JPH0883862A - Circuit board and method for manufacturing circuit board - Google Patents

Abstract

PURPOSE: To prevent a bump from being bonded to an IC chip or separated from a lead by making a hole, corresponding to the lead, through a board in the vicinity of the IC chip. CONSTITUTION: A lead 32 is formed, at first, on an insulating sheet 2 and a bump 38 is formed at a part where the lead 32 touches the IC chip 33. Subsequently, the IC chip 33 is face down mounted on the lead 32 and pressed or heated to bond the IC chip 33 and the lead 32 through the bump 38. The insulating sheet 2 is then irradiated with excimer laser light from the side provided no lead 32. Since the excimer laser light can remove the polyimide composing the insulating sheet 2 selectively, a hole 34 corresponding to each lead 32 can be made through the insulating sheet 2 without damaging the insulating sheet 2 or the IC chip 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board and a method for manufacturing the circuit board.

[0002]

2. Description of the Related Art Conventionally, a bare chip mounting method for mounting an IC chip, which is not provided with a package called a bare chip on a circuit board, has been often performed for the purpose of miniaturizing a circuit board and mounting IC chips at a high density. ,Also,
Circuit boards on which IC chips are mounted by this bare chip mounting method are used in various devices.

A flip chip method is known as a bare chip mounting method. This method consists of
This is a method of arranging the IC chip in a face-down manner in which the circuit surface of the C chip is turned down, and directly connecting the terminals of the IC chip and the conducting wires on the substrate. In this method, the terminals of the IC chip and the conductive wires are usually joined by solder plating or the like, and all the joining points are joined simultaneously for each IC chip. Therefore, the flip-chip method is very suitable when a large number of bonding points are required, and since each bonding point is on the projection plane of the IC chip on the substrate, it is also excellent in high-density mounting of IC chips. There is a feature that

This IC chip mounting method by the flip chip method is disclosed in Japanese Patent Application No. 5-1068 filed by the present applicant.
It can also be applied to the case of manufacturing the recording head for the image forming apparatus disclosed in the specification of No. 84. In this recording head for an image forming apparatus, as shown in FIG. 9, an insulating sheet 102 made of polyimide is held on a holding member 130, and a conductive wire 132 is formed on the insulating sheet 102. Then, a plurality of IC chips 133 are formed on the insulating sheet 2.
Are placed in a line in the longitudinal direction of the insulating sheet 2, and the terminals of the IC chip 133 are connected to the conducting wires 132.

At the mounting portion of the IC chip 133, as shown in the enlarged views of FIGS. 10 and 11, the conductive wire 132 made of a copper film is fixed on the insulating sheet 102 made of polyimide.
The leads 132 and the terminals of the IC chip 133 are joined by bumps 138.

[0006]

However, in the circuit board adopting the flip chip method as described above, the polyimide forming the insulating sheet 102 and the IC chip 13 are formed.
Since the coefficient of thermal expansion of the silicon constituting 3 is different,
As the temperature changes, the insulating sheet 102 and the IC chip 13
There may be a difference in the expansion amount of No. 3. At this time, since the conductor wire 132 to which the terminals of the IC chip 133 are joined is fixed on the insulating sheet 102, the conductor wire 132 is restrained by the insulating sheet 102 and cannot follow the expansion of the IC chip 133. . Therefore, the IC chip 133
There is a case where distortion occurs in the bump 138 portion that joins the lead wire 132 and the lead wire 132, and the IC chip 133 and the bump 138 may come off, or the bump 138 and the lead wire 132 may come off, causing a serious problem in terms of reliability. Was becoming.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a circuit board and a method of manufacturing the circuit board which are inexpensive and have excellent reliability.

[0008]

In order to achieve this object, in a circuit board according to a first aspect of the present invention, there is provided a substrate formed of an insulating base material, a conductor wire provided on the substrate, and the substrate. And an IC chip mounted on the substrate and connected to the conducting wire, and a hole provided in the substrate in the vicinity of the IC chip so as to correspond to the conducting wire.

In the method of manufacturing a circuit board according to a second aspect of the present invention, the step of providing a conductive wire on a substrate made of an insulating base material and the IC chip placed on the surface of the substrate on which the conductive wire is provided. Then, a step of connecting the conducting wire and the IC chip and a step of selectively removing the insulating base material from the surface of the substrate on which the IC chip is not mounted are provided.

Further, in the method of manufacturing a circuit board according to a third aspect of the present invention, in the process of selectively removing the insulating base material according to the second aspect of the invention, corresponding to each conductor wire connected to the IC chip. The insulating base material of the substrate is removed in the vicinity of the IC chip.

Further, in the method of manufacturing a circuit board according to a fourth aspect of the invention, in the step of removing the insulating base material of the second or third aspect of the invention, the insulating base material is removed by laser light irradiation. I am trying.

[0012]

In the circuit board according to the first aspect of the present invention having the above structure, the conductive wire is provided on the board made of the insulating base material, and the IC chip is mounted. With this board,
Holes are formed in the substrate in the vicinity of the IC chip so as to correspond to the conductive wires, and the strain between the IC chip and the substrate due to thermal expansion is prevented because the conductive wires straddling the holes are not bound by the substrate. It is absorbed by the expansion and contraction of the conductor part that crosses over. Therefore, the terminal of the IC chip and the connecting point of the conductive wire are not displaced or displaced due to the coefficient of thermal expansion.

According to another aspect of the invention of the method of manufacturing a circuit board, the conductive wire is formed on the substrate made of an insulating base material, and then the IC chip is placed on the surface of the substrate on which the conductive wire is provided. , The conductor and the IC chip are connected. After that, since the insulating base material of the substrate is selectively removed from the surface of the substrate on the side where the IC chip is not mounted, the substrate on which the IC chip is held by the conductive wire is manufactured.

According to the invention of the method for manufacturing a circuit board of claim 3, in the step of selectively removing the insulating base material of the invention of the method for manufacturing a circuit board according to claim 2, each conductive wire connected to the IC chip is connected. Corresponding to, the insulating base material of the substrate is
Since each is removed in the vicinity of the chip, the circuit board having holes in the board is manufactured in correspondence with the respective conductive wires in the vicinity of the IC chip without impairing the strength of the circuit board.

In the invention of the method for manufacturing a circuit board according to claim 4, in the step of selectively removing the insulating base material of the invention of the method for manufacturing a circuit board according to claim 2 or 3, the irradiation with laser light is performed. The insulating base material is removed. Therefore, the insulating base material can be easily and surely removed, and the conductor wire is not broken.

[0016]

An embodiment of the present invention will be described below with reference to the drawings.

First, the structure of a recording head 1 for an image forming apparatus, which is an embodiment of the circuit board of the present invention, will be described with reference to FIG.

In the recording head 1 for the image forming apparatus, the insulating sheet 2 made of polyimide having a thickness of 25 μm is placed on the holding member 30 having the slit portion 35 which is continuous in the longitudinal direction at the center thereof. A plurality of conductors 32 made of a copper film having a thickness of 8 μm are formed in parallel on the sheet 2. On the insulating sheet 2 at the end of the conductor 32, a plurality of IC chips 33 are placed in a line in the longitudinal direction of the insulating sheet 2, and each terminal of the IC chip 33 is connected to the conductor 32.

Although not shown, a plurality of apertures each having a diameter of about 60 μm for allowing toner to pass through are provided at the end of the conductor 32 on the side where the IC chip 33 is not mounted, in the longitudinal direction of the insulating sheet 2. Are formed in a row. Also,
Around each aperture, a control electrode (not shown) for controlling the toner flow by turning on / off an electric field in the aperture is provided.

Here, the IC chip 33 is provided to control the application of a voltage to each control electrode (not shown) via the conductor 32.

As a material for the insulating sheet 2, polyimide is usually preferable because of its electrical and mechanical characteristics.
It can also be used with polyester. Furthermore, the insulation sheet 2
A connecting portion 36 serving as a connector is provided at an end portion in the longitudinal direction of the.

Then, the recording head 1 for the image forming apparatus.
Are fixed on the holding member 30 as shown in FIG. Here, the holding member 30 is sufficient as long as it is a rigid body, but it is preferable that the holding member 30 is made of a member having a coefficient of thermal expansion similar to that of polyimide, which is a material of the insulating sheet 2. For example, as the material of the holding member 30, an aluminum alloy such as duralumin, a copper alloy such as bronze or brass, or a metal material such as stainless steel can be used. Further, the slit portion 35 provided at the center of the holding member 30 is provided for supplying the toner to the aperture.

Next, the structure of the mounting portion of the IC chip 33 of the recording head 1 for the image forming apparatus will be described with reference to FIG.

FIG. 2 shows the recording head 1 for the image forming apparatus.
3 is an enlarged view of a mounting portion of an IC chip 33 of FIG. FIG. 3 shows an IC chip 33 of the recording head 1 for the image forming apparatus shown in FIG.
FIG. 9 is a cross-sectional view taken along the line AA ′ of the enlarged view of the mounting portion of FIG.

One IC chip 3 is formed on the insulating sheet 2.
A large number of conducting wires 32 are inserted into the number 3. Where I
The C chip 33 and the conductive wire 32 are joined via a bump 38 described later. In addition, as shown in FIG. 2 and FIG.
Each conductive wire 32 is attached to the insulating sheet 2 near the IC chip 33.
Holes 34 having a width slightly wider than that of the conductors 32 are provided corresponding to the conductors 32, respectively.

Next, a method of manufacturing the recording head 1 for the image forming apparatus will be described with reference to FIG.

FIG. 4 is a diagram showing a manufacturing process of the recording head 1 for an image forming apparatus according to an embodiment of the present invention.

First, as shown in FIG. 4A, the conductive wire 32 is formed on the insulating sheet 2 made of polyimide. The conductive wire 32 can be formed by any conductive wire forming method such as an etching method or a printing method, but in order to form a rigid conductive wire, for example, copper is formed on the insulating sheet 2 made of polyimide. It is desirable to use an etching method in which a film with a film is adhered, a protective film is formed on a portion of the copper film to be left as a pattern, and then the copper film portion having no protective film is dissolved with an acid.
In this etching method, a protective film may be formed on a portion to be left as a pattern by a printing method or may be formed by a photographic method.

Next, as shown in FIG.
The bumps 38 are formed on the portions that come into contact with the IC chip 33. The bump 38 is a member made of gold, solder, or the like and having a thickness of several tens of μm, and is provided so that the IC chip 33 and the conductive wire 32 are well bonded. The bump 38 may be provided on the conductive wire 32 as in the present embodiment, or may be provided on the terminal side of the IC chip 33. To form the bumps 38 on the conductive wire 32, the bumps 38 are transferred onto the conductive wire 32 by a method such as a transfer bump. Further, the IC chip 33 and the conductive wire 32 may be directly bonded without providing the bump 38.

Next, as shown in FIG. 4C, the IC chip 33 is mounted face down on the conductive wire 32. Then, by applying pressure or heating, the IC chip 33 and the conductive wire 32 are joined by the bump 38.

Next, as shown in FIG. 4 (d), the surface of the insulating sheet 2 on which the conductive wire 32 is not provided is cut off from the surface of the insulating sheet 2.
The excimer laser light is irradiated to. Since the excimer laser light can selectively remove the polyimide forming the insulating sheet 2 by the ablation action, the polyimide in the irradiated area disappears, and the conductive wire 32 and the IC are removed.
It is possible to form the holes 34 in the insulating sheet 2 corresponding to the conductors 32 without damaging the chips 33.
Here, the beam of excimer laser light may be shaped and irradiated in the shape of the hole 34, or may be scanned so as to have the shape of the hole 34. As shown in FIGS. In the vicinity, the recording head 1 for an image forming apparatus having the holes corresponding to the conductive wires 32 in the insulating sheet 2 can be manufactured.

As described above in detail, in the recording head 1 for the image forming apparatus of this embodiment, the holes 34 corresponding to the conductors 32 are formed in the insulating sheet 2 made of polyimide in the vicinity of the IC chip 33. Therefore, the IC chip 33 formed of silicon is held by the conductive wire 32,
The chip 33 is less likely to be constrained by the insulating sheet 2 made of polyimide. Therefore, the distortion caused by the thermal expansion of the insulating sheet 2 made of polyimide and the IC chip 33 made of silicon, which have a large difference in the coefficient of thermal expansion, is caused by the conductive wire 32 straddling the hole 34.
Is absorbed by the expansion and contraction of the portion of FIG.
The joint part of 2 does not come off or shift. Further, the insulating sheet 2 is provided in the vicinity of the IC chip 33 so that each conductor 3
Since only a part of the polyimide corresponding to 2 is removed to form the holes, the strength of the insulating sheet 2 is not impaired. Therefore, the recording head 1 for a highly reliable image forming apparatus
Can be provided.

Further, in the method of manufacturing the recording head for the image forming apparatus of this embodiment, the conductive wire 32 is formed on the insulating sheet 2, the IC chip 33 is placed, and then a part of the insulating sheet 2 is selectively selected. Moreover, since the back surface of the insulating sheet 2 is removed by excimer laser light, the selective removal of the insulating sheet 2 can be performed easily and reliably. Furthermore, since it is removed by the excimer laser light, it is possible to selectively remove a part of the insulating sheet 2 without damaging the conducting wire 32 and the IC chip 33.

The present invention is not limited to the embodiments described in detail above, and various modifications can be made without departing from the spirit of the invention.

For example, as shown in FIG. 5 and FIG.
The back surface insulating sheet 2 on which the chip 33 is placed may be removed in an area larger than the area of the IC chip 33. As a result, the IC chip 33 is completely held only by the conductive wire 32, and the absorption of strain due to thermal expansion by the conductive wire 32 becomes more reliable.

Further, instead of removing the insulating sheet 2 made of polyimide to form the holes, as shown in FIGS. 7 and 8, part of the portion close to the IC chip 33 is left by stepwise processing. May be. Even with such a shape, the partially left polyimide is subordinate to the thermal deformation of silicon of the IC chip 33 and prevents damage to the connection between the IC chip 33 and the bump 38 or between the bump 38 and the conductive wire 32. be able to.

Further, in the present embodiment, the holes 34 are processed by the excimer laser, but carbon dioxide laser, YAG
Other optical processing methods such as a laser and a semiconductor laser, a chemical etching method, a mechanical processing method using a milling machine and the like can also be used.

[0038]

As is apparent from the above description,
In the circuit board of the invention of claim 1, since holes are formed in the board in the vicinity of the IC chip so as to correspond to the respective conducting wires, the strain between the IC chip and the board due to thermal expansion is
It is absorbed by the expansion and contraction of the conductive wire in the portion that straddles this hole, and the connection between the IC chip terminal and the conductive wire is disconnected due to stress due to strain.
It is possible to prevent shifting.

Further, in the invention of the method for manufacturing a circuit board according to claim 2, by holding the IC chip by the conductive wire, the strain between the substrate and the IC chip due to thermal expansion is absorbed by the expansion and contraction of the conductive wire, and the stress caused by the strain is applied. It is possible to manufacture a substrate in which the conductor wire and the IC chip are not disconnected or displaced.

Further, in the invention of the method for manufacturing a circuit board according to claim 3, the insulating base material of the substrate is removed in the vicinity of the IC chip in correspondence with each conductive wire connected to the IC chip, Since each of the holes is provided in the substrate, the strength of the substrate is not impaired, and the strain between the substrate and the IC chip due to thermal expansion is absorbed by the conductor wire portion that crosses the hole, and the stress due to the strain connects the conductor wire and the IC chip. It is possible to manufacture a substrate that does not come off or shift.

In the invention of the method for manufacturing a circuit board according to claim 4, since the insulating base material is removed by laser light irradiation, the insulating base material can be easily and surely removed, and the conductor wire can be disconnected. Absent.

[Brief description of drawings]

FIG. 1 is a perspective view showing a recording head which is an embodiment of the present invention.

FIG. 2 is an enlarged view of the vicinity of an IC chip mounting portion of the recording head shown in FIG.

FIG. 3 is a cross-sectional view taken along the line AA ′ of the enlarged view of the vicinity of the IC chip mounting portion of the recording head shown in FIG.

FIG. 4 is a cross-sectional view showing the manufacturing process of the recording head according to the embodiment of the invention.

FIG. 5 is an IC of a recording head according to a second embodiment of the present invention.
It is an enlarged view of the vicinity of the chip mounting portion.

6 is a cross-sectional view taken along the line AA ′ of the enlarged view of the vicinity of the IC chip mounting portion of the recording head shown in FIG.

FIG. 7 is an IC of a recording head according to a third embodiment of the present invention.
It is an enlarged view of the vicinity of the chip mounting portion.

8 is a cross-sectional view taken along the line AA ′ of the enlarged view of the vicinity of the IC chip mounting portion of the recording head shown in FIG.

FIG. 9 is a perspective view showing a conventional recording head.

10 is an enlarged view of the vicinity of an IC chip mounting portion of the recording head shown in FIG.

11 is a cross-sectional view taken along the line AA ′ of the enlarged view of the vicinity of the IC chip mounting portion of the recording head shown in FIG.

[Explanation of symbols]

 1 Aperture electrode body 2 Insulating sheet 30 Holding member 32 Conductive wire 33 IC chip 35 Slit part 34 Hole 36 Connection part 38 Bump

Claims (4)

[Claims] 1. A substrate formed of an insulating base material, a conductor wire provided on the substrate, an IC chip mounted on the substrate and connected to the conductor wire, and in the vicinity of the IC chip. And a hole provided in each of the boards in correspondence with the conductor wire. 2. A step of providing a conductive wire on a substrate made of an insulating base material, a step of placing an IC chip on a surface of the substrate on which the conductive wire is provided, and connecting the conductive wire and the IC chip. And a step of selectively removing the insulating base material from the surface of the substrate on which the IC chip is not mounted, the method for manufacturing a circuit substrate. 3. In the step of selectively removing the insulating base material, corresponding to each conductive wire connected to the IC chip,
The method for manufacturing a circuit board according to claim 2, wherein the insulating base material of the board is removed in the vicinity of the IC chip. 4. The method of manufacturing a circuit board according to claim 2, wherein the means for removing the insulating base material is laser light irradiation.