JPH04250643A - Arrangement substrate of fine metal ball - Google Patents

Abstract

PURPOSE:To provide an arrangement substrate for arranging fine metal balls required for manufacturing TAB with a bump and manufacture thereof. CONSTITUTION:Fine throughholes to be provided on a bump arrangement substrate are bored larger than a target hole diameter and narrowed by a plated layer. Extremely fine through holes unable to be realized by a present processing method is enabled to be provided so as to be able to arrange finer metal balls. Consequently, manufacture of a TAB with bumps for high density mounting is made possible, moreover the peripheral part of through holes is smoothed by plating so that efficiency of transcription to a TAB tape of the arranged bumps is heightened.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to TAB (Tape Auto), which is one of the mounting techniques for semiconductor elements of IC chips.
The present invention relates to an array substrate of fine metal balls used for arranging fine metal balls to be bumps for bonding according to a predetermined array pattern and transferring them to the lead tips of a TAB tape in mated bonding, and a method for manufacturing the same.

0002

[Prior Art] The TAB method connects the lead wires to the electrodes of an IC chip by bonding the tips of the leads, which are patterned on a TAB tape, and the electrodes of the IC chip using bumps. This is a method of joining via metal protrusions. The bumps are attached in advance to the lead part on the TAB tape side or the electrode part on the IC chip side.
The TAB tape and the IC chip are bonded by applying heat and pressure using a bonding machine.

A method of forming bumps on the TAB tape side rather than on the IC chip side (TAB with bumps) has become widely used in recent years because there is no risk of damaging the IC chip during bump formation. Conventional methods for manufacturing TABs with bumps include making the leads thicker and then etching them off leaving the parts that will become bumps to make them thinner, or forming them in advance by plating on a substrate such as glass. There are methods such as transferring the bumps to the lead tips. However, since the bumps of the bumped TAB tape produced by these methods have a nearly rectangular shape, 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 spherical bumps at the leading ends of TAB tapes in Japanese Patent Application No. 1-234917. FIG. 1 schematically shows the steps from manufacturing a new bumped TAB using this method to using it for bonding with an IC chip. The primary bonding is a step in which fine metal balls 4 that will become bumps are sucked onto the through holes of the array substrate 5 and temporarily fixed, and then bonded all at once to the tips of the leads 3 formed on the TAB tape 2. It is. Further, the secondary bonding is a process of bonding the lead portion of the TAB tape on which bumps have been formed in the primary bonding to the electrode portion of the IC chip 1. Secondary bonding is performed when mounting an IC chip, whereas 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 balls that will become the bumps according to a fixed array pattern, but the performance of the array substrate is one of the important factors that determines the practicality of this method. It is.

[0005]

SUMMARY OF THE INVENTION Spherical bumps are easier to deform than conventional rectangular bumps formed by plating on glass substrates, etc., and are advantageous in terms of bonding. However, when forming bumps by plating, it is possible to specify and form the predetermined positions from the beginning where they should be arranged, whereas spherical bumps are manufactured in pieces, so they cannot be formed at the predetermined positions. It is necessary to reliably join the leads arranged in an efficient manner to the lead portions on the TAB tape. Conventionally, to solve this problem, an array substrate having through holes provided at the positions where bumps are to be arrayed has been used, as described in Japanese Patent Application No. 2-179266 and Japanese Patent Application No. 2-183645, for example. There is. There are methods such as laser machining, electroforming, and precision electrical discharge machining to form through holes in substrates, but no matter which method is used, it is difficult to form circular through holes with a diameter of about 60 μm. was the limit of processing for substrates of practical thickness. It goes without saying that it is desirable for these through-holes to be able to temporarily fix fine metal balls that will become bumps in a soft manner without damaging them. Despite this, due to limitations in processing methods, in practice the only option was to drill holes.

[0006] On the other hand, semiconductor packaging technology is becoming more dense, and along with this, smaller fine metal balls as bumps are also required. That is, as the distance between the leads becomes narrower, if large bumps are used, there is a risk that the bumps will deform when bonded to the chip and cause a short circuit with the bumps of adjacent leads. Furthermore, in TAB, the inner lead pitch is 1
It is naturally expected that high-density packaging of 00 μm or less can be supported, and in this case, the diameter of the fine metal balls used as bumps will necessarily be required to be small. Specifically, there is a growing demand for a precisely arrayed substrate that can process bumps with extremely fine diameters of 50 μm or less. Furthermore, as the size of the bump becomes smaller, even small burrs remaining around the through hole are more likely to become an obstacle to bonding the temporarily fixed bump to the lead portion of the TAB tape. For this reason, there is a strong demand for array substrates that are not only machined with minute through-holes, but also machined so that the periphery of the hole is smooth so that the bumps are not damaged as much as possible.

The present invention has been made based on the above-mentioned circumstances, and is a method of fine metal balls used for arranging fine metal balls to serve as bumps and efficiently bonding them to the lead tips, especially for high-density TAB. The purpose of this invention is to provide an array substrate and a method for manufacturing the same.

[0008]

[Means for Solving the Problems] To achieve the above object, the present invention includes a through hole corresponding to an arrangement pattern of fine metal balls, the through hole is narrowed by a plating layer,
An array substrate of fine metal spheres with an opening diameter of 100 μm or less,
Then, a through hole is formed in the substrate corresponding to the arrangement pattern of the fine metal balls, and when forming the through hole, the through hole is made slightly larger than the target hole diameter, and the hole diameter is reduced by plating to achieve the target. It is characterized by obtaining the hole diameter. Note that the hole diameter of the through hole in the board is
There is no problem even if the front side and back side of the board are different.

The reason why the opening diameter is limited to 100 μm or less is as follows. Normally, the bump size used in TAB, for example, is approximately 150 μm or less, so the opening diameter of the through hole of the substrate used is naturally within a range smaller than the bump size. Moreover, an opening having an opening diameter of 100 μm or more can be formed without any particular difficulty using current processing techniques. The present invention takes into consideration the actual situation where it is necessary to use increasingly smaller bumps in accordance with the requirements for high-density packaging, and specifically targets the extremely fine opening diameter range of 100 μm or less for through-holes, which is difficult in current processing. Established.

As mentioned above, the present invention relates to the bump array substrate 5 used in the primary bonding process of FIG. It has uniform through-holes smaller than the diameter of , ■ Only one fine metal ball is reliably sucked and temporarily fixed in each through-hole without being damaged, and ■ Fine metal balls are attached to the lead part of the TAB tape. They are required to be easy to separate after being bonded, and have durability that can withstand repeated use.

By the way, it is generally very difficult to process a sufficiently durable thick substrate so that a large number of fine and uniform through holes form a certain pattern. For example, in the case of electroforming, the maximum board thickness that can form a through hole of 60 μm in diameter is about 30 μm, and even if special electrical discharge machining is used, a through hole of about 60 μm in diameter can be formed in a board with a thickness of 100 μm. The current situation is that processing is the best we can do. Although the laser machining method is capable of machining holes that are slightly smaller than these methods, the limit for ensuring the roundness of the through hole is essentially the same as the electric discharge machining method described above.

[0012] In the present invention, after a through hole of a certain size is previously machined by a method such as electric discharge machining, the hole diameter is reduced by plating, so that a through hole with a small diameter that exceeds the limits of conventional machining methods can be formed. is easily formed. Therefore, if the board thickness is the same, it can withstand high-density mounting.
A through hole with a small hole diameter that can be used for arranging smaller fine metal spheres is obtained. Furthermore, if the through-hole diameters are the same, a thick substrate with high strength can be selected, and the life of repeated use can be extended.

[0013] Furthermore, in the case of through holes drilled using other conventional processing methods, minute burrs are often formed around the hole, and these may damage the temporarily arranged fine metal spheres.
Furthermore, it may become a cause of inhibiting separation from the substrate after being bonded to the tape. On the contrary,
In the present invention, the corners and burrs around the holes are rounded by the plating layer, so that the fine metal balls sit very well and are easily separated after bonding. Further, as a plating method, conventionally known chemical plating such as nickel can be used.

Furthermore, the array substrate has different hole diameters on the front and back sides, either by changing the diameter of the through holes midway through the thickness of the substrate, or by stacking two substrates with different through hole diameters. It may be manufactured as such. 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 back side larger is to strengthen the strength of the substrate. vice versa,
Making the hole diameter on the back side smaller than the diameter of the fine metal ball and making the hole diameter on the front side slightly larger than the diameter of the fine metal ball is as follows.
The aim is to prevent multiple fine metal balls from gathering and being sucked into one through hole. Furthermore, a board that aims to combine both effects, that is, a case where the hole diameter in the middle part of the board is smaller than the hole diameter on the front side and the back 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-mentioned effects are similarly brought about, and therefore it is included in the scope of the present invention. .

[0015]

[Operation] By reducing the pressure on the back side of the arrangement substrate, a suction force is generated in the through-hole portion on the front surface side, and by suctioning the fine metal balls that will become bumps, arrangement can be easily performed. In the substrate according to the present invention, a hole slightly larger than the target through hole diameter is first drilled by laser, electrical discharge machining, electroforming, etc., and then the hole diameter is reduced by plating until the hole diameter reaches the target size. At the same time, the area around the hole is rounded by the plating, making it possible to arrange and temporarily fix extremely fine bumps that were previously unheard of, as well as to smoothly transfer and bond the bumps to the leads.

[0016]

[Example] Example 1 In order to bond a gold bump to the lead part of a TAB tape used for mounting an IC chip, which has a total of 200 electrodes at a pitch of 140 μm on the outer periphery of four sides, a stainless steel tape with a thickness of 0.1 mm was used. array substrate was used. There are two types of array substrates used.Substrate 1 has 200 through holes with a diameter of 60 μm made by precision electrical discharge machining to match the array pattern of the chip's electrodes.
This is a conventional type board (comparative example) with individual holes. The other substrate 2 of the present invention is made by drilling a through hole with a diameter of 65 μm by precision electrical discharge machining, and then applying nickel by chemical plating to reduce the hole diameter so that the inner diameter of the through hole is 60 μm, the same as that of the substrate 1. It is something that

[0017] Using these two types of substrates, a diameter of 80 μm was obtained.
The bump was bonded to the lead portion of the TAB tape (primary bonding) using the fine metal sphere as a bump. The bump bonding conditions were a tool temperature of 500° C. and a pressure of 20 g/lead, and primary bonding was performed for 10 frames on each of substrates 1 and 2.

The test results are shown in Table 1. The primary bonding situation is
There is a difference in bonding rate between the series of substrates 1 and 2. In the board 1 series, the bumps did not bond to the leads quite often, but this was the result of the bumps getting caught in the burrs around the through holes of board 1 and not being released properly. With the substrate 2 series, this type of defect did not occur at all, and extremely stable primary bonding was achieved. From these results, it can be seen that the primary bonding rate of bumps is improved even when the substrate of the present invention is used for a through hole of 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 with a thickness of 0.1 mm was coated with a diameter of 60 μm by electrical discharge machining.
After drilling a through hole with a diameter of m, the diameter of the through hole was reduced to 50 μm by plating with nickel. Using this substrate, the diameter is 60 μm.
The fine gold spheres were arranged and primary bonded to the lead part of 10 pieces of TAB tape. The bump bonding rate of all primary bonding was 100%.

Next, 10 frames of TAB tape to which bumps of 60 μm in diameter were bonded and the N
o. A secondary bonding test with an IC chip was conducted using 10 pieces of TAB tape shown in Nos. 11 to 20 to which bumps with a diameter of 80 μm were bonded.

In the case of TAB tape using bumps with a diameter of 80 μm, there were a few cases in which short circuits occurred between adjacent leads due to deformation of the bumps during bonding. TA bonded with one bump of 60μm in diameter
With tape B, no such inconvenience occurred. This means that even if the lead pitch is not particularly narrow and high-density, it is better to use somewhat small bumps to ensure stable TAB mounting without worrying about short circuits between adjacent leads. Shown. The substrate of the present invention was confirmed to be effective in providing an array substrate with smaller through holes that can be used to array smaller bumps.

Example 3 Conductive ceramics with a thickness of 0.3 mm was used to bond gold bumps to the leads of a TAB tape used for mounting an IC chip, which has a total of 328 electrodes at a pitch of 102 μm on the outer periphery of each side. An array substrate manufactured by Kogyo Co., Ltd. was used. Step-shaped through holes were machined in the array substrate to match the electrode array pattern. That is, first, a hole with a diameter of 100 μm was drilled to a depth of about 250 μm from the back side by precision electric discharge machining, and then a hole with a diameter of 40 μm was drilled at the same position by laser machining to penetrate. In this case, a hole with a diameter of 100 μm on the back side overlapped with an adjacent hole so that it did not form an independent hole, but a through hole with a diameter of 40 μm was formed on the front side of the substrate. This kind of two-stage hole drilling was performed with a diameter of 0.3 mm.
This is because it is impossible to directly process a thin through hole with a diameter of 40 μm in such a thick substrate, but it was necessary to use a thick substrate in order to ensure the strength of the substrate.

The substrate thus obtained was plated with nickel to reduce the hole diameter on the front side to 35 μm. In the case of conductive ceramics, compared to the case of stainless steel in Example 1, there is a strong tendency for the processed surface to become rough if laser processing is performed, so in addition to the effect of reducing the hole diameter by plating,
We also hoped that it would have the effect of smoothing the area around the hole and making it easier to remove the bump. Reduce the pressure on the back side of this array board,
A primary bonding test was conducted in which fine gold spheres with a diameter of 45 μm were arranged in a through hole portion with a diameter of 35 μm on the front side and bonded to the lead portion of the TAB tape as a bump. The bonding conditions were a tool temperature of 520° C. and a pressing force of 20 g/lead. 10
The primary bonding rate performed on the TAB tape of the frame was 100% in all cases. Furthermore, a secondary bonding test was conducted using this bumped TAB tape with a chip at a tool temperature of 540°C and a pressure of 60 g/lead, and the result was 100% without any short circuit between adjacent leads. We were able to obtain a bonding rate of .

Example 4 In order to bond gold bumps to the leads of a TAB tape used for mounting an IC chip, which has a total of 328 electrodes at a pitch of 102 μm on the outer periphery of the four sides as in Example 3,
A stainless steel array substrate with a thickness of 0.1 mm was used. The array substrate has step-shaped through holes opposite to those in Example 3.
Processed to match the electrode arrangement pattern. In other words, first, a 30 μm hole with a diameter of 50 μm was created from the surface side by precision electrical discharge machining.
A hole with a diameter of 40 μm was drilled at the same location by laser processing to penetrate the hole. It was difficult to make a hole with a diameter of 40 μm through the thickness of 70 μm of the substrate by laser processing, but with repeated irradiation with a narrowed laser spot, the hole was cut through the substrate in a plane perpendicular to the laser beam irradiation direction. By rotating the , a through hole with good roundness was obtained.

[0026] With respect to this substrate, a diameter of 50 μm on the surface side
The diameter of the hole is 40 μm when it enters 30 μm from the surface of the substrate.
Nickel plating was carried out until the diameter of the part narrowed down to μm became 35 μm. At this time, the hole with a diameter of 50 μm on the surface side had also shrunk to about 45 μm.

A primary bonding test in which ultrafine gold spheres with a diameter of 40 μm were bonded to the lead portion of a TAB tape using this array substrate was conducted as follows. First, when the pressure is reduced on the back side and an ultrafine gold ball with a diameter of 40 μm is sucked, the ultrafine gold ball falls into a hole with a diameter of 45 μm on the front side and becomes 35 μm in diameter.
It was temporarily fixed by being held in the step-like part of the. When trying to arrange ultrafine gold spheres like this example on a normal flat substrate, it often happens that a plurality of gold spheres are attracted to one hole. The substrate according to the present invention used in this example has a hole on the surface side with a diameter of 45 μm, which is slightly larger than the diameter of the ultrafine gold sphere, so that the first ultrafine gold sphere falls into this hole, and then When the suction force is supplemented by the reduced pressure from the back side of the substrate around the 35 μm diameter hole at the bottom, even if another ultrafine gold ball comes near the same hole, the suction force will no longer act. Therefore, multiple ultrafine gold spheres were not arranged in the same through hole.

Moreover, 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 spheres, so the heads of the ultrafine gold spheres arranged by suction are 5 μm from the surface of the substrate. TA
There was no problem in overlapping and joining the lead of tape B.

As described above, it has been confirmed that the array substrate having two stages of through-holes, in which the hole diameter on the front side is larger than that on the back side, is very effective when processing extremely fine bumps. .

[0030]

[Effect of the invention] A practical array substrate of fine metal spheres that can be used in the bump bonding process to the tape lead part, which is necessary to manufacture TAB tape with fine pitch bumps, has been realized, and ultra-fine metal balls, which were previously difficult to As a result of the availability of spherical bumps, it has become possible to achieve high-density mounting, which is a feature of TAB, using spherical bumps with good bonding properties. There is no need to worry about the smooth transfer of the bumps, and stable primary bonding can now be performed. In addition, it has become possible to use smaller spherical bumps for TABs with the same pitch that was conventionally achieved.
It is now possible to reliably avoid the risk of short circuiting with adjacent leads during secondary bonding between the TAB tape and the IC chip.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a process of bonding a TAB with bumps.

[Explanation of symbols]

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

Claims (4)

[Claims] 1. An array substrate of fine metal spheres, comprising through holes corresponding to an array pattern of fine metal spheres, the through holes being narrowed by a plating layer, and having an opening diameter of 100 μm or less. 2. The fine metal sphere array substrate according to claim 1, wherein the diameter of the opening of the through hole is different between the front side and the back side of the substrate. [Claim 3] A through-hole is formed in the substrate corresponding to the arrangement pattern of the fine metal balls, and when the through-hole is formed, the through-hole is made slightly larger than the target hole diameter, and the hole diameter is reduced by plating. A method for manufacturing an array substrate of fine metal spheres, characterized in that a target hole diameter is obtained by: 4. The method of manufacturing a fine metal sphere array substrate according to claim 3, wherein the diameter of the opening of the through hole is different between the front side and the back side of the substrate.