JP2009113083A - Ultrasonic joining tool, and fitting method for ultrasonic joining tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic joining tool where ultrasonic joining can be performed even in the case a distance from a resonance body to a joining point is long by an obstacle or the like, and a tool must be prolonged, and in the case a high joining load is required, and its fitting and exchange to a horn are facilitated, and to provide a fitting method for the ultrasonic joining tool. <P>SOLUTION: The ultrasonic joining tool 6 pressurizing the second copper plate 12 at the tip face 6d thereof and ultrasonic-joining the first and second copper plates 11, 12 by applying ultrasonic vibration is composed of: a columnar substrate part 6a whose terminal is fitted to a horn 5; and a columnar tip part 6b elongated from the substrate part 6a to the lower part and having a diameter smaller than the substrate part 6a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to ultrasonic metal bonding in which metals are bonded by ultrasonic vibration, and particularly relates to an ultrasonic bonding tool used for ultrasonic metal bonding and a method for attaching the ultrasonic bonding tool.

  Various methods have been conventionally used for joining metal materials. Among them, there is an ultrasonic metal bonding method as a method capable of bonding different or similar metals in the air in a relatively short time. The ultrasonic metal bonding method destroys and exposes the oxide film and adsorbate formed on the surfaces of the bonded metals to be bonded by applying ultrasonic vibration of lateral vibration while applying pressure to the bonded metal. Joining is performed by generating plastic flow between clean atomic surfaces to form interatomic bonds.

  As an ultrasonic bonding apparatus for performing such ultrasonic metal bonding, for example, a columnar ultrasonic bonding tool (lead) having a tip attached to the tip is erected, and the tip of a horn (wedge) that transmits ultrasonic waves is used. There is known an ultrasonic bonding apparatus that attaches to an intermediate part of an ultrasonic bonding tool to transmit ultrasonic waves to the ultrasonic bonding tool and the chip, and applies a bonding load from above the ultrasonic bonding tool to bond the metals to be bonded together. (For example, refer to Patent Document 1). Also, a column-shaped ultrasonic welding tool (chip) is erected, a horn that transmits longitudinal vibration ultrasonic waves is attached to the side surface, and a vertical welding load is applied from the horn to the ultrasonic welding tool. A sonic bonding device or the like is also known (see, for example, Patent Document 2).

  On the other hand, in the manufacture of small electronic components such as semiconductor packages, an ultrasonic bonding apparatus used for bonding conductive wires to bonding pads on a semiconductor chip and leads on a semiconductor package has a small tool mounting hole near the tip of the horn. The bonding tool is fixed to the horn by bolting the bonding tool inserted into the tool mounting hole from the front end side of the horn (see, for example, Patent Document 3).

  As this type of bonding tool, a pencil-shaped tool in which a cylindrical tip is tapered in accordance with a dimension of a conductor is generally used. (For example, refer to Patent Document 4). The ultrasonic bonding apparatus converts the ultrasonic vibration of the longitudinal vibration transmitted from the resonator into an n-order bending vibration with a bonding tool, and applies the ultrasonic vibration to the conductor by using the tool tip as a vibration loop. In the ultrasonic bonding apparatus adopting the above configuration, the bonding tool can be easily replaced according to the dimensions of the conductor to be bonded.

By the way, a bonding tool for bonding conductors has a V-shaped or U-shaped cross section at the tip of the tool so that ultrasonic vibrations can be efficiently transmitted to a circular cross-section wire or a rectangular cross-section ribbon (tape) used as a conductor. Are formed, or knurls or the like in which protrusions are arranged in a lattice shape are formed, so that the wire or ribbon can be easily engaged (see, for example, Patent Documents 4 and 5).
JP 2003-266180 A JP 2005-138172 A JP 2007-35827 A JP 2004-87822 A JP 2007-67342 A

  However, in the ultrasonic bonding tools described in Patent Documents 1 and 2, when the distance to the bonding point is long due to an obstacle or the like, or when the length of the tool must be increased, or when a high bonding load is required, Since the tool tip is constrained and a vibration mode change occurs in the tool, and the nth-order vibration is not maintained, bonding is not performed.

  In addition, in the bonding tools described in Patent Documents 3 and 4, it is necessary to increase the thickness of the bonding tool in order to apply a large bonding load. However, if the diameter of the bonding tool is increased, a tool mounting hole formed in the resonator is provided. Therefore, even if the performance of the horn is sufficient, the ultrasonic vibration system including the horn must be enlarged in accordance with the increase in the tool size, and there is a problem in terms of handling and cost. is there. In addition, since bolting from the horn tip face cannot withstand a large bonding load, it is necessary to provide an engaging part that engages the horn and the bonding tool. It will adversely affect the characteristics.

  The present invention has been made in view of such a background. When the distance from the resonator to the joining point is long due to an obstacle or the like and the tool length must be increased, or when a large joining load is required. However, an object of the present invention is to provide an ultrasonic bonding tool that can perform ultrasonic bonding and can be easily attached to and replaced with a horn, and a method for mounting the ultrasonic bonding tool.

  In order to solve the above-described problems, the present invention provides an ultrasonic bonding method in which the base end is attached to an ultrasonic resonator, pressurizes the metal to be bonded at the tip, and applies ultrasonic vibration to the metal to be bonded. An ultrasonic bonding tool that includes a columnar base portion having a first cross section and a columnar body extending from the base portion and having a second cross section smaller than the first cross section. Constitute. In this case, the tip may be configured to be a smooth surface orthogonal to the axis, and the boundary between the base portion and the tip portion may be disposed at a position other than the vibration node.

  According to another aspect of the present invention, there is provided a columnar base portion having a first cross section, and a columnar body portion extending from the base portion and having a second cross section smaller than the first cross section. In a tool mounting method for attaching an ultrasonic bonding tool that pressurizes a metal to be bonded and applies ultrasonic vibration at the tip thereof to an ultrasonic resonator, the base end of the ultrasonic bonding tool extends along the axis thereof. Bolt holes are drilled, and bolt insertion holes perpendicular to the axis thereof are drilled near the tip of the resonator, and the bolts are inserted through the bolt insertion holes and disposed on the axis of the ultrasonic welding tool. Thus, the ultrasonic bonding tool is configured to be fastened to the resonator in an orthogonal state.

  According to the ultrasonic welding tool of the present invention, by accurately matching the resonance frequency to the driving frequency of the resonator, the tool tip becomes a vibration loop and the tool length must be increased, Even when a load is required, the vibration mode change of the ultrasonic welding tool is suppressed and the vibration loop at the tool tip is maintained, so that ultrasonic energy is reliably transmitted to the metal to be joined. Can be joined. As a result, even when the distance from the resonator to the joining point is long due to an obstacle or the like, joining is possible. In addition, by making the tip surface of the tip part a smooth surface perpendicular to the axis, ultrasonic metal bonding can be performed without adversely affecting the bonding performance, the tool shape is simplified, and the manufacturing cost is reduced. Can be reduced. Further, the metal to be joined is not damaged such as a dent.

  Further, according to the tool mounting method of the present invention, even if a large bonding load is applied, the ultrasonic bonding tool does not come off or shift from the resonator. In addition, since the ultrasonic bonding tool can be easily attached to the resonator, it can be easily replaced with a desired ultrasonic bonding tool that accurately matches the resonance frequency according to the type and thickness of the metal to be bonded. Is possible.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<< Configuration of Embodiment >>
FIG. 1 is a side view showing the ultrasonic metal bonding apparatus 1 with a part thereof broken. The ultrasonic metal bonding apparatus 1 includes an ultrasonic oscillator 2, a BLT vibrator 3 that generates ultrasonic vibration from an electric signal oscillated from the ultrasonic oscillator 2, and a resonance that transmits the ultrasonic vibration generated from the BLT vibrator 3. It has a cone 4 as a body, a horn 5 as an ultrasonic resonator, and an ultrasonic bonding tool 6 attached near the tip of the horn 5. The BLT vibrator 3, the cone 4 and the horn 5 are connected so that their axes all coincide. A block 8 is disposed above the BLT vibrator 3, the cone 4, and the horn 5, and a position serving as a vibration node of the cone 4 is held by a holder 9 suspended from the block 8.

  The ultrasonic welding tool 6 extends downward from the lower surface near the tip of the horn 5, and is fixed by a bolt 7 in a state where its axis is perpendicular to the axis of the horn 5. The ultrasonic bonding tool 6 is disposed on the horn 5 side (upper side in FIG. 1), has a base portion 6a having a cylindrical shape, a cylindrical shape having a diameter smaller than the diameter of the base portion 6a, and a tip side (see FIG. 1 and a boundary portion 6c that connects the base body portion 6a and the front body portion 6b. The base body portion 6a and the front body portion 6b are integrally formed and are arranged so that their axes coincide with each other. The boundary portion 6c is a step formed at an intermediate portion of the ultrasonic welding tool 6, and in this embodiment, is formed by a plane orthogonal to the axis. The front end surface 6d of the forming ultrasonic bonding tool 6 forms a circular smooth surface that is orthogonal to the tool axis (that is, the axis of the base portion 6a and the tip portion 6b) and has the same dimensions as the cross section of the tip portion 6b. Yes.

  Below the ultrasonic metal bonding apparatus 1, an anvil 10 for placing a metal to be bonded is disposed in parallel with the tip surface 6 d of the ultrasonic bonding tool 6. The first copper plate 11 and the second copper plate 12, which are to-be-joined metals, are placed on the anvil 10 in a state where the joint portions 11 a and 12 a to be ultrasonically joined are overlapped with each other. The ultrasonic metal bonding apparatus 1 is movable relative to the anvil 10, and the tip surface 6d of the ultrasonic bonding tool 6 is brought into contact with the upper surface of the bonding portion 12b of the second copper plate 12 so that the tool length is increased. The first copper plate 11 and the second copper plate 12 are ultrasonically bonded by applying a lateral ultrasonic vibration while applying a bonding load in the vertical direction (downward).

  FIG. 2 is an enlarged sectional view of a portion II in FIG. In the vicinity of the tip of the horn 5, a bolt insertion hole 14 perpendicular to the axis 5d of the horn 5 is formed. On the other hand, a bolt hole 15 is formed on the axis 6 d of the ultrasonic welding tool 6 on the base end surface (the upper end surface in FIG. 2) of the ultrasonic welding tool 6. Then, the bolt 7 is inserted from above the bolt insertion hole 14 of the horn 5 and screwed into the bolt hole 15 of the ultrasonic bonding tool 6, so that the ultrasonic bonding tool 6 is fixed to the horn 5. A stepped portion 5a that matches the upper end shape of the ultrasonic bonding tool 6 is formed on the proximal end portion of the surface of the horn 5 on which the ultrasonic bonding tool 6 abuts, so that the ultrasonic bonding tool 6 can be easily positioned with respect to the horn 5. Can be done.

<< Effects of Embodiment >>
Next, the effect of this embodiment is demonstrated. FIG. 3 is an operation explanatory view of the ultrasonic metal bonding apparatus 1. (A) shows the side surface of the ultrasonic metal bonding apparatus 1, (B) shows the longitudinal vibration mode from the tip of the BLT vibrator 3 to the tip of the horn 5, and (C) shows the ultrasonic welding tool. 6 shows a bending vibration mode from the base end to the tip end.

  The electrical signal oscillated from the ultrasonic oscillator 2 is converted into longitudinal ultrasonic vibration by the BLT vibrator 3, transmitted by resonating the cone 4 and the horn 5, and attached to the vicinity of the tip of the horn 5. It is converted into flexural vibration by the sonic bonding tool 6. As shown in FIG. 6B, the tip of the horn 5 has a maximum vibration amplitude (vibration loop), and an ultrasonic bonding tool 6 is attached in the vicinity of the tip. Thereby, attenuation | damping of the ultrasonic vibration at the time of converting from a longitudinal vibration to a bending vibration is suppressed.

  As shown in FIG. 6C, the bending vibration in the ultrasonic bonding tool 6 is such that the base end (upper end) of the ultrasonic bonding tool 6 forms a vibration loop. In the present embodiment, the vibration node comes to be above the boundary portion 6c between the base portion 6a and the tip portion 6b of the ultrasonic bonding tool 6, that is, in the base portion 6a. That is, the base portion 6a has a length of 1/4 or more of the wavelength λ. The amplitude is small in the base portion 6a of the tool having a large diameter, but the amplitude is large in the tip portion 6b of the tool having a diameter smaller than that of the base portion 6a. And since the front-end | tip of the ultrasonic joining tool 6 is a vibration loop and is a free end which is not restrained, the vibration amplitude is the maximum.

  The vibration node comes to be in the base body portion 6a. When the vibration node comes to the boundary portion 6c between the base body portion 6a and the front body portion 6b, the boundary portion 6c is damaged due to stress concentration or metal fatigue. This is because the ultrasonic welding tool 6 is easily broken, and thus the ultrasonic bonding tool 6 having high durability capable of withstanding a large bonding load is provided by shifting the position of the boundary portion 6c from the vibration node. .

  The shape of the ultrasonic bonding tool 6, that is, the cross-sectional dimensions of the base portion 6 a and the tip portion 6 b and the position of the boundary portion 6 c are such that the tip of the tool (lower end) is a vibration loop in consideration of various conditions such as resonance frequency and sound speed. Is set to be The ultrasonic welding tool 6 efficiently applies ultrasonic energy at the tip by applying a horizontal vibration (left and right direction in the figure) with the maximum amplitude at the same time as applying a bonding load in the downward direction in the figure to the metal to be joined. It transmits and joins to-be-joined metals.

  With a conventional ultrasonic bonding tool, when a large bonding load is applied, the tip of the ultrasonic bonding tool is restrained by the ribbon. That is, the vibration mode in the ultrasonic welding tool changes, the vicinity of the tool tip becomes a vibration node, and the ribbon does not vibrate so that the bonding is not performed. However, in the ultrasonic bonding tool 6 according to the present embodiment, by arranging the base section 6a having a large cross section in a portion that does not interfere with the second copper plate 12, a change in vibration mode of the ultrasonic bonding tool is suppressed. Since the vibration loop at the tip is maintained, ultrasonic energy can be reliably transmitted to the metal to be bonded, and ultrasonic bonding with a small distance from the horn 5 to the second copper plate 12 is possible.

  Further, since the tip surface 6d of the ultrasonic welding tool 6 is a smooth surface perpendicular to the axis of the tool, not only can ultrasonic vibration be transmitted without adversely affecting the bonding performance, but also the second copper plate 12 is not damaged such as a dent. In addition, the ultrasonic bonding tool 6 can be easily manufactured. Furthermore, since the ultrasonic bonding tool 6 is mounted so that the base end thereof is in contact with the lower surface of the horn 5, not only the mounting position is shifted or detached from the horn 5 even when a large bonding load is applied. Transmission of ultrasonic vibration is also performed efficiently.

<< Modified Embodiment >>
FIG. 4 is a cross-sectional view showing a joint (principal part) between the horn and the ultrasonic joining tool of the ultrasonic metal joining apparatus 1 according to a modified embodiment. In the description of the present modified embodiment, only differences from the above-described embodiment will be described, and members having the same configuration and function are denoted by the same reference numerals and description thereof will be omitted. On the base end portion 6b of the ultrasonic welding tool 6, a stud bolt 16 extending on the axis 6d is integrally formed at the center of the base end surface (upper end surface in FIG. 4). The stat bolt 16 is longer than the thickness near the tip of the horn 5, and is threaded on the tip (upper end in FIG. 4) side. When a nut 17 is screwed into a threaded portion that is inserted by inserting the stud bolt 16 into the bolt insertion hole 14, the base end surface of the ultrasonic bonding tool 6 comes into contact with the distal end of the horn 5 and the upper end shape of the ultrasonic bonding tool 6. Is aligned with the step portion 5 a of the horn 5, and the ultrasonic bonding tool 6 is fixed to the horn 5 at a predetermined position. Also in the ultrasonic bonding apparatus according to this modified embodiment, the same effects as the above-described effects are exhibited.

  This is the end of the description of specific embodiments, but the present invention is not limited to these embodiments. For example, in the said embodiment, although the base | substrate part and the front-end | tip part of an ultrasonic joining tool are made into the column shape, other shapes, such as a square column and a hexagonal column, may be sufficient if it is a column shape. Moreover, the front end surface of the ultrasonic bonding tool does not need to have the same shape as the cross section of the front body portion, and may be formed into a desired shape as necessary. Furthermore, in the above embodiment, the boundary portion is set to be below the vibration node, but the boundary may be set to a position that becomes a vibration node or a vibration loop. A predetermined length may be provided in the tool axis direction, and the shape may be a truncated cone (taper) whose diameter gradually decreases. Moreover, in the said embodiment, although two copper plates are used as a to-be-joined metal, a to-be-joined metal is not limited to this, For example, iron, aluminum, steel other alloys, etc., and these are combinations, Also good. As a further modification, an ultrasonic bonding tool may be used for bonding three or more members, and the shape of the metal to be bonded may be a shape other than a plate material, for example, a wire or the like, and does not depart from the spirit of the present invention. If so, it can be appropriately changed.

Side view showing a partially broken ultrasonic metal bonding apparatus Section II enlarged sectional view in FIG. Action explanatory diagram of ultrasonic metal bonding equipment Sectional drawing of the principal part of the ultrasonic metal joining apparatus by deformation | transformation embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic metal joining apparatus 2 Ultrasonic oscillator 3 BLT vibrator | oscillator 4 Cone 5 Horn 6 Ultrasonic joining tool 6a Base | substrate part 6b Tip part 6c Boundary part 6d Tip surface 7 Bolt 8 Block 9 Holder 10 Anvil 11 1st copper plate 12 Second copper plate 14 Bolt insertion hole 15 Bolt hole 16 Stud bolt 17 Nut

Claims (4)

The base end is attached to the ultrasonic resonator, and is an ultrasonic bonding tool for ultrasonically bonding the metals to be bonded by applying pressure to the metal to be bonded at the tip and applying ultrasonic vibration,
A columnar base portion having a first cross section;
An ultrasonic bonding tool comprising: a columnar tip portion extending from the base portion and having a second cross section smaller than the first cross section.   The ultrasonic bonding tool according to claim 1, wherein the tip is a smooth surface orthogonal to the axis.   The ultrasonic bonding tool according to claim 1, wherein a boundary portion between the base body portion and the front body portion is disposed at a position other than a vibration node. A columnar base portion having a first cross section, and a columnar body extending from the base portion and having a second cross section that is smaller than the first cross section; A tool attachment method for attaching an ultrasonic bonding tool for applying ultrasonic vibration while applying pressure to an ultrasonic resonator,
In the vicinity of the tip of the ultrasonic resonator, a bolt insertion hole perpendicular to its axis is drilled,
A tool mounting method, wherein the ultrasonic welding tool is fastened in an orthogonal state with respect to the resonator by a bolt that is inserted through the bolt insertion hole and disposed on an axis of the ultrasonic welding tool.

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