WO2011155115A1

WO2011155115A1 - Connecting structure and manufacturing method thereof

Info

Publication number: WO2011155115A1
Application number: PCT/JP2011/002345
Authority: WO
Inventors: 伸一藤原; 薫内山; 時人諏訪; 雅彦浅野
Original assignee: 日立オートモティブシステムズ株式会社
Priority date: 2010-06-09
Filing date: 2011-04-22
Publication date: 2011-12-15
Also published as: JP2011258732A; JP5577161B2

Abstract

Decreased connection reliability due to rotation of a lead when vibration is applied, and variability in the connection surface area, are problematic when ultrasonically connecting a lead and a conductive layer disposed on a substrate. This problem is addressed by the disclosed connection structure. When ultrasound processing is started, the contact surface area of the lead and the ultrasound tool is increased to a level greater than the contact surface area of the lead and the conductive layer. For example, one side surface of a lead having a circular cross-section is planarized and the ultrasound tool is pressed against said side surface to form the ultrasonic connection. Because the contact surface between the lead and the ultrasonic tool is greater, rotation of the lead is suppressed, and by having a smaller contact surface between the lead and the conductive layer, stress is concentrated at the connection area and the connection is formed more easily.

Description

Connection structure and manufacturing method thereof

This invention relates to the connection structure which connects the lead | read | reed used for household appliances, consumer electronics, industry, and automobiles to other components.

Today, electronic products are used in many products, from consumer products to industrial products. Inside these electronic devices, a printed wiring board in which electronic components are mounted on an insulating plate having metal wiring is included, and each electronic component obtains electrical continuity with wiring on the board. Plays the role of parts.

One of the main electronic components is a coil, which is an essential component for high-frequency circuits and switching power supplies. The coil is mainly made of a cylindrical metal wire, and the coil is connected to the wiring on the board by passing both ends of the coil through a through-hole formed in the board, and connecting the wiring on the board and the coil end. Often soldered. FIG. 10 shows an example of the connection between the coil and the wiring on the substrate. 11 is a pad on the substrate, 12 is a substrate, 13 is solder, and 21 is a coil. In this soldering method, first, the end portion of the coil 21 is inserted and fixed in the through hole of the substrate 12 in which the pad 11 on the substrate is formed. Next, the coil 21 is held so as not to be detached from the through hole, and solder is sprayed from the opposite side of the coil 21 with a flow soldering apparatus. After that, the soldering is completed by taking it out from the soldering apparatus and cooling it. When the board size is small or the number of parts is small, soldering may be performed manually. As described above, soldering is performed by melting and connecting the solder while holding the coil so that it does not leave the through-hole. Therefore, soldering must be performed while holding the coil. The problem is that it needs to be formed. In this connection method, soldering may be performed by a thermal process, which is considered to have a large environmental load, and development of a soldering alternative technology is urgent.

As connection methods that do not use solder, connection by conductive resin, contact connection by caulking, ultrasonic connection, etc. are conceivable. Connection by conductive resin can be made at a temperature lower than the soldering temperature. In addition, the caulking contact connection is a mechanical contact connection, and thus can be realized at room temperature. However, the conductive resin connection requires a heat load and a high connection resistance, and the contact connection has a high contact resistance and requires a caulking member. On the other hand, the ultrasonic connection is a method in which a member to be connected is metal-connected at room temperature with energy by ultrasonic waves and pressure, and a low resistance room temperature connection can be realized.

As a method for connecting a wiring and a pad on a substrate using ultrasonic waves, in Patent Document 1, a plurality of bumps are formed on a conductive pattern in advance, wiring is placed so as to be sandwiched between the bumps, and then applied from above. There has been proposed a method of connecting a wiring and a conductive pattern by applying ultrasonic waves while pressing. In addition, as a method of connecting the printed circuit board electrode and the metal terminal, Patent Document 2 discloses that the printed circuit board electrode formed on the printed circuit board end is sandwiched from above and below by the metal terminal formed on the flexible substrate, and ultrasonic waves are applied to the sandwiched portion. There has been proposed a method of metal-connecting an electrode on a printed circuit board and a metal substrate by applying. These methods are examples in which metal connection at room temperature, which is a feature of ultrasonic connection, is proposed.

Japanese Patent Laid-Open No. 11-288961 Japanese Patent No. 3856656

As described above, connecting a cylindrical metal wire onto a substrate electrode without using solder is a technology having a great merit. However, in the method described in Patent Document 1, bumps must be formed, which increases manufacturing man-hours and costs, and improves bump strength when connecting copper or aluminum cylindrical metal wires. There is concern about the need to Moreover, in patent document 2, since a connection part is restricted to a board | substrate outer periphery, the freedom degree of design falls, and since a flexible board | substrate is used, there is a possibility that material cost will raise.

Another problem is misalignment during connection. An example will be given in which a metal on the ultrasonic tool side (for example, a cylindrical metal wire, metal A) and a metal on the anvil side (for example, a pad on the substrate, metal B) are connected by ultrasonic waves. The tip of the ultrasonic connection tool is provided with a protrusion for preventing slippage between the ultrasonic tool and the metal A during ultrasonic vibration. Since the protrusion is hard to get into the metal A, the metal A is held so as to follow the movement of the ultrasonic tool. However, when connecting the cylindrical metal wire, the curved surface is pressed by the protrusion at the tip of the ultrasonic tool, so that the contact position varies, and the position shift and the metal wire move. If misalignment occurs, there is a concern about the effect on connection reliability.

In the present invention, in order to solve the above-mentioned problem, when ultrasonically connecting a metal body to a conductor layer on a substrate, the area where the metal body contacts the ultrasonic tool at the start of ultrasonic connection, It was larger than the contact area.

According to the present invention, since the ultrasonic tool contacts the metal body with a large area, the displacement and rotation of the metal column during pressurization can be suppressed, and the contact area between the metal body and the conductor layer is small. In the initial pressurization, the power tends to concentrate on the contact portion, and the connection can be made with less energy.

It is the connection schematic of the lead | read | reed and electrode concerning one Example of this invention. It is a schematic diagram of the Example of an ultrasonic connection to the coil concerning one Example of this invention. It is a schematic diagram of the Example of an ultrasonic connection to the coil concerning one Example of this invention. It is an enlarged view of the lead tip before ultrasonic connection concerning one example of the present invention. It is an enlarged view of the lead tip after ultrasonic connection concerning one example of the present invention. These are sectional drawings of the lead length direction before the ultrasonic connection concerning one Example of this invention. It is sectional drawing of the lead length direction in the ultrasonic connection concerning one Example of this invention. It is sectional drawing of the lead length direction after the ultrasonic connection concerning one Example of this invention. It is sectional drawing of the lead radial direction before the ultrasonic connection concerning one Example of this invention. It is sectional drawing of the lead radial direction in the ultrasonic connection concerning one Example of this invention. It is sectional drawing of the lead radial direction after the ultrasonic connection concerning one Example of this invention. It is sectional drawing explaining the connection of a lead with a circular cross section concerning a prior art. It is sectional drawing explaining the connection of a square cross-section concerning a prior art. It is sectional drawing after the connection of the connection part concerning one Example of this invention. It is a schematic diagram of the fracture surface of the pad on a board | substrate after the shear test concerning one Example of this invention. It is sectional drawing of the lead radial direction before the ultrasonic connection concerning the other Example of this invention. It is the connection schematic of the conventional lead | read | reed and electrode.

Hereinafter, embodiments of the present invention will be described.

FIG. 1 shows a connection form of a coil 21 and a substrate 12 according to an embodiment of the present invention. The coil 21 is formed by winding a lead and has two leads 1 for electrical and mechanical connection to the substrate. A plurality of electrode pads 11 made of a conductor layer are formed on the substrate 12, and the lead 1 is bent about 90 degrees, and the side surfaces thereof are connected to the electrode pads 11 by ultrasonic connection.

The connection method between the coil and the substrate according to this embodiment will be described with reference to FIGS. 1 and 2A and 2B. First, as shown in FIG. 2A, the coil 21 is placed on the substrate such that the side surface of the lead 1 faces the electrode pad 11. Then, an ultrasonic tool 20 is prepared.

Next, as shown in FIG. 2B, the ultrasonic tool 20 is pressed from the lead 1 to the electrode pad 11 side while applying a force. In this state, by applying ultrasonic waves to the ultrasonic tool 20, the lead 1 and the metal of the electrode pad 11 are rubbed together to remove the surface oxide film and the like on the contact surface, and the new metal surface comes into contact. Thus, the coil 21 and the substrate 12 are connected.

3 (a) and 3 (b) are schematic perspective views of the present embodiment before and after connection, and FIGS. 4 (a), 4 (b), and 4 (c) are cross-sectional views along the axial direction of the lead 1. FIG. 5 (a), (b) and (c) are cross-sectional views along the radial direction of the lead 1. FIG. 3A, FIG. 4A, and FIG. 5A are diagrams showing a state before connection. Reference numeral 1 denotes a lead, 3 denotes a processed portion on the lead, 11 denotes an electrode pad, and 20 denotes an ultrasonic tool. As shown in the drawing, the lead 1 is disposed on the electrode pad 11. At this time, the electrode pad 11 and the side surface of the cylindrical portion of the lead 1 are in contact. Processing is performed on the side surface portion of the lead opposite to the contact portion to form a processed portion 3 on the lead. The on-lead processed portion 3 is processed so that the vibration surface of the ultrasonic tool 20 has a larger area than the region in contact with the lead 1. Although it is desirable that the processed surface shape of the R-soil processed portion 3 is a flat surface, it is not limited to a flat surface, and there are some irregularities on a substantially flat surface, or other portions (particularly a contact surface that contacts the electrode pad 11). It may be a curved surface with a smaller curvature. As a method of forming the on-lead processed portion 3, press processing, cutting, blasting, or the like is performed from the lead 1 having a circular cross section, or the cross section is partially cut to have a circular shape so as to have the processed portion on the lead. The lead 1 may be cast, but any method may be used as long as the above-mentioned processed portion 3 on the lead is formed.

As shown in FIGS. 4B and 5B, the ultrasonic tool 20 is pressed against the processed area 3 on the lead, and the lead 1 and the electrode pad 11 are connected by applying ultrasonic waves. The protrusion formed on the vibration surface of the ultrasonic tool 20 increases the restraining force of the lead 1 when applying ultrasonic waves, and concentrates the ultrasonic power on the connection surface.

FIG. 4B is a schematic cross-sectional view of the connecting portion when the lead 1 being connected is viewed from the tip direction of the lead, but as shown in FIG. 5B, on the lead where the ultrasonic tool 20 is in contact. The processing point 3 is deformed following the shape of the tip protrusion of the ultrasonic tool 20 and suppresses slippage between the ultrasonic tool 20 and the lead 1 when an ultrasonic wave is applied. Further, the lead 1 is crushed in the thickness direction by pressurization. On the other hand, the contact surface 30 is rubbed at the initial contact location, so that the surface oxide film and the like on the contact surface between the lead 1 and the substrate pad 11 are removed, and the metal newly connected surface comes into contact with the metal. The connection surface 30 spreads from the initial connection surface toward the side surface of the lead 1 as the lead 1 is deformed as the ultrasonic wave is applied and pressurized.

3 (b), 4 (c), and 5 (c) are external views of the lead 1 and the electrode 10 after connection. As shown in this figure, a trace of the shape of the tip of the ultrasonic tool 20 remains in the pressurized part 2 on the lead pressed by the ultrasonic tool 20 in the processed part 3 on the lead. Most of the upper machining location 3 remains the initial machining surface. In the above process, the lead 1 and the electrode 10 are connected by ultrasonic connection.

The operational effects of this embodiment will be described. 6 (a) and 6 (b) are diagrams for explaining conventional ultrasonic connection. Conventionally, a lead 1a having a circular cross section or a square lead 1b has been used. FIG. 6A is a diagram showing connection in the case of the lead 1a having a circular cross section. When the on-lead processed portion 3 is not formed on the lead, the pressure contact surface of the ultrasonic tool 20 and the surface where the lead 1 is initially contacted are curved surfaces, so that the initial contact area between the ultrasonic tool 20 and the lead 1 is large. Get smaller. Therefore, when pressure is applied, stress is applied as shown by the arrows in the figure, and there is a high possibility that the lead 1 is displaced or rotated with respect to the electrode 11. When this misalignment or rotation occurs, the connection area between the lead 1 and the electrode 10 varies, so that the connection reliability is lowered, and when the other end of the lead is fixed, stress is generated at the connecting portion at the other end. There is concern about reducing reliability.

In addition, if the lead 1b having a square cross section is used as shown in FIG. 6B, the lead is not easily displaced or rotated, but the contact area between the lead 1b and the electrode pad 11 is large at the start of ultrasonic application, The power applied to the connection location is dispersed, and a large power is required for the connection.

On the other hand, in this embodiment, by forming the on-lead processed portion 3, variation in the initial contact area when the ultrasonic tool 20 contacts the lead 1 is suppressed, and the curved surface on the side surface of the circular lead is pressed. Compared to the case, the initial contact area between the ultrasonic tool 20 and the lead 1 can be increased. In addition, since a load can be applied uniformly from the initial state, the displacement and rotation of the lead 1 can be suppressed.

Furthermore, since the area of the tip of the ultrasonic tool 20 and the lead 1 in the initial state of ultrasonic vibration can be made larger than the initial contact area of the lead 1 and the electrode 10, it is possible to connect with less input energy from the initial connection stage. Power can be concentrated on the surface. Further, when the curved surface is pressurized and vibrated without forming the processed portion 3 on the lead, the shape along the tip of the ultrasonic tool 20 from the curved surface is applied by pressing the surface where the ultrasonic tool 20 and the lead 1 are in contact with each other. However, energy required for deformation can be reduced by forming the on-lead processed portion 3. In addition, since the initial contact area between the lead 1 and the electrode pad 11 is small, ultrasonic waves and pressure for connection are concentrated on the contact area having a small area, and the connection is facilitated. Therefore, it is possible to realize low-energy connection for a short time by reducing the load at the time of connection, shortening the excitation time, and reducing the amplitude.

The lead 1 may be made of any material, but is preferably a metal containing at least one of copper, aluminum, iron and nickel as a main component. The surface of the lead 1 may be coated with a metal (including solder) whose main component is tin, gold, nickel, copper or the like. The electrode 11 may be made of any material, but is preferably a metal containing at least one of copper, aluminum, iron, and nickel as a main component. Further, the surface of the electrode 11 may be coated with a metal (including solder) whose main component is tin, gold, nickel, copper or the like. Further, in this embodiment, an example in which the lead cross-sectional shape before lead processing is circular is described, but the cross-sectional shape of the lead may be an ellipse, a polygon such as a triangle, a quadrangle, or an octagon.

Furthermore, the direction in which the ultrasonic tool is vibrated when applying ultrasonic waves is preferably the longitudinal direction of the lead, but it may be the short direction, the licking direction, or the circumferential direction.

In this embodiment, as shown in FIGS. 4 (a), (b), (c) and FIGS. 5 (a), (b), and (c), the area where the ultrasonic tool 20 is pressed when viewed from the side is processed on the lead. Although depicted as a part of the location 3, the area where the ultrasonic tool 20 is pressed is the machining area on the lead in FIGS. 4 (a), (b), (c) and FIGS. 5 (a), (b), and (c). If the lead other than 3 is not pressed, it may be equal to or less than the total length of the processed portion 3 on the lead, and the same effect can be obtained by pressing the tip of the lead 1.

In this embodiment, the length of the ultrasonic tool 20 in the horizontal direction in FIGS. 5A, 5B, and 5C is depicted as being approximately the same as the diameter of the lead 1, but FIG. The lateral lengths in a), (b), and (c) may be longer or shorter than the diameter of the lead 1, and are not limited to those shown in FIGS. 5 (a), (b), and (c).

At the end of connection, as shown in FIGS. 3B, 4C, and 5C, the lead 1 formed with the tip shape of the ultrasonic tool 20 and the substrate pad 11 are connected to the pressurizing portion. Shape. In the above process, the lead 1 and the substrate pad 11 are connected by ultrasonic connection. After the connection, in FIG. 5C, which is a cross section in the radial direction, the lead 1 is similarly crushed from the upper side and the lower side, so the upper side of the lead 1 than the connection area between the lead 1 and the electrode pad 11 The area of the substantially flat portion is large.

FIG. 7 is an enlarged view of the cross-sectional shape of the connecting portion when viewed from the tip end direction of the lead after being connected using the present embodiment. Reference numeral 1 denotes a lead, 11 denotes a pad on the substrate, 12 denotes a substrate, and 31 denotes an outer peripheral portion near the connection surface. As shown in FIGS. 5 and 6, the contact area between the lead 1 and the substrate pad 11 is very small at the initial stage of connection, and the contact location is near the center of the substrate pad 11. By applying ultrasonic waves and a load, the contact surfaces of the lead 1 and the pad 11 on the substrate are rubbed to expose each new metal surface, and the connection proceeds by metal bonding. As the connection progresses, the surface film such as an oxide film on the connection surface is pushed out of the connection portion, and is easily deposited near the outer peripheral portion 31 in the vicinity of the connection surface. As the connection process progresses and the connection area increases, the outer peripheral portion 31 near the connection surface also moves outward compared to the initial connection surface, and when the connection is completed, it becomes the location of the outer peripheral portion 31 near the connection surface shown in FIG. In addition, surface films such as oxide films tend to deposit.

FIG. 8 is a schematic view of the fracture surface of the pad on the substrate after the shear test of this embodiment of the present invention. 11 is a pad on a substrate, 12 is a substrate, 30 is a connection surface, 31 is an outer peripheral portion near the connection surface, and 32 is a shear test mark. FIG. 8 shows an example in which the shear test mark 32 is formed in the vertical direction. However, since the shear test mark 32 tends to be formed in the same direction as the ultrasonic wave application direction, the direction of the shear test mark 32 is any direction. It does not matter if it is in the direction. As shown in FIG. 7, since a surface film such as an oxide film is likely to be deposited on the outer peripheral portion 31 in the vicinity of the connection surface after connection, when the shear test of the test piece of FIG. It is estimated that

FIG. 9 is a cross-sectional view of the state before connection when the present invention is applied to the connection of the coil according to the second embodiment of the present invention, as viewed from the leading end side of the lead 1. Reference numeral 1 is a lead, 3 is a processing location on the lead, 4 is a lead initial contact location, 11 is a pad on the substrate, 12 is a substrate, 20 is an ultrasonic tool, and 30 is a connection surface. In the state before the connection, since the lead on-machined portion 3 is formed on the lead 1 as shown in FIG. 9, the protrusion at the tip of the ultrasonic tool 20 contacts the lead on-machined portion 3 evenly. Therefore, the rotation and displacement of the lead 1 when the ultrasonic tool 20 and the lead 1 are in contact can be suppressed. In addition, since the initial contact area between the lead 1 and the pad 11 on the substrate is smaller than the area of the lead processing portion 3 where the ultrasonic tool 20 pressurizes, the power applied to the connection portion tends to concentrate. Therefore, initial connection is possible with less energy, and fine powder generated at the time of connection can be suppressed.

The difference from the first embodiment is that the unevenness 4 is formed in the lead initial contact portion 4 where the pad 11 on the substrate and the lead 1 are in contact. The unevenness is formed by forming a groove along the longitudinal direction of the lead 1. A line connecting the tips of the irregularities 4 is formed so as to be substantially parallel to the processed portion 3 on the lead, and a plurality of the tips of the irregularities 4 are in contact with the electrode pads 11 in the initial stage of ultrasonic application. By forming the irregularities, the lower surface of the lead 1 is not circular, and the lead 1 becomes difficult to roll, and the positional deviation of the lead during ultrasonic connection can be suppressed. Rolling can also be prevented by flattening the lower surface of the lead 1 in the same manner as the upper surface. However, in this embodiment, there is a gap between the tips of the concave and convex portions at the start of ultrasonic connection, so that the contact area becomes small and the load is uneven. It is easy to connect by concentrating on the tip. In addition, since the coil is stable and can stand on its own, the component support step before connection can be omitted. The concavo-convex shape may be any shape as long as two or more fulcrums can be formed. However, the concavo-convex shape is in a region immediately below the processed portion 3 on the concavo-convex tip lead, and the center of gravity of the cross section of the lead 1 is surrounded by a plurality of concavo-convex tips. It is desirable to lie on a designated area. Concavities and convexities may be formed at the time of manufacture, applied to a press or mold, applied by physical processing such as laser processing or blasting, or processed by chemical processing such as etching. But it ’s okay.

The cross-sectional view after the start of connection is the same as in Example 1, and is as shown in FIG. 5B during connection and as shown in FIG. 5C after connection. The same is true for the on-lead processed portion 3, the material of the lead 1, and the connection process of ultrasonic connection.

DESCRIPTION OF SYMBOLS 1 ... Lead, 2 ... Pressing location on lead, 3 ... Initial processing location on lead, 4 ... Initial contact location on lead, 10 ... Electrode, 11 ... Pad on substrate, 12 ...... Substrate, 13 ... solder, 20 ... ultrasonic tool, 21 ... coil, 30 ... connection surface, 31 ... outer periphery near connection surface, 32 ... shear test trace.

Claims

A substrate,
An electrode pad provided on the substrate;
In a connection structure comprising a metal body connected to the electrode pad by ultrasonic connection,
On the surface opposite to the surface connected to the electrode pad of the metal body, has a substantially flat portion,
The connection structure characterized in that an area of the substantially planar portion is larger than an area where the metal body is connected to the electrode pad.
In claim 1,
The metal body is a lead;
A connection structure characterized in that a cross section of a portion of the lead that is not connected to the electrode pad is substantially circular or elliptical.
In claim 2,
The connection structure, wherein the lead forms a coil.
4. The connection structure according to claim 1, wherein a material of the surface of the metal body and the electrode pad contains at least one of copper, nickel, aluminum, and tin as a main component.
Disposing the first metal body on the second metal body;
The side surfaces of the first metal body facing away from the second metal body are pressed while applying ultrasonic waves with an ultrasonic tool, and the first metal body and the second metal body are pressed. And a step of ultrasonically connecting
In a manufacturing method of a connection structure including:
The method for manufacturing a connection structure, wherein the first metal body has a contact area with the ultrasonic tool larger than a contact area with the second metal body at the start of application of ultrasonic waves.
In claim 5,
The method of manufacturing a connection structure, wherein the first metal body is a lead, and the second metal body is an electrode pad or a wiring provided on a substrate.
In claim 6,
The method of manufacturing a connection structure, wherein the lead has a substantially circular or elliptical cross-sectional area at a portion where the ultrasonic connection is not performed.
In claim 6 or claim 7,
The lead has undergone a process of flattening the side surface or reducing the curvature,
The method of manufacturing a connection structure, wherein the ultrasonic tool performs ultrasonic application while being in contact with the processed region.
In any of claims 5 to 8,
At the start of the application of ultrasonic waves, the first metal body and the second metal body are in a region where ultrasonic waves are applied, and are in contact with each other at a plurality of locations. Method.
In claim 9,
The first metal body has irregularities on a surface connected to the second metal body,
A method for manufacturing a connection structure, wherein at the start of application of ultrasonic waves, the plurality of tips of the irregularities are in contact with the second metal body.
In any of claims 5 to 10,
The method of manufacturing a connection structure, wherein the first metal body is a lead constituting a coil.