JP2780502B2 - Array substrate of fine metal spheres and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TAB (Tape Automated Bon
The present invention relates to an arrangement substrate of fine metal spheres used when arranging fine metal spheres to be used as bonding bumps in accordance with a predetermined arrangement pattern and transferring them to the leading end of a TAB tape, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a TAB method, a lead wire to an electrode portion of an IC chip is connected to a tip portion of a lead patterned and formed on a TAB tape and an electrode portion of the IC chip by bonding called a bump. Is a method of bonding via metal projections. The bumps are previously attached to the lead portion on the TAB tape side or the electrode portion on the IC chip side, and the joining of the TAB tape and the IC chip is performed by applying heat and pressure using a bonding machine.

The method of forming bumps on the TAB tape side instead of the IC chip side (TAB with bumps) has been widely used in recent years because there is no fear of damaging the IC chip during bump formation. As a conventional method of manufacturing this TAB with bumps, a method is used in which a lead is made thicker and then thinned by etching or the like to leave a portion to be a bump, and then a lead is formed in advance by plating on a substrate such as glass. The transferred bump is transferred to the tip of the lead. However, since the bumps of the TAB tape with bumps manufactured by these methods have a shape close to a rectangle, there is a drawback that the bonding with the electrodes of the IC chip tends to vary.

The present inventors previously filed a new method for forming a spherical bump on the leading end of a TAB tape as Japanese Patent Application No. 1-234917. FIG. 1 schematically shows the steps from the production of a new bumped TAB by this method to the use of the TAB with an IC chip. The primary bonding is a process in which the fine metal spheres 4 serving as bumps are sucked onto the through holes of the array substrate 5 and temporarily fixed, and then collectively bonded to the tips of the leads 3 formed on the TAB tape 2. It is. The secondary bonding is a step of bonding the lead portion of the TAB tape on which the bump is formed by the primary bonding and the electrode portion of the IC chip 1. The secondary bonding is performed in mounting an IC chip, whereas the primary bonding is a process performed for manufacturing a TAB with bumps. In this primary bonding process, an array substrate is used to temporarily arrange the fine metal spheres to be bumps according to a predetermined array pattern, and the performance of the array substrate is one of the important factors that determines the practicality of this method. It is.

[0005]

The spherical bumps are more easily deformed than conventional rectangular bumps formed by plating on a glass substrate or the like, and are advantageous in terms of bonding. However, when bumps are formed by plating, predetermined positions to be arranged from the beginning can be specified and formed. On the other hand, since spherical bumps are manufactured in a discrete state, predetermined positions can be specified. It is necessary to surely join the elements arranged efficiently to the leads on the TAB tape. Conventionally, to solve this problem, for example, an arrangement substrate having a through hole at a position where a bump should be arranged as described in Japanese Patent Application No. 2-179266 or Japanese Patent Application No. 2-183645 has been used. I have. As a means for forming a through hole in a substrate, there are methods such as laser processing, electroforming, and precision electric discharge machining. Is the limit of processing for a substrate having a practical thickness. In these through holes, it is naturally desirable to be able to softly and temporarily fix the fine metal spheres serving as bumps without damaging them. Despite the fact, there were practically all that could be done due to the limitations of processing methods.

On the other hand, the mounting technology of semiconductors has been increasing in density, and accordingly, small metal spheres as bumps have been required to be small. That is, when the distance between the leads is reduced, the use of large bumps may deform the bumps at the time of bonding with the chip and cause a short circuit between the bumps of adjacent leads. Further, TAB is naturally expected to support high-density mounting in which the pitch of the inner leads is 100 μm or less. In this case, the diameter of the fine metal sphere used as a bump is necessarily required to be small. Will be. Specifically, there is a demand for a precise array substrate capable of processing a bump having an extremely fine diameter of 50 μm or less. Furthermore, as the size of the bumps becomes smaller, even small burrs left around the through holes tend to hinder the bonding of the temporarily fixed bumps to the leads of the TAB tape. For this reason, there is a tendency that not only a small through hole is processed but also that the peripheral portion of the hole is processed smoothly so as not to damage the bumps as much as possible.

The present invention has been made based on the above circumstances. Particularly, for a high-density TAB, fine metal spheres used for arranging fine metal spheres serving as bumps and efficiently joining them to the tips of the leads are described. It is an object of the present invention to provide an array substrate and a manufacturing method thereof.

[0008]

The present invention for achieving the above object has a through hole corresponding to an array pattern of fine metal spheres, wherein the through hole is narrowed by a plating layer,
An array substrate of fine metal spheres having an opening diameter of 100 μm or less,
And a through hole corresponding to the array pattern of the fine metal spheres is formed on the substrate, and in forming the through hole, the through hole is slightly larger than the target hole diameter, and the target is achieved by narrowing the hole diameter by plating. It is characterized by obtaining a hole diameter. The diameter of the through hole of the substrate is
The front side and the back side of the substrate may be different.

The reason for limiting the size to only the case where the opening diameter is 100 μm or less is as follows. Usually, for example, the bump size used in TAB is almost 150 μm or less, so that the opening diameter of the through hole of the substrate used naturally falls within the range smaller than the bump size. Moreover, those having an opening diameter of 100 μm or more can be formed without any particular difficulty by the current processing technology. The present invention considers the actual situation that requires the use of increasingly smaller bumps in accordance with the requirements of high-density mounting, and particularly targets an extremely fine range of 100 μm or less as the opening diameter range of a through hole accompanied by difficulties in the current processing. I decided.

As described above, the present invention relates to the arrangement substrate 5 for bumps used in the primary bonding step shown in FIG. It has a uniform through hole smaller than the diameter, and only one fine metal ball is sucked and temporarily fixed without damage to one through hole, and the fine metal ball is joined to the lead of the TAB tape. It is required to be easily detachable after the use and to have durability to withstand repeated use.

In general, it is extremely difficult to process a thick and sufficiently thick substrate so that a large number of fine and uniform through holes form a fixed pattern. For example, in the case of the electroforming method, the maximum thickness at which a through hole having a diameter of 60 μm can be formed is about 30 μm. Even when a special electric discharge machining is used, a through hole having a diameter of about 60 μm is formed for a substrate having a thickness of 100 μm. At present, processing is the best. Although the laser machining method is capable of machining a hole slightly smaller than these, the limit that can ensure the roundness of the through hole is substantially the same as the electric discharge machining method described above.

In the present invention, since a through hole having a predetermined size is previously formed by a method such as electric discharge machining, the hole diameter can be reduced by plating, so that the through hole having a small hole diameter exceeding the limit of the conventional machining method. Are easily formed. For this reason, if the board thickness is the same, a through hole having a small hole diameter that can withstand high-density mounting and can be used for arrangement of smaller fine metal balls can be obtained. Further, when the diameter of the through hole is the same, a thick substrate having high strength can be selected, so that the service life can be repeatedly prolonged.

In the case of a through-hole formed by another conventional processing method, fine burrs are often formed around the hole, and this may damage fine metal balls temporarily arranged,
Further, it may be a factor that hinders separation from the substrate after being bonded to the tape. On the contrary,
In the present invention, the corners and burrs around the hole are rounded by the plating layer, and as a result, the seating of the fine metal sphere and the separation after bonding are extremely excellent. As a plating method, conventionally known chemical plating of nickel or the like can be used.

Further, in the arrayed substrate, the diameter of the through hole differs between the front surface side and the back surface side by changing the diameter of the through hole in the middle of the thickness of the substrate or by overlapping two substrates having different through hole diameters. It may be manufactured as follows. The purpose of making the hole diameter on the front side smaller than the diameter of the fine metal sphere and making the diameter on the rear side larger is to reinforce the strength of the substrate. vice versa,
To make the hole diameter on the back side smaller than the diameter of the fine metal sphere and make the hole diameter on the front side slightly larger than the diameter of the fine metal sphere,
The purpose is to prevent a plurality of fine metal spheres from being collected and sucked in one through hole. Further, a substrate aiming for a combination of the two effects, that is, a case where the hole diameter of the intermediate portion of the substrate is smaller than the hole diameter of the front surface side and the back surface side may be adopted as necessary. Even when a plating layer is formed on a substrate having through holes with different hole diameters on the front and back surfaces of the substrate, the above-described effects can be similarly obtained, and thus are included in the scope of the present invention. .

[0015]

By reducing the pressure on the back side of the array substrate, a suction force is generated in the through hole on the front side, and the array can be easily performed by sucking the fine metal spheres serving as bumps. The substrate according to the present invention is reduced in diameter until the hole diameter becomes a target size by plating, after first drilling a hole slightly larger than the target through hole diameter by laser, electric discharge machining, electroforming, or the like. At the same time, as a result of plating around the hole is rounded,
It enables unprecedented arrangement and provisional fixing of extremely fine bumps and smooth bump transfer bonding to leads.

[0016]

EXAMPLE 1 A 0.1 mm-thick stainless steel plate was used to bond gold bumps to the leads of a TAB tape used for mounting an IC chip having a total of 200 electrodes at 140 μm pitches on the outer periphery of the four sides. Was used. There are two types of array substrates used, and the substrate 1 has a through hole having a diameter of 60 μm formed by precision electric discharge machining in accordance with the array pattern of the chip electrodes.
It is a conventional type substrate (comparative example) that has been opened. On the other hand, the substrate 2 of the present invention has a through hole having a diameter of 65 μm formed by precision electric discharge machining, and then nickel is adhered by a chemical plating method. It is a thing.

Using these two types of substrates, a diameter of 80 μm
Using the fine metal spheres as bumps, bonding (primary bonding) of the bumps to the lead portions of the TAB tape was performed. The bonding conditions of the bumps were set such that the temperature of the tool was 500 ° C. and the pressure was 20 g / lead, and primary bonding of 10 frames was performed on each of the substrates 1 and 2.

Table 1 shows the test results. The primary joining situation is
There is a difference in the bonding ratio between the series of the substrate 1 and the substrate 2.
In the series of the substrate 1, the bumps did not bond to the leads quite frequently, but this was a result of the bumps caught on the burrs around the through holes of the substrate 1 and the bumps did not come off well. In the series of the substrate 2, this kind of trouble did not occur at all, and extremely stable primary bonding was performed.
From this result, it is understood that the primary bonding rate of the bump is improved even when the substrate of the present invention is used for a through hole having the same size as the conventional substrate.

[0019]

[Table 1]

Example 2 Using the same TAB tape as in Example 1, a stainless steel array substrate having a thickness of 0.1 mm was subjected to electrical discharge machining to a diameter of 60 μm.
After forming a through hole of m, nickel was plated to reduce the diameter of the through hole to 50 μm. 60 μm in diameter using this substrate
Of fine gold balls were arrayed, and primary bonding was performed on the lead portions of a 10-frame TAB tape. The bump bonding rates of the primary bonding were all 100%.

Next, 10 frames of the TAB tape to which the bumps having a diameter of 60 μm were bonded, and N frames in the first embodiment described above.
o. A secondary bonding test with an IC chip was performed using ten TAB tapes to which bumps of 80 μm in diameter shown in FIGS. 11 to 20 were bonded.

In the case of a TAB tape using bumps having a diameter of 80 μm, short-circuiting occurred between adjacent leads due to deformation of the bumps at the time of bonding, although in some cases. TA with one 60 μm diameter bump bonded
No such inconvenience occurred at all with the B tape. This means that even if the lead pitch is not particularly high and the pitch is not particularly narrow, using small bumps to a certain extent will not cause a short circuit between adjacent leads and allow stable TAB mounting. Indicated. And it was confirmed that the substrate of the present invention was effective in providing an arrayed substrate having a smaller through hole that could be used to arrange smaller bumps.

Example 3 A conductive ceramic having a thickness of 0.3 mm was used to bond a gold bump to a lead of a TAB tape used for mounting an IC chip having a total of 328 electrodes at a pitch of 102 μm on the outer periphery of four sides. Was used. On the array substrate, step-like through holes were machined according to the electrode array pattern. That is, first, a hole having a diameter of 100 μm was dug from the back surface side by precision electric discharge machining to a depth of about 250 μm, and then a hole having a diameter of 40 μm was formed in the same position by laser processing and penetrated. In this case, the hole having a diameter of 100 μm on the back surface does not have an independent shape because the adjacent hole overlaps the periphery, but a through hole having a diameter of 40 μm was formed on the front surface side of the substrate. It was 0.3 m
This is because it is impossible to directly process a thin through hole having a diameter of 40 μm on a substrate having a thickness of m, but a thick substrate must be used in order to secure the strength of the substrate.

The substrate thus obtained was plated with nickel to narrow the hole diameter on the front side to 35 μm. In the case of conductive ceramics, as compared with the case of stainless steel of Example 1, the processed surface is more likely to be roughened when laser processing is performed.
The effect of facilitating the peeling of the bump by smoothing the periphery of the hole was also expected. Depressurize the back side of this array substrate,
A primary bonding test was performed in which fine gold spheres having a diameter of 45 μm were arranged in a through-hole portion having a diameter of 35 μm on the front side and bonded as bumps to a lead portion of a TAB tape. The joining conditions were a tool temperature of 520 ° C. and a pressure of 20 g / lead. 10
The primary bonding rate performed on the top TAB tape was 100%. Furthermore, a secondary bonding test was performed between the chip and the chip using the TAB tape with bumps at a tool temperature of 540 ° C. and a pressing force of 60 g / lead. Was obtained.

Embodiment 4 In order to bond a gold bump to a lead portion of a TAB tape used for mounting an IC chip having a total of 328 electrodes at a pitch of 102 μm on the outer periphery of the same four sides as in Embodiment 3 above,
An array substrate made of stainless steel and having a thickness of 0.1 mm was used. In the arrangement substrate, a step-like through hole opposite to that of the third embodiment is provided.
Processing was performed according to the electrode arrangement pattern. That is, first, a hole having a diameter of 50 μm was formed by 30 μm from the surface side by precision electric discharge machining.
The hole was dug to a depth of m, and then a hole having a diameter of 40 μm was formed in the same position by laser processing and penetrated. It was difficult to penetrate a hole with a diameter of 40 μm by the thickness of 70 μm of the substrate by laser processing. By rotating, a through hole with good roundness was obtained.

The substrate has a diameter of 50 μm on the front side.
When the hole of 30 μm enters from the surface of the substrate, the diameter 40
Nickel plating was performed until the diameter of the portion narrowed down to μm became 35 μm. At this time, the hole having a diameter of 50 μm on the surface side was also contracted to about 45 μm.

The primary bonding test for bonding a very fine gold ball having a diameter of 40 μm to the lead portion of a TAB tape using this array substrate was performed as follows. First, when the back side is decompressed and the ultrafine gold sphere having a diameter of 40 μm is sucked, the ultrafine gold sphere falls into a hole having a diameter of 45 μm on the front surface, and the diameter becomes 35 μm
Temporarily fixed in the form of being held by the step-shaped part of When arranging ultra-fine gold spheres as in this example on a normal flat substrate, a plurality of gold spheres may often be attracted to one hole. The substrate according to the present invention used in this example has a hole with a diameter of 45 μm slightly larger than the diameter of the ultrafine gold sphere on the surface side, so that the first ultrafine gold sphere falls into this hole and further If it is captured by the suction force from the back side of the substrate around the hole with a diameter of 35 μm in the lower part, the suction force will not work even if another ultra-fine gold ball comes next to the same hole next time. Therefore, the arrangement of a plurality of ultrafine gold balls in the same through hole did not occur.

Further, since the depth of the 45 μm diameter hole on the surface side is 30 μm, which is slightly shallower than the diameter of the ultrafine gold sphere, the head of the ultrafine gold sphere arranged by suction is 5 μm from the surface of the substrate. It will be sticking out, TA
There was no problem in superposing and joining with the lead of the B tape.

As described above, it has been confirmed that an arrayed substrate having a two-stage through-hole in which the hole diameter on the front side is larger than that on the rear side is very effective in processing very fine bumps. .

[0030]

According to the present invention, it is possible to realize a practical arrayed substrate of fine metal spheres which can be used in a step of bonding a bump to a tape lead portion, which is necessary for manufacturing a TAB tape with bumps of fine pitch. As a result of the use of large spherical bumps, high-density mounting, which is a feature of TAB, can be realized by spherical bumps with good bonding properties, and fine leads such as fine burrs etc. There is no need to worry about the smooth transfer of the bumps, and stable primary bonding can be performed. In addition, since it became possible to use smaller spherical bumps even for TAB having a pitch of the degree conventionally realized,
In the secondary joining between the TAB tape and the IC chip, the danger of short-circuiting with the adjacent lead can be reliably avoided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a bonding step of a TAB with a bump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 IC chip 2 TAB tape 3 Lead 4 Spherical bump 5 Array board

Claims (4)

(57) [Claims] 1. A through hole corresponding to an arrangement pattern of fine metal spheres, wherein the through hole is narrowed by a plating layer,
An array substrate of fine metal spheres having an opening diameter of 100 μm or less. 2. The array substrate of fine metal spheres according to claim 1, wherein the diameter of the opening of the through hole differs between the front surface side and the rear surface side of the substrate. 3. A through hole corresponding to an array pattern of fine metal spheres is formed on a substrate, and in forming the through hole, the through hole is made slightly larger than a target hole diameter, and the hole diameter is reduced by plating. A method for manufacturing an array substrate of fine metal spheres, wherein a target hole diameter is obtained by the method. 4. The method according to claim 3, wherein the diameter of the opening of the through hole differs between the front surface side and the back surface side of the substrate.