JPH04287938A - Formation of metallic projection, supply method of metallic brazing material and jig for them - 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

[Industrial Application Field] The present invention relates to a method for forming metal protrusions,
This invention relates to a method for supplying a metal brazing filler metal and a jig therefor.

0002

BACKGROUND OF THE INVENTION In recent years, the fields of application of semiconductor products such as LSIs have been increasingly expanding, including various consumer devices and industrial devices. These devices are becoming less expensive and more portable in order to expand their field of use. Therefore, in order to meet these demands, semiconductor products are also required to have high-density packaging, such as lower costs, lighter weight, thinner thickness, and smaller size in packaging and equipment integration processes.

Generally, the TAB method is known as a method suitable for high-density packaging of semiconductor products, 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 Sn-plated Cu that is 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 an Al electrode of a semiconductor element and a metal lead, it is necessary to make the bonding part convex, and a metal protrusion called a bump is provided on the Al electrode part or the metal lead. A thermocompression bonding method is usually used to bond the Al electrode and the metal lead via the metal protrusion.

As a conventional method for forming metal protrusions, the so-called plating bump method has been widely used. Figure 7 (a
) to (c) are cross-sectional views showing the first conventional example in the order of steps. First, an adhesive layer 25 made of Ti, Cr, etc., and a diffusion prevention layer 26 made of Cu, Pt, etc. are laminated on the semiconductor element 20 by sputtering. (Figure 7(a)). Next, the Al electrode section 21
After lithographically forming a resist layer 27 covering the
An Au plating layer 28 having a thickness of about 30 μm is formed on the Al electrode portion 21 . (Figure 7(b)). After that, after removing the resist layer 27, a resist layer is formed to cover the Al electrode part 21, and the diffusion prevention layer 26 and the adhesive layer 25 other than the Al electrode part 21 are formed.
is removed by etching (FIG. 7(c)). Through the steps described above, metal protrusions are formed on the Al electrode by plating.

Other than the plating bump method, FIGS.
The ball bump method using the Au wire ball bonding technique shown in c) is attracting attention and its development is progressing. First, the tip of the Au wire 31 exposed below the capillary 30 is melted by discharge using an electric torch 32 to form an Au ball 33 (FIG. 8(a)). Next, the Au ball 33 is
After ultrasonic bonding with the capillary 30 to the l electrode 21 (Fig. 8
(b)), pull up the capillary 30 and Au wire 31 and tear off the Au wire 31 from the neck part of the Au ball, leaving only the ball part 34 on the Al electrode 21 (Fig. 8(c)
)). This method does not require a wet process and has a simple process, and is suitable for producing a wide variety of products in small quantities because it is formed one point at a time on the electrode.

[0006] 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. In this method, after forming Au protrusions by electroplating on a plating substrate having conductor openings corresponding to Al electrodes, T
The Au protrusions are transferred from the plating substrate onto the TAB metal leads by overlapping them with the AB metal leads and applying heat and pressure.

[0007] In recent years, there has been a trend toward higher density in surface mounting methods, and electronic components mounted on both industrial and consumer devices have been made into chips, packaged parts have become smaller, and electrodes on circuit boards have become smaller. Progress is being made towards narrower pitches. Accordingly, there is a need for a method for electrically and mechanically connecting components and circuit boards with high density and high reliability.

[0008] 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 and flux of an appropriate alloy composition, by screen printing has been widely used.

FIGS. 9(a) to 9(c) show steps of a general screen printing method. First, a metal mask 41 whose portion corresponding to the connection electrode 36 on the circuit board 37 has been removed by etching is placed on the circuit board with a gap of several millimeters (FIG. 9(a)). A cream solder 42 whose viscosity has been adjusted appropriately is supplied onto the metal mask 22, and the metal mask 4 is pressed against it with a hard rubber squeegee 40.
Move 1 up. The periphery of the metal mask 41 is supported by an elastic film 43, and by moving the squeegee 40 while pressing the metal mask 41, cream solder 42 is sequentially filled into the metal mask 41, and the film 43 supporting the metal mask 41 is filled with cream solder 42. Due to its elasticity, it gradually comes out of the mask 41 (FIG. 9(b)), leaving cream solder 42 on the electrode, completing the supply of cream solder (FIG. 9(c)).
.

0010

The above-mentioned conventional techniques have the following drawbacks. (1) 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. It has the disadvantage of being expensive. Although the ball bump method has the advantage of not requiring a wet process, there are variations in the size of the Au balls and variations in the height after tearing the wire, and since the Au balls are used, the electrode pitch is approximately 100 μm. This is the limit, and it is said that fine bonding below this limit is difficult. Furthermore, T.A.
The reliability of the bonded portion is a problem because mechanical stress is applied to the electrode portion not only when bonding the B film but also when forming bumps. The transfer bump method has no effect on 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 and it is difficult to transfer the Au protrusions onto the TAB film without any problems. This requires advanced management and know-how in the formation of plating substrates and the plating process. (2) The method of supplying metal brazing material to circuit boards by screen printing has the following drawbacks. When applying solder onto a circuit board using a mask, the amount of solder supplied is determined by the precision of the mask and the characteristics of the cream solder. However, the accuracy of creating a mask by etching is low, and the amount of solder supplied is not constant. Insufficiency also causes short circuits between adjacent electrodes, ie solder bridges, etc., resulting in a decrease in product yield. In particular, as the electrode pitch becomes narrower to 0.5 mm or less, cream solder printing becomes difficult. In addition, cream solder, which is a mixture of flux and solder powder, has disadvantages in terms of management, such as long-term storage, because the solder wettability deteriorates due to corrosion caused by the powdered flux. Furthermore, since a mask is required, it is disadvantageous in terms of delivery time, and it is not possible to respond quickly and flexibly especially when there is a change in the design.

[0011]

[Means for Solving the Problems] The method for forming metal protrusions of the present invention involves feeding out a certain length of metal wire through the feed hole of a pillar-shaped support tool having a metal wire feed hole, and lowering the support tool. After holding down the metal lead or board with the tip of the tool, the column-shaped pressure tool that contacts the supporting tool at one end in the longitudinal direction is slid to cut and apply pressure to the metal wire protruding a certain length from the feed hole. The method includes the steps of crimping the cut metal wire onto the metal lead or substrate by continuing to slide the pressure tool.

The metal protrusion forming jig of the present invention also includes a columnar support tool provided with a feed hole for the metal wire near its tip, and a columnar support tool that slides in contact with the support tool at one end surface in the longitudinal direction. The pressure tool includes a pressure tool, a sliding guide for supporting and slidingly guiding at least one of the pressure tools, and a mechanism for feeding a metal wire a certain length into a feed hole.

In the metal brazing material supply method of the present invention, a columnar support tool having a feed hole for a linear metal brazing material is positioned at a predetermined position on an electrode, and the metal brazing material is fed to the length of the electrode through the support tool feed hole. Accordingly, the metal brazing material is fed out for a predetermined length, and the metal brazing material fed out for a predetermined length is cut by a pressure tool that slides in contact with the support tool at one end surface in the longitudinal direction.Then, the pressure tool continues to slide and is cut. It consists of crimping a metal brazing material to an electrode.

Further, the metal brazing material supply jig of the present invention slides with a columnar support tool having a feeding hole for the metal brazing material near the tip thereof while contacting each other at one end surface in the longitudinal direction. It consists of a column, a pressure tool, a sliding guide for slidingly guiding at least one of the support tool and the pressure tool, and a feeding mechanism that feeds the metal brazing material into the feed hole by a predetermined length according to the electrode length. .

[0015]

Embodiments Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a metal protrusion 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 tapered tip.
These pair of tools 1 and 2 can be slid against each other in the longitudinal direction while being in contact with each other at one end surface 12 by a sliding 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 a fixed length by a feed mechanism 11. A piezoelectric element with an amplitude expansion mechanism is used as a pressure mechanism for the tool pressures 13 and 14. Alternatively, only the pressure tool 2 may be slid within the sliding guide, the support tool 1 may be fixed to the sliding guide, and the movement may be performed by moving the mechanism that supports the entire jig.

FIGS. 2(a) to 2(d) are cross-sectional views showing the 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 that it is above the tip of the metal lead 6. (Figure 2(a)). Next, the support tool 1 and the pressure tool 2 are lowered by applying a predetermined pressure in the direction of the arrow 18b, and the metal lead 6 is held down by the support tool 1 (Fig. 2
(b)). Next, only pressure is applied to the pressure tool 3 and it is lowered to cut the metal material 3, while the pressure tool 2 is continuously lowered and the cut piece of the metal wire is crimped onto the metal lead 6 (Fig. 2 (c)). Thereafter, when it is raised together with the support tool 1 and the pressure tool 2, the process of forming the metal protrusion 8 is completed (FIG. 2(d)).

In this manner, pieces of metal wire are successively crimped onto the metal leads of the TAB, thereby forming metal protrusions corresponding to the series of A1 electrodes of the semiconductor element. In the method of the present invention, the supporting tool is used to hold down the side of the metal protrusion forming part in advance, so even if the metal lead is warped and floating off the stage, it will be pressed against the stage when the metal protrusion is crimped, improving the bonding strength. Positioning accuracy becomes stable. When cutting metal wire, the support tool acts as a die and the pressure tool acts as a punch.

[0018] By the method of the example, a metal wire with a diameter of 50 μm was prepared.
Using a pressure tool with a square tip of 60 μm in diameter, the lead pitch was 100 μm and the lead width was 60 μm.
The .mu.m and TAB films were crimped onto the Au-plated leads. At this time, cutting could be performed with a pressure of 70 g or more. Since Au has the property of being soft and easily stretchable, when the clearance between the tools is large, the cut Au pieces will have high burrs on the upper part of the cut surface, which is undesirable.

In the case of the present invention, since the cutting is in one plane,
Since the clearance can be reduced to 0, an Au section with a good shape can be formed. When the heating temperature of the stage is 170° C., the lead can be crimped with a punch pressure of 40 g. After cutting, the Au small piece cut into a cylindrical shape was crushed into an Au protrusion with a height of about 30 μm and a flat top surface when it was crimped onto a metal lead. The bonding strength with the lead is strengthened in the subsequent thermocompression bonding process with the Al electrode of the semiconductor element, so it is sufficient that it does not come off during absorption.

It is desirable to reduce the punch force after punching and press the lead against the lead with a low pressure, and a piezoelectric element is suitable as a means for applying such pressure. Al of lead and semiconductor element with Au protrusions formed in this example
When the electrodes were bonded by thermocompression, good bonding properties were confirmed. Note that if you want to make the bonding force of the Au protrusion sufficiently strong in advance, it is sufficient to punch it out with a constant pressure and then bond it to the lead. However, in this case, the Au section is severely crushed during crimping.

FIG. 3 shows a third embodiment of the present invention, and is a sectional view showing the shape of a metal protrusion when the tip end 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 end surface 15 of the pressure tool 2, a metal projection with high precision in height and shape can be obtained.

As described above, in the case of the present invention, since the metal wires fed in one after another are simply cut and crimped one after another, the apparatus is simple and the processing capacity can be increased. Since 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, the precision is good, and the reliability of 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, so it can also be used for TABs with narrow pitch leads of 100 μm or less. Furthermore, in the case of the present invention, since the metal protrusions can be formed on the metal leads, mechanical stress is not applied to the electrodes of the semiconductor element unlike the ball bump method, and the reliability of the joint can be increased.

In the embodiment, a wire is used as the metal material, but a metal wire such as a ribbon may also be used. Moreover, it can be applied not only to forming metal protrusions on the metal leads of the TAB film, but also to forming metal protrusions on other metal leads. Since a machining method is used as the material for the metal protrusion of the present invention, various materials can be selected. When applied to connection between electrodes of semiconductor elements and metal leads, the main components are Au and A.
G, Al, Cu, In, various solder alloys, etc. can be used. Cost reduction can be achieved by using inexpensive materials.

FIG. 4 is a perspective view showing a metal brazing material supply 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 tapered tip, and these pair of tools can slide against each other in the longitudinal direction while being in contact with each other at one end surface by a sliding guide 9. A feed hole 10 for a 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 predetermined length by a feeding mechanism 11. A piezoelectric element with an amplitude expansion mechanism is used as a pressure mechanism for the tool pressures 13 and 14. In addition, only the pressure tool has sliding guide 9.
The supporting tool 1 is integrated with a sliding guide 9, and its movement is performed by moving the mechanism that supports the entire jig.

FIGS. 5A to 5D are cross-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 support tool 1
Feed the metal brazing material 35 into the feed hole 10 and position the pressure tool 2 so that it is above the electrode 36 (
Figure 5(a)). Next, both the support tool 1 and the pressure tool 2 are lowered by applying a predetermined pressure in the direction of the arrow 18b, and the circuit board 37 is held down by the support tool 1 (FIG. 5(b)). Then, pressure is applied only to the pressure tool 2 and lowered to cut the metal brazing material 35, and the pressure tool 2 is continuously lowered to attach the cut piece of the metal brazing material 35 to the electrode 36 on the circuit board 37. Crimp it (Fig. 5(c)). Thereafter, when both the support tool 1 and the pressure tool 2 are raised, the metal brazing material supply process is completed (FIG. 5(d)). Note that the mechanism for holding down the circuit board by the support tool 1 may be omitted, 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 support tool 1 functions as a die and the pressure tool 2 functions as a punch. By the method of the example, a solder wire with a diameter of 0.1 mm was used as a metal brazing material for electrodes with a pitch of 0.5 mm and a shape of 0.2 mm x 1.0 mm, and the tip was 0.1 m.
A pressure tool having a rectangular shape of m x 1.5 mm was used to supply the solder material. At this time, the heating temperature of the stage is 100
℃, the wire could be cut with a pressure of 30 g or more, and crimping could be performed well. Since solder is soft and easily stretchable, if the clearance between the tools is large, the cut solder wire will undesirably have high burrs on the upper part of the cut surface. In the case of the present invention, since cutting is performed in one plane, the clearance can be reduced to zero, and solder can be supplied in a good shape. The shape of the small solder piece after crimping is crushed by a pressure tool so that the top surface is flat and the height is 0.06 mm.
It took on the shape of The bonding strength between the electrode and the solder piece needs to be such that it does not come off during handling, since the solder bond is perfected by the solder melting process with the electronic component placed thereon. When electronic components were bonded using a circuit board supplied with solder according to this example, good bonding performance was confirmed.

FIG. 6 is a structural diagram showing the solder supply shape 39 when the pressure tool tip surface 15 is made concave. As shown in the figure, the top surface of the metal brazing material 35 has a convex shape corresponding to the shape of the tip end surface of the pressure tool 15, so that the height and shape are accurate and contact with adjacent electrodes can be prevented.

As described above, in the case of the present invention, since the metal brazing filler metals that are successively fed are simply cut and crimped one after another, the apparatus is simple and the processing capacity can be increased. Unlike the screen printing method using a metal mask,
It is possible to easily change the shape of the tool, and it is possible to precisely supply the required amount of brazing filler metal set in advance to electrodes arranged at a narrow pitch or complex electrode arrangements of mixed sizes.

In the embodiment, a wire is used as the metal material, but a ribbon-shaped metal material may also be used. Furthermore, it can be applied not only to electrodes on circuit boards, but also to the case where a metal brazing material is supplied and bonded to metal leads of electronic components.

[0030]

[Effects of the Invention] The method for forming metal protrusions of the present invention has a simple process without a wet process, and requires only equipment with a simple structure and processing capacity, resulting in low material costs and equipment investment. This has the effect of forming metal protrusions at low cost. Since metal protrusions can be formed on the metal leads, there is no concern that the reliability of the joint will deteriorate due to mechanical stress.

[0031] Furthermore, since the shape and height of the metal protrusion can be controlled by the tip shape of the pressure tool, the metal protrusion can be formed with high precision, making it possible to make the welding highly reliable and also support narrow pitch welding. There are advantages. Furthermore, the material for the metal protrusions can be selected depending on the mounting configuration, which has the effect of realizing a low-cost, high-reliability structure.

[0032] The metal brazing material supply method of the present invention is capable of supplying metal brazing material without the need for a mask based on data designed using a computer, etc., and is compatible with changes in design and production of a wide variety of products in small quantities. , the process is simple as there is no wet process like the screen printing method, and the equipment has a simple structure and processing capacity, so it has the advantage of being able to supply brazing material at a low cost, such as requiring less material and equipment investment. . In addition, since the amount of metal brazing filler metal supplied is controlled by the wire diameter, highly accurate supply management is possible, and high reliability can be achieved by solving problems such as excess or shortage of solder. It has the advantage that the shape of the brazing material is controlled, no short circuit occurs with adjacent electrodes during melting and solidification, and it can also be used for narrow pitch bonding.

[Brief explanation of the drawing]

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

FIGS. 2(a) to 2(d) are process cross-sectional views showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing the shape of a metal protrusion 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.

FIGS. 5(a) to 5(d) are process cross-sectional views of the fourth embodiment.

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

FIGS. 7(a) to 7(c) are cross-sectional views showing a first conventional example in the order of steps.

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

FIGS. 9(a) to 9(c) are cross-sectional views showing the screen printing method, which is a conventional metal brazing material supply method, in 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 protrusion 9 Sliding guide 10 Feed hole 11 Feed mechanism 13, 14 Tool pressure 15 Pressure tool tip surface 16 Metal protrusion Object top surface 17, 17c, 18b, 18d Tool movement direction 20 Semiconductor element 21 Al electrode section 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 part 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

Claims (10)

[Claims] Claim 1: A fixed length of the metal wire is fed through the feed hole of a columnar support tool having a feed hole for the metal wire, and the support tool is lowered to hold down a metal lead or a substrate with the tip of the support tool. After that, a column-shaped pressure tool that contacts the supporting tool at one end surface in the longitudinal direction is slid to cut the metal wire extending a certain length from the feed hole, and the pressure tool continues to slide. A method for forming a metal protrusion, characterized in that the cut metal wire is crimped onto the metal lead or the substrate using a metal protrusion. 2. The method for forming metal projections according to claim 1, wherein the metal lead or the substrate is a metal lead of a TAB type film carrier or a semiconductor element. 3. A columnar support tool having a feed hole for a metal wire near its tip; a columnar pressure tool that slides while touching the support tool at one end surface in the longitudinal direction;
A metal protrusion forming jig comprising: a sliding guide for slidingly guiding at least one of the support and pressure tools; and a mechanism for feeding a metal wire a certain length into the feed hole. 4. The metal protrusion forming jig according to claim 3, wherein a recess is provided in the tip end surface of the pressure tool. 5. Positioning a columnar support tool having a feed hole for a linear metal brazing material at a predetermined position on the electrode, and feeding the metal brazing material a predetermined length according to the electrode length from the support tool feed hole, After cutting the fed-out metal brazing material by a pressure tool that slides in contact with the support tool at one end surface in the longitudinal direction, the pressure tool continues to slide and the cut metal brazing material is attached to the electrode. A method for supplying a metal brazing filler metal, which is 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 an electronic component and a metal lead. 8. A column-shaped support tool having a feeding hole for a metal brazing material near its tip, a column-shaped pressure tool that slides while touching the support tool at one end surface in the longitudinal direction, and the support tool. and a sliding guide for slidingly guiding at least one of the pressurizing tools, and a feeding mechanism that feeds the metal brazing material a predetermined length according to the electrode length from the feed hole. jig. 9. The metal brazing material supply jig according to claim 8, wherein a recess is provided in the tip end surface of the pressure tool. 10. After driving a columnar support tool or a substrate stage having a metal wire feed hole and positioning the support tool so that the tip end surface of the support tool and the substrate surface are at a predetermined distance, A column-shaped pressure tool that is in contact with one end surface in the longitudinal direction is slid to cut the metal wire fed out to a certain length from the feed hole, and the pressure tool continues to slide to cut the cut metal wire. A method for forming metal protrusions, characterized by crimping them onto a substrate.