JP3117825B2 - Substrate for bump arrangement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a TAB (Tape Automated Bonding), which is one of the mounting techniques for semiconductor devices, in which fine metal spheres serving as bonding bumps are arranged according to a predetermined arrangement pattern. The present invention relates to a bump arrangement substrate used when transferring to a lead tip.

[0002]

2. Description of the Related Art In a TAB method, when lead wiring is performed on an electrode portion of a semiconductor chip, a tip portion of a lead (finger lead) formed in a pattern on a TAB tape (film carrier) and a semiconductor are connected. This is a method of joining the chip to an electrode portion via a metal projection for joining, that is, a bump. The bumps are previously attached to the leads on the TAB tape side or the electrode portions of the semiconductor chip, and when the TAB tape and the semiconductor chip are joined, they are heated and pressed using a bonding machine.

FIGS. 2 and 3 show examples of the TAB method and its configuration such as a TAB tape. In the figures, reference numeral 1 denotes a semiconductor chip, 2 denotes a base film of a TAB tape,
It has a device hole 2a at its center. Also,
Reference numeral 3 denotes a finger lead formed to protrude into the device hole 2a, and reference numeral 4 denotes a bump. When joining the TAB tape and the semiconductor chip 1, a so-called IC bump method shown in FIG. 3A is generally widely used.
In this IC bump method, the bumps 4 are previously placed on the semiconductor chip 1.
According to this method, since the semiconductor chip 1 is housed in the device hole 2a opened in the base film 2 of the TAB tape, the thickness after mounting can be reduced. Has features.

On the other hand, bumps are not formed on the semiconductor chip side but on the TA.
The method of forming on the B tape side (TAB with bump) has been widely used in recent years because there is no risk of damaging the semiconductor chip during the formation of the bump. In the mounting using such a TAB with bumps, FIG.
As shown in (c), there are two cases depending on which side of the TAB tape the bump 4 is attached to. Usually, the bumps 4 are provided on the side opposite to the base film 2 as shown in FIG. In this case, since the semiconductor chip 1 is not accommodated in the device hole 2a of the base film 2, the thickness after mounting becomes considerably larger than that of the IC bump method (FIG. 3A).
Therefore, in order to reduce the mounting thickness, it is possible to attach the bump 4 to the base film 2 as shown in FIG.

However, when a bump is attached to a finger lead, the bump formed by plating on a flat glass substrate is transferred to the tip of the finger lead. The thickness of the film is an obstacle, making it virtually impossible to attach. In this case, if the thickness of the bump is made larger than the thickness of the base film so that the head of the bump projects above the base film, it is possible to join the bump to the finger lead itself. is there. However, when such a thick bump is used, usually, a large amount of expensive bump material metal using gold (Au) is used, which increases the cost and increases the thickness of such a thick bump. Is formed as shown in FIG. 3C, the original purpose of reducing the mounting thickness cannot be achieved.

The present applicant has previously proposed a new method of forming a spherical bump on the leading end of a TAB tape (Japanese Patent Application Laid-Open No. 3-174737). But,
Also in this method, when the size of the bump is reduced so that the diameter of the bump is smaller than the thickness of the base film, the bump is formed in a shape as shown in FIG. Becomes difficult.

Here, FIG. 4 schematically shows a novel bumped TAB proposed by the present applicant and a joining process of the same with a semiconductor device. In the drawing, in the primary bonding step, the fine metal spheres 4 serving as bumps are sucked onto the through holes of the array substrate 5 and temporarily fixed, and then the TAB base film 2 is formed.
It is collectively joined to the tip of the finger lead 3 formed above. In the secondary bonding step, the finger leads 3 of the TAB tape, on which the bumps are formed in the primary bonding step, and the electrode portions of the semiconductor chip 1 are aligned and bonded. The secondary bonding is performed in mounting a semiconductor chip, whereas the primary bonding is performed for producing a TAB with bumps. Then, in the primary bonding step, an array substrate 5 for temporarily arranging the fine metal spheres 4 to be bumps according to a predetermined pattern is used. The fine metal spheres 4 adsorbed on the array substrate 5 form the base film 2 of the TAB tape.
Regarding whether or not it is attached to the
The relationship between the size of the bumps 4 and the thickness of the base film 2 becomes a problem.

FIG. 5 is a view for explaining a primary bonding step. FIG. 5A shows a TAB in which the bumps 4 are adsorbed on the through holes 6 of the array substrate 5 and are aligned above the bumps 4.
This shows a state in which the finger lead 3 of the tape is on standby. In the figure, reference numeral 7 denotes a substrate pedestal for bringing the through-hole 6 of the array substrate 5 into a reduced pressure state.
A pressure reducing passage 9 communicating with the through-hole 6 is formed in the inside of the device. The other end of the pressure reducing passage 9 is connected to a pressure reducing device (not shown) via a pressure reducing suction port 8.

If the bumps 4 are larger than the thickness of the base film 2 of the TAB tape, the finger leads 3 are brought close to the bumps 4 in the state shown in FIG. 5B, and a bonding tool (not shown) is lowered from above. The bumps 4 can be fixed to the base film 2 side of the finger leads 3 by heating and pressing. However, when the size of the bumps 4 becomes smaller than the thickness of the base film 2, as shown in FIG. It contacts the base film 2 of the TAB tape. If the base film 2 is set so that the base film 2 faces upward, the mounting of the bumps 4 to the finger leads 3 can be performed without any trouble. In this case, the configuration after mounting the semiconductor chip 1 is shown in FIG. ), And the purpose of reducing the mounting thickness cannot be realized. That is, T with bump
In any conventional method, it is difficult for AB to reduce the amount of bump metal used and to reduce the mounting thickness.

[0010]

As a method of attaching the bump to the base film side of the finger lead on the TAB tape, a design is made such that the tip of the inner lead of the finger lead projects long into the device hole, or conversely. The relative relationship as shown in FIG. 6 may be realized by making the array substrate and the array substrate receiving table receiving it small enough to fit in the device hole without changing the TAB tape side. Is easily conceived. However, if the tip end of the finger lead 3 is lengthened, lead deformation is likely to occur. Particularly, when the bonding is performed with accurate positioning at a fine pitch, there is a risk that the yield of TAB mounting may be significantly reduced.

On the other hand, when the arrangement board and its receiving stand are formed small, it is possible in principle to reduce the size to just outside the through-hole row formed on the arrangement board. In practice, it is difficult to realize the state shown in FIG. 6 by this means unless a substrate and a pedestal reduced to the limit are used. However, the array substrate 5
Is reduced as described above, the size of the end portion 10 of the array substrate 5 cannot be substantially secured, so that the array substrate 5 can be stably set on the substrate receiving table 7. It becomes difficult to do. Even if the array substrate 5 can be set, if the end portion 10 is short, the reduced-pressure suction force is applied to portions other than the through holes 6 of the array substrate 5.
The small gap between the arrangement substrate 5 and the substrate receiving table 7 extends to a small gap between the arrangement substrate 5 and the through hole 6 of the arrangement substrate 5 when the bumps 4 are sucked. Also, the bumps 4 are adsorbed, which causes problems such as disturbing the primary bonding process.

In view of the above situation, the present invention can reduce the mounting thickness to about the same as a normal TAB method while using a TAB method with bumps, and can perform primary bonding and mounting of a semiconductor device. An object of the present invention is to provide a bump arrangement substrate that does not hinder other operations including the above.

[0013]

According to the present invention, a bump arrangement substrate according to the present invention corresponds to an arrangement pattern of bumps to be connected to a semiconductor chip, which is to be joined to the tip of a lead formed on a base film. With a large number of through holes,
In the bump arrangement substrate capable of mounting the bump on each through-hole, the thickness of the outer peripheral portion on the side on which the bump is mounted, such that the base film facing portion is reduced in thickness, It is configured by laminating a plurality of plates having a thickness smaller than the plate thickness of the opening portion of the through hole or having the same arrangement pattern and different peripheral sizes so that the through holes coincide with each other. Substrate for bump arrangement.

[0014]

According to the present invention, the thickness of the peripheral portion of the substrate for bump arrangement is formed smaller than the thickness of the substrate body portion having the through hole. By setting the thickness difference between the thick portion and the thin portion to be substantially the same as the thickness of the base film of the TAB tape, even when the size of the bump becomes extremely small, the device hole of the finger lead is formed. A spherical bump can be joined to the side surface without any trouble. In addition, since the thin portion of the arrangement substrate is spread around the periphery, it can be set on the substrate receiving table without any trouble, and it is not necessary to form the projecting portion of the finger lead into the device hole long.

The substrate for bump arrangement according to the present invention can be formed using a metal such as nickel or stainless steel, ceramics or the like. As a method for providing a difference in plate thickness between the substrate main body portion and its peripheral portion, etching, machining, or the like can be used. When a through hole is formed, it is difficult to form a small-diameter through hole as the thickness of the portion where the through hole is formed becomes larger as compared with the case of a normal bump arrangement substrate. When it is difficult to form such a through hole, it is advantageous to use a method in which a plurality of substrates are stacked. In this case, after forming through holes of the same pattern on each substrate to be superimposed, the substrates are superimposed so that the through holes are aligned. By increasing the size of the substrate to be overlapped on the end portion of the plurality of substrates, the thickness of the peripheral portion can be easily reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a bump arrangement substrate according to the present invention will be described with reference to FIG. In the first embodiment, a spherical bump 4 is primarily bonded to a finger lead 3 of a TAB tape used for mounting a semiconductor chip (not shown) having a total of 200 electrodes at 140 μm pitches on the outer periphery of the four sides. An array substrate 11 made of stainless steel and having a thickness of 0.2 mm is manufactured.

The arrangement substrate 11 is formed by cutting a stainless steel plate having a thickness of 0.2 mm into 15 mm square, and then cutting 3.2 mm around the periphery.
The thinner portion 12 is formed by etching the edge portion having a width of m to a thickness of 0.1 mm by etching. Thereafter, a through-hole 6 having an inner diameter of 40 μm
Is formed at a pitch of 140 μm by an electric discharge machining method. The thickness of the TAB tape base film 2 is 100 μm.
m. In the present embodiment, the thickness difference between the central portion and the peripheral portion of the arrangement substrate 11 is set to 0.1 mm, which is the same as the thickness of the base film 2. Also, the primary bonding can be appropriately and appropriately performed to the base film 2 side of the finger lead 3 of the TAB tape.

In the above case, if the bump 4 is extremely small,
When the bump 4 sinks deeply into the through-hole 6, and the base film 2 is pressed against the bump 4 temporarily fixed to the through-hole 6 from above to perform primary bonding, the bump 4 forms an opening edge of the through-hole 6. And the bumps 4 penetrate into the array substrate 1
1 may be difficult to move away from. For this reason, when bumps 4 having a diameter of 50 μm or less are used, it is necessary to set the diameter of the through-hole 6 to 30 μm or less, as well as the difference in thickness between the central portion and the peripheral portion of the arrangement substrate 11. Become.

As described above, in the bump arrangement substrate 11 of the present invention, the thin portion 12 is provided in the peripheral portion,
Substrate support 7 having a groove for vacuum suction formed on its surface
When the bump 4 is set on the upper side, the pressure drop leaks from the peripheral portion thereof, and furthermore, when the bump 4 is sucked, the bump 4 is sucked in the gap between the bump arrangement substrate 11 and the substrate receiving table 7. It can be completely eliminated. In addition, by keeping the size of the bump arrangement substrate 11 as it is and making the peripheral portion thinner, it is possible to effectively prevent the base film 2 of the TAB tape from coming into contact with the bump arrangement substrate 11 at the time of the primary bonding. Therefore, the bumps 4 can always be properly bonded to predetermined positions on the base film 2 side of the finger leads 3 of the TAB tape.

In the second embodiment of the bump arrangement substrate according to the present invention, the bump arrangement substrate for joining the spherical bumps to the TAB tape having the same pattern as in the first embodiment is as follows.
A nickel plate (A plate) having a thickness of 40 μm and 15 mm square, a nickel plate (B plate) having a thickness of 40 μm and 8 mm square, and a thickness of 5 mm
It is manufactured by superposing three substrates of a stainless steel plate (C plate) of 8.6 mm square at 0 μm. In the center portions of the A plate, the B plate and the C plate, through holes for mounting bumps are formed in accordance with the same arrangement pattern.
In the A plate and the B plate, through holes having a diameter of 30 μm were formed at the same time when they were formed by the electroforming method.
Individually formed. In the case of a C plate, the diameter is 4 by etching.
Similarly, 200 through-holes of 0 μm are formed. The arrangement of these through holes is 140 μm, as in the first embodiment.
50 pieces are arranged on four sides at a pitch. Then, the A plate, the B plate, and the C plate are polymerized in this order and bonded to each other with an adhesive.

In the substrate for bump arrangement according to the second embodiment, the thickness of the peripheral portion is 40 μm, and the thickness of the portion where the through hole is formed is slightly more than 140 μm. The reason why the size of the through hole of the C plate is larger than that of each of the A plate and the B plate is that, in order to form the through hole with high accuracy by etching, in the case of a stainless steel plate having a thickness of 50 μm, 40 μm is required. This is because the diameter is limited. Even in this case, no inconvenience occurs because the through-hole having a diameter of 30 μm in the A-plate is used at the time of bump suction. According to the second embodiment, even with a small bump having a diameter of about 35 μm, it is possible to guarantee proper and reliable primary bonding of the bump to the finger lead of the TAB tape.

In the third embodiment of the substrate for bump arrangement according to the present invention, a boride-based ceramic (trade name: SELABOREX) which is a kind of conductive ceramic is used, and a substrate of 0.16 mm in thickness and 15 mm square is used. Is produced. Further, a 3.2 mm wide portion is polished down to 0.1 mm along the periphery to make it thinner. In this case, it is not possible to obtain a completely sharp corner by thinning processing by polishing, so it is necessary to set the polishing width in consideration of the radius of this corner. Further, in the polishing process, the radius of the corner is likely to be large, so that it is preferable to perform the electric discharge machining after the polishing process. In this way, the bump arrangement substrate having a step at its peripheral portion has a through hole having a diameter of 30 μm in the thick portion at the center.
200 pieces are formed at a pitch of 0 μm. According to the third embodiment, the spherical bump having a diameter of about 65 μm can be properly and reliably primarily bonded to the finger lead of the TAB tape.

[0023]

As described above, according to the present invention, TAB
Even when a small bump is used for the primary bonding of the bump to the tape, it can be securely bonded to the base film side of the finger lead, and when this TAB tape is applied to semiconductor mounting, the mounting thickness is effective. Decrease to
It has the advantage that it can be made as thin as the conventional IC bump method.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a use state of a bump arrangement substrate according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a structural example of a TAB tape.

FIG. 3 is a diagram showing various TAB methods.

FIG. 4 is a diagram for explaining a method of manufacturing a TAB tape with bumps and a semiconductor mounting method using the same.

FIG. 5 is a longitudinal sectional view showing an aspect of a primary bump bonding performed using a conventional bump arrangement substrate.

FIG. 6 is a longitudinal sectional view showing another aspect of the primary bonding of bumps performed by using a conventional bump arrangement substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor chip 2 Base film 3 Finger lead 4 Bump 6 Through hole 7 Substrate pedestal 8 Decompression suction port 9 Decompression passage 11 Arrangement substrate 12 Thin part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-30140 (JP, A) JP-A-3-196659 (JP, A) JP-A-62-243535 (JP, A) JP-A-3-25 174737 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/60 311

Claims (2)

(57) [Claims] 1. A semiconductor device comprising: a plurality of through-holes corresponding to an arrangement pattern of bumps to be connected to a semiconductor chip, the bumps being bonded to the tips of leads formed on a base film; In the bump arrangement substrate on which the bumps can be placed, the thickness of the outer peripheral portion on the side on which the bumps are placed is set so that the thickness of the base film facing portion is reduced. A substrate for bump arrangement, characterized in that the thickness is smaller than the thickness of the opening portion. 2. The bump arrangement substrate according to claim 1, wherein the substrate has a plurality of plates having the same arrangement pattern and different peripheral sizes overlapped with each other so that their through holes coincide with each other.