JPH09293943A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mount an LSI which generates heat such as a TCP highly efficiently by simple process control by not providing a through hole in a fixed range inside and outside an edge of an LSI chip of a mount region of an LSI chip. SOLUTION: A printed wiring board 3 is not provided with a through hole 3 in a specified region 11 of a part whereon an LSI chip 1 is mounted. An outer diameter of the specified region 11 is made larger than an outer diameter of the LSI chip 1 and than a region whereto and adhesive agent 2 for fixing the LSI chip 1 to be mounted is applied. An inner diameter of the specified region 11 is made smaller than an outer diameter of the LSI chip 1 by a specified amount. Therefore, it is possible to avoid contact defect, etc., generated by change of the state of the adhesive agent 2 caused by the fact that preliminary solder stops up the through hole 3 provided for heat dissipation of the LSI chip 1 which generates heat without complicating control of an application amount and an application region of the adhesive agent 2.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an LSI (Large Sc
Related to printed wiring boards with ale integration, large-scale integrated circuits, especially exposed chip type TCP (Tap
The present invention relates to a printed wiring board suitable for mounting a heat-generating LSI such as an e carrier package) with high reliability and efficiency.

[0002]

2. Description of the Related Art In a printed wiring board on which a heat-generating LSI such as TCP is mounted, through holes are provided in a grid pattern in a region where the LSI is mounted, and L is provided through the through holes.
The heat generated by the SI is passed to the back side of the printed wiring board and is radiated by the heat sink provided on the back side. Conventionally,
Through holes in printed wiring boards are, for example, "Su
As described in "TCP mounting of sub-notebook personal computer" in rface Mounting Technology Forum '95 ", it is provided in a grid pattern regardless of the chip size (end face) or the adhesive application area.

FIG. 5 is an explanatory view showing a state in which an LSI is mounted on a conventional printed wiring board, and FIG. 6 is an explanatory view showing an arrangement example of through holes on the conventional printed wiring board. FIG. 5 shows an example of TCP mounting.
Is TCP, 2 is an electrically and thermally conductive adhesive (die attach agent), 3 is copper-plated through-holes for heat dissipation provided in a grid pattern, 4 is a ground solid pattern, and 5 is TC.
P cover, 6 is a film for TCP1 wiring, 7 is TC
An outer lead as a wiring terminal of P1, 8 is a copper pattern for wiring on the film 6, 9 is a solder pad for the outer lead 7, and 10c is a printed wiring board.

Normally, the TCP 1 cannot be mounted and soldered in the same manner as other surface mounted components (collective solder reflow mounting), and it is necessary to individually solder the printed wiring board 8. At this time, the through holes 3 and TC provided in the ground solid pattern 4 on the printed wiring board 8
The positional relationship with P1 is as shown in FIG. 6, that is, the through hole 3 is also provided near the edge of the TCP1, and the problems described below occur.

That is, in such a printed wiring board 10c on which the TCP1 is mounted, a preliminary solder (pre-solder) for soldering the outer lead 7 of the TCP1 body to the solder pad 9 of the printed wiring board 10c.
However, it is also attached to the ground solid pattern 4 under TCP1. The spare solder may enter the through hole 3 and block the through hole 3. Further, in the area where the TCP1 is mounted, the area which is almost the same as the lower surface of the TCP1
An adhesive agent 2 for fixing the TCP 1 to the printed wiring board 10c is applied.

When the adhesive 2 under the TCP 1 is cured (dried), the air in the through hole 3 closed by the solder expands and lifts the adhesive 2, and the adhesive 2 rises from the edge of the TCP 1 and erupts. It may be in a different state. Here, the TCP 1 is attached to the film 6 due to its structure, and the film 6 is wired up to the outer lead 7 portion. That is, the film 6 is provided with a copper pattern 8 formed by etching a copper foil attached in advance, and the outer lead 7 is provided via the copper pattern 8.
It is wired up to the part. This TCP1 copper pattern 8
Or, the solder in an erupted state may approach the connection portion (inner lead) between the copper pattern 8 and the outer lead 7, or may cause a short circuit in some cases.

In order to deal with such a problem, it is considered that the application amount of the adhesive 2 is reduced and the application area is narrowed. By doing this, even if the adhesive is lifted by the expanded air during curing,
It does not protrude from the edge of TCP1. But like this,
When the application amount of the adhesive 2 is reduced or the application area is narrowed, the adhesive force is reduced, and the printed wiring board 10c of the TCP1 is
Problems such as peeling from the surface occur. In order to deal with such a peeling problem, it is necessary to accurately control the application amount of the adhesive agent 2, which increases the production cost.

Further, the pre-solder of the printed wiring board 10c enters the through hole 3 to block or not block the through hole, so that the TCP of the adhesive 2 is formed.
In some cases, the coating amount under 1 does not become constant, uniform and sufficient adhesive strength cannot be obtained over the whole, and the TCP 1 peels off from the printed wiring board 10c.

[0009]

The problem to be solved by the prior art is that, in the prior art, a conductive heat conductive adhesive agent resulting from preliminary solder flowing into a through hole provided for heat dissipation of a heat generating LSI such as TCP. That is, it is impossible to avoid the contact failure or the like that occurs due to the state change without complicating the management of the adhesive application amount and the application area. The object of the present invention is to solve the problems of these conventional techniques, and to
Highly reliable mounting of heat-generating LSI with simple process control
In addition, it is to provide a printed wiring board that can be performed with high efficiency.

[0010]

In order to achieve the above object, the printed wiring board of the present invention is (1) for releasing heat generated by an LSI chip (TCP1) fixedly mounted with an adhesive 2. A printed wiring board having a plurality of through holes 3 in a mounting area of an LSI chip, wherein the through holes 3 are not provided at least in a predetermined range inside and outside the edge of the LSI chip in the mounting area of the LSI chip. And (2) A printed wiring board having a plurality of through holes 3 for releasing heat generated by an LSI chip (TCP1) fixedly mounted with an adhesive 2 in a mounting area of the LSI chip, which is at least LS
It is characterized in that the through hole 3 is not provided in the application area of the adhesive 2 for fixing the I-chip and a predetermined area outside the contact area with the application area. (3) In the printed wiring board described in (1) or (2), the LSI chip includes at least an LSI chip.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, by arranging the arrangement of through holes for heat dissipation, it is possible to prevent spare solder for connecting outer leads from flowing into the through holes without special process control. . For example, TC
No through hole is provided in a predetermined range of the area where the P is mounted, particularly inside and outside the edge of the TCP. In addition, TC
A through hole is provided in the central portion of P to radiate heat.
As a result, even if the through hole is blocked by the preliminary solder in the central portion of the TCP, the adhesive that is pushed by the rising of the preliminary solder due to the air in the through hole expanded by the heat during curing. Stays in the lower surface of the TCP and does not overflow from the edge of the TCP and come into contact with the copper pattern for wiring of the film or the connecting portion (inner lead) of the outer lead with TCP.

It is also possible that no through hole is provided in the entire area that is wider than the area of the lower surface of the TCP by a predetermined amount. In this case, the heat generated by TCP is radiated to the back side through through holes provided in the periphery. Alternatively, only a portion facing the lower surface of the TCP is directly radiated by using a material having high thermal conductivity. As a result, it is possible to completely prevent the contact of the adhesive due to curing. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view showing a first embodiment of the printed wiring board of the present invention. This example shows an example of mounting a TCP. In FIG. 1, 1 to 9 are TCP 1, a conductive and thermally conductive adhesive 2, a heat radiating through hole 3, a ground solid pattern 4, respectively in FIG. The TCP cover 5, the wiring film 6, the outer leads 7, the copper patterns 8, and the solder pads 9, 10 is a printed wiring board according to the present invention, and 11 is a specific area where the through holes 3 are not provided.

Usually, the mounting of the TCP1 on the printed wiring board 10 is performed by individual reflow, not by batch reflow. Techniques for mounting and mounting the outer leads 7 on the printed wiring board 10 include a heat tool bond method (the principle is the same as that of a soldering iron, the outer leads 7 are pressed by a pulse heating method heating tool), and laser beam reflow. There are various methods such as a method (irradiating the soldering portion with a laser) or an IR reflow method (infrared rays emitted from an infrared lamp are condensed by a reflecting mirror and soldered).

In any of these techniques, in order to mount the outer leads 7 on the printed wiring board 10,
On the mounting pad 9 of the printed wiring board 10 of TCP1,
It is necessary to provide a spare pre-solder. In general,
Techniques for providing solder on the surface of the printed wiring board 10 include a solder coat (solder leveler) and electrolytic solder plating. However, it is difficult to secure a fixed amount of solder of about 20 to 30 μm necessary for such soldering. There are the following techniques for forming a solder on the printed wiring board 10 to cope with such a problem.

(A) Partial solder peeling method: Like the conventional printed wiring board, electric solder plating is performed, and after etching, unnecessary portions of solder are removed. (B) Super solder method: Organic acid lead and organic acid tin are applied and a heat treatment reaction is performed to synthesize solder in the paste. (C) Superjafite method: A chemical treatment that selectively reacts with copper is applied. (D) Beam solder PC: Substitution type electroless plating is used. However, in any of these techniques, there are many cases in which the solder is or is not buried in the through hole 3 of the printed wiring board 10. In order to completely prevent the solder from being buried in the through hole 3, there are problems in the manufacturing method such as discoloration of the copper foil and an increase in purchase price.

The mounting process of the TCP 1 on the printed wiring board 10 generally includes the following steps. (B) Solder paste printing on the printed wiring board 10. (B) Parts mounting. (C) Reflow. (D) Mounting of TCP1 (application of adhesive 2 and soldering). (E) Heat sink attached.

Through holes 3 for radiating heat to the back surface of the printed wiring board 10 are provided inside the ground solid pattern 4 provided on the printed wiring board 10 on which the TCP 1 is mounted. (For example, 1 mm intervals). Through hole diameter is 0.2-0.
About 4 mm is suitable. A conductive adhesive 2 having a high thermal conductivity is applied to the central portion of the ground pattern 4.

In the printed wiring board 10 of this example, T
The through hole 3 is not provided in the specific region 11 where the CP1 is mounted. The outer diameter of the specific area 11 is at least larger than the outer diameter of the TCP1 and larger than the area to which the adhesive 2 for fixing the mounted TCP1 is applied. In addition, the specific area 11
The inner diameter of is at least smaller than the outer diameter of TCP1 by a predetermined amount.

As described above, the through hole 3 is not provided in the printed wiring board 10 of this example near the edge of the mounted TCP 1. As a result, the solder pad 9
The state in which the through hole 3 is blocked by the spare solder for use occurs only in the central portion of the TCP 1. As a result, even if the adhesive 2 is applied in a range slightly protruding from the lower surface of the TCP 1, the adhesive 2 is not pushed by the expansion of the air in the through hole 3 at the time of curing. It is easy to control range without requiring high accuracy. Further, even if the adhesive 2 is pushed in the central portion of the TCP 1 due to the expansion of the air in the through hole 3 at the time of curing, the adhesive 2 does not overflow from the edge of the TCP 1 and the adhesive 2 The copper pattern 8 below the film 6 does not come into contact with it to cause a short circuit.

FIG. 2 is an explanatory view showing an arrangement example of through holes on the printed wiring board of the present invention. This example shows a mounting example of TCP1 as in FIG.
A specific region 11 without the through hole 3 is provided around the edge of the TCP 1 and the adhesive may overflow from the edge of the TCP 1 due to the expansion of the air in the through hole 3 during curing. Instead, the adhesive is the film 6 of FIG.
It does not come into contact with the lower copper pattern 8 to cause a short circuit.

FIG. 3 is an explanatory view showing a second embodiment of the printed wiring board of the present invention. Printed wiring board 10 of this example
In a, the through holes 3 for heat dissipation are arranged in a zigzag pattern instead of a grid pattern. in this way,
By arranging the through holes 3 in a zigzag pattern,
Compared to the case shown in FIGS. 1 and 2, the through hole 3
The number of can be doubled, and the heat dissipation effect can be improved.

FIG. 4 is an explanatory view showing a third embodiment of the printed wiring board of the present invention. Printed wiring board 10 of this example
In b, the through holes 3 for heat dissipation are not provided at all under the TCP 1 and in the vicinity of the edge thereof. As a result, there is no difference in the presence or absence of the closed state of the through hole 3 due to the preliminary solder, and the presence or absence of inflow of the adhesive 2 into the through hole 3 due to the difference in the closed state, and the adhesive 2 under the TCP 1 The amount becomes constant. In this case, the heat of TCP1 is radiated to the back side through through holes 3 provided in the periphery. Alternatively, only a portion facing the lower surface of the TCP1 is directly radiated by using a material having high thermal conductivity.

As described above with reference to FIGS. 1 to 4, in the printed wiring boards 10 to 10b of this embodiment, since there is no through hole 3 for heat dissipation at least in the vicinity of the edge of the TCP 1, a spare is formed. The solder does not block the through holes 3 and the adhesive 2 does not overflow during curing. As a result, it is possible to improve the reliability and efficiency of the process related to TCP mounting, and as a result, to improve the performance of the TCP mounted printed wiring board. Further, by arranging the through holes 3 in a zigzag pattern, the number of through holes can be doubled and the heat dissipation effect can be improved. Furthermore, since the through hole 3 is not provided over the entire area where the adhesive 2 is applied under the TCP 1, the amount of the adhesive 2 applied can be kept constant.

The present invention is not limited to the embodiment described with reference to FIGS. 1 to 4, and various modifications can be made without departing from the scope of the invention. For example, the area where the adhesive 2 is applied is made smaller than the area of the lower surface of the TCP 1,
Manage the adhesive 2 so that it is not applied around TCP1,
By limiting to the central portion of CP1, more effective results can be obtained.

[0026]

According to the present invention, L, which generates heat, such as TCP
Avoid contact failure and the like caused by the change in the state of the adhesive due to the blockage of the through-hole provided for SI heat dissipation without complicating the management of the amount and area of application of the adhesive. It is possible to mount TCP and the like with high reliability and high efficiency by simple process control.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a first embodiment of a printed wiring board of the present invention.

FIG. 2 is an explanatory view showing an arrangement example of through holes on the printed wiring board of the present invention.

FIG. 3 is an explanatory diagram showing a second embodiment of the printed wiring board of the present invention.

FIG. 4 is an explanatory diagram showing a third embodiment of the printed wiring board of the present invention.

FIG. 5 is an explanatory diagram showing a state in which an LSI is mounted on a conventional printed wiring board.

FIG. 6 is an explanatory diagram showing an arrangement example of through holes on a conventional printed wiring board.

[Explanation of symbols] 1: TCP, 2: adhesive, 3: through hole, 4: ground solid pattern, 5: TCP cover, 6: film,
7: outer lead, 8: copper pattern, 9: solder pad, 10, 10a to 10c: printed wiring board, 11: specific region.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigetoshi Yoshinaga 1 Ikegami, Haruoka-cho, Owariasahi-shi, Aichi Stock Company Hitachi Office Systems Division (72) Inventor Noboru Kawakami 1 Ikegami, Haruoka-cho, Owariasaichi, Aichi Stock Hitachi Systems Office Systems Division

Claims (3)

[Claims] 1. A printed wiring board having a plurality of through holes for releasing heat generated by an LSI chip fixedly mounted with an adhesive, the printed wiring board having at least the LSI chip mounting area. A printed wiring board, wherein the through hole is not provided in a predetermined range inside and outside the edge of the LSI chip in the mounting area. 2. A printed wiring board having a plurality of through holes for releasing heat generated by an LSI chip fixed by an adhesive and mounted therein, the printed wiring board having at least the LSI chip. A printed wiring board characterized in that the through hole is not provided in a predetermined area outside the area where the adhesive is applied and for fixing the adhesive. 3. The printed wiring board according to claim 1 or 2, wherein the LSI chip includes at least TCP.