JP2669478B2 - How to connect terminals to a printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method for connecting a terminal for external connection of a lead frame to a printed wiring board used for a semiconductor package or the like.

[Prior art]

Various methods have conventionally been provided for attaching the external connection terminals 3 of the lead frame formed of metal to the metal conductive circuit 2 formed on the printed wiring board 1, for example, as shown in FIG. Thus, the connection between the conductor circuit 2 and the terminal 3 is performed. That is, in FIG. 6, the connection is made by brazing the terminal 3 to the conductor circuit 2 on the surface of the printed wiring board 1 using a brazing material 8 such as solder or silver brazing. When the connection is made by brazing in this manner, the high heat of the molten brazing material 8 acts on the printed wiring board 1, causing mechanical deterioration such as deformation and delamination of the printed wiring board, and circuit-to-circuit deterioration. There is a possibility that deterioration of the printed wiring board such as deterioration of electrical characteristics such as reduction of resistance may occur, and problems associated with the use of the brazing material 8, such as generation of solder bridges and solder balls, conduction failure due to flux contained in solder, etc. Therefore, there is a possibility that the conduction reliability of the printed wiring board is reduced. For this reason, the present inventors can connect the terminal 3 to the printed wiring board 1 without having to perform brazing by bringing the terminal 3 into close contact with the conductor circuit 2 of the printed wiring board 1 and performing metal diffusion bonding. In developing the technology and performing this metal diffusion bonding, it has been found that metal diffusion bonding can be easily performed by applying ultrasonic vibration to the terminal 3, and these technologies have already been applied for patent applications.

[Problems to be solved by the invention]

However, when applying ultrasonic vibration to the terminal 3 and performing metal diffusion bonding, if the terminal 3 is as thin as about 18 to 50 μm like a terminal of TAB (Tape Automated Bonding), it is easy to apply ultrasonic vibration. Although it can be metal diffusion bonded, it has a thickness of 50 μm or more and is rigid like a terminal of a lead frame, and in the case of a narrow rectangular terminal, it is possible to apply ultrasonic vibration to perform metal diffusion bonding. difficult. That is, a large number of terminals 3 formed at the end of the lead frame 9 are integrally connected by a dam bar 10, and the terminals 3 are superimposed on the conductor circuit 2 of the printed wiring board 1 and the ultrasonic vibration is applied to the upper surface of the terminals 3. When the ultrasonic vibration is applied by pressing the vibration transmission tool of the child, the amplitude direction of the ultrasonic vibration is parallel to the longitudinal direction of the terminal 3 as shown by an arrow in FIG. If it works, the terminal 3 is hard to vibrate due to the rigidity of the terminal 3 itself and the reinforcing effect by the dam bar 10, and it is difficult to perform metal diffusion bonding by friction between the terminal 3 and the conductor circuit 2. To this end, it is considered to set the direction of the vibration so that the amplitude direction of the ultrasonic vibration is perpendicular to the longitudinal direction of the terminal 3, that is, the width direction, as indicated by the arrow in FIG. 5 (a). ,
In this case, although it is easy to vibrate the terminal 3, the terminal 3 rolls in the narrow width direction as shown by an arrow in FIG. In this case, it is difficult to cause the terminal 3 to be connected to the conductor circuit 2 by metal diffusion bonding. The present invention has been made in view of the above points, and provides a method of connecting a terminal to a printed wiring board in which an elongated terminal of a lead frame can be easily metal-diffused by the action of ultrasonic vibration. It is intended to do so.

[Means for Solving the Problems]

The method of connecting the terminal to the printed wiring board according to the present invention is such that when connecting the elongated terminal 3 integrally connected by the dam bar 10 of the lead frame 9 to the printed wiring board 1, ultrasonic vibration is applied to the terminal 3. The vibration direction is set in a direction oblique to the longitudinal direction of the terminal 3, and the terminal 3 is metal-diffusion bonded to the conductor circuit 2 of the printed wiring board 1.

[Operation]

In the present invention, the ultrasonic vibration is applied to the terminal 3 because the ultrasonic vibration is applied to the terminal 3 with the vibration direction set in a direction oblique to the longitudinal direction of the terminal 3. The terminal 3 does not hardly vibrate as in the case of acting in the longitudinal direction, and the terminal 3 does not roll as in the case of acting in the width direction of the terminal 3, so that the terminal 3 is efficiently vibrated. It becomes possible.

【Example】

Hereinafter, the present invention will be described in detail with reference to examples. The printed wiring board 1 is insulated with a resin laminate such as a glass cloth base epoxy resin laminate, a glass cloth base polyimide resin laminate, a glass cloth base fluororesin laminate, or a glass cloth base polyphenylene oxide resin laminate. In addition to forming a base material, a conductive circuit 2 is formed on the surface by processing a metal foil such as a copper foil or an aluminum foil by a subtractive method, or by plating by an additive method. Alternatively, an arbitrary material can be used, such as one in which an insulating base material is formed from a ceramic plate and a conductive circuit 2 made of a metal conductive paste is provided on the surface thereof. By mounting a semiconductor chip such as an IC chip on the printed wiring board 1 while being electrically connected to the conductor circuit 2, a semiconductor package such as a QFP can be produced. Further, as the terminal 3, for example, a lead frame 9 made of copper, a copper alloy, a 42 alloy, iron, an iron alloy, aluminum, or the like can be used. The lead frame 9 is generally formed with a thickness exceeding 50 μm, and furthermore, a plurality of terminals 3, 3.
The terminals are connected together by the dam bar 10 so that the terminals 3
Has rigidity. In connecting the terminal 3 to the conductor circuit 2 of the printed wiring board 1, as shown in FIG.
The tip of the terminal 3 is overlapped on the surface of the terminal 3 and is brought into close contact therewith. At this overlapped portion, the transmission tool 11 of the ultrasonic transducer is pressed against the upper surface of the terminal 3 to apply ultrasonic vibration. At this time, the vibration direction of the ultrasonic wave is set obliquely with respect to the longitudinal direction of the terminal 3 and applied so that the amplitude of the ultrasonic vibration is directed obliquely to the longitudinal direction of the terminal 3. If the direction of the ultrasonic vibration is set to be parallel to the longitudinal direction of the terminal 3, it is difficult to vibrate the terminal 3 due to the rigidity of the terminal 3, and if the direction of the ultrasonic vibration is set to a direction perpendicular to the longitudinal direction of the terminal 3, Terminal 3 rolls, but the second
As shown by the arrow in the figure, the vibration direction of the ultrasonic vibration
The terminal 3 is vibrated sufficiently without rolling, and the friction between the terminal 3 and the conductor circuit 2 is generated by the vibration. The bonding based on the metal diffusion phenomenon of the contact portion between the metal 2 and the metal of the terminal 3 can be performed. In this way, the terminals 3 can be joined and connected to the conductor circuit 2 by reliable and strong metal diffusion bonding. Here, in the vibration direction of the ultrasonic wave with respect to the longitudinal direction of the terminal 3, the arrow in FIG. 3 indicates the longitudinal direction of the terminal 3, the point O indicates the point where the ultrasonic wave is applied, the angle A is 5 °, and the angle B is 85 °. Assuming that the angle C is 95 ° and the angle D is 175 °, the angle range of BA is an angle of 5 to 85 ° (preferably 15 to 70 °) or an angle of DC, that is, 95 to 175. The angle is set to ゜ (preferably 105 to 165 °). In addition, as described above, by applying heat at the same time as applying the ultrasonic vibration, the metal diffusion bonding can be performed more firmly. The heating temperature is preferably in the range of 130 to 300 ° C. Further, the frequency of the ultrasonic wave is in the range of 50 to 80 KHz, preferably 55 to 65 kHz, and the output is 10 W or more, preferably 15 W or more. By further pressing, the metal surface of the conductor circuit 2 and the terminal 3 can be brought into close contact with each other, and the tip of the vibration transmission tool 12 can be cut into the terminal 3 to improve the transmission efficiency of ultrasonic waves. The applied pressure at this time is preferably about 0.5 to 1 kg or more when the tip end surface of the vibration transmission tool 11 has an area of 0.15 mm square.

【The invention's effect】

As described above, in the present invention, when connecting an elongated terminal integrally connected by a dam bar of a lead frame to a printed wiring board, ultrasonic vibration is applied to the terminal with respect to the longitudinal direction of the terminal. Because it is set in a diagonal direction and added, it is not difficult to vibrate the terminal as in the case where ultrasonic vibration is applied in the longitudinal direction of the terminal, and when it is applied in the width direction of the terminal. As described above, the terminal is elongated and does not roll, and the terminal reinforced and connected integrally by the dam bar can be vibrated efficiently and sufficiently. By generating friction therebetween, it is possible to join and connect the terminals to the conductor circuit by reliable and strong metal diffusion bonding.

[Brief description of the drawings]

1 is a perspective view of one embodiment of the present invention, FIG. 2 is a partial perspective view of the same, FIG. 3 is a partial plan view of the same, and FIG. 4 is a partial perspective view of a conventional example. FIG. 5 (a) is a perspective view of a part of the conventional example, FIG. 5 (b) is a cross-sectional view taken along the line II in FIG. 5 (a), and FIG. 6 is a cross-sectional view of another conventional example. FIG. 1 is a printed wiring board, 2 is a conductor circuit, 3 is a terminal, and 9 is a lead frame.

Front page continued (72) Inventor Takeshi Kano 1048 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Works, Ltd. (72) Toru Higuchi, 1048 Kadoma, Kadoma City, Osaka Matsushita Electric Works, Ltd. (56) Reference Reference JP-A-56-106385 (JP, A) JP-A-62-117391 (JP, A)

Claims (1)

(57) [Claims] When connecting an elongated terminal integrally connected by a dam bar of a lead frame to a printed wiring board, ultrasonic vibration is set to the terminal in a direction oblique to the longitudinal direction of the terminal. A method of connecting a terminal to a printed wiring board, wherein the terminal is metal-diffusion-bonded to a conductor circuit of the printed wiring board.