JPS6388833A - Tape-carrier mounting tape - Google Patents

Abstract

PURPOSE:To solve problems such as defective connection to a lead frame of an outer lead by forming a connecting surface to the lead frame of the outer lead shaped to a mounting tape used in a tape carrier mounting system in size thicker than other sections and plating the connecting surface with a low melting-point metal such as tin or solder. CONSTITUTION:Leads 4 are shaped onto a tape 1 consisting of a polyimide film, and tin or solder plating 21 is executed selectively to the outer end sections of the leads 4, connecting sections to at least a lead frame of an outer lead, previously partially. On the other hand, other end sections of the leads 4 are connected to bumps 6 in an element 5, the leads 4 are cut, leaving the plating 21 sections, and the leads 4 are bent similarly through press molding, etc. The outer lead sections and the lead frame 9 are faced oppositely, said plating 21 is interposed among the opposed sections, a bonding tool 22 is pushed against the leads 4, the leads 4 are thermocompression-bonded by pulse currents, and the plating 21 by tin or solder is melted and the leads 4 and the lead frame are connected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to improvements in tape carrier mounting tapes,
In particular, the present invention relates to a tape carrier mounting tape in which the tin plating thickness of the outer lead portion is thicker than that of the inner lead portion.

(Conventional technology) Conventionally, when manufacturing a packaged body of a semiconductor device, IC.

Various methods have been developed for electrically leading out externally leading electrode terminals on elements such as LSIs to external connection leads.

The most well-known method is to deposit 25-40 μm of Au
There is a so-called wire bonding technique in which wires to the external lead-out electrode terminals are interconnected by mutual thermocompression bonding or ultrasonic bonding using thin metal wires such as , AI, or the like.

This method also provides high reliability for the connecting portion when the number of external lead-out electrode terminals is relatively small. However, in recent years, unlike LSIs, where the number of element functions is not extremely high, the number of external lead-out electrode terminals has reached 100 to 150 terminals, and such connections require twice as much bonding on the element side and external connection lead side. As a result, the number of connections is significantly increased, and the reliability of these connections inevitably decreases, making it difficult to reduce costs.

On the other hand, in order to overcome such a decrease in the reliability of the connection portion, a so-called wireless technology that does not use thin metal wires has been put into practical use, in which the above-mentioned element-side electrode terminals are processed all at once.

One method is, for example, a tape carrier method. In this method, metal protrusions (usually gold, tin, or solder) are used on the electrode terminals of the device at the wafer processing stage.
(hereinafter also referred to as bumps), and the tin-plated copper foil leads on a separate polyimide carrier are pressurized and heated all at once to melt and connect the metal protrusions of B.

In this case, as the number of electrode terminals increases, the electrode pitch becomes significantly smaller, and processing of the copper foil leads requires extremely high precision. At the same time, the tip of the lead becomes thinner, making it extremely difficult to process it.

Here, the tape carrier system will be explained in more detail with reference to FIGS. 5 and 6. For example, similar to a movie film, a large number of holes 3 for semiconductor elements are formed in the longitudinal direction of a heat-resistant tape 1 made of polyimide or the like in which feed holes (2) are formed. Next, copper foil (not shown) is applied to the hole 3 and etched into a predetermined pattern designed in advance.

By this etching process, the copper foil lead 4 is configured to protrude toward the center of the hole 3 in the direction of the semiconductor element 5 arranged as shown in the figure (this protrusion toward the center is also referred to as an inner lead section). The surface of the copper foil lead 4 is plated with solder or tin.

Next, a bonding tool is pressed against the inner lead portion (to be described later) of the copper foil lead 4 corresponding to the bump 6 formed on the external lead electrode of the semiconductor element 5, and a pulse current is applied thereto to establish the connection. These parts are then sealed with epoxy resin or the like in the usual manner.

Note that 7 in the figure is a support frame for the inner lead portion. - square element 5
The copper foil lead 4 is cut within the peripheral opening 8 to separately separate punched elements in the shape shown in FIG.

Next, the copper foil lead 4 extending outward from the element 5 (hereinafter this part is also referred to as the outer lead part) is bent by press molding or the like and mounted on the center part of the lead frame 9 as shown in FIG. An outer lead is positioned at the inner end 9a of the wire 9, and similarly welded using a bonding tool to establish an electrical connection.

(Problems to be Solved by the Invention) However, in such a conventional method, the outer lead portion extending outward from the element 5 has a small material thickness and a narrow width, so that when the material is cut and bent by the pressing means, Their tip shapes are not necessarily constant.

That is, the above-mentioned bending process or the like causes pitch deviation or vertical positional fluctuation of the tip of the outer lead, resulting in poor connection to the lead frame, reduction in its strength, and the like. Furthermore, there have been problems in that the heating and compression conditions by the bonding tool are not constant, resulting in lower reliability and lowering workability and yield, resulting in economic disadvantage.

The present invention particularly provides a tape carrier implementation tape that solves problems such as poor connection of the outer lead to the lead frame.

(Means for Solving the Problems) The present invention provides that the connection surface of the outer lead formed on the mounting tape used in the tape carrier mounting method to the lead frame is thicker than other parts and is made of a low melting point metal such as tin or solder. It is plated.

(Function) According to the invention of Party B, since the tape carrier mounting tape is configured as shown in 9 above, when the outer lead is connected to the inner end of the lead frame, the partially thickened low melting point metal is applied to the outer lead. There is a plating part, and the defective position of the outer lead can be covered by the thickened plating layer, thereby eliminating problems such as the poor connection.

(Embodiments) Examples of the present invention will be described below with reference to FIGS. 1 to 4. In particular, FIGS. 1 and 2 correspond to FIGS. 5 and 6 above, and the same parts are given the same reference numerals and their explanations will be omitted.

In the present invention, the leads 4 are provided on the tape 1 made of polyimide film in the same manner as in the tape carrier system already described, and the outer ends, that is, at least the connection portions of the outer leads to the lead frame, are locally coated with tin or Solder plating 21 is selectively applied. On the other hand, the other end of the lead 4 is connected to the bump 6 of the element 5, and then cut as shown in FIG. 2, leaving the plated portion 21, and similarly bent by press molding or the like.

Next, the outer lead part and the lead frame 9 are made to face each other,
The plating 21 is interposed between the opposing parts, and a bonding tool 22 is pressed against them as shown in FIG. 3, and the plating 21 made of tin or solder is melted and connected by heating and pressing with a pulse current. Note that 30 in the figure is an island.

FIG. 4 shows the state of fusion connection of the outer lead portion of this lead 4, and in the figure, 23 indicates the eutectic connection formed at this time;
24 is Golden Metsuki Elijah.

In the present invention, the plating 21 made of tin or solder is preferably provided on the connection surface of the outer lead to the lead frame 9. When the bonding tool 22 is crimped, the plating 21 does not melt and adhere to the bonding tool 22, which is suitable for continuous connection work.

In the present invention, as described in the above conventional example, the copper foil lead 4 is entirely plated, and the tin plating preferably has a normal thickness of about 0.4 μm. If the plating thickness is increased too much, molten tin may short-circuit adjacent bumps or circuits when connecting the inner lead to the bump 6, and cracks may occur on the plating surface when bending the outer lead, resulting in defective products. This is not desirable because it causes

Further, it is generally considered that the parallelism between the bonding tool surface and the outer lead crimping portion should be adjusted to about 1.2 degrees or less. This is preferable because even if there is a certain amount of stiffness, it can be absorbed by dissolving the plating 21 of the present invention. Furthermore, although the crimp temperature of the honding tool 22 is set at 300° C. to 500° C., in actual work, both ends may not melt properly due to air cooling, which may cause a decrease in connection strength.

This may increase the temperature of the central portion, but if the tin plating is thin as described above, the plating tin will diffuse into the shell, resulting in a decrease in connection strength. In this invention, as described above, since a large amount (thickly) of plated tin is present in the central portion, it is possible to set the temperature to obtain good bonding conditions.

(Effects of the Invention) As described above in detail, according to the present invention, a low melting point metal such as tin or solder is partially applied to the outer lead portion of the mounting tape in the tape carrier mounting method, at least on the lead frame connecting portion side. Since the amount is increased by plating, the amount of molten eutectic at the connection between the two increases, and as a result, connection failures due to uneven positions due to lifting in the vertical direction caused by machining of the outer lead etc. can be avoided. obtain.

In addition, as mentioned above, the setting range of working conditions is widened, such as being able to set the temperature of the bonding tool on the high temperature side, improving workability and at the same time improving yield, which is advantageous in terms of economy.

By applying the above-mentioned plating to the opposite side of the connection part, workability can be improved by avoiding adhesion of molten tin to the bonding tool during pressurization and heating by the bonding tool.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining the connection process between the lead frame and the outer lead in one embodiment of the tape carrier mounting tape of the present invention, and FIG. 4 is the connection portion between the lead frame and the outer lead in the same process. FIG. 5 is a plan view of a conventional tape carrier mounting tape, FIG. 6 is a sectional view taken along line A-A in FIG. 5, and FIGS. 7 and 8 are views of a conventional tape carrier mounting tape. FIG. 3 is a diagram for explaining a process of connecting a lead frame and an outer lead. Topolyimide film (tape), 4, lead, 5
...Semiconductor element, 6. Bump, 7. Support frame, 8.
- Peripheral opening, 9... Lead frame, 9a... Inner end of lead frame, 22... Bonding tool, 2
3...Collection connection part. -11= 9 Shea 匈 Soi Footwork's Taylor 4 Yariyabuki 3 Chi 7' Me Return Door βh6Q
Figure 5 Figure 18

Claims (3)

[Claims] (1) In a tape carrier mounting tape made of heat-resistant tape and used in a tape carrier mounting method, (a) a first plating capable of thermocompression bonding is applied to the entire surface of the lead material formed on the mounting tape, and (b) the lead A tape carrier mounting tape formed by applying a second plating that can be selectively bonded by thermocompression to at least the external lead-out connection side of the outer lead portion of the tape carrier mounting tape. (2) The tape carrier mounting tape according to claim 1, wherein the first plating is tin, solder, or lead-gold. (3) The second plating is a plating of a low melting point metal such as tin, solder, or lead.
Tape carrier mounting tape as described in section.