JP2000251463A - Memory module - Google Patents

Abstract

(57) [Problem] To radiate electromagnetic noise increases as the operating frequency of a memory module increases. Also, CS
With the adoption of a high-density mounting method such as P, the occurrence of chip connection failure due to vibration or the like becomes a problem. Further, due to an increase in power consumption of the memory chip, measures against heat radiation are also required. SOLUTION: The memory module according to the present invention includes a shield sheet in which at least an adhesive sheet and an aluminum sheet are laminated, is bonded to an upper surface of the memory chip and an upper surface of the printed circuit board so as to cover the memory chip. And secure it to the printed circuit board. Thus, the electromagnetic noise radiated from the memory chip is shielded by the aluminum sheet.
Further, since the memory chip is fixed by the adhesive sheet, occurrence of connection failure due to vibration is suppressed. Furthermore, as a result of the aluminum sheet acting as a heat sink,
The heat dissipation of the memory module is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory module, and more particularly, to the prevention of noise and the improvement of vibration resistance of a memory module in which semiconductor memory chips operating at high speed are mounted at high density.

[0002]

2. Description of the Related Art In recent years, in the field of the computer industry, with the speeding up and miniaturization of notebook PCs and the like, memory modules used as main memories are also being sped up, downsized and highly integrated.

That is, in order to increase the speed of a memory module,
The operating frequency of memory modules is becoming higher. Further, in order to reduce the size and integration of the memory module, instead of the conventional mounting method of fixing the chip to the substrate via a lead frame, chip size packaging (hereinafter, CSP) in which the chip is directly fixed to the substrate by solder bumps.
High-density mounting methods such as those described above) have become mainstream.

[0004]

As the operating frequency of the memory module increases, electromagnetic noise radiated from the memory module increases. In addition, the operating frequencies of circuits other than the memory module are also increasing, and the electromagnetic noise entering the memory module is also increasing. For this reason, noise countermeasures for memory modules have become an important issue. However, with respect to the noise problem, conventionally, measures have been taken to surround a signal line inside the memory module substrate with a ground layer, but this is not sufficient, and no measure has been taken against noise from outside the module.

Further, when the memory module vibrates or the like, stress is applied to the connection between the memory chip and the printed circuit board. In the conventional mounting method, the stress caused by the vibration or the like is reduced by the lead frame. However, in a high-density mounting method such as CSP, it is difficult to alleviate the stress because it is fixed with small solder bumps. In addition, solder bumps generally have a small contact area,
Connection strength is weak. For this reason, a memory module using a high-density mounting method such as CSP has a problem that chip connection failure is likely to occur due to vibration or the like.

Further, as the operating frequency of the memory chip increases, the power consumption of the memory chip also increases, and it is necessary to take measures against heat radiation of the memory chip.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a memory module in which high-speed operating memory chips are mounted at high density, which is excellent in noise resistance and vibration resistance. The purpose is to do. Another object is to improve the heat dissipation of the memory module.

[0008]

In order to achieve the above object, a memory module according to the present invention is a memory module having a plurality of semiconductor memory chips mounted on a printed circuit board, comprising at least an adhesive sheet and an aluminum sheet. Are bonded to the upper surface of the semiconductor memory chip and the upper surface of the printed circuit board, covering the semiconductor memory chip, electromagnetically shielding the semiconductor memory chip, and fixing the semiconductor memory chip to the printed circuit board. It is characterized by doing.

Thus, electromagnetic noise radiated from the memory chip and electromagnetic noise entering the memory chip from the outside are shielded by the aluminum sheet. Further, since the memory chip is fixed to the printed circuit board by the adhesive sheet, occurrence of connection failure due to vibration is suppressed. Furthermore, the adhesive sheet is thin,
When heat from the memory chip is well conducted to the aluminum sheet via the adhesive sheet, the aluminum sheet acts as a heat radiating plate, so that the heat dissipation of the memory module is also improved.

Preferably, the pressure-sensitive adhesive sheet has an opening, and the aluminum sheet is connected to a ground electrode on the printed circuit board through the opening.
Thereby, the potential of the aluminum sheet is fixed to the ground potential, and the effect of shielding electromagnetic noise is improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 1A is a perspective view, FIG. 1B is a plan view, and FIG. 1C is a sectional view showing an example of a memory module according to the present invention.

The memory module of the present invention comprises a plurality of semiconductor memory chips 12 mounted on a printed circuit board 10, and an aluminum sheet 16 and an adhesive sheet 18.
Is laminated on the upper surface of the semiconductor memory chip 12 and the upper surface 10 of the printed circuit board so as to cover the semiconductor memory chip 12.

The printed circuit board 10 may be a board generally used for a memory module. For example, a board in which a wiring pattern made of copper or the like is formed on an insulating board made of glass epoxy or the like can be used.

On the printed circuit board 10, a plurality of semiconductor memory chips 12 are mounted by a mounting method such as CSP. The structure of the semiconductor memory chip 12 is as follows.
Although not particularly limited, for example, it has a structure in which a silicon substrate on which a memory element such as a DRAM is formed is sealed with an epoxy resin on an insulating substrate such as a polyimide. Although the mounting method is not particularly limited, for example, solder bumps are arranged in a matrix on the lower surface of the semiconductor memory chip 12 and the solder bumps are formed on the terminals formed on the printed circuit board 10. Implemented by connecting.

The shield sheet 14 is formed, for example, by laminating an aluminum sheet 16 and an adhesive sheet 18 as shown in FIG. 2 (a) plan view and (b) sectional view. The shield sheet 14 is adhered to the upper surface of the semiconductor memory chip 12 and the upper surface of the printed circuit board 10 so as to cover the semiconductor memory chip 12 with the adhesive sheet 18 as the lower surface. In order to secure a sufficient fixing strength of the semiconductor memory chip 12 to the printed circuit board 10, it is preferable that the shield sheet 14 has an area capable of covering a sufficiently wider range than the semiconductor memory chip 12.

The aluminum sheet 16 is not particularly limited as long as it can shield electromagnetic noise and can play a role as a heat radiating plate. However, since the shield sheet 14 preferably has flexibility so as to cover the semiconductor memory chip 12, it is preferable to reduce the thickness of the aluminum sheet 16 as long as the noise shielding effect and the heat radiation effect are not hindered. .
Although other metal sheets may be used instead of the aluminum sheet, the use of an aluminum sheet is preferable from the viewpoint of economy, thermal conductivity, and the like.

The adhesive sheet 18 is made of the aluminum sheet 1
6 can be used, as long as it can fix the semiconductor memory chip 12 to the printed circuit board 10, and any of paper, cloth, and polymer can be used. In addition, the adhesive sheet 1
8 is preferably a material having a high electrical insulation property so as to be in contact with the wiring pattern on the printed circuit board 10. The adhesive sheet 18 is preferably made of a material that can be repeatedly attached and detached. After bonding the shield sheet 14,
This is because work such as replacement of a semiconductor memory chip of a memory module may be required.

Further, it is preferable that the pressure-sensitive adhesive sheet 18 be capable of transmitting heat generated from the semiconductor memory chip 12 to the aluminum sheet 16 well. This is because aluminum has a high thermal conductivity and conducts heat to the aluminum sheet 16 so that the aluminum sheet 16 functions as a heat sink. Therefore, the pressure-sensitive adhesive sheet 18 is preferably thin as long as necessary insulation and adhesive strength can be maintained, and is preferably a material having high thermal conductivity.

In this embodiment, the case where the shield sheet has a two-layer structure of an adhesive sheet and an aluminum sheet has been described as an example, but the present invention is not limited to this structure. For example, the upper surface of the aluminum sheet may be covered with a thinner electrically insulating sheet to prevent a short circuit with another circuit board close to the memory module.

Embodiment 2 3A and 3B are a plan view and a cross-sectional view illustrating a shield sheet according to the present embodiment. The shield sheet 14 of the present embodiment is also formed by laminating the aluminum sheet 16 and the adhesive sheet 18,
The adhesive sheet 18 has an opening 18 a in a region directly adhered to the upper surface of the printed circuit board 10. The aluminum sheet 16 is processed so that it can contact the upper surface of the printed circuit board 10 through the opening 18a. That is, as shown in FIG. 3B, the aluminum sheet 16 is pressed so as to form a projection 16a projecting from the opening 18a. Further, instead of forming the projection 16a by press working, another metal member may be joined to the aluminum sheet 16 so as to project from the opening 18a.

FIG. 3C is a perspective view of the memory module according to the present embodiment. The shield sheet having the structure shown in FIGS.
And is adhered to the upper surface of the semiconductor memory chip 12 and the upper surface of the printed circuit board 10. A ground electrode 20 is formed on the printed circuit board 10, and is arranged so as to be in electrical contact with the protrusion 16 a of the aluminum sheet 16. Projection 16a of aluminum sheet 16
The electrical contact between the electrode and the ground electrode 20 is maintained by the adhesive force of the adhesive sheet 18 surrounding the protrusion 16a.

The ground electrode 20 is connected to a ground wire of a circuit constituting the memory module, and is formed by flash plating gold, for example.

In the present embodiment, since the potential of the aluminum sheet 16 is fixed to the ground potential by the ground electrode 20, the electromagnetic noise coming into and out of the memory module can be more effectively cut off. Further, since the area of the ground electrode of the memory module circuit itself is increased, noise in the memory module is also reduced.

[0024]

According to the memory module of the present invention, the semiconductor memory chip is shielded from the electromagnetic noise by the shield sheet and is fixed to the printed circuit board. High vibration resistance. In addition, since the aluminum sheet in the shield sheet can serve as a heat radiating plate, heat dissipation is also good.

Also, by connecting the aluminum sheet in the shield sheet to the ground electrode of the printed circuit board, the effect of shielding the electromagnetic noise of the aluminum sheet is improved, and the electromagnetic noise emitted from the memory module of the present invention to the outside is further improved. Can be reduced.

[Brief description of the drawings]

1A is a perspective view, FIG. 1B is a plan view, and FIG. 1C is a cross-sectional view illustrating a memory module according to a first embodiment of the present invention.

FIG. 2A is a plan view and FIG. 2B is a cross-sectional view illustrating the shield sheet according to the first embodiment of the present invention.

3 (a) and (b) show Embodiment 2 of the present invention.
It is a plan view and a cross-sectional view showing a shield sheet,
(C) is a perspective view showing a memory module according to Embodiment 2 of the present invention.

[Explanation of symbols]

10 printed circuit board, 12 semiconductor memory chip,
14 Shield sheet, 16 Aluminum sheet, 1
8 adhesive sheet, 20 ground electrode, 16a protrusion, 1
8a Opening.

Claims (2)

[Claims] 1. A memory module comprising a plurality of semiconductor memory chips mounted on a printed circuit board, comprising: a shield sheet formed by laminating at least an adhesive sheet and an aluminum sheet; A memory module adhered to an upper surface of the semiconductor memory chip and an upper surface of the printed circuit board to electromagnetically shield the semiconductor memory chip and to be fixed to the printed circuit board; 2. The adhesive sheet according to claim 1, wherein the adhesive sheet has an opening, and the aluminum sheet is connected to a ground electrode on the printed circuit board through the opening.
A memory module as described.