JPH0368150A - Film carrier provided with lump bump and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable a bump of high quality to be formed at a precise position by a method wherein a bump main body is joined to the tips of the inner leads of a synthetic resin film carrier main body through a eutectic bonding or a thermocompression bonding. CONSTITUTION:At processing, a film carrier 1 is previously plated with tin, and a gold wire is used as a bonding wire 6. A blade 10 is made to descent to press a wire 6 against a lead 3, and the wire 6 is pressed by the blade 10 together with an anvil 12 located at the rear side. By heating and pressing, the tin plating layer formed on the lead 3 and gold of the wire 6 are eutectically bonded together to be surely joined, and the wire 6 is cut off at a device hole 4 by a cutter 11 located at the side of the blade 10. Next, the wire 6 joined to the lead 3 is processed to be divided, for instance, by a wire 13 of a discharge wire cutter machine.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to wireless bonding of semiconductor chips for ultra-thin high-density integrated circuit elements, in which a TiSO1 bonding bang is made of gold m or the like on the film carrier side. The present invention relates to a film carrier with bulk bumps formed thereon and a method for manufacturing the same.

[Prior Art] Generally, when manufacturing ICs, LSIs, etc., after a semiconductor chip is bonded to a lead frame pad, a bonding wire such as an ultra-fine pure gold wire is connected between each electrode of the chip and the outer lead of the lead frame. Wire bonding, in which wires are bonded one by one, is well known.

However, in the case of ultra-high-density integrated LSIs, the number of pins corresponding to the outer leads is in the hundreds, so the distance between each bin is close to each other at intervals of several tens of microns. There are limits to the manufacturing process and quality.

For this reason, tape automated bonding (TAB) method, in which each electrode of the semiconductor chip is directly thermocompression bonded to the inner lead, has recently been widely used.

Conventional TAB is made by laminating copper foil about 35μ thick on a long tape film about 125μ thick made of polyimide resin, boester resin, glass epoxy resin, etc. Perforations and device poles that mesh with the feeding sprocket are drilled,
In addition, a film in which predetermined circuit patterns, inner leads, etc. are formed in a continuous manner as a large number of frames similarly to photographic film by photoresist and etching, and each lead portion is subjected to electroless complex metal plating or electrolytic gold plating. It uses a carrier.

In addition, the semiconductor chip has a protrusion (bump) for thermocompression formed on the pad part of the diffused wafer, and a barrier layer (barrier metal) is formed on the back surface of the chip with a predetermined metal. Bumps of a predetermined size are formed on the top using metal such as gold or tin, and these bumps are thermocompression bonded to each of the leads to connect the chip electrodes and an external circuit by wireless bonding.

The conventional example of this TAB method is to form bonding protrusions (bumps) on the semiconductor chip side using gold, tin, etc. 5 steps to form a gold film on a diffused wafer ~ photolithography process ~ strike treatment process ~ plating process ~ It requires a resist removal process, a photolithography process, a photolithography process, an etching process, a resist removal process, an annealing process, etc., and the bumped wafers obtained in this way are pasted one by one on a nest plate with wax, then diced. After chipping,
The bonding is performed.

Therefore, the manufacturing process is quite complicated, and it is difficult to precisely plate a large number of minute bumps on each electrode of a small chip, which inevitably increases production costs and makes the chip only suitable for special purposes.

For this reason, in recent years, means for forming bumps with a thickness of 10 to 30 microns using metal such as gold on the inner lead side of a film carrier have become common, and the following method is well known.

The first example is a method in which the end of the inner lead is photo-etched and a mesa-shaped bump slightly raised above the inner lead surface is formed thereon by spray plating.

The second example is a transfer bump method, in which only a predetermined number of gold bumps are deposited by plating using a mask on a glass substrate, and then these are thermocompressed onto the inner lead side of the film carrier. The method is to transfer the bump thereto.

[Problems to be Solved by the Invention] Therefore, in the above-mentioned No. 11vl, since a minute cracked part is formed at the tip of the inner lead by conventional partial plating means, although it is a mesa-shaped bump, the plating deposit layer is actually thin. Moreover, since the bump surface is irregularly shaped, the plating thickness will vary, and if left as is, bonding with the chip will be hindered, so the surface of the bump needs to be shaped in post-processing.

On the other hand, according to the 1N method, the process is troublesome because precise positioning is required twice: when forming bumps on the glass substrate and when transferring the bumps to the film carrier. It has been pointed out that mounting a semiconductor chip with a bottle structure is difficult.

This is due to the following reasons.

First, when a bump is formed on a glass substrate, it becomes a sharp mesa-shaped bump at that time, but when it is thermally transferred to a film carrier side, it becomes upside down.

That is, the sharp portion is stuck to the surface of the inner lead,
The bottom surface of a wider area is upwardly facing (reversely tapered), and the diameter of the top of the bump is larger than that of the bottom and also larger than the width of the inner lead, so the lead spacing cannot be reduced to 11 m, making it possible to create a wintering bottle structure. Not suitable for chips.

Moreover, since the top of the bump is wide and flat,
When bonding with a chip, the top surface of the bump is not easily deformed (difficult to bond) due to heating and pressing force, and the top surface of the bump collapses under the pressing force while bonding to the chip electrode. This is because the fresh metal surface (new surface) inside the bump is not exposed one after another, resulting in a decrease in bonding ability.

Next, bonding of conventional film carriers including the above-mentioned known examples will be explained.

-A film carrier with bumps forms bumps only on the inner leads, so the chips are first bonded by inner lead bonding (ILB), and then outer lead bonding (OLB) is performed in a separate process to external It was connected to a circuit board electrode.

In the case of this OLH, unlike the above-mentioned chip bonding, the surface treatment material of the bonding part uses metal such as tin, and the plating thickness is quite thin (2 to 3μ) compared to the bumps, so ILB This requires a completely different joining function.

In other words, conventionally, ILB for the same film carrier
This was one of the causes of increased manufacturing costs, as the OLB and OLB had to be processed in separate processes.

Furthermore, there were also the following problems regarding the bump forming means.

First, in both the first and second known examples, when forming bumps, the plating deposition rate is 1 μ≠, so it takes a considerable amount of time to form a bump for one frame, and productivity is extremely poor.

Furthermore, as is well known, the hardness of the metal deposited by plating is considerably higher than the hardness of the metal itself, so there is a risk that the electrode portion on the chip side will be destroyed when bonded to the semiconductor chip.

Furthermore, when forming bumps by plating, due to variations in the plating area due to forming dimensional tolerances such as the inner lead width of the workpiece, it is difficult to ensure that the plating thickness is within sufficient accuracy even if a plating time control method is used to measure the plating current. It's difficult to hold down,
In particular, the larger the number of pins, the more difficult it is.

[Means for Solving the Problems] The present invention has been devised in view of the above-mentioned problems, and is a method of bumping directly onto the lead ends of lead frames and film carriers for semiconductor chip mounting, or onto circuits such as printed circuit boards. A method of forming.

The purpose of the present invention is to provide a film carrier with lumpy bumps and a method for manufacturing the same, in which the bumps can be formed in precise positions and high quality products can be obtained, and semiconductor chips in wintering bottles can also be mounted with high efficiency. It is a thing.

As a means for achieving the above object, for example, a gold wire for wire bonding is arranged so as to straddle a tin-plated inner lead formed on a film carrier, and the inner lead and the gold wire are cohesively bonded. Then, only the gold wire protruding between each inner lead is cut and removed, and a precise bump is formed at the tip of each inner lead.

In addition, the bumps formed at the tips of the inner leads are designed so that new surfaces can be sequentially exposed from the surface during bonding, and are smaller in size than the width of the inner leads, making them suitable for semiconductor chips with a winter bottle structure.

Furthermore, a main bump for bonding (ILB) with the semiconductor chinobu is formed at the tip of the inner lead as described above, and a sub bump for bonding (OLB) with the external circuit electrode is formed at a predetermined portion of the outer lead. , for example, by using a solder wire in the same manner as the above method.

[Function] When forming a bump using a metal wire, the connection between the metal wire and the inner lead part is achieved by eutectic bonding of gold and tin by applying heat and pressure from the outside, or by heat bonding between gold and gold. Bonding is achieved by crimping, and during crimping, it is possible to coin the gold wire into an appropriate cross-sectional shape depending on the shape of the pressure plate, but it is possible to coin the gold wire into a suitable cross-sectional shape according to the shape of the pressure plate. By using the above method, a bump with a desired cross-sectional shape can be obtained, and since the shape of this bump is an important factor in determining the quality of the bonding during subsequent thermocompression bonding with a semiconductor chip, it is preferable to use a predetermined bump shape. Getting is important.

After joining the gold wire and the inner lead, the excess portion protruding between the inner leads may be cut mechanically using a wire cutter or a thin blade rotating at high speed.
By melting and cutting the gold wire with a laser beam, it is possible to form bumps only in predetermined locations, and it is also possible to make the bumps smaller than the width of the inner lead, and it is easy to form a new surface on the bonding surface of the bumps during ILB. It is also easy to shape it.

Furthermore, a second bump (secondary bump) for the OLB can be formed in the same manner on the outer lead using a gold wire such as tin or solder.

[Implementation rIA2 Next, embodiments of the present invention will be described based on the drawings.

The film carrier 1 shown in the first [J] is made of, for example, a polyimide film 2 and an inner lead 3 formed of copper foil.
This is a well-known device having device holes 4 formed at predetermined locations.

This film carrier 1 is sequentially fed frame by frame at a constant speed by a separate work transfer mechanism (not shown) using perforations (not shown) provided on both sides of the film carrier 1, and is moved to a predetermined position by the above-mentioned film carrier. This is so that the device hole 4 is kept stationary.

On the other hand, wire supply mechanisms 5 are disposed above and below this device hole 4.

The wire supply 1 [5 has a holder 7 that sequentially feeds out bonding wires (gold wire) 6 below the device hole 4, and the bonding wires 6 that come out from there.
A chuck 8 for grasping and pulling out a predetermined length is disposed above the device hole 4, and the chuck 8 itself is movable up and down and horizontally pivotable within a predetermined angle range on the upper surface of the inner lead 3. It's Toshide.

Also, in parallel with this wire supply mechanism 5, a flat press! ! There are 9 horizontal sections.

A blade 10 with a built-in heater that can be moved up and down is placed directly above the inner lead 3, and a cutter 11 is provided protruding from the side of the blade 10 to cut the gold wire fed out from the holder 7. It is.

Also, the blade 1 is located on the back side of the inner lead 3.
An anvil 12 with a built-in heater is fixed in opposition to the blade 10, and both the anvil 12 and the blade 10 are
It is heated to 400 to 600°C, and both are pressed with a predetermined pressure.

This pond is provided with a cutting mechanism for cutting the gold wire protruding between each inner lead 3 as described later.
In the embodiment, a wire-cut electric discharge machine is used.

During processing, the film carrier 1 is plated with silk in advance, and the bonding wire 6 is a gold wire (general-purpose wire material for wire bonding).

First, the film carrier 1 is sequentially fed at a predetermined speed and stopped when the device hole 4 is located at the holder 7.

A bonding wire (gold wire) 6 is made to slightly protrude from the tip of the boulder 7 in advance.

Under the above conditions, the chuck 8 first descends, clamps the bonding wire 6, rises, and then stops.

After that, the chuck 8 makes a horizontal turning movement (arc movement) on the inner lead 3 while holding the bonding wire 6, and when it stops at the end of the finger 3, each inner lead is aligned in parallel with the device hole 4. The bonding wire 6 is stretched across all of the wires 3. (See FIG. 2) Next, as shown in FIG. 3, the blade 10 descends, presses the bonding wire 6 against the inner lead 3, and presses it together with the anvil 12 located on the back side with a predetermined pressure.

Due to this heating and pressure, the tin plating layer on the surface of the inner lead 3 and the gold of the bonding wire 6 are eutectic bonded,
Cuffer 11 on the side of blade 10 that is securely joined
As a result, the bonding wire 6 is cut at the device hole 4.

Furthermore, if the film carrier 1 is plated with gold, similar metals will be bonded together by thermocompression bonding.

In this way, when bonding the inner lead 3 and the bonding wire 6, extremely precise processing can be achieved by appropriately adjusting the positioning of the blade 10, the stroke during pressing, the pressure, etc.

When the series of bonding processes are completed as described above, as shown in FIG. 4, the blade 10 rises while the chuck 8 also returns to its original position.

Next, the cutting process of the joined bonding wire 6 will be explained based on FIG. 5 and subsequent figures.

FIG. 5 shows the case where the bonding wire 6 is cut by a wire-cut electric discharge machine, and as is well known, there are many types of wires 13 used in the machine, including extremely thin ones.
In addition, the tension state is maintained by the pulley 14, and the discharge is carried out while being fed sequentially.

When this wire 13 enters the gap of the inner lead 3, the bonding wire (gold wire) 6 of the part protruding into the gap of the inner lead 3 is melted and cut by an arc.
The bonding wire 6 remains only on the inner lead 3, and a lumpy bump 15 is formed.

In addition, no stress is applied to the inner leads 3 during cutting, so the dimensions and shape accuracy of the inner leads 3 are not disturbed, and the finishing accuracy of the lumpy bumps 15 is high, so that it is easy to cut the inner leads 3 with chips (not shown). The bonding accuracy is significantly improved.

The next embodiment shown in FIG. 6 shows a method of cutting the bonding wire 6 by rotating a thin wIwl or the like at high speed.

A shaft 21 rotates at high speed by electric power or air,
A copper foil cutter 22 made of copper foil formed into a disk shape is fixed.

When cutting the bonding wire 6 protruding into the gap between the inner leads 3, when the copper foil cutter 22 is rotated at high speed, the thin copper foil cuffer 22, which is originally soft, becomes rigid due to centrifugal force, and the first cutter becomes a sharp cutter. do.

Therefore, the cutting process can be performed by entering the gap between the inner leads 3 while rotating at high speed.

This embodiment has a feature that the cutting shape can be determined according to the outer peripheral cross-sectional shape of the copper foil cutter 22.

The next embodiment shown in FIG. 7 is a method of cutting the bonding wire 6 using a laser beam.

A laser beam 32 output from a carbon dioxide laser oscillator 31 is irradiated into the gap of the inner lead 3 through an optical system prism lens 33, and a detection signal from a sensor 34 that detects the inner lead 3 is used to irradiate the carbon dioxide. This is to control the gas laser oscillator 31.

The ginning wire (gold wire) 6 has been roughened by chemical etching or gold plating in order to reduce the light reflection on the surface and improve the laser beam absorption rate. It is necessary to keep

As described above, when cutting the bonding wire 6 bonded to the inner lead 3, the carbon dioxide laser oscillator 31, the sensor 34, and the optical system prism lens 33 are used.
is swept to the left in the figure at a constant speed.

Only when the sensor 34 does not detect the inner lead 3, the carbon dioxide laser oscillator 31 outputs a laser beam, and the bonding wire 6 protruding into the gap between the inner leads 3 is exposed.

By dividing and removing the excess bonding wire 6 protruding into the gap between the inner leads 3 using the above-mentioned means, a lump-like bonding wire, that is, a lump-like bump 15 is formed at the tip of each inner lead 3. However, as described above, since this bump itself is a bonding wire (gold wire), it has lower hardness than metal deposited by plating and is suitable for bonding ink.

In addition, the bumps formed as described above have a so-called semi-cylindrical cross-sectional shape, and when bonding with a chip, they tend to collapse from the top one by one, and the newly formed surface is always exposed, so that reliable bonding is possible. The cross-sectional shape can be made into a desired shape in order to provide properties.

In this case, as shown in FIG.
The bonding wire 6 to be stretched over the top is coined in advance into an arbitrary cross-sectional shape, such as an elliptical or trapezoidal cross-section, and then the bonding wire 6 is coined into a land that is eutectic bonded or thermocompressed, and the bonding wire 6 is By dividing, a lumpy bump 41 can be formed at the end of each inner lead 3 as shown in FIG.

As a result, a shape and hardness optimal for bonding with a chip can be obtained with high precision.

In the above embodiment, only the lumpy bumps 15 are formed on the inner leads 3, but dedicated bumps can be formed on the outer leads as well.

In this case, the film carrier 1 itself is treated with gold or tin plating in the same manner as described above.

Bumps for bonding with chips (hereinafter referred to as main bumps) are formed by thermocompression bonding or eutectic bonding to form bulk main bumps with gold wire on the inner leads 3 of the film carrier 1 according to each of the above embodiments.

On the other hand, the outer lead (not shown) of the film carrier 1 uses a base metal suitable for bonding with an external circuit. After bonding, the portion of each outer lead protruding from the gap is separated and removed to form a sub-bump made of solder in the form of a lump.

In this way, by using the conventional film carrier as is and using the same gold wire and solder wire for wire bonding, the main bumps that are most suitable for chip bonding and the sub-bumps that are most suitable for bonding with external circuits are the same. Can be formed into a film carrier.

[Effects of the Invention] As explained above, the present invention has the following effects.

(2) When eutectic bonding or thermocompression bonding of the bump to the inner lead of the film carrier, it is possible to achieve extremely high accuracy by deciding to press the blade.

■As the bump material, it is possible to use the same material used for IC wire bonding, so it is possible to manufacture bumps with extremely ideal purity and hardness. It is.

■, IN of the bang for the outer lead of the film carrier
Bumps can be formed extremely easily by using a general-purpose solder wire or the like and using the same method as for inner leads.

(2) It is extremely practical because both the main bumps (gold) for chip bonding and the sub-bumps (base metal) for external circuit bonding can be formed on the same film carrier.

(2) The method of forming bumps on a film carrier is much more streamlined and precise than conventional known means, and the yield can be improved to a great extent, making it possible to provide high-quality products at extremely low prices.

[Brief explanation of drawings]

Each country is related to an embodiment of the present invention, and FIG. 1 is a perspective view of the main part showing a state in which a film carrier, which is a work, is set, FIG. 2 is a perspective view of the main part showing a state in which the bonding wire is pulled out, and FIG. Figure 3 is a perspective view of the main parts showing the state in which the bonding wire is bonded to the film carrier;
The figure is a perspective view of the main part after this joining is completed, Figures 5 to 7 show the state in which the part protruding into the gap of the inner lead is separated, and Figure 5 is an example of wire-cut electrical discharge machining. Fig. 6 is a perspective view of the main part showing an example of fA foil disk rotating at high speed, Fig. 7 is a perspective view of the main part showing an example of separation IT using a laser beam, and Fig. 8 is a perspective view of the main part showing an example of separation using a laser beam. FIG. 9 is a perspective view of a main part showing an example in which a bonding wire is used, and FIG. 9 is a perspective view of a main part showing a bump formed with the same bonding wire as described above. 1 Film carrier 3 Inner lead 4 Device hole 5 Wire supply mechanism 6 Bonding wire 7 Holder 8 Chuck 9 Breath mechanism 10 □ Blade 11 □ Cutter 12 □ Anvil 13 □ Wire cut 15 □ Bump 22 - Copper foil disk 31 - Carbon dioxide laser oscillator electrical discharge machine wire

Claims (1)

[Claims] 1. A lumpy bump body whose cross section is formed into an arbitrary shape from a material suitable for bonding semiconductor chips is attached to each tip of the inner lead of a synthetic resin film carrier body by eutectic bonding or thermal bonding. A film carrier with lumpy bumps joined by pressure bonding. 2. The film carrier with lumpy bumps according to claim 1, wherein the lumpy bump main body is formed of a gold wire whose cross section is coined into an arbitrary shape. 3. A lumpy bump body whose cross section is formed into an arbitrary shape from a material suitable for bonding semiconductor chips is bonded to each tip of the inner lead of a synthetic resin film carrier body by eutectic bonding or thermocompression bonding, and At the tip of each outer lead of the film carrier body, there is a massive sub-bump body made of a material suitable for bonding with external circuit electrodes, whose cross section is formed into an arbitrary shape, and joined by eutectic bonding or thermocompression bonding. Comes with a film carrier. 4. The film carrier with lumpy bumps according to claim 3, wherein the lumpy sub-bump main body is formed of a base metal wire such as tin or solder whose cross section is coined into an arbitrary shape. 5. Each inner lead of the film carrier body is tin-plated, a bonding wire such as a gold wire whose cross section is formed into an arbitrary shape is stretched across the plurality of inner leads, and both are pressed together with a predetermined pressing force. The bonding wire and the inner lead are eutectic bonded together, and then the bonding wire protruding into each gap of the inner lead is cut and removed, leaving a lump of bonding wire at the end of each inner lead, and forming a lump of bump using this as a bump. A method for manufacturing a film carrier with a tape. 6. The method for manufacturing a film carrier with lumpy bumps according to claim 5, wherein each inner lead of the film carrier body is gold-plated, a gold wire is used as a bonding wire, and both are bonded by thermocompression. 7. The method for manufacturing a film carrier with lumpy bumps according to claim 5 or 6, wherein the bonding wire protruding from the gap between each inner lead is separated by wire-cut electrical discharge machining. 8. The method for manufacturing a film carrier with lumpy bumps according to claim 5 or 6, wherein the bonding wire protruding from the gap between each inner lead is cut by a cutter in the form of a metal foil plate rotating at high speed. 9. The method of manufacturing a film carrier with lumpy bumps according to claim 5 or 6, wherein the bonding wire protruding from the gap between each inner lead is separated by a laser beam.