil in order to improve the heat dissipation. The semiconductor chip mounting portion 16
In this embodiment, although the number is one, it is provided in the same number as the number of mounted semiconductor chips. The semiconductor chip connection electrode 14 is formed around the semiconductor chip mounting portion 16.

Of the electrodes for connecting the semiconductor chip, the wiring 10 connected to the power supply electrode 20 and the ground electrode 19,
Reference numeral 17 is drawn inward from the electrode for connecting the semiconductor chip. Then, the other wiring 15 is drawn outward. In the present specification, the meanings of "inside" and "outside" mean that the side of the semiconductor chip mounting portion from the electrode for connecting the semiconductor chip is referred to as "inside" and the side opposite to the semiconductor chip mounting portion is "outside". ". Also,
The power supply electrode and the ground electrode for connecting the semiconductor chip are electrodes respectively connected to the power supply electrode and the ground electrode of the semiconductor chip. By forming the wirings 15, 10, and 17 in this manner, after the wirings are drawn out from the electrodes, the power supply electrode,
The wiring connected to the ground electrode and the wiring of other potentials,
The adjacent wires are not provided adjacent to each other, and the distance between other wires near the power supply electrode and the ground electrode is increased, so that the characteristic impedances are not affected by each other.

In the above example, both the wirings 10 and 17 connected to the power supply electrode 20 and the ground electrode 19 are drawn inward from the electrodes for connecting the semiconductor chip, but either one of them has a considerable effect. Obtainable. Of course, it is more effective to bring out both of them as described above. On the other hand, on the lower surface, the wiring 2 connected from the wiring 15 on the upper surface through the through hole 12
6. External connection electrode 21 connected from the wiring
Are formed. The wiring connected to the power supply electrode and the ground electrode is connected to the external connection electrode 23 on the back surface through the through hole 13 and the wiring 25. Further, in this embodiment, the wiring connected to the ground electrode 19 is also connected to the copper foil of the semiconductor chip mounting portion 16. This reduces the number of through holes 13 inside the electrodes for connecting semiconductor chips. The copper foil of the semiconductor chip mounting portion 16 is the through hole 18 and the copper foil 22 provided in the central portion of the lower surface.
Is electrically connected to. And the copper foil 22 is the wiring 24
And is connected to the external connection electrode 23. The wiring 24 is
It was formed thick so that the electric resistance was lowered and a stable ground potential could be supplied. In this way, the copper foil 22
By forming the, the heat generated from the semiconductor chip is efficiently dissipated.

As the printed wiring board, as described above,
The present invention is not limited to the double-sided plate, and a multi-layered plate may be used. That is, each has a power supply layer and a grounding layer that have a power supply and a ground potential, and a wiring board of four layers including the upper and lower layers, or a combination of the power supply layer and the grounding layer. Thus, a three-layer wiring board may be used. In addition, the power supply,
The wiring for signals other than the ground may be provided by providing one or more layers in addition to the upper surface and the lower surface. It is necessary to increase the number of layers and provide signal wiring other than power supply and ground.
In particular, there is a high demand for a printed wiring board on which a plurality of semiconductor chips are mounted. In addition, when there are several types of power supplies for the semiconductor chip, there may be a plurality of power supply layers having different potentials. Even when a plurality of semiconductor chips are mounted and the potentials of the respective operating power supplies are different, it is conceivable to make the power supplies multilayer. As described above, the power supply electrode 20 and the ground electrode 19 for connecting the semiconductor chip may be connected to the power supply layer or the ground layer provided in the inner layer.

The electrode 1 for connecting the semiconductor chip on the upper surface
4, 19, 20 and the portion excluding the semiconductor chip mounting portion 16, and the portion excluding the external connection electrodes 21 and 23 on the lower surface,
A protective layer (not shown) is formed. A protective layer may be formed on the semiconductor chip mounting portion 16. The protective layer may be a solder resist used in a usual printed wiring board, and an epoxy-based material or the like is generally used. The upper surface side was provided with a shape as shown in FIG. In this way, the protective layer 31 on the outside of the semiconductor chip connecting electrode is formed.
Not only this, by providing the protective layer 32 also at a portion between the semiconductor chip mounting portion 33 and the semiconductor chip connecting electrode portion 34, the semiconductor chip electrode and the semiconductor chip connecting electrodes 14, 19, 20 are provided. When the bonding wires are connected to each other, there is no risk of insulation failure between the bonding wire and the wiring or through hole between the semiconductor chip mounting portion and the semiconductor chip connecting electrode.

A semiconductor chip is mounted on the wiring board thus obtained, and the electrodes of the semiconductor chip and the electrodes 14, 19 and 20 for connecting the semiconductor chip are connected by wire bonding, and the semiconductor chip mounting portion is provided if necessary. 16 and bonding wires and the vicinity of electrodes for connecting semiconductor chips are sealed with a resin such as epoxy to form a semiconductor module, which is mounted on, for example, a printed wiring board serving as a parent board. The connection of the parent board to the printed wiring board is performed by connecting the electrodes provided on the printed wiring board to the external connection electrodes 21 and 23 of the wiring board.
It is possible to connect between and using a solder bump. Specifically, as an example, the external connection electrode 2
Solder bumps can be formed on Nos. 1 and 23, mounted on a printed wiring board, heated by infrared rays, etc. to melt the solder bumps for connection. Further, as described above, the present invention can be applied even when not used as a semiconductor module and used as a COB.

Example 2 By the same method as in Example 1, a wiring board as shown in FIG. 4 was formed on the insulating substrate 11.
FIG. 4 is a top view. As the semiconductor chip mounting portion 46,
A portion where the copper foil remained was provided, and a semiconductor chip connecting electrode 44 was provided around it. The wiring from the power electrode and the ground electrode was drawn out toward the inside and connected to the external connection terminal provided on the lower surface side through the through hole 43, as in the first embodiment. Then, the wirings other than the power source and the ground electrode were led out to the outside and connected to the external connection electrodes 42 provided in the peripheral portion. Further, the protective layer may be formed in a shape as shown in FIG. 3 as in the first embodiment.

Then, as in the first embodiment, the semiconductor chip is mounted, the electrodes of the semiconductor chip and the electrodes for connecting the semiconductor chip 44 are connected by wire bonding, and if necessary, the semiconductor chip mounting portion 46 and the bonding wire, The semiconductor chip connecting electrode 44 is sealed with a resin such as epoxy and mounted on a printed wiring board for use. The printed wiring board of the present invention and the printed wiring board are connected to each other by wire bonding between the external connection electrode 42 of the wiring board and the electrode of the printed wiring board, or to the external connection electrode 42. A method of connecting the lead frame by thermocompression bonding or using solder and then connecting the lead frame to the printed wiring board is adopted. The external connection electrode on the back surface, which is connected to the power supply and the ground electrode, is connected to the printed wiring board using a solder bump or the like.

[0026]

According to the present invention, the characteristic impedance of the other wiring is not affected by the wiring electrically connected to the power supply electrode or the ground electrode, and the characteristic impedance of the other wiring is outside the electrode for connecting the semiconductor chip. Even if the distance between the wirings that are drawn out in the same direction is increased, the effect of the characteristic impedances of other wirings on each other can be reduced, making it easier to match the characteristic impedances with external circuits. Therefore, it is possible to obtain a printed wiring board from which electrical equipment is unlikely to generate electrical noise.

Furthermore, when a semiconductor chip is mounted and wire bonding is performed, it is possible to enhance the insulation between the wiring and the bonding wire. Therefore, when the semiconductor chip is mounted and wire bonding is performed. Thus, it is possible to obtain a printed wiring board that is unlikely to cause an electrical short.

[0028]

[Brief description of drawings]

FIG. 1 is a top view of a printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a bottom view of the printed wiring board according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a protective layer shape on the upper surface of the printed wiring board according to the first embodiment of the present invention.

FIG. 4 is a top view of a printed wiring board according to a second embodiment of the present invention.

[Explanation of symbols]

 10, 25 Power supply wiring 11 Insulating substrate 12, 13, 18, 43 Through hole 14, 44 Semiconductor chip connecting electrode 15, 26, 45 Wiring 16, 33, 46 Semiconductor chip mounting portion 17, 24, 47 Ground wiring 19 Ground electrode 20 power supply electrode 21, 23, 42 external connection electrode 22 copper foil 31, 32 protective layer 34 semiconductor chip connection electrode part

Claims (2)

[Claims] 1. A semiconductor chip mounting portion, an electrode for connecting a semiconductor chip formed around the semiconductor chip mounting portion, a wiring electrically connected to the electrode, and a surface of the wiring on an insulating substrate. In a printed wiring board having a protective layer for protecting the semiconductor chip, at least one of the wirings electrically connected to a power supply electrode or a ground electrode of a mounted semiconductor chip is an electrode for connecting a semiconductor chip. The printed wiring board is characterized in that it is drawn inward from the other wiring and the other wiring is drawn outward from the electrode for connecting the semiconductor chip. 2. The printed wiring board according to claim 1, wherein the protective layer is formed at least at a portion between the semiconductor chip mounting portion and the semiconductor chip connecting electrode.