JPH04290294A - Wire bonding method - Google Patents

Abstract

PURPOSE:To improve reliability by irradiating a bonding chip with a laser beam to heat it to a predetermined temperature, and heating a connecting part of the pad to the wire to effectively connect them. CONSTITUTION:A wire 8 is positioned on a pad 2, and a joint 9 is pressed by a bonding chip 3 to vibrate the chip 3. Here, an arm 4 is vibrated, a command S is simultaneously sent to a controller 7, a predetermined position of the chip 3 is irradiated with a laser beam 5 from a laser beam output unit 6 to to the pad 2 while being heated. Thus, an irregularity in a heating temperature is eliminated, thereby obviating a bonding malfunction.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding method in which a bonding chip presses a wire against a pad formed on a substrate, and the pad and wire are bonded by diffusion bonding.

[0002] In ceramic substrates having inner layer patterns used in electronic devices, discrete wires are laid on the surface of the ceramic substrate by modification or repair.
A signal propagation path is formed by discrete wires.

Usually, such discrete wires are laid by bonding the ends of the discrete wires to pads formed on the surface of a ceramic substrate.

[0004] In recent years, as such bonding,
By pressing the end of a discrete wire against a pad and applying vibration, it has become possible to join the end of a discrete wire to a pad through diffusion bonding.

[0005]

2. Description of the Related Art Conventionally, a device has been constructed as shown in the conventional explanatory diagram of FIG. FIGS. 3(a), 3(b), and 3(c) are configuration diagrams.

As shown in FIG. 3(a), the substrate 1 is placed on a heater plate 10, and the heater plate 10 heats the substrate 1 to a predetermined temperature by heating as indicated by the arrow. The end of the wire 8 is overlapped with the pad 2 which has been
The bonded portion 9 where the two are overlapped is pressed with a predetermined pressure P by the tip of the bonding chip 3 fixed to the tip of the arm 4.

Further, the arm 4 is vibrated by a vibrating mechanism 11 and is formed to vibrate in the horizontal direction of arrow A. In this way, the bonding part 9 is pressed by the bonding chip 3, vibration is applied, and further, the heater plate 10 heats the bonding part 9 to a predetermined temperature, and the pad 2
Conventionally, the ends of the wires 8 were joined by diffusion bonding.

By heating with such a heater plate 10, the entire board 1 is heated, and the electronic components mounted on the board 1 and the electronic components mounted on the board 1 are heated by melting solder that has already been connected, thermal expansion, etc. This will have a negative impact.

Therefore, for example, as shown in (b),
The pad 2 is irradiated with a laser beam 13 focused by a lens 12, and the joint 9 is heated by the laser beam 13.
Also, as shown in (c), high-temperature gas 15 heated with an inert gas such as nitrogen N
is ejected by the nozzle 14 and the joint part 9 is heated by the high temperature gas 15.
Consideration is being given to directly heating the electronic components and the substrate 1 to minimize heat damage to the electronic components and the substrate 1.

In addition, in such bonding, the bonding portion 9 is usually heated to a temperature of 150° C., and the pressure P exerted by the bonding tip 3 is approximately 50 to 100° C.
By vibrating at a frequency of approximately 60 KHz, wires 8 having a wire diameter of 30 to 70 μm are bonded.

[0011]

[Problems to be Solved by the Invention] However, heating the pad 2 by irradiating the laser beam 13 or heating the joint part 9 by the high-temperature gas 15 may cause problems in the substrate 1 and the mounting on the substrate 1. However, since the heat capacity of the pad 2 and the joint 9 is small, it is difficult to maintain the heating temperature at a predetermined temperature at all times.
The heating temperature fluctuates greatly, and especially when the laser beam 5 is irradiated to the pad 2, the absorption rate of the laser beam 5 in the pad 2 is poor, resulting in a low heating efficiency. Furthermore, depending on the surface condition of the pad 2, the light absorption rate differs, making the heating temperature unstable.

Therefore, there is a problem in that the pad 2 and the end of the wire 8 are not completely bonded by diffusion bonding, resulting in problems due to poor bonding. Therefore, an object of the present invention is to ensure the bonding between the pad and the wire and to improve reliability.

[0013]

[Means for Solving the Problems] FIG. 1 is a diagram explaining the principle of the present invention. As shown in FIG. 1, a pad 2 formed on a surface 1A of a substrate 1 and an arm vibrated in a predetermined direction A A wire 8 to be bonded to the pad 2 is placed on the pad 2 and pressed by the bonding tip 3 with a predetermined pressure P. A wire bonding method in which the bonding chip 3 is heated to a predetermined temperature and the wire 8 is bonded to the pad 2 by diffusion bonding by heating the bonding portion 9 with the wire 8 to a predetermined temperature. The bonding tip 3 heated to
The bonding chip 3 is further provided with a laser beam output unit 6 for irradiating the bonding chip 3 with a laser beam 5, so that the bonding chip 3 is heated to a predetermined temperature by the irradiation of the laser beam 5. ,
Further, when the bonding chip 3 starts to vibrate, a control unit 7 is controlled to irradiate the laser beam 5 from the laser beam output unit 6 in response to a predetermined command S to heat the pressure welding part 9. Equipped with
The heating of the bonding portion 9 is performed in conjunction with the vibration of the bonding chip 3.

[0014] With this configuration, the above-mentioned problem is solved.

[0015]

[Operation] That is, the bonding chip 3 , which is vibrated by the arm 4 , is irradiated with the laser beam 5 , and the bonding chip 3 is heated to a predetermined temperature, so that the bonding portion 9 between the pad 2 and the wire 8 can be heated. In addition, this kind of heating is applied to the bonding chip 3.
This is done in conjunction with the vibrations of the bonding chip 3, so that heating is performed reliably when the bonding chip 3 is vibrating.

With this configuration, the heat capacity of the bonding chip 3 itself is equal to that of the pad 2 or the bonding portion 9 described above.
Since the capacity is larger than that of , the heating temperature can be stabilized at a predetermined value.

Furthermore, when performing bonding, the wire 8
By positioning the wire 8 on the pad 2 , pressing it with the bonding tip 3 , and vibrating the bonding tip 3 , heating to a predetermined temperature is automatically performed, and the wire 8 can be reliably bonded to the pad 2 .

[0018] Therefore, damage caused by heat as described above is eliminated, and troubles due to poor bonding are also eliminated.
Quality and reliability can be improved.

[0019]

EXAMPLES The present invention will be explained in detail below with reference to FIG. FIG. 2 is an explanatory diagram of an embodiment according to the present invention, (a) is a configuration diagram, (b) is an explanatory diagram of a bonding chip, and (c) is a graph of the relationship between the temperature rise of the bonding chip and time. The same reference numerals indicate the same objects throughout the figures.

As shown in FIG. 2(a), the vibration mechanism 1
Arm 4 is excited in the horizontal direction of arrow A by 1.
is provided with a bonding chip 3 , while the substrate 1 is provided with a bonding chip 3 .
The end of the wire 8 is overlapped with the pad 2 formed on the surface 1A of the bonding chip 3, and the tip of the bonding chip 3 is pressed with a predetermined pressure P against the joint 9 where the wire 8 is overlapped with the pad 2. It is.

Furthermore, a laser beam 5 from a laser beam output section 6 is placed at a predetermined location on the bonding chip 3.
is formed so that it is irradiated. Therefore, the joint 9
is pressed, and the excitation mechanism 11 is driven by the command S from the drive circuit 16 to vibrate the arm 4. At the same time, the command S is sent to the control section 7, and under the control of the control section 7, the vibration mechanism 11 is driven by the command S from the laser beam output section 6. laser beam 5
is irradiated to heat the bonding chip 3.

Therefore, the bonding chip 3 having a large heat capacity is heated to a predetermined temperature, thereby heating the bonding portion 9, and the heating temperature can be maintained within a predetermined range. It is possible to eliminate bonding defects caused by variations in heating temperature.

In reality, the bonding chip 3 is made of a material such as titanium carbide TiC, tungsten carbide WC, or alumina ceramic Al2O3, and its size is a diameter D as shown in (b).
is about 2 mm, the length L is about 20 mm, and the laser beam 5 is irradiated to part B at a distance L1 (5 mm) from the tip.

In this case, a semiconductor laser is used as the laser beam 5, with a wavelength of 810 mm and a spot diameter of 1.0 mm.
, the work distance is 40 mm, and the output is 10 W (continuous wave).The horizontal axis is the irradiation time (sec) of the laser beam 5 shown in (c), and the vertical axis is the temperature rise in the heating temperature of the bonding chip 3 (°C). As is clear from the graph, the bonding chip 3 can be heated to 400° C. by irradiation for about 1 second.

Therefore, the bonding chip 3 is 150
Heating the bonding chip to a temperature of 3
It is sufficient to irradiate part B with the laser beam 5 for 0.2 to 0.3 seconds.

Therefore, by heating the bonding tip 3 to a predetermined temperature and further heating the bonding portion 9 by the bonding tip 3, it is possible to easily bond the wires 3 having a wire diameter of 50 to 70 μm as described above. can.

[0027]

[Effects of the Invention] As explained above, according to the present invention,
By heating the bonding chip to a predetermined temperature by irradiating the bonding chip with a laser beam, and further heating the bonding portion between the pad and the wire using the bonding chip, it is possible to reliably perform the bonding by diffusion bonding.

[0028] Therefore, it is possible to prevent electronic components and substrates from being adversely affected by heating as in the past, and moreover, it is possible to perform bonding more reliably than in the past, improving quality and reliability. The practical effects are great.

[Brief explanation of the drawing]

[Figure 1] Diagram explaining the principle of the present invention

[Fig. 2] Explanatory diagram of an embodiment according to the present invention

[Figure 3]
Conventional illustration

[Explanation of symbols]

1 board
1A Surface 2 Pad
3 Bonding chip

Claims (3)

[Claims] Claim 1: A pad (2) formed on the surface (1A) of a substrate (1), and a bonding chip (3) provided at the tip of an arm (4) that is vibrated in a predetermined direction (A). By overlapping the wire (8) to be bonded to the pad (2) on the pad (2), a predetermined pressure (P) is applied by the bonding chip (3).
by pressing the pad (2) and the wire (8)
A wire bonding method in which the pad (2) and the wire (8) are bonded by diffusion bonding by heating the bonding part (9) to a predetermined temperature, the bonding chip (3) being heated to a predetermined temperature. A wire bonding method characterized in that the bonding portion (9) is heated by the bonding chip (3) heated to a predetermined temperature. 2. The bonding chip according to claim 1 (
3) A wire characterized in that the bonding chip (3) is heated to a predetermined temperature by the irradiation of the laser beam (5), and the bonding chip (3) is heated to a predetermined temperature by the irradiation of the laser beam (5). Bonding method. 3. The bonding chip according to claim 1 (
3) When the vibration starts, the laser beam output section (6) is controlled to irradiate the laser beam (5) with a predetermined command (S) to heat the joint section (9). the bonding chip (3);
A wire bonding method characterized by being performed in conjunction with the vibration of.