JPS63215306A - Manufacture of copper or copper alloy foil for tape carrier - Google Patents

Abstract

PURPOSE:To easily obtain copper or copper alloy foils with smooth surfaces by annealing the foils to have fine crystal grain sizes smaller than the final foil thickness and again performing cold rolling on the foils. CONSTITUTION:A performed rolled stock of copper or copper alloy is annealed so that its crystal grain sizes are brought to be smaller than the final foil thickness and the stock is again cold rolled to be a foil. Thus, a foil having good rollability, flat shape, and fine surface roughness is obtained. Preferable annealing is such that crystal grain sizes are regulated to <=about 1/2 of the final foil thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a copper or copper alloy foil for a tape carrier suitable for mounting semiconductor chips on a wiring board.

[Conventional technology]

Semiconductor chips are usually small pieces a few millimeters square and about 100 microns thick, so it is difficult to mount them on a wiring board as is. Therefore, it is generally housed in a type of container called an IC package.

The basic form of this IC package is that a semiconductor chip is mounted on a heat sink, which is a metal plate for heat dissipation, and the fl! It has a structure in which an electrode terminal and a lead wire for external circuit connection are joined.

The lead wires protrude outside the package like centipede legs and are also called pins.

There are two types of IC and LSI packages: the dual in-line package (DIP), in which the pins protrude vertically downward from both sides in two rows, and the flat package (FP), in which the pins protrude in the plane of the four sides. is currently the mainstream.

The FP method has the advantage that the number of leads (pins) can be relatively increased compared to the DIP method, so that the packaging density on the wiring board can be increased somewhat.

However, in recent years, LSIs have become more highly integrated, and the number of pins has also increased rapidly in proportion to this, so the FP and DIP methods described above are no longer sufficient, and new packaging methods that can accommodate increased pin counts are being developed. It was wanted.

Under these circumstances, a packaging method called tape carrier (also called film carrier) was developed.

As shown in Figure 1, this tape carrier system consists of a long tape 2 with a sprocket wheel 1 attached, and the base material of the tape 2 is polyimide, polyester, polyether sulfone (PES), polyparapanic acid ( PPA)
using resins such as

Copper foil is pasted thereon, and then photo-etched to form copper chip bonding fingers 3 and steel external connection fingers 4.

Bumps are formed on the electrodes of the semiconductor chip, and the electrodes (bumps) of the chip are bonded to the fingers by means of gigantic bonding, in which all terminals are bonded simultaneously. Next, the semiconductor element with copper external connection fingers is mounted on the punched wiring board from the carrier.

The tape carrier formed in this way has a tape-like shape (
It can be handled as a long piece and can be positioned using the sprocket hole.

■ Compared to the wire bonding method, there is almost no crushing of the fingers during bonding, so the terminal pitch can be significantly reduced (up to about 80 microns).

■ Because it uses a gigantic bonding method, the bonding process is done only once and is independent of the number of terminals.

■ Chip burn-in tests can be performed while attached to the carrier.

■ The carrier is thin and flexible, making it thin.

Flexible implementation possible.

■ Chip replacement after mounting is easy.

It has many advantages such as, and is particularly suitable for high-density mounting type LSI requiring a large number of pins.

By the way, copper foil with a thickness of 20 to 50 .mu.m is used as the metal conductor used in such a tape carrier method, and copper foil with an even thinner plate thickness is also being considered. Since the metal conductor for the tape carrier has an IC element bonded to the back side of a part of the finger, it is required that the back side of the copper foil be as smooth as possible. 1. Usually, rolled steel foil is used, but 1. It is extremely difficult to produce good ultra-thin copper foil, and a high-quality steel foil with good yield has been desired.

[Problem that the invention seeks to solve]

The present invention was made in view of the above-mentioned situation, and it is an object of the present invention to provide a method for easily manufacturing copper or copper alloy foil with a smooth surface.

The present invention will be explained in detail below.

[Structure of the invention]

A copper or copper alloy for a tape carrier, characterized in that an intermediate rolled steel or copper alloy material is annealed so that the crystal grain size becomes smaller than the final thickness of the foil, and then cold rolled again to form a foil. This invention relates to a method for producing foil.

[Means for solving problems]

The present inventors conducted various studies on the manufacturability, shape (flatness), surface quality, etc. of copper foil, and found that there is a strong correlation between these properties and crystal grain size.

That is, when a foil whose crystal grain size is equal to or larger than the thickness of the final foil through annealing is cold rolled, the foil will be in a state where there is only one crystal grain in the thickness direction. If a foil material made of a material having such a crystal grain size is attempted to have the final thickness, the rolling resistance will become significantly large and the rolling properties will deteriorate. Furthermore, if a large tension is applied to improve the rolling properties, the material tends to become S-shaped, and the surface roughness also deteriorates (becomes rougher). For this reason, as in the present invention, by annealing the foil to a grain size smaller than the final thickness and then cold rolling it again, it is possible to achieve good rollability and a flat shape. It became possible to produce foil with fine surface roughness. Preferably, it is recommended that the foil be annealed to a grain size of 172 or less of the final thickness of the foil.

Copper foil has conventionally been used as the metal conductor for tape carriers, but since heat is applied during the tape carrier manufacturing process, a material with good heat resistance is desired. Therefore, a copper alloy in which trace amounts of additional elements are added to I is more preferable.

The manufacturing method of the present invention can also be applied to these steel alloys.

Specifically, copper alloys include P, Sn, Ni, Fe, Go, and C.
r, Zr, Ti, Si, Mg, Ag, Cd, In, T
It refers to a product to which one or more of elements such as e, Be, Hf, B, and Mn are added at a maximum of 1.0% by weight.

〔Example〕

Various coppers or copper alloys shown in Table 1 were melted and cast in a high frequency melting furnace. This ingot was hot rolled to form a plate of 811I11, and further cold rolled to a thickness of 1 mm.

This was annealed at 400° C. for 1 hr, then cold rolled to a diameter of 0.2 m, then annealed under various conditions to obtain the various grain sizes shown in Table 1, and then cold rolled to 0.025 m. In this case, the cold rolling rolls were Rmaxo,
A material having a diameter of 3 μm was used, and Lotus CC was used as the rolling oil.

The surface roughness of such test materials can be measured using a surface roughness meter.
max was measured, and the shape was visually observed wt for the presence or absence of curls, sticklebacks, etc. when placed on a surface plate.

In addition, regarding manufacturability, from 0.2am to 0.025I
Judgment was made based on the number of rolling passes.

The results are shown in Table 1. These results show that by making the crystal grain size smaller than the final thickness of the foil, copper or copper alloy foil for tape carriers with a flat surface roughness of 1, and with good shape and manufacturing properties can be produced. 1 table

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an example of a tape carrier system. 1: Sprocket wheel 2: Resin film 3: Chip bonding finger 4: External connection finger 5: Test pad

Claims (1)

[Claims] Copper or copper alloy for tape carrier, characterized in that an intermediate rolled copper or copper alloy material is annealed so that the crystal grain size becomes smaller than the final thickness of the foil, and then cold rolled again to form a foil. Method of manufacturing foil.