JPS63136535A - Wire bonding method - Google Patents

Abstract

PURPOSE:To obtain excellent bonding characteristics while improving yield by correcting a search section distance at the time of the next bonding operation at every bonding operation. CONSTITUTION:A distance L between a node 31 at the time fo ofnding processing at one node 31 and a reference position 32 is measured every time said bonding processing is executed, and the distance S of a search section 34 for bonding processing at the adjacent next node is corrected from the distance L. Consequently, actual distances C on correction sections 33 at each node 31 ranging from No.1 to No.n are made approximately the same distance C already set. A bonding tool 18 is brought into contact with respective node 31 under always constant best conditions, thus acquiring stable bonding characteristics.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a wire bonding method in which a bonding tool automatically connects a wire to each connection point on a semiconductor pellet attached to a substrate, for example. Regarding.

(Prior Art) For example, as one of the semiconductor manufacturing processes, as shown in FIG. There is a wire bonding process in which the provided lead terminals 4 are connected with thin wires 5. Usually, in this wire bonding process, as shown in FIGS. 5 and 6,
A bonding tool 7 for performing wire bonding is located at a reference position 6 spaced upward from the substrate 1 by a distance LD. As shown in FIG. 6, the distance ML from the reference position 6 to the connection point position of the semiconductor pellet 3 is divided into a search section (distance S) 8 and a correction section (distance IC) 9. Then, the bonding tool 7 is attached to the semiconductor pellet 3.
When connecting the wire 5 to the connection point by lowering the bonding tool 7 to the connection point, the bonding tool 7 is lowered at high speed within the search section 8, and after passing the search section 8 and within the correction section 9, the bonding tool 7 is lowered at a constant speed slower than within the search section 8. I am trying to lower it with

It should be noted that the distance S of the search section 8 is determined in advance by key input from an operation panel or the like by an operator for each type of semiconductor pellet 3 to be wire-bonded.

By controlling the descending speed of the bonding tool 7 in two steps in this manner, the bonding processing speed can be increased and the impact when the bonding tool 7 contacts the semiconductor pellet 3 can be reduced.

However, even in the wire bonding method in which the descending speed of the bonding tool 7 is controlled in two stages as described above, there are still problems to be solved as follows. That is, if the semiconductor pellet 3 to be wire-bonded is correctly attached to the substrate 1 as shown in FIG. 5, there is no problem, but as shown in FIG. A situation occurs where the distribution is not uniform between the two. In this case, the semiconductor pellet 3 is bonded to the substrate 1 in an inclined state. As a result, for example, an error ΔL occurs between the distance between the connection point at the left end of the upper surface of the semiconductor pellet 3 and the reference position 6 and the distance between the right end connection point and the reference position 6.

On the other hand, as explained in FIG. 6, the distance of search section 8! !
! Since 8 is a constant value for each type of semiconductor pellet 3,
The actual distance mc of the correction section 9 will change. Therefore, the distance and time from when the bonding tool 7 passes through the lower end position of the search section 8 (the upper end position of the correction section) 10 until it reaches each connection point of the semiconductor pellet 3 vary.

As a result, since the impact load upon contact varies, there is a problem that stable wire bonding characteristics cannot be obtained. Furthermore, if a large impact load is applied to the semiconductor pellet 3, there is a fear that the semiconductor pellet 3 itself may be damaged. Therefore, the product yield in the entire wire bonding process is reduced.

(Problems to be solved by the invention) In this way, with the conventional wire bonding method,
When the semiconductor pellet 3 is attached to the substrate at an angle, there is a problem that good bonding characteristics cannot be obtained.

The present invention was made based on these circumstances, and by correcting the search interval distance for the next bonding operation for each bonding operation, it is possible to obtain a good result even if the semiconductor pellet is attached at an angle. It is an object of the present invention to provide a wire bonding method that can obtain good bonding characteristics and improve yield.

[Structure of the Invention] (Means for Solving Problems) In the wire bonding method of the present invention, the distance from the reference position provided above the substrate to the connection point position of the semiconductor pellet is divided into a search section and a correction section. Each time a wire is connected by touching the bonding tool to the connection point of the semiconductor pellet, the distance from the reference position set above the board to the connection point is measured, and the measured distance and correction interval are The search interval distance in the bonding operation for the next connection point is calculated based on the distance.

(Function) With the wire bonding method configured in this way, when the bonding tool comes into contact with one connection point on the semiconductor pellet and the wire is connected, the distance from the reference position to the connection point at this time is Based on this distance and the corrected section distance, the search section distance when the bonding tool is lowered when bonding the next connection point is calculated. In this way, the search section distance is constantly corrected by the distance of the previous connection point, so the actual distance of the correction section at each connection point becomes a substantially constant value. Therefore, uniform and good bonding characteristics can be obtained at each connection point.

<Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the main parts of a wire bonding apparatus to which the wire bonding method of the embodiment is applied. The yoke (stator) 12a of the linear motor 12 is mounted on the fixed base 11.
is fixed. Stator 12 of this linear motor 12
A permanent magnet 12b is attached to the center of a, and a moving coil 12G is arranged around the permanent magnet 12b with a minute interval. Then, the yoke 12a, the permanent magnet 12
b. The linear motor 12 consisting of a moving coil 12c receives an electric current from the moving linear motor drive circuit 13 to the moving coil 12c.
%f flow is supplied, ? ! ! By changing the direction of the flow, the movable coil 12C moves up and down.

The movable coil 12C of the linear motor 12 is connected to the movable arm 14.
is fixed to the bottom of the That is, the linear motor 12
When driven, the movable arm 14 moves up and down. Yoke 1 of near motor 15 is glued to the upper surface of movable arm 14 for pressurizing.
5a is attached, and the moving coil 15C is fixed to the upper end of the L-shaped support member 16. This ribbon-shaped support member 1
The lower end of the movable arm 14 passes through a through hole formed in the movable arm 14, and is connected to the lower surface of the movable arm 14 via a leaf spring 17. The other end of a tool arm 19 having a bonding tool 18 attached to its tip is fixed near the lower end of the L-shaped support member 16. Therefore, when the excitation current is supplied from the pressurizing linear motor drive circuit 20 to the moving coil 15G of the linear motor 15, the L-shaped support member 16 tends to move forward. However, since the lower end is connected to the movable arm 14 by the leaf spring 17, the L-shaped support member 16 rotates in the six directions of the arrows. As a result, the bonding tool 18 attached to the tip of the tool arm 19 moves downward. Also, excitation to moving coil 15C! ! When the current is supplied to 'arIfI', the restoring force of the leaf spring 17 causes the L-shaped support member 16 to return to its original position.

The bonding tool 18 heats and melts the tip of the wire 21 supplied from behind and connects it to the connection point of the semiconductor pellet 22.

Further, a gap sensor 23 is attached to the end of the movable arm 14 on the bonding tool 18 side. When the distance between the gap sensor 23 and the tool arm 19 changes, the gap sensor 23 generates a voltage corresponding to the amount of change and sends it to the A/D conversion circuit 24. That is, when the movable arm 14 descends, the bonding tool 18 contacts the connection point, and the tool arm 19 bends.
Gap sensor 23 outputs a contact signal. This contact signal is then converted into a digital value by the A/D conversion circuit 24 and input to the bonding control circuit 25. When the bonding control circuit 25 receives a contact signal from the gap sensor 23 via the A/D conversion circuit 24, it sends a drive signal to the pressurizing linear motor drive circuit 20. Then, the pressure linear motor 15 operates, the L-shaped support member 16 rotates in the six directions of the arrow, and the bonding tool 18 is further pressed against the connection point of the semiconductor pellet 22.

Furthermore, a non-contact distance sensor 26 is attached to the other end of the movable arm 14 to detect a change in distance between the movable arm 14 and the fixed base 11. The distance signal detected by the non-contact displacement sensor 26 is input to the position detection control circuit 27. This position detection control circuit 27 includes a bonding control circuit 25.
According to the control signal and the distance signal sent from
The moving linear motor drive circuit 13 is driven to control the vertical position of the movable arm 14.

Next, using the bonding device configured as described above, the tips of the wires 21 are connected to n connection points on the upper surface of the semiconductor pellet 22 attached to the substrate in an inclined state, as shown in FIG. 7, for example. The method will be explained using FIG. That is, as shown in the figure, from Nα1 to N(l
There are up to n connection points 31, and the distance I between each connection point 31 and the reference position 32! Assume that IL changes from [1 to n. First, before starting the bonding operation of the connection point 31 of Nα1, the operator
2, the distance I of the correction section 33 assuming that the wire 21 is bonded under the best conditions! 1IIC can be connected to the bonding control circuit 25 from the keyboard of the operation panel, etc.
Set to Furthermore, the operator
The distance of the search section 34 in is set as an initial value So in the bonding control circuit 25 (indicated by i).

When the above initial settings are completed, the bonding control circuit 2
5 starts the linear motor 12 using the set value via the position detection control circuit 27 and the moving linear motor drive circuit 13. Then, the bonding tool 18 attached to the tip of the tool arm 19 starts to descend. Then, it descends at high speed by the distance 11So of the search section 34 that was initialized earlier, and changes to a low constant speed at the boundary point 35 position. Next, it descends at a constant speed by a distance C in the correction section 33 below. Then, when the contact point 31 is contacted, the gap sensor 23 is activated and a contact signal is input to the bond ink control circuit 25. When the contact signal is input, the bonding control circuit 25 sends a drive signal to the pressurizing linear motor drive circuit 20 and also sends a control command to the position detection control circuit 27 to determine the reference position 32 and connection point 31 at this point in time. Read the distance Ls between. Note that this distance is determined using a distance signal from the non-contact displacement sensor 26.

When the process of connecting the wire 21 to the connection point 31 is completed, the linear motor 12 is driven in the opposite direction again to move the bonding tool 18 back to a predetermined position.

Next, bonding processing for the second connection point 31 is started. In this case, the search section 34 of the connection point 31 of Nα2
The distance l1lS2 is calculated as the value (L+ -C) obtained by subtracting the preset correction section distance C from the distance ILx obtained during the bonding process of the connection point of NQ1. Then, similarly to Nα1, the bonding tool 18 is lowered at high speed within the search section (distance S2), and the correction section (distance S2) is
The distance 11c) is lowered at a constant speed. Then, when the bonding tool 18 contacts the connection point 31 of Nα2,
The distance between the connection point 31 and the reference position 32 at that point! I
Find L2.

In this way, each time the bonding process is performed at one connection point 31, the distance between the connection point 31 and the reference position 32 at that time is measured, and the connection of the next adjacent NO is determined from that distance. Distance I of the search section 34 of the bonding process at the point! 1lIS is corrected. Therefore, the maximum error in the actual distance C of the correction section 33 in which the bonding tool 18 descends at a constant low speed is suppressed to within the difference between the previous distance and the current distance. As a result, the actual distance MC of the correction section 33 at each connection point 31 from N(11 to mn) hardly changes from the set distance wiC. Each connection point 3 with conditions
1, and stable bonding characteristics can be obtained.

FIG. 3 is a diagram showing the operation of the bonding tool 18 whose movement is controlled as described above. The horizontal axis indicates time t, and the vertical axis indicates the vertical movement distance of the bonding tool 18.

In this way, even if the semiconductor pellet 22 is attached to the substrate in an inclined state, wire bonding is performed under the best conditions at each connection point 31, suppressing the occurrence of pellet cracks, etc. Product yield in the bonding process can be significantly improved.

[Effects of the Invention] As explained above, according to the wire bonding method of the present invention, the search section distance for the next bonding operation is corrected for each bonding operation.

Therefore, even if the semiconductor pellet is attached at an angle, good bonding characteristics can be obtained, and the yield of products can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the main parts of a wire bonding apparatus to which a wire bonding method according to an embodiment of the present invention is applied;
Figures 2 and 3 are diagrams showing the operation of the bonding tool in the same embodiment, Figure 4 is a diagram showing a general semiconductor pellet and substrate. FIG. 3 is a diagram for explaining a wire bonding method. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Adhesive, 3.22... Semiconductor pellet, 4... Lead terminal, 5.21... Wire, 6.31... Reference position, 7.18... ...Bonding tool, 11...Fixed base, 12.15...Linear motor, 14...Movable arm, 23...Gap sensor, 25...Bonding control circuit, 26...Non-contact displacement Sensor, 31... Connection point, 33... Correction section, 34... Search section. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (2)

[Claims] (1) Divide the distance from a reference position provided above a substrate on which a semiconductor pellet having a plurality of connection points on the upper surface is attached to the connection point into an upper search section and a lower correction section, A wire bonding method in which each wire is sequentially connected to each connection point by lowering the bonding tool at high speed within the search section and at a constant speed during the correction section and bringing the bonding tool into contact with the connection point. Each time the bonding tool is brought into contact with the connection point to connect a wire, the distance from the reference position to the connection point is measured, and the next connection point is determined based on the measured distance and the distance of the correction section. A wire bonding method characterized by calculating a search interval distance in a bonding operation for a wire bonding method. (2) The distance of the correction section is input and set from the outside via an input device.
The wire bonding method described in section 1).