JPH0465846A - Method and jig for forming metal protrusion forming - Google Patents

Abstract

PURPOSE:To save material cost by a method wherein, after linear metal material is arranged between a punch and a die, the punch is operated, the metal material is press-worked, a small metal segment having a specified shape is formed, and said segment is bonded to a metal lead. CONSTITUTION:Linear metal material 3 is sent through a metal material sending guide part 21. The tip part is made to abut against a stopper part 24 and positioned, which part 24 is formed on the part where an inner wall on the side opposite to the guide part 21 of a work hole of a die 2 is stretched upward. The sectional shape of a punch 1 is rectangular. When pressure is applied to the punch 1, it is fitted in the work hole of the die 2. On a side 23 of the sending guide part 21 side of the work hole, the metal material 3 is cut, and a small metal segment is formed. Thereby the metal material 3 of the same length as that of the small metal segment 8 is sent when each segment 8 is formed, so that the loss of the metal material 3 is not generated, and the material cost can be saved. Further pressure is continuously applied to the punch 1, it is made to descend, the small metal segment is compression-bonded on a metal lead 6, thereby forming a metal protrusion 8 of the metal lead 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming metal protrusions, and particularly to a method for forming metal protrusions for mounting semiconductor elements.

[Prior Art] In recent years, the fields of application of semiconductor products such as LSIs have been increasingly expanding, including various consumer devices and industrial devices. Due to the ability to expand the use of these devices, their prices are becoming lower and portability is being promoted. Therefore, in order to meet these demands in semiconductor products, there is a demand for high-density packaging such as lower costs, lighter weight, thinner thickness, and smaller size in packaging sinks and equipment integration processes.

Generally, the TAB method is known as a method suitable for high-density packaging of semiconductor elements, and efforts have been made to expand its practical use. For connection between a semiconductor element and a mounting wiring board using the TAB method, a metal lead made of Au or Cu plated with Sn and patterned to match the electrode arrangement of the semiconductor element is bonded to a polyimide film for holding the metal lead. A film carrier with a structure similar to the above is used. Here, in order to bond between the At electrode of the semiconductor element and the metal lead, it is necessary to make the bonding part convex, and a metal protrusion called a bump is provided on the At electrode part or the metal lead. A thermocompression bonding method is usually used to bond the At electrode and the metal lead via the metal protrusion.

As a conventional method for forming metal protrusions, the so-called metal bump method has been widely used. FIG. 8 shows the process of forming a bump on a boat. First, an adhesive layer 40 of Ti, Cr, etc., and a diffusion prevention layer 41 of Cu, Pt, etc. are formed on the semiconductor element 30 by sputtering (FIG. 8(a)).
. In the figure, 35 is an A1 layer, 36 is a protective layer, and 37 is a silicon substrate. Next, after forming a resist layer 42 covering areas other than the At electrode part 31 by lithography, Au is applied to the electrode part 31.
A plating layer 43 of about 30 μm is formed (FIG. 8(b)).

After that, after removing the resist layer 42, the At electrode part 31
The diffusion prevention layer 41 and the adhesive layer 40 other than the At electrode part 31 are removed by etching while protecting with a resist layer covering them (FIG. 8(C)). Through the steps described above, metal protrusions are formed on the A1 electrode by plating.

Other than the metsuki bump method, ball pan 1 using the Au wire ball bonding ink technique shown in the process diagram of FIG.
The law is attracting attention and development is progressing. First, capillary 5
The tip of the Au wire 51 exposed below 0 is melted by electric discharge using an electric torch 2 to form an Au ball 53 (see Fig. 9).
a)).

Next, the Au ball 53 is attached to the At electrode 31 through the capillary 5.
After ultrasonic bonding at 0 (Fig. 9(b)), the capillary 5
0. This method involves pulling up the Au wire 51 and tearing it off from the neck part of the Au ball 54, leaving only the ball part 54 on the At electrode 31 (FIG. 9(c)). The process is simple and one point is formed on each electrode, making it suitable for small-lot production of a wide variety of products.

In addition, the transfer bump method is considered to be a promising method as it allows metal protrusions to be formed on the TAB film side. This method is A1
After forming Au protrusions by electroplating on a plating substrate with conductor openings corresponding to the electrodes, the Au protrusions are superimposed on the TAB metal leads and heated and pressed from the plating substrate onto the TAB metal leads. It is to be transcribed into.

[Problem to be solved by the invention]

The conventional method for forming metal protrusions described above has the following drawbacks. In other words, the plating bump method has a complicated process and requires high material costs and man-hours to apply a thick plating film, requires large capital investment, and causes a decrease in device yield, resulting in high formation costs. There are drawbacks.

In the case of the ball bump method, although it has the advantage of not being as easy as wet method 1, there are variations in the size of the Au balls and variations in the height after tearing the wire, and there are also
Since balls are used, the electrode pitch is limited to about 100 μm, and it is said that fine bonding smaller than that is difficult.

Furthermore, since mechanical stress is applied to the electrode portion not only when bonding the TAB film but also when forming bumps, reliability of the bonded portion becomes a problem. The transfer bump method does not affect the chip yield compared to the plating bump method because the plating is performed on the plating substrate, but it does not eliminate the complexity of the process.
In order to transfer the Au protrusions onto the TAB film without any problems, advanced management and know-how are required for the formation of the plating substrate, the metal plating process, etc.

[Means to solve the problem]

The method for forming metal protrusions of the present invention is a method of forming metal protrusions on metal leads or electrodes on a substrate using a press method, in which a linear metal material is inserted between a punch and a die of a press jig. The structure includes the steps of activating a punch to press the metal material to form a metal piece of a predetermined shape, and joining the formed metal piece to a metal lead or an electrode on the substrate. Here, the metal piece can be joined to the metal lead or the electrode on the substrate using a press punch.

The method for forming a metal protrusion of the present invention is a method of forming a metal protrusion on a metal lead or an electrode on a substrate using a press working method, in which a linear metal material is cut into a predetermined length using a press jig. It consists of cutting into small metal pieces and then using a punch of a press working jig to press the small metal pieces onto metal leads or electrodes on the substrate that are aligned in advance with the punch axis. However, it is effective to use a punch that has a recessed portion on its tip. The material composition of the metal material can be selected and multilayered depending on the configuration of the metal leads and the electrodes on the substrate.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention in the order of steps. First, the metal lead part 6 of the TAB film 5 is placed on the heating stage 4, and a press working jig having a punch 1 and a die 2 is positioned so that the punch axis is at the tip of the metal lead 6 (first Figure (a)). The press working jig main body 2o is an integrated type including a die 2, a metal material feed guide section 21, and a punch guide section 22 that continues below the machined hole of the die 2. A linear, wire-shaped or ribbon-shaped metal material 3 is fed through the metal material feed guide section 21, and the tip thereof extends upward from the inner wall of the machined hole of the die 2 on the opposite side from the metal material feed guide section 21. It is positioned in contact with the stopper portion 24 of. The cross-sectional shape of the punch 1 is rectangular, and when pressure is applied from the punch 1, the die 2
By fitting into the machined hole, the feed guide part 2 of the machined hole
Cut the metal material 3 on the side 23 of the first side to obtain a small metal piece (the first
Figure (b)) is formed. In this way, each time the small metal piece 8 is formed, the metal material 3 is
Since the metal material 3 is sent, there is no waste of the metal material 3, and there is an effect of saving material costs.

After cutting a small metal piece 8 from the metal material 3, the punch 1 is further lowered under continuous pressure to press the small metal piece onto the metal lead 6, thereby forming a metal protrusion 8 of the metal lead 6. (Figure 1(b)).

When the press jig is removed, the process of forming the first metal protrusion 8 is completed (FIG. 1(C)). In this way, the metal material 3 is sequentially cut from the tip, and the metal pieces 8 are crimped onto the plurality of reeds 6 of the TAB to form a series of A semiconductor devices.
Metal protrusions corresponding to one electrode can be formed.

Note that the machined hole of the die 2 can be formed by precision electric discharge machining.

Punch 1 can be made by grinding. The length 11 of the small tip of the punch should be up to 10 times the diameter 12 to withstand bending stress.

Suitable materials for the die 2 and punch 1 include high speed steel, cemented carbide, and die steel.

In the method of this example, the metal material is an Au ribbon with a thickness of 40 μm, and a lead punch with a square cross section of 50 μm on the side and a flat tip is used to punch a TAB with a lead pitch and a notch of 100 μm.
The film was crimped onto the Au plating lead. At this time, the Au ribbon could be cut with a punch pressure of 130 g or more.

Since Au is soft and easily stretchable, when there is a large axis misalignment or clearance between the punch and the die, the punched Au small piece becomes distorted in shape and the outer periphery on the punch side becomes especially large, which is not preferable.

With a clearance of 8% or less and an axis misalignment of 2 μm or less, small pieces of Au with a good shape could be formed. Stage 4 heating temperature 1
At 70°C, crimping to the lead requires 40g of punch pressure.
But it was possible because the strength was small. On the other hand, in order to obtain sufficient bonding strength, a punch force of 120 g or more was required.

The bonding strength with the lead is strengthened by the thermocompression bonding process with the Al electrode of the semiconductor element on the ridge, so it is good as long as it does not come off during handling.The pressing force of punch 1 is small after punching, and the Au It is preferable to press the small pieces against each other.

The bonding pressure was set to 40 g, and the lower surface of the die was brought into contact with the lead surface as shown in FIGS. 1(a) and (b). f, HA u
As shown in the cross-sectional view of FIG. 2, the protrusion had a thin burr 13 several μm in height, but the protrusion was formed in a good rectangular parallelepiped shape as a whole. At this time, the shape has no variation,
The center height was stable at 30 to 35 μm. In FIG. 2, 14 indicates the operation of the punch 1.

Note that if it is desired to increase the bonding force of the Au protrusion in advance, it is sufficient to punch it out with a constant pressure and bond it to the lead. However, in this case, since Au is extruded between the punch and the die during pressing, the pressure becomes somewhat high. When the distance between the lower surface of the die 2 and the surface of the die 6 is large, as shown in Fig. 3,
The u protrusion 8a is crushed and the upper surface 16a becomes concave. In this case, when the semiconductor element is crimped with the Al electrode, it is difficult to apply pressure to the central part of the electrode, resulting in a decrease in bonding strength.

The die 2 and the lead 6 must be in contact with each other or must be set lower than the height of the punched piece. When the lead on which the Au protrusion of good shape was formed according to this example was bonded to the A1 electrode of the semiconductor element by thermocompression, good bonding performance was confirmed.

FIGS. 4 and 5 show the cross-sectional shapes of metal protrusions when they are cut by changing the shape of the tip of the punch and crimped onto metal leads. FIG. 4 shows a case where the tip surface 15 of the punch 1b is concave, and FIG. 5 shows a case where the tip surface 15 of the punch IC has a mesh-like groove. The upper surfaces 16b, 16c of the formed metal protrusions 8b, 8c are formed with convex surfaces corresponding to the shape of the punch tip 15. If you do this,
When crimping a semiconductor element with an Al electrode, the contact with the central surface of the electrode is improved, the influence of the burr 13 around the metal protrusion can be completely eliminated, and the reliability of the bonding is further improved.

When using a wire with a circular cross section as the metal material 3 and a punch with a flat tip, it is difficult to control the height of the metal protrusion because the small metal piece deforms greatly from its original shape. It is desirable to form a concave shape corresponding to the pattern shape of the Al electrode.

As described above, the shape and height of the metal protrusion formed by the method of the present invention can be controlled by the thickness of the metal material and the shape of the punch tip, so the accuracy is good and the subsequent bonding with the semiconductor element electrode is reliable. It is also highly sexual. Unlike the ball bump method for making Au balls, the present invention can also be applied to TABs with narrow pitch leads of 100 μm or less by reducing the punch diameter. In the above example, the small metal piece was joined to the lead using a processing punch, but it is also possible to send the small metal piece using a guide mechanism after forming the metal piece and press it to the lead using a special jig. good.

Since a press working method is used as the material for the metal protrusion of the present invention, various materials can be selected.

When applied to the connection between electrodes of semiconductor elements and metal leads, materials whose main components are Au, Ag, AI, Cu, In, and various solder alloys can be used. Costs can be reduced by using inexpensive materials.

Furthermore, the metal protrusion of the present invention can be multilayered by using a metal material that has been multilayered in advance.

FIG. 6 shows that the TA is
FIG. 6 is a cross-sectional view illustrating a case where multilayered metal protrusions 8d are formed on the metal lead 6 of the B film. The figure shows a three-layered plate metal material that is processed into small pieces and crimped onto a metal lead 6 to form a metal protrusion f! IJ8d has just been formed. For example, when connecting the TAB's Au plating lead 6 to the AI electrode 31 of the semiconductor element 30, the bonding layer 33 of the bonding layer 32 with the lead and the AI electrode is made of Au, which has a proven bonding experience, and the intermediate layer 34 is made of Au, which has a proven bonding performance. It is better to use inexpensive Cu. Since such a three-layer material can be easily formed by rolling or plating, the material cost can be reduced compared to when a single-layer Au material is used.

In addition, the same as above or the bonding layer with the metal lead may be
- It is also effective to use Sn-based solder alloy. In this case, the pressure welding to the REIT is performed lightly with low pressure, and the bonding strength can be obtained by thermally melting the solder. In addition, since it is a metal protrusion material and has good bonding properties with Au, it has the advantage that it is possible to use low-cost materials such as Au, which has been widely used conventionally, or solder as the plating material for TAB metal REITs. . As described above, the present invention allows various metal protrusion materials and configurations to be selected for various electrodes and metal REETs, and is therefore highly effective in reducing costs and increasing the reliability of bonding.

Up to this point, we have taken as an example the case where a metal protrusion is formed in the shape of a metal lead of a TAB film, but the method of the present invention can also be used to form a metal protrusion on other metal leads, the A1 electrode of a semiconductor element, the electrode of a wiring board, etc. It can also be applied to formation. Figure 7 shows
FIG. 3 is a cross-sectional view showing a case where a metal protrusion is formed on an AI electrode of a semiconductor element and then a metal lead is bonded. The method for forming the metal protrusion 8e in this case may be the same as that for attaching it to the metal lead first. However, like the ball bump method, mechanical stress is applied to the AI electrode portion 31 of the semiconductor element 30 when forming the metal protrusion. If it is not necessary to apply mechanical stress again when bonding to the metal lead 6, it is preferable to form the metal protrusion 8e in a multilayer structure as described above. FIG. 7 shows an example of a two-layer structure in which the layer 39 on the AI electrode side is made of Au.
If the layer 38 on the metal lead side has a two-layer structure of AU-3i solder, the thermal melting properties of the solder can be used when thermocompression bonding the metal lead 6, so it can be performed with a small pressure force, and the reliability of the joint is improved. can ensure sex. In this way, the present invention
Applicable to various mounting methods.

〔Effect of the invention〕

The method for forming metal protrusions of the present invention is not as wet as 1, and 1
The process is simple because a single press machine can form a small metal piece and bond it onto a lead or substrate electrode.
This method has the advantage of being able to form metal protrusions at low cost, such as requiring less material costs and equipment investment. In addition, since the shape and height of the metal protrusion can be controlled by the thickness of the metal material and the shape of the punch tip, it is possible to form metal protrusions with high precision, making the joining highly reliable and also compatible with narrow pitch joining. There are some advantages. Furthermore, there is the advantage that metal materials and configurations can be selected depending on the mounting configuration to realize a low-cost, highly reliable structure.

In the present invention, small pieces of metal are formed by sequentially cutting a linear metal material to a certain length starting from the tip, so there is no waste of metal material, and there is an effect of saving material costs.

[Brief explanation of the drawing]

Figures 1 <a) to (c) are cross-sectional views showing an embodiment of the present invention in the order of steps, and Figures 2 to 5 are cross-sectional shapes of metal protrusions formed using the embodiment shown in Figure 1. A cross-sectional diagram explaining
Figure 2 shows the case when the punch tip surface is flat, Figure 3 shows the case when the punch tip surface is flat but the bonding conditions to the metal lead are poor, and Figure 4 shows the case when the punch tip surface is concave. 5 is a sectional view showing another embodiment of the present invention, FIG. 6 is a sectional view showing a further embodiment of the present invention, and FIG. 8 is a sectional view showing a further embodiment of the present invention. FIG. 9 is a sectional view showing the process order of the plating bump method, which is a conventional method for forming metal protrusions, and FIG. 9 is a sectional view showing the process order of the ball bump method, which is another conventional method for forming metal protrusions. 1, lb, lc...punch, 2...dice, 3...
・Metal material, 4... Stage, 5... TAB film, 6... Metal lead, 7... Polyimide film, 8,
8a to 8e... Metal protrusion, 9... Punching remaining part, 10... Die hole part, 11... Punch length, 12
. . . Punch diameter, 13 .
...Metal material feeding guide section, 22... Punch guide section, 25... Feeding length, 30... Semiconductor element, 31.
・・A1 electrode part, 32.33, 34, 38.39...
Layer in metal protrusion, 35... A1 layer, 36... Protective layer, 37... Silicon substrate, 40... Adhesive layer, 41
...Diffusion prevention layer, 42...Resist layer, 43...
Au plating layer, 50...capillary, 51...Au
Wire, 52... Electric torch, 53... Au hole, 54... Au hole part.

Claims (1)

[Claims] 1. A step of cutting a linear metal material to a certain length from the tip by a press processing method using a punch and a die to form a small metal piece, and cutting the small metal piece to a metal lead or a substrate. A method for forming a metal protrusion, comprising the step of bonding it to an upper electrode. 2. A punch that cuts a linear metal material at a certain length from its tip in cooperation with a die to form a small metal piece is continuously moved to press the small metal piece to a metal lead or an electrode on a substrate. 1. The method for forming a metal protrusion according to 1. 3. The method of forming a metal protrusion according to claim 2, wherein a concave portion is provided at the tip of the punch to form a convex portion on the surface of the small metal piece crimped onto the metal lead or the electrode on the substrate. 4. The method for forming a metal protrusion according to claim 3, wherein the recesses are a plurality of grooves and the protrusions are a plurality of protrusions. 5. The method for forming metal protrusions according to claim 1, 2, 3, or 4, wherein the main component of the metal material is one selected from gold, silver, aluminum, copper, incidium, and solder alloy. 6. Claims 1, 2, and 3, wherein the metal material has a multilayer structure.
, 4 or 5. The method for forming a metal protrusion according to . 7. The method for forming metal projections according to claim 6, wherein at least one layer of the multilayer structure is one selected from gold, copper, and a solder alloy. 8. The method of forming a metal protrusion according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the metal lead or the electrode on the substrate is a metal lead of a TAB type film carrier or an electrode of a semiconductor element. 9. A stage, a die provided above the stage, a metal material feed guide section for introducing a linear metal material onto the processed hole of the die, and the metal material feed guide section for the processed hole of the die. and a stopper portion that is an extension of the inner wall on the opposite side, and the linear metal material that is fitted into the machined hole of the die hole, guided by the metal material feed guide portion, and whose tip is in contact with the stopper portion, is inserted into the die. a punch that cuts the machined hole on the side of the metal material feed guide section side to form a small metal piece and then presses the small metal piece to a metal lead placed on the stage or an electrode on the substrate. A jig for forming metal protrusions. 10. The metal protrusion forming jig according to claim 9, wherein a recess is provided at the tip of the punch. 11. The metal protrusion forming jig according to claim 10, wherein the recess is a plurality of grooves. 12. Claims 9 and 10, wherein the distance between the lower surface of the die and the metal lead or the electrode on the substrate is smaller than the thickness of the metal piece.
or 11. The metal protrusion forming jig according to 11.