JP2555915B2 - Method of forming metal protrusion, method of supplying metal brazing material, and jigs therefor - Google Patents

Abstract

PURPOSE:To provide a method and a jig for forming a metallic projection such as TAB package of a semiconductor element at a low cost and a narrow pitch. CONSTITUTION:A metallic lead 6 is held by a supporting tool 1 wherein a metallic line material 3 is passed through a feed hole 10, a pressure tool 2 which slides mutually with the supporting tool 1 in contact with an edge face 12 of a longitudinal direction, and a metallic line material 3 which is fed out by a fixed length by a feed mechanism 11 is cut and fixed by pressure on the metallic lead 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for forming metal projections,
The present invention relates to a method for supplying a metal brazing material and jigs for them.

[0002]

2. Description of the Related Art In recent years, semiconductor products such as LSIs have been further expanded in their application fields such as various consumer equipments and industrial equipments. In order to expand the field of use of these devices, they are being made portable along with lower prices. Therefore, in order to meet these requirements also in semiconductor products, there is a demand for high-density packaging such as cost reduction, weight reduction, thinning, and miniaturization of packaging and assembling steps into devices.

Generally, the TAB method is known as a method suitable for high-density mounting of semiconductor products, and its practical application has been expanded. For connection between the TAB type semiconductor element and the mounting wiring board, a metal lead made of Cu plated with Au or Sn and patterned with the electrode arrangement of the semiconductor element and a polyimide film for holding the metal lead are attached. The film carrier having the above structure is used. here,
In order to join the Al electrode of the semiconductor element and the metal lead, it is necessary to make the joint portion convex, and a metal projection called a bump is provided on the Al electrode portion or the metal lead. A thermocompression bonding method is usually used for joining the Al electrode and the metal lead via the metal protrusion.

A so-called plating bump method has been widely used as a conventional method for forming metal projections. Figure 7
(A)-(c) is sectional drawing which shows the 1st example of the prior art in order of process. First, an adhesive layer 25 of Ti, Cr or the like and a diffusion preventing layer 26 of Cu, Pt or the like are laminated and formed on the semiconductor element 20 by sputtering. (FIG. 7 (a)). Next, after forming a resist layer 27 covering the portion other than the Al electrode portion 21 by lithography, an Au plating layer 28 is formed on the Al electrode portion 21 by about 30 μm. (FIG. 7 (b)). Then, the resist layer 27
After removing Al, a resist layer covering the Al electrode portion 21 is formed, and the diffusion prevention layer 26 and the adhesive layer 25 other than the Al electrode portion 21 are removed by etching (FIG. 7C). As described above, the metal projections are formed on the Al electrode by plating through the steps.

Other than the plating bump method, FIG.
The ball bump method using the Au wire ball bonding technique shown in (c) is drawing attention and is being developed.
First, the tip of the Au wire 31 protruding under the capillary 30 is discharge-melted using an electric torch 32 to form an Au ball 33 (FIG. 8A). Then, the Au ball 33
After ultrasonic bonding to the 1-electrode 21 with the capillary 30 (see FIG. 8).
(B)) The capillary 30 and the Au wire 31 are pulled up to tear off the Au wire 31 from the neck portion of the Au ball, leaving only the ball portion 34 on the Al electrode 21 (FIG. 8).
(C)). This method has no wet process and the process is simple,
Since it is formed on the electrode one point at a time, it is suitable for a small number of products.

In addition, the transfer bump method is regarded as promising because it can form a metal projection on the TAB film side. In this method, after Au protrusions are formed by electroplating on a plating substrate having conductor openings corresponding to Al electrodes, T
The metal bump of AB is superposed and heated and pressed to transfer the Au protrusion from the plating substrate onto the metal lead of TAB.

In recent years, the surface mounting method tends to have a higher density, and electronic parts mounted in both industrial equipment and consumer equipment are made into chips, package parts are miniaturized, and electrodes on a circuit board are miniaturized. Progressing to narrower pitch. Accordingly, there is a demand for a high-density and highly reliable method of electrically and mechanically connecting a component and a circuit board.

In recent years, as a method of supplying a metal brazing material for connection to a circuit board, a method of supplying cream solder, which is a mixture of solder powder having an appropriate alloy composition and flux, by screen printing has been widely used.

FIGS. 9A to 9C show steps of a general screen printing method. First, the metal mask 41, which has been removed by etching from the portion corresponding to the connection electrode 36 on the circuit board 37, is placed on the circuit board with a gap of several millimeters (FIG. 9A). The cream solder 42 having an appropriately adjusted viscosity is supplied onto the metal mask 22, and the metal mask 4 is pressed against the squeegee 40 made of hard rubber.
Move up 1. The metal mask 41 is supported on the periphery by an elastic film 43, and the cream solder 42 is sequentially filled in the metal mask 41 by moving while pressing the squeegee 40. By elasticity, the mask 41 is sequentially removed (FIG. 9 (b)), the cream solder 42 remains on the electrodes, and the supply of the cream solder is completed (FIG. 9 (c)).

[0010]

The conventional technique described above has the following drawbacks. (1) In the plating bump method, the process cost is complicated and a thick plating film is applied, which requires material costs and man-hours, large equipment investment is required, and it causes a decrease in device yield. It has the drawback of being expensive. The ball bump method has the advantage that there is no wet process, but there are variations in the size of the Au balls and variations in the height after the wire is torn off, and because the Au balls are used, the electrode pitch is about 100 μm. It is considered to be a limit and it is difficult to perform fine bonding below that. Furthermore, T
The reliability of the bonded portion is a problem because mechanical stress is applied to the electrode portion not only when the AB film is bonded but also when the bump is formed. The transfer bump method does not affect the chip yield as compared with the plating bump method because it performs plating on the plating substrate, but the complexity of the process cannot be eliminated and the Au protrusions are transferred onto the TAB film without any problems. In order to do so, high level management and know-how such as formation of plating substrate and plating process are required. (2) The method of supplying the metal brazing material to the circuit board by the screen printing method has the following drawbacks. For coating on a circuit board with a mask, the solder supply amount is determined by the accuracy of the mask and the characteristics of the cream solder. Insufficiency, short circuit between adjacent electrodes, that is, solder bridge or the like is caused, resulting in a decrease in product yield. In particular, cream solder printing becomes difficult as the electrode pitch becomes narrower than 0.5 mm. Further, cream solder, which is a mixture of flux and solder powder, has drawbacks in management such as long-term storage because the solder wettability is deteriorated due to corrosion of powder flux. In addition, since a mask is required, it is disadvantageous in terms of delivery time, and it is not possible to respond promptly and flexibly, especially when there is a change in design.

[0011]

According to the method for forming a metal projection of the present invention, a metal wire rod is fed for a certain length through a feed hole of a columnar support tool having a feed hole for a metal wire rod, and the support tool is lowered to lower the support tool. After pressing the metal lead or substrate at the tip of the, press the column-shaped pressure tool that is in contact with the support tool at one end surface in the longitudinal direction of each other, and cut the metal wire rod protruding from the feed hole for a certain length. It comprises a step of continuously sliding the pressure tool and crimping the cut metal wire to the metal lead or the substrate.

Further, the metal projection forming jig of the present invention comprises a columnar support tool having a feed hole for a metal wire near the tip, and a columnar slide with the support tool in contact with each other at one end face in the longitudinal direction. Of the pressure tool, a slide guide for sliding guide of at least one of the support tool and the pressure tool, and a mechanism for feeding the metal wire rod into the feed hole for a certain length.

According to the metal brazing material supply method of the present invention, a columnar support tool having a linear metal brazing material feed hole is positioned at a predetermined position on the electrode, and the metal brazing material is made to have an electrode length from the support tool feed hole. The metal brazing material is fed by a predetermined length according to the above, and the metal brazing material fed by the predetermined length is cut by a pressure tool that comes into contact with the supporting tool at one end face in the longitudinal direction and slides, and then the pressure tool continues sliding and is cut. It consists of crimping a metal brazing material to the electrode.

Further, the metal brazing material supply jig of the present invention slides while being in contact with the supporting tool in the form of a column having a feed hole for the metal brazing material in the vicinity of the tip and one end face in the longitudinal direction of the supporting tool. A columnar and pressure tool, a slide guide for guiding slide of at least one of the support tool and the pressure tool, and a feed mechanism for feeding a metal brazing material into the feed hole for a predetermined length according to the electrode length. .

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a metal projection forming jig according to a first embodiment of the present invention. The support tool 1 and the pressure tool 2 have a columnar shape with a thin tip,
The pair of tools 1 and 2 can slide in the longitudinal direction while contacting each other on the one end face 12 by the slide guide 9.
A feed hole 10 for the metal wire 3 is provided near the tip of the support tool 1, and the metal wire 3 is sequentially fed by a feed mechanism 11 for a certain length. A piezoelectric element with an amplitude enlargement mechanism or the like is used for the pressure mechanism of the tool pressure 13, 14. Alternatively, only the pressure tool 2 may slide in the slide guide, the support tool 1 may be fixed to the slide guide, and the movement may be performed by moving a mechanism that supports the entire jig.

2A to 2D are sectional views showing a second embodiment of the present invention in the order of steps. First, the metal lead 6 of the TAB film 5 is placed on the heating stage 4, the metal wire 3 is fed into the feed hole 10 of the support tool 1, and the pressure tool 2 is positioned so as to come on the tip of the metal lead 6. (FIG. 2 (a)). Next, the support tool 1 and the pressure tool 2 are applied with a predetermined pressure in the direction of arrow 18b to be lowered, and the metal lead 6 is held by the support tool 1 (FIG. 2).
(B)). Next, pressure is applied only to the pressure tool 3 to lower the metal material 3 and the metal material 3 is cut, and the pressure tool 2 is continuously lowered to press the cut metal wire pieces onto the metal leads 6 (FIG. 2). (C)). After that, when the support tool 1 and the pressure tool 2 are lifted up, the process of forming the metal protrusions 8 is completed (FIG. 2D).

In this manner, the metal wire rod pieces are sequentially pressed onto the metal leads of the TAB to form metal projections corresponding to the series of A1 electrodes of the semiconductor element. In the method of the present invention, since the support tool is used to press the side of the metal projection forming portion immediately in advance, even when the metal lead has a warp and is floating from the stage, the metal projection is pressed against the stage during crimping, and the bonding strength and Positioning accuracy is stable. When cutting a metal wire rod, the support tool serves as a die and the pressure tool serves as a punch.

According to the method of the embodiment, the metal wire rod has a diameter of 50 μm.
Au wire with a 60 μm square tip pressure tool and a lead pitch of 100 μm and a lead width of 60 μm.
It was crimped to the Au plated lead of the TAB film. At this time, the cutting could be performed under a pressure of 70 g or more. Since Au has the property of being soft and easily stretched, when the clearance between the tools is large, the cut Au small piece is not preferable because a high burr is formed on the upper portion of the cut surface.

In the case of the present invention, since the cutting is one plane,
Since the clearance can be set to 0, an Au segment having a good shape can be formed. When the stage heating temperature is 170 ° C., crimping to the lead is possible with a punch pressure of 40 g. By pressure bonding to the metal lead after cutting, the Au small piece cut into a cylindrical shape was crushed to become an Au protrusion having a flat upper surface and a height of about 30 μm. The bonding strength with the leads may be strengthened in the subsequent thermocompression bonding with the Al electrode of the semiconductor element, and therefore may be such that it does not come off during absorption.

It is desirable that the punch pressure is reduced after punching and pressed against the lead with low pressure. A piezoelectric element is suitable as a means for applying such pressure. According to the present embodiment, the lead having the Au protrusion formed thereon and the Al of the semiconductor element are formed.
When the electrodes were bonded by thermocompression bonding, good bondability was confirmed. If it is desired to sufficiently increase the bonding force of the Au protrusions in advance, the Au protrusions may be punched with a constant pressure and bonded to the leads. However, in this case, the crushing of the Au slice becomes severe during pressure bonding.

FIG. 3 shows a third embodiment of the present invention and is a sectional view showing the shape of a metal projection when the tip surface of the pressure tool is made concave. Since the shape of the upper surface 16 of the metal projection 8 is a convex shape corresponding to the shape of the tip surface 15 of the pressure tool 2, it is possible to obtain a metal projection having a high height and shape.

As described above, in the case of the present invention, since the metal wire rods to be sequentially fed are simply cut and pressure-bonded, the apparatus is simple and the processing capacity can be increased. The shape and height of the formed metal protrusion can be controlled by the pressure of the pressure tool and the shape of its tip, so accuracy is good,
The reliability of the subsequent bonding with the semiconductor element electrode is also high. Unlike the ball bump method for making Au balls, the present invention can easily reduce the tool diameter, and therefore can be applied to TAB having a narrow pitch lead of 100 μm or less. Also,
In the case of the present invention, since the metal protrusion can be formed on the metal lead, the electrode of the semiconductor element is not subjected to mechanical stress unlike the ball bump method, and the reliability of the joint can be improved.

Although the wire is used as the metal material in the embodiment, a metal wire material such as a ribbon may be used. Further, the present invention can be applied not only to the case where it is formed on the metal lead of the TAB film but also to the case where the metal projection is formed on another metal lead. Since the machining method is used as the material of the metal projection of the present invention, various materials can be selected. When applied to the connection between the electrode of the semiconductor element and the metal lead, the main components are Au, A
g, Al, Cu, In, various solder alloys, etc. can be used. Cost can be reduced by using an inexpensive material.

FIG. 4 is a perspective view showing a metal brazing material supplying jig according to a fourth embodiment of the present invention. The support tool 1 and the pressure tool 2 have a columnar shape with a thin tip, and a pair of these tools can slide in the longitudinal direction while contacting each other at one end surface by a slide guide 9. A feed hole 10 for the metal brazing material 35 is provided near the tip of the support tool 1, and the metal brazing material 35 is sequentially fed by a feeding mechanism 11 for a predetermined length.
A piezoelectric element with an amplitude magnifying mechanism is used for the pressing mechanism of the tool pressing units 13 and 14. Only the pressure tool slide guide 9
The support tool 1 is slidable inside, and the support tool 1 is integrated with the slide guide 9, and the movement is performed by movement of a mechanism that supports the entire jig.

FIGS. 5A to 5D are sectional views showing the steps of the fourth embodiment of the present invention. First, the electrode 36 on the circuit board 37 is placed on the heating stage 38, and the supporting tool 1
The metal brazing material 35 is fed into the feed hole 10 and the positioning is performed so that the pressure tool 2 is placed on the electrode 36 (FIG. 5A). Next, the support tool 1 and the pressure tool 2 are both lowered by applying a predetermined pressure in the arrow direction 18b, and the circuit board 37 is pressed by the support tool 1 (FIG. 5B). Then, only the pressure tool 2 is pressed and lowered to cut the metal brazing material 35, and the pressure tool 2 is continuously lowered to cut the cut pieces of the metal brazing material 35 onto the electrodes 36 on the circuit board 37. It crimps (FIG.5 (c)). After that, when the supporting tool 1 and the pressure tool 2 are both raised, the metal brazing material supply process is completed (FIG. 5D). The support tool 1 does not need to have a mechanism for pressing the circuit board, and the lowering position of the tip of the support tool 1 can be freely set depending on the type of electrode.

In cutting the metal brazing material 35 with this jig, the supporting tool 1 serves as a die and the pressing tool 2 serves as a punch. According to the method of the example, a solder wire having a diameter of 0.1 mm was used for the electrodes having a pitch of 0.5 mm and a shape of 0.2 mm × 1.0 mm, and the tip was 0.1 m.
A soldering material was supplied using a pressure tool having a rectangular shape of m × 1.5 mm. At this time, the heating temperature of the stage is 100
C., the wire could be cut with a pressure of 30 g or more, and the crimping could be performed well. Since the solder is soft and has a property of being easily stretched, if the clearance between the tools is large, the cut solder wire is not preferable because of a high burr on the cut surface. In the case of the present invention, since the cutting is performed on one plane, the clearance can be zero and the solder can be supplied in a good shape. The shape of the solder piece after crimping is crushed by a pressure tool, the top surface is flat, and the height is 0.06 m.
It had a shape of m. The bonding strength between the electrode and the solder piece is such that it does not come off during handling because the solder bonding is completed by the solder melting process with the electronic component placed on it. When the electronic components were joined on the circuit board to which the solder was supplied according to this example, good joining properties were confirmed.

FIG. 6 is a structural view showing a solder supply shape 39 when the tip surface 15 of the pressure tool is concave. As shown in the figure, the shape of the upper surface of the metal brazing material 35 is a convex shape corresponding to the shape of the tip end surface of the pressing tool 15, so that the height and shape of the metal brazing material 35 are good in accuracy and contact with an adjacent electrode can be prevented.

As described above, in the case of the present invention, since the metal brazing material fed in sequentially is simply cut and pressure-bonded, the apparatus is simple and the processing capacity can be increased. Unlike the screen printing method that uses a metal mask, the shape of the tool can be easily changed, and electrodes with a narrow pitch are arrayed, and the required amount of brazing material that has been set in advance for complex electrode arrays of mixed sizes. Can be supplied precisely.

Although the wire is used as the metal material in the embodiment, a ribbon-shaped metal material may be used. Further, the present invention can be applied not only to the electrodes on the circuit board but also to the case where the metal brazing material is supplied to and bonded to the metal leads of the electronic component.

[0030]

The method of forming metal projections of the present invention does not require a wet process, the process is simple, and an apparatus having a simple structure and processing capacity is sufficient. Therefore, material costs and facility investment can be reduced. There is an effect that a low-cost metal projection can be formed. Since the metal protrusions can be formed on the metal leads, there is an effect that there is no concern about deterioration of reliability of the joint portion due to mechanical stress.

Further, since the shape and height of the metal projection can be controlled by the tip shape of the pressing tool, the metal projection can be formed with high accuracy, the joining can be made highly reliable, and the narrow pitch joining can be coped with. There are advantages. Further, there is an effect that a metal protrusion material can be selected according to the mounting configuration, and a cost reduction and a high reliability structure can be realized.

The metal brazing material supply method of the present invention can supply the metal brazing material without the need for a mask based on the data designed by a computer or the like, and can correspond to the design change and the production of a large number of small-lot products. Since there is no wet process like the screen printing method, the process is simple, and the device has a simple structure and processing capacity, there is an advantage that it is possible to supply brazing filler metal at low cost such as less material cost and capital investment . In addition, since the supply amount of metal brazing material is controlled by the wire diameter, it is possible to control supply with high accuracy, and to solve problems such as excess and deficiency of solder, it is possible to make the joint highly reliable. Since the shape of the brazing material is controlled, a short circuit with an adjacent electrode does not occur at the time of melting and solidifying, and there is an advantage that it is possible to handle narrow pitch bonding.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

2A to 2D are process cross-sectional views showing a second embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the shape of a metal projection formed when the pressure tool shown in FIG. 1 is concave.

FIG. 4 is a perspective view showing a fourth embodiment of the present invention.

5A to 5D are process cross-sectional views of the fourth embodiment.

6 is a perspective view showing the shape of a brazing metal material formed when the pressure tool shown in FIG. 4 is concave.

7A to 7C are cross-sectional views showing a first conventional example in the order of steps.

8A to 8C are cross-sectional views showing a second conventional example in the order of steps.

9A to 9C are cross-sectional views showing a screen printing method, which is a conventional metal brazing material supplying method, in the order of steps.

[Explanation of symbols]

 1 Support Tool 2 Pressure Tool 3 Metal Material 4 Stage 5 TAB Film 6 Metal Lead 7 Polyimide Film 8 Metal Projection 9 Sliding Guide 10 Feed Hole 11 Feed Mechanism 13,14 Tool Press 15 Press Tool Tip Surface 16 Metal Projection Object upper surface 17, 17c, 18b, 18d Tool moving direction 20 Semiconductor element 21 Al electrode part 22 Al layer 23 Protective layer 24 Silicon substrate 25 Adhesive layer 26 Diffusion prevention layer 27 Resist layer 28 Au plating layer 30 Capillary 31 Au wire 32 Electricity Torch 33 Au ball 34 Au ball portion 35 Metal brazing material 36 Electrode 37 Circuit board 38 Heating stage 39 Brazing material supply shape 40 Squeegee 41 Metal mask 42 Cream solder 43 Support film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshimasa Kato 5-7-1 Shiba, Minato-ku, Tokyo Inside NEC Corporation (56) References JP-A-2-33944 (JP, A) JP-A 2-206137 (JP, A) JP-A-2-273945 (JP, A) JP-A-4-65846 (JP, A)

Claims (10)

(57) [Claims] 1. The metal wire rod is fed for a certain length through the feed hole of a columnar support tool having a feed hole for the metal wire rod, and the support tool is lowered to hold a metal lead or substrate at the tip of the support tool. After that, slide a columnar pressure tool that contacts the support tool at one end surface in the longitudinal direction of each other to cut the metal wire rod with a certain length from the feed hole and continue sliding of the pressure tool. A method of forming a metal projection, comprising: pressing the cut metal wire rod onto the metal lead or substrate. 2. The method for forming a metal projection according to claim 1, wherein the metal lead or the substrate is a metal lead of a TAB type film carrier or a semiconductor device. 3. A column-shaped support tool having a feed hole for a metal wire near the tip, a column-shaped pressure tool that slides in contact with the support tool at one end face in the longitudinal direction, and the support and presser. A jig for forming a metal projection, comprising: a slide guide that guides at least one of the pressure tools, and a mechanism that feeds a metal wire into the feed hole for a certain length. 4. The metal projection forming jig according to claim 3, wherein a concave portion is provided on the tip end surface of the pressing tool. 5. A columnar support tool having a linear metal brazing material feed hole is positioned at a predetermined position on the electrode, and the metal brazing material is fed from the support tool feed hole to a predetermined length according to the electrode length. After cutting the metal brazing material sent out by a pressure tool that is in contact with the supporting tool at one end face in the longitudinal direction and slides, the metal brazing material cut by continuing to slide the pressure tool to the electrode. A method for supplying a metal brazing material, characterized by crimping. 6. The method for supplying a metal brazing material according to claim 5, wherein the electrode is an electrode on a printed circuit board. 7. The method for supplying a metal brazing material according to claim 5, wherein the electrodes are electronic parts and metal leads. 8. A column-shaped support tool having a feed hole for a metal brazing material in the vicinity of the tip, and a column-shaped pressure tool that slides on the support tool at one end face in the longitudinal direction while contacting each other.
A metal having a sliding guide for guiding sliding of at least one of the support tool and the pressure tool, and a feed mechanism for feeding a metal brazing material through the feed hole for a predetermined length according to the electrode length. Brazing material supply jig. 9. The metal brazing material supply jig according to claim 8, wherein a concave portion is provided on the tip surface of the pressing tool. 10. A columnar support tool having a feed hole for a metal wire rod or a substrate stage is driven to position the tip surface of the support tool and the substrate surface at a predetermined distance, and then the support tool and the support tool are placed on each other. Slide the columnar pressure tool that contacts at one end face in the longitudinal direction to cut the metal wire rod that has been fed from the feed hole for a certain length, and continue sliding of the pressure tool to cut the cut metal wire rod. A method for forming a metal protrusion, which comprises press-bonding to a substrate.