JPH06254690A - Laser beam welding method - Google Patents

Abstract

PURPOSE:To reduce a laser beam energy input and to stabilize the quality by preheating a welding place by an infrared beam and subsequently, irradiating specified places of materials to be welded located at the preheating place with a laser beam to perform welding. CONSTITUTION:The wider range A than two connecting terminals 3a and 3b of a quartz oscillator 2 is preheated with the infrared beam. Heat energy of the laser beam is then inputted instantaneously to a remarkably converged section toward the terminals 3a and 3b, in other words, the spot range B. Consequently, the respective connecting terminals 3a and 3b of the quartz oscillator 2 are welded to the specified places of lead frames 1a and 1b and the input of the laser beam energy is reduced, hence the fluctuation of the quality at the time of welding can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of welding a minute electronic component including a lead wire of a coil to a conductive pattern of a lead frame or a printed circuit board, a mechanical component of micromechanical (micromechanical) or the like by laser.

[0002]

2. Description of the Related Art Conventionally, as a conventional method for welding electronic parts to a printed circuit board, a soldering method or resistance (spot) welding has been used for a long time. Recently, laser welding has been developed and applied to various fields.

[0003]

However, in the above-mentioned soldering method, since the solder flux, which causes instability of soldering quality and corrosion, is used, post-cleaning is required and the work becomes complicated, Therefore, automatic welding is difficult and unsuitable for large-scale welding work.

Although resistance welding is also used to weld electronic parts to the lead frame by the resistance welding described above, the change in the electrode state with time cannot be avoided because it is due to the characteristics of the resistance welding itself. The electrical resistance of the electrical component that should be changed changes depending on the surface condition, and also changes depending on the strength of the pressing force.Therefore, it is necessary to pay close attention to the stability of the welding quality, and it is a technical problem in terms of practicality. There is.
Further, it is currently difficult to perform resistance welding on the conductive pattern of the printed circuit board.

Further, although the above-mentioned laser welding has been improved in the technical field of mechanical welding which does not require electrical connection, it has electrical reliability in the case of electronic parts which require electrical connection. Therefore, strict quality control is necessary, especially when welding micro electronic parts such as coils and crystal oscillators, the spots are partially narrowed and heated with a laser, but when the heat capacity of the work piece is small. The laser welding is not generally practiced because the heat energy density is too high and the workpiece to be welded is instantly scattered around, and the welding quality is not stable. Therefore, the present inventor investigated why the quality of the small-capacity laser welding is not stable, and as a result, investigated the heat capacity of the electronic parts to be welded and the instantaneous input of thermal energy to the laser beam locally. We came to the conclusion that the balance between the rise in temperature and the height of the gradient was out of balance.

It is therefore an object of the present invention to provide a method of laser welding a welded substance which is a minute electronic component, for example, a lead wire having a diameter of the order of microns to a conductive pattern such as a lead frame or a printed circuit board. .

[0007]

A feature of the present invention is that a welding portion such as a lead frame is preheated by an infrared beam, and then a laser beam is locally applied to a predetermined portion of a welded object located at this preheating portion. Irradiating and welding.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows two lead frames 1a and 1b.
2 shows a structure in which two connection terminals 3a and 3b of the crystal oscillator 2 are connected to each other. The connection between the two is performed according to the method described below. First, they are close to each other 2
An infrared beam Aa preheats a region A, which is considerably wider than the terminal, at a predetermined position at the tip of one lead frame, near the terminal. Lead frame 1 at this time
In the present embodiment, the heating temperatures of a and 1b were about 30% of the melting temperature (melting point). Next, the thermal energy of the laser beam Ba is momentarily injected toward the terminals 3a and 3b of the crystal oscillator 2 in the locally converged region, that is, the spot range B. Thereby, the connection terminals 3a and 3b of the crystal oscillator 2 are connected to the lead frames 1a and 1b.
It is welded to a predetermined part of b. This point will be further described with reference to FIG. 2. Infrared beam Aa and laser beam Ba
This infrared beam is used for the lead frame 1a
It is intended to irradiate the enlarged area A near the terminal 3a (3b) located on the upper surface of (1b), but after being preheated by this irradiation, the laser beam Ba is obliquely positioned at this terminal. The spot area B that is being irradiated is irradiated.

The beam timing will be described with reference to FIG. 3. In this figure, the beam timing of the composite processing of the infrared beam and the laser beam, in which the vertical axis is temperature and the horizontal axis is time, and the heating target, that is, the material to be welded A certain connection terminal 3
It is a graph which shows the temperature profile of a, 3b.

First, an infrared beam Aa shown by a chain line
To preheat the area A to a predetermined temperature T ₁ (t ₁
= 2000 to 3000 msec), and then, when the laser beam Ba is irradiated in spots toward the connection terminals 3a and 3b of the crystal oscillator 2 (t ₂ = 10 to ₂₀ msec), the temperature rise of this connection terminal is
As shown by the curve C, the melting point temperature T ₂ is instantaneously exceeded. Therefore, the laser energy required for welding can be significantly reduced. Therefore, the connection terminals 3a, 3
The balance between the heat capacity of b and the height of the gradient of the temperature rise due to the instantaneous application of heat energy to the laser beam Ba is prevented from being unbalanced, and the variation in quality during welding is reduced because the amount of laser energy input is small. be able to. The energy amounts of the infrared beam and the laser beam are adjusted by balancing the heat capacities of the two to be welded.

[0012]

According to the present invention, a welding portion such as a lead frame is preheated by an infrared beam, and then a predetermined portion of the object to be welded located at this preheating portion is irradiated with a spot of a racer beam for welding. Therefore, it is possible to significantly reduce the amount of laser energy input required for welding, which stabilizes the quality of welding.

[Brief description of drawings]

FIG. 1 is a perspective view showing an irradiation range of an infrared beam and a laser beam of a lead frame and a connection terminal.

FIG. 2 is a front view showing an irradiation state of an infrared beam and a laser beam on a lead frame and a connection terminal.

FIG. 3 is a graph showing a beam timing of combined processing of an infrared beam and a laser beam and a temperature profile of a heating target.

[Explanation of symbols]

 1a Lead frame 1b Lead frame 3a Welding object (connection terminal) 3b Welding object (connection terminal) A Preheating range by irradiation of infrared beam Aa Infrared beam B Laser beam irradiation range Ba Laser beam

Claims (1)

[Claims] 1. When welding a material to be welded to a lead frame or the like, a welding portion of the lead frame or the like is preheated by an infrared beam, and then a laser beam is applied to a predetermined portion of the material to be welded located at the preheating portion. A laser welding method characterized by locally irradiating a laser beam.