JP2553264B2 - TAB tape carrier - 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 carrier into which an LSI or the like is incorporated.

[0002]

2. Description of the Related Art In the mounting technology of semiconductor elements, automation is attempted in order to mass-produce products having a performance of a certain level or higher at high speed.

As one of the semiconductor element mounting technologies developed for the purpose of automation, a semiconductor element is incorporated into a long tape carrier by wireless bonding.
There is an AB (Tape Automated Bonding) method.

In this TAB, bumps are provided on the respective electrode terminals of the semiconductor element, the bumps and the corresponding inner leads of the tape carrier are thermocompression-bonded with a bonding tool, and then resin-sealed with an insulating fluid resin. The operation of applying the surface protection coat is continuously performed.

Recently, by the TAB tape carrier I
The C package is widely used in conventional consumer products such as watches, personal computers, and high-quality liquid crystal televisions, and is rapidly being put into practical use in the fields of so-called high-end consumer products to commercial products.

The problem here is high reliability, but a major problem peculiar to TAB has been highlighted.

The problem is that the inner lead of the copper foil pattern lead is broken when the temperature cycle test is performed.

Regarding this problem, FIG. 6 shows a conventional TA.
A configuration example up to mounting using the B tape carrier is shown.

As shown in the figure, in the conventional TAB tape carrier, a surface treatment layer 12 is formed on the surface of a copper foil pattern lead 11, and the surface treatment layer 12 is further provided via bumps 15 of electrodes of a semiconductor element 14. Then, the semiconductor element 14 and the surface-treated copper foil pattern lead 11 were sealed with the sealing resin 7, and the protective layer 13 was applied onto the semiconductor element 14 and the surface-treated copper foil pattern lead 11 for assembly.

However, since the difference in thermal expansion between the inner lead portion of the copper foil pattern lead 11 and the resin is large, the inner lead cannot withstand the large thermal expansion of the resin due to a temperature change such as in a temperature cycle test, and the resin is broken. There was a fear of doing.

For this reason, it is difficult to switch to high-grade equipment. The cause of this fracture is the surface treatment layer 12
Is usually Sn or Sn-Pb alloy plating, so Sn and C
By the reaction of u, an intermetallic compound layer is formed on the surface (5-6
(μmt) The fact that this surface layer is hard also shortens the breaking life remarkably.

As a countermeasure against this, there is a concept of alloy copper foil or the like for the purpose of increasing the strength of the copper foil, but it has not been realized yet.

As another measure, the use of a sealing resin having a low coefficient of thermal expansion and the surface treatment of the copper foil pattern lead have been considered, but they have not been realized. This is because these methods inevitably lead to an increase in cost, and the development of another TAB tape carrier having a simple temperature cycle resistance has been awaited.

Reference numeral 9 is a substrate (printed board), and 10 is a polyimide film.

[0015]

Problems to be solved in the prior art are as follows. (1) Sn and Cu in Sn or Sn-Pb alloy plating
A Cu—Sn intermetallic compound is formed by the reaction with, and the Cu foil pattern lead becomes hard and breaks at the bending mounting portion and the like (see the outer lead bending portion 32a in FIG. 7). (2) Due to the same reason as in (1), the inner lead portion cannot withstand the temperature cycle stress due to the difference in thermal expansion from the sealing resin even if it is not the bending mounting portion, and the inner lead is easily broken. (3) Cu-Sn intermetallic compound means ε phase Cu ₃ S
The n and η phases are Cu ₆ Su _{5 and the} like, and a compound layer is formed on the bonding surface of Sn and Cu by mutual diffusion during heating.
Since this layer grows in proportion to the heating time, in a TAB tape carrier having thin copper foil pattern leads, the entire thickness of the copper foil pattern leads may be an intermetallic compound layer, which is dangerous. (4) TAB package (TCP =
120) for Tape Carrier Package)
There are a high temperature holding test of 150 ° C. and a temperature cycle test of −50 to 150 ° C. This assumes an actual load temperature of 90 to 100 ° C. for in-vehicle use or the like. Although the TCP technology is still new, there is concern about breakage, breakage, cracks, etc. of the Cu foil pattern lead due to reaction of Cu-Sn, and it is a serious problem that it cannot actually endure the above durability test. . (5) In addition, Sn plating or solder plating of the upper layer is
If the Cu—Sn intermetallic compound is formed in the TAB tape carrier manufacturing process before the connection with the LSI bump, there arises a problem that the connection with the LSI bump becomes difficult. This is because the plating thickness of the upper layer required for actual connection is reduced. Not only this intermetallic compound but also a simple diffusion layer progresses about 0.3 μm in 6 months at room temperature, which is a problem. That is, even in the diffusion layer, the plating thickness of the upper plating layer can be reduced. (6) We tried to apply Ni plating based on the reaction barrier concept of Cu-Sn to apply the principle that Ni is difficult to diffuse with Cu and Sn, but Ni plating is hard by itself, so it easily breaks when bent. In addition, Ni plating was found to be prone to migration and highly dangerous when bias voltage was applied, and was abandoned. The reason is that even in the nickel plating of the base layer, migration occurs from the thin portion or the defective portion of the upper layer plating.

The object of the present invention is to solve the above problems and to provide Cu
(EN) It is intended to provide a TAB tape carrier in which the formation of a -Sn intermetallic compound is suppressed to prevent the inner lead from breaking.

[0017]

To achieve the above object, according to the present invention, a copper foil pattern having a device hole for mounting a semiconductor element and extending toward a device hole opening attached to the surface thereof is provided. In the TAB tape carrier used for mounting the electrodes of the semiconductor element and the inner leads of the copper foil pattern leads at the tip end of the inner leads, which is then resin-sealed and mounted, Provided is a tape carrier for TAB, which has Sn or Sn alloy plating through Zn or Zn alloy plating on the surface of at least the inner lead of the foil pattern lead.

Here, the copper foil is preferably a rolled copper foil or an electrolytic copper foil.

The present invention will be described in more detail below.

In the TAB tape carrier of the present invention, necessary through holes such as device holes and sprocket holes are formed in a flexible insulating film, a conductor foil is attached to the film, and the conductor foil is subjected to etching processing. Is processed to form a lead pattern having an inner lead electrically connected to the semiconductor element and an outer lead.

The TAB tape carrier of the present invention may be either a two-layer tape carrier in which a conductor foil is coated with an insulating film without a structural adhesive or a three-layer tape carrier using an adhesive.

A copper foil is used as the conductor foil.

Using this copper foil pattern lead, the inner lead and the electrode of the semiconductor element are joined and sealed with resin.

The TAB tape carrier of the present invention will be described below with reference to the preferred embodiments shown in the accompanying drawings.

FIG. 1 is a partial plan view of the TAB tape carrier 1. As shown in FIG. 1, the TAB tape carrier 1 is made of a resin such as a polyimide resin, a polyethylene resin, a polyester resin, or a flexible epoxy resin, or a flexible and insulating material such as paper. A lead 3 to which a copper foil having a desired pattern is attached is attached to the film 2 with an adhesive or the like.

The copper foil of the lead 3 (hereinafter referred to as copper foil pattern lead 11) to which the copper foil is attached is preferably a rolled copper foil or an electrolytic copper foil. The lead 3 has an inner lead 31 at the tip and an outer lead 32 for connecting the outer surface.

The outer lead 32 is connected to an external terminal by soldering or the like when it is cut from the film at the time of mounting or peeled off by dissolving the adhesive.

The copper foil pattern lead 11 has Zn or Z on the surface of at least the portion excluding the inner lead.
The n alloy plating layer 20 is formed, and Sn is further formed on the surface of the n alloy plating layer 20.
Alternatively, the Sn alloy plating layer 30 is formed.

By applying Zn or Zn alloy plating as the undercoat of Sn or Sn alloy plating in this way, it is possible to prevent the formation of a hard intermetallic compound caused by the reaction between Cu and Sn, and to break the inner lead. Can be prevented.

The Zn or Zn alloy plating layer 20 is
It can be coated by plating or vapor deposition of Zn or a Zn alloy. The thickness of this plating layer 20 is 0.0
The thickness is preferably 1 to 0.1 μm. This is based on the minimum plating thickness that suppresses the formation of the alloy layer and the upper limit plating thickness that does not hinder solderability.

The Sn or Sn alloy plating layer 30 is
It can be covered by plating or vapor deposition of Sn, Sn-Pb, solder or the like. The thickness of this plating layer 30 is
The thickness is preferably 0.3 to 1.0 μm. This is to improve the bondability with the element.

A device hole 4 for mounting a semiconductor element is formed near the center of the tape carrier 1, and a sprocket hole 6 is formed on the outer periphery for facilitating positioning and feeding operations.

Then, the inner leads 31 projecting into the device holes 4 and the bumps 15 of the corresponding electrodes of the semiconductor element 14 are bonded to each other as shown in FIG.

Then, the inner lead 31 and the semiconductor element 14 are sealed with resin 7. This sealing resin 7
Generally, epoxy or the like is used.

After that, the entire surface is covered with the protective layer 13.
The protective layer 13 can be covered with an epoxy solder resist or the like.

The thickness of this protective layer is preferably 2 to 3 μm.

Generally, the tape carrier 1 is a long product in which one tape carrier shown in FIG. 1 is continuously present.

[0038]

Hereinafter, the present invention will be described in detail with reference to examples. (Example 1) A 200-pin, TAB tape carrier having a width of 35 mm was first manufactured. 75 μm for film base
The polyimide film of t was used, and the adhesive used was an epoxy foil having a thickness of 20 μm. In addition, the copper foil is 25 μm
A thick electrolytic copper foil was used. The width of the Cu foil pattern lead of the inner lead was 50 μm, and the width of the copper foil pattern lead of the outer lead was 100 μm.

Pure copper plating was applied to the entire surface of the copper foil pattern lead of this TAB tape carrier with a zinc sulfate electroplating solution to a thickness of 0.1 μm, and the surface thereof was made of 80% Sn-.
An electric solder plating of 20% Pb was applied with a borofluoride bath electroplating solution to a thickness of 0.7 μm. At the same time, a sample having no underlying Zn plating was prepared and a performance test was conducted (Comparative Example 1). The test results are shown in Table 1 and FIG.

A migration test was conducted on Example 1 and Comparative Example 1. At the same time, instead of pure Zn plating, N
i The same test as in Example 1 (reference example) except that the undercoating of 0.5 μm was applied was added to perform the test. The results are shown in Table 2.

Example 2 A two-layer TAB tape carrier without an adhesive having the same pattern shape as in Example 1 was manufactured and evaluated. As a method for producing the two-layer TAB tape carrier, a method of forming a polyimide film layer by casting a polyimide varnish on an electrolytic copper foil 25 μm (forming a film of the varnish by a roller coating method or the like) was adopted.

For the device hole, a method of forming a photoresist film, dissolving and removing the polyimide with an alkali-hydrazine solution, and then peeling off the photoresist film as a mask was adopted. The comparative test was performed on the sample without Zn plating as in Example 1 (Comparative Example 2). Table 1 shows the test results. The bending test was omitted because the copper foil film was the same.

Example 3 The samples of Example 1 and Comparative Example 1 were stored at room temperature, and the relationship between the storage period and the gang bonding property (method of heating and pressing the LSI bump and inner lead with a heat tool) was compared. The results were investigated, and the results were evaluated by a peel strength test of the inner leads (20 for each test) (see FIG. 4).

Example 4 The same procedure as in Example 1 was carried out except that gold plating was applied only to the inner lead portions (0.5 μm) and solder plating under the Zn plating was applied on the outer side and the film pattern. Since the inner lead side is not bent, A on hard Ni plating (thickness 1.0 μm)
u plating was used. In this case, Ni was used as the barrier plating for the diffusion reaction of Cu and Au. As a result, it was possible to prevent copper from diffusing into gold at the inner lead bonding temperature of 430 ° C. and improve the gang bonding property. At the same time, regarding the bendability on the outer lead side, the same effect as in Example 1 was obtained.

(Embodiment 5) The solder plating of the uppermost layer is performed 100 times.
% Sn was performed in the same manner as in Example 1 except that pure tin electroplating was performed. The bending test result is shown in FIG.

<Test method> The temperature cycle test is conducted by EIA.
Using J1C-121, the high temperature and low temperature regions were alternately held for a certain period of time under the following conditions, and the number of lead breaks caused by this environmental change was determined.

High temperature side 150 ° C., low temperature side −50 ° C. High temperature side holding time: 30 minutes Low temperature side holding time: 30 minutes Normal temperature (intermediate temperature 25 ° C.): 30 minutes Atmosphere: In air

The number of packages in which inner lead fracture occurred after 100 to 500 cycles was defined as the fracture rate. The number of test packages was 25 each, and breakage was observed by a soft X-ray transmission method. The sealing resin is epoxy type (coefficient of thermal expansion 6.3 ×
10 ⁻⁵ / deg) was used.

The bending test after holding at a high temperature was 500 at 120 ° C.
After being kept in the air for up to an hour, 0.1R by hand bending
Bending test (As shown in FIG. 5, the sample 40 was bent from the vertical position to the right and left at a bending angle of 90 degrees in the order of A → B → C → D, and this was shown as the number of bendings 4 and the number of times until breakage The migration test was carried out as follows: Applied voltage: DC 50 V Pattern: 50 μm Pattern length: 15 mm Atmosphere: 85 ° C., 85% RH Test period: 500 hours resistance between patterns was measured with a megohmmeter and three times. The average value (unit: ohm) is shown.

[0050]

[0051]

As described above, it can be seen that the lead of the present invention has considerably excellent durability as compared with the conventional one.

[0053]

Since the present invention is configured as described above, it is possible to prevent the formation of Cu-Sn intermetallic compound and prevent the breakage of the inner lead and the corrosion disconnection in a corrosive environment. became. Therefore, it is possible to use the TAB tape carrier for mass production even when manufacturing high-precision equipment.

[Brief description of drawings]

FIG. 1 is a partial plan view of a TAB tape carrier of the present invention.

FIG. 2 is a schematic sectional view when mounted on a substrate using the copper foil pattern lead of the present invention.

FIG. 3 is a graph showing the relationship between the heating time in a bending test after holding at high temperature and the number of times of bending until breakage.

FIG. 4 is a graph showing the relationship between the storage period and the peel strength per lead.

FIG. 5 is an explanatory diagram of the number of times of bending in a bending test after holding at high temperature.

FIG. 6 is a schematic sectional view of conventional inner lead bonding.

FIG. 7 is an explanatory diagram of an outer lead bending portion.

[Explanation of symbols]

 1 TAB Tape Carrier 11 Copper Foil Pattern Lead 12 Surface Treatment Layer 13 Protective Layer, 14 Semiconductor Element 15 Bump 2 Film 3 Lead 31 Inner Lead 32 Outer Lead 32a Outer Lead Bending Part 4 Device Hole 6 Sprocket Hole 7 Sealing Resin 9 substrate (printed board) 10 polyimide film 20 Zn or Zn alloy plating layer 30 Sn or Sn alloy plating layer 40 sample

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-357847 (JP, A) JP-A-3-276738 (JP, A) JP-A-3-276739 (JP, A) JP-A-3- 276654 (JP, A) JP-A-3-64939 (JP, A) JP-A-2-213495 (JP, A)

Claims (2)

(57) [Claims] 1. A semiconductor device mounting device hole is provided,
Having a copper foil pattern lead extending toward the device hole opening attached to the surface, after bonding the electrode of the semiconductor element and the inner lead of the copper foil pattern lead at the tip of the inner lead,
In a TAB tape carrier used for resin-sealing and mounting, at least the surface of the copper foil pattern lead excluding the inner leads is plated with Zn or Zn alloy to form an S
TA characterized by having n or Sn alloy plating
B tape carrier. 2. The tape carrier for TAB according to claim 1, wherein the copper foil pattern lead is a rolled copper foil or an electrolytic copper foil.