JPS6224942B2 - - Google Patents

Abstract

PURPOSE:To implement high speed, by providing a control mechanism part, which can control the speed of up and down movement and the amount of movement of a bonding terminal, and performing wire bonding based on the up and down movement profile of the bonding terminal in conformity with a body to be bonded. CONSTITUTION:The up and down movement of a wedge is set in low-speed descending times T1 and T2 of the wedge with enough allowance. A pad electrode 22a of a semiconductor pellet 22 is connected to a corresponding lead 24a by a bonding wire based on said up and down movement of the wedge. The low-speed operation range when the wedge is lowered to the pad electrode is specified as a region of + or -DELTAalpha with the position of Dal as a center with respect to the height of the wedge (a). The range of the lead is specified as the region of + or -DELTAbeta with the position Dfm as a center. The up and down movement profile of the wedge is determined based on said specifications. Based on the movement of the wedge in this profile, the pad electrode and the corresponding lead are wire-bonded by aluminum wire. Thus the wire bonding of one body to be wire-bonded is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire bonder, and in particular, an object of the present invention is to speed up the vertical movement of a wedge (terminal for bonding) in ultrasonic wire bonding technology, and to increase the bonding speed. It is.

In general, the ultrasonic wire bonding method uses ultrasonic energy to pressurize and vibrate a bonding wire against a bonded object while exposing the mutually fresh surfaces to perform solid phase bonding by plastic deformation. Therefore, if the bonding wire is deformed, such as crushed, before wire bonding, it will not be possible to bond with good bonding properties. It is necessary to bring them into contact and then perform bonding using ultrasonic vibration of the wedge.

For this reason, in the conventional ultrasonic wire bonding method, the vertical movement of the wedge during wire bonding is as shown in Figures 1a to 1b, in which the bonding wire is slowly lowered when the wedge approaches the object to be wire bonded. The wedge is lowered at a low speed so that the wire does not deform when it comes into contact with the object to be bonded.

In addition, in FIG. 1b showing the vertical movement profile of the wedge, A to D in the figure show the modes of the vertical movement speed of the wedge, where A shows the wedge in a normal position, B shows the wedge in a high-speed downward speed state, C indicates that the wedge is in a low-speed descending speed state, and D indicates that the wedge is in a high-speed rising speed state. Further, each point indicated by a to k indicates a point where the operating speed of the wedge changes.

However, in the conventional ultrasonic wire bonding method, the lowering operation of the wedge requires a long time, which is an obstacle to increasing the speed of bonding.

In the case of a ceramic package as the object to be bonded, this is due to variations in the precision of the ceramic and leads, variations in the depth of embedding of pellets in the bonding material, and variations in the depth of embedding of leads in glass. The variation in the latter is large, especially as much as ±0.3mm, and the bonding height between each bonded object differs greatly due to variation in component precision, so the variation in height becomes noticeable, and it is necessary to absorb this variation. As much time as possible (in Figure 1)
T ₁ , T ₂ ), this is due to the fact that the wedge must continue to descend at a low speed.

As a countermeasure to this problem, it is possible to increase the lowering speed of the wedge or shorten the period of low-speed lowering, but in this case, the high-speed lowering of the wedge may cause the bonding wire to come into contact with the pellet or lead that is the object to be bonded. Such countermeasures naturally have their limits, as they lead to a loss of bonding properties and deteriorate bonding properties.

For this reason, it is necessary to take up a large amount of time for the wedge to fall during the vertical movement of the wedge, and this time becomes large, which becomes a hindrance to increasing the bonding speed.

On the other hand, the vertical movement mechanism of the wedge in conventional ultrasonic wire bonders moves the bonding arm to which the wedge is attached in one direction using a cam having a cam diagram that allows the wedge to move as shown in Figure 1. The wedge is moved up and down while rotating.

Therefore, in such a conventional wedge vertical movement mechanism, the width and speed of the vertical movement of the wedge are determined by the cam diagram and the rotation speed of the cam. To change the aspect, it is necessary to replace the cam with a cam of a different specification that has a corresponding cam diagram. Therefore, there is a drawback that the movement of the wedge cannot be easily changed and various types of bonding cannot be performed using one bonder.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems caused by the conventional wire bonding method and to provide a wire bonder capable of high-speed wire bonding.

Another object of the present invention is to provide a wire bonder that can easily change the vertical movement of the wedge, perform various types of bonding with one bonder, and can be automated.

The wire bonder according to the present invention is a wire bonder that has a control mechanism that can control the vertical movement speed and movement amount of the bonding terminal, and performs wire bonding according to the vertical movement profile of the bonding terminal that matches the bonding target object. be.

Hereinafter, the present invention will be specifically described in detail with reference to an example of an ultrasonic wire bonding method using the wire bonder of the present invention.

Figures 2a to 2b are views showing a dual-in-line type ceramic package which is an example of the object to be bonded. be. In the figure, 2
1 is a ceramic package body, 22 is a semiconductor element pellet provided with IC, and 14
There are pad electrodes 22a to 22n, and the adhesive material 2
3, the ceramic package body 21 is die-bonded. 24a-24n
are the 14 pad electrodes 22a in the pellet 22
22n, and is attached to the ceramic package body 21 by a low melting point glass 25.

An ultrasonic wire bonding method using a wire bonder according to the present invention for wire bonding to this type of wire bonded object will be explained step by step.

(1) Vertical movement of the wedge set with a margin for the low-speed lowering time T ₁ and T ₂ of the wedge (see Figure 3)
Accordingly, the pad electrode 2 of the semiconductor pellet 22
2a and the lead 24a corresponding to the pad electrode 22a are interconnected with an aluminum wire serving as a bonding wire. In this case, the reason why a margin is provided for the low speed lowering times T ₁ and T ₂ of the wedge is that the positions of the pad electrode 22a and the lead 24a are not clearly known at this point.

In this case, the distance Dal from the initial position a of the wedge to the position of the pad electrode 22a (distance until the wedge descends and lands on the pad electrode 22a) is measured;
After wire bonding, the distance Dfm from the raised positions e and f of the wedge to the position m of the lead 24a (the distance from which the wedge descends until it lands on the lead 24a) is measured.

(2) Individual pad electrodes 22a, 22b,...22
The value of the variation in the mutual positions of the leads 24a, 24b, . . . It is selected as a positional variation that can be suppressed within the object to be bonded. Then, the low-speed operating range when the wedge descends relative to the pad electrode is defined as the area of ±Δα centered on the Dal position, with the height of the wedge as the range of low-speed operating when the wedge descends relative to the lead. to the height of the wedge
A region of ±Δβ is defined with the position of Dfm as the center, and the vertical motion profile of the wedge is determined based on this regulation. This profile is illustrated in FIG. 4a.

(3) Move the wedge according to the vertical movement profile of the wedge as shown in Figure 4a,
The pad electrodes 22b and the leads 24b are wire-bonded with an aluminum wire, and then the pad electrodes 22c, 22
d, ..., 22n and the corresponding lead 24
c, 24d, . Fourth
FIG. b is a diagram showing the vertical movement profile of the wedge in wire bonding as described above.

(4) Next, when wire bonding is performed on each wire-bonding object in sequence, the steps (1) to (3) described above are performed.
This procedure will be carried out.

As is clear from the above, in the ultrasonic wire bonding method according to the present invention, the low-speed lowering time of the wedge (T ₁ ′, T ₂ ′ in FIG. 4) is short, so the wedge vertical movement time is shortened. becomes extremely short, allowing high-speed bonding. This applies to each bonded object.
The reference position Dal for the wedge to descend in advance,
This is because the dfm is measured in advance, and based on this, the range of low-speed descending motion when descending relative to the pad electrode and lead of the wedge is determined. In addition, the value selected as the wedge height variation ±Δ
α, ±Δβ are determined based on the parts accuracy and assembly accuracy of each bonded object, so
This is because the variation in bonding height between the respective bonding objects is eliminated and the value becomes small.

That is, in the ultrasonic wire bonding method according to the present invention, as shown in _FIG.
However, the pad electrodes 22b, 22c, ..., 2
2n and the corresponding leads 24b, 24c,...
The time required for wire bonding with ..., 24n is (n-1) t ₂ , and the time required for wire bonding to one bonded object is t ₁ + (n-1) t ₂ . . On the other hand, the time required for wire bonding to one bonded object using the conventional method is nt ₁ . Therefore, in the present invention, the time required for wire bonding to one bonding object is reduced by nt ₁ - {t ₁ + (n-1) t ₂ } = (n-1 ) (t ₁ - t ₂ )
As mentioned above, T ₁ + T ₂
Since ≫T ₁ ′+T ₂ ′, t ₁ ≫t ₂ , and the present invention can significantly shorten the wire bonding time.
This allows high-speed wire bonding.

Next, an ultrasonic wire bonder according to the present invention will be explained.

FIG. 5 is a schematic view showing an ultrasonic wire bonder which is an embodiment of the present invention, and particularly shows the vertical movement mechanism of the wedge. In the figure, 1 is a wedge that is a bonding terminal, and an aluminum wire 2 that is a bonding wire is led to the tip of the wedge. Reference numeral 3 denotes a horn to which an ultrasonic vibrator is connected, which is moved up and down by the rotation of a cam 5 through a horn support 4, thereby moving the wedge up and down.

6 is a drive motor that rotates the cam 5. 7
is an XY table for moving the wedge back and forth, right and left, 8 is a body to be bonded, and 9 is a support base for supporting the body 8 to be bonded.

10 is a wedge landing detector, and a horn support 4
The wedge 1 is electrically connected to a lever 11 which is electrically insulated from the bonding target 8. When the wedge 1 descends and comes into contact with the bonded object 8, the lever 11 separates from the grounded cam and the lever voltage increases. It is possible to detect the state when the bonding object 8 lands (contacts) on the bonding target body 8.

The cam 5 has a cam diagram as shown in FIG. 7, and the relationship between rotation angle and cam lift is linear.

Further, this wire bonder is equipped with a control mechanism section as shown in FIG. This control mechanism section is
It is capable of controlling the vertical movement speed and amount of movement of the wedge, and includes a motor 6, a rotary encoder (for detecting the rotation angle) 12 and a tachometer generator (for detecting the rotation speed) 13, which are directly connected to the motor 6. It has a mechanical circuit and an electric circuit for controlling it, that is, a memory circuit 14 capable of storing rotation angle command data, a rotation angle determination circuit 15, a speed control circuit 16, a motor driver circuit 17, and when bonding wedges, etc. The main element is a timer 18 that can be stopped as appropriate.

Therefore, if the vertical movement speed and movement amount of the wedge 1 corresponding to the rotation angle of the control cam 5 are stored in the memory 14, this control mechanism section will control the motor 6 according to the command from the memory 14. , and correspondingly rotates the cam 5 to move the wedge 1 up and down at a desired high-speed descending speed, low-speed descending speed, and rising speed, and to stop the operation of the wedge 1 through a timer 18. It is.

The operation of this type of ultrasonic wire bonder will be explained step by step with respect to the manner in which wire bonding is performed on the objects to be bonded shown in FIGS. 2a to 2b.

(1) By vertically moving the wedge 1 (see Fig. 3), which is set with a margin for the low-speed lowering times T ₁ and T ₂ of the wedge 1, the pad electrode 22a of the semiconductor pellet 22 and its pad electrode 22a can be adjusted. The aluminum wires 2 interconnect the leads 24a. In this case, the slow descent time of wedge 1 is
The reason why a margin is provided for T ₁ and T ₂ is that the positions of the pad electrode 22a and the lead 24a are not clearly known at this point.

During this wire bonding, the wedge landing detector 10 detects that the wedge 1 descends and contacts the pad electrode 22a, and the output of the rotary encoder 12 at this time is stored in the memory 14 inside the control section. Similarly, the wedge landing detector 10 detects that the wedge 1 has descended and made contact with the lead 22a, and the output of the rotary encoder 12 at this time is stored in the memory 14 inside the control section.

This information is obtained by measuring the distance Dal until the wedge descends and lands on the pad electrode 22a, and after wire bonding to the pad electrode 22a, the wedge 1 in the stopped state descends again and lands on the lead 24a. This corresponds to measuring the distance Dfm.

(2) Individual pad electrodes 22a, 22b, ..., 2
2n and the mutual positional variation value ±Δβ of the individual leads 24a, 24b, . . The low-speed operating range when wedge 1 descends relative to the pad electrode is defined as the range of ±Δα centered on the Dal position, and the low-speed operating range when wedge 1 descends relative to the lead is defined as the wedge height. Adjust the range of motion to the height of the wedge.
A region of ±Δβ is defined with the position of Dfm as the center, and a vertical motion profile of the wedge 1 is determined based on this definition, and this is stored in the memory circuit of the control section. This profile is illustrated in FIG. 4a.

(3) When the memory circuit outputs a signal according to the wedge vertical movement profile described above, the motor 6
performs a rotation accordingly. By this operation, the wedge 1 is moved up and down, and the pad electrodes 22b, 22c, . . . , 22n and the corresponding leads 24b, 24c, . Wire bonding of two ceramic packages, ie, one body to be wire bonded, is completed.

(4) Next, when wire bonding is performed on each wire-bonded body in sequence, the steps (1) to (3) described above are performed.
Perform the following operations.

As is clear from the above, the ultrasonic wire bonder according to the present invention has the following features.

(1) The vertical motion of the wedge can be easily changed by the wedge vertical motion profile stored in the memory circuit.

(2) Since the vertical movement of the wedge requires only the exchange of information stored in the memory circuit, and therefore can be easily changed, various types of bonding can be performed with one bonder.

(3) Wire bonding can be performed in accordance with the wire bonding method according to the embodiment, and the wire bonding operation can be automated.

(4) Since wire bonding can be performed in accordance with the wire bonding method according to the embodiment, high-speed wire bonding can be performed.

The present invention is not limited to the ultrasonic wire bonding method, but can also be applied to wire bonding methods such as thermocompression bonding.

[Brief explanation of the drawing]

Figures 1a to 1b are diagrams showing the vertical movement profile of the wedge in the conventional ultrasonic wire bonding method, and Figures 2a to 2b are diagrams showing a ceramic package, which is a type of object to be bonded.
is a plan view, figure b is a vertical cross-sectional view taken along arrow AA' in figure a,
3 to 4 a to 4 b are diagrams showing vertical movement profiles of the wedge according to the present invention, and FIGS. 5 to 6
The figure is a schematic diagram showing an ultrasonic wire bonder according to the present invention, and FIG. 7 is a cam diagram of a cam according to the present invention. 1... Wedge, 2... Aluminum wire, 3...
...Horn, 4...Horn support, 5...Cam, 6
... Motor, 7 ...
Memory circuit, 15...Rotation angle determination circuit, 16...
...Speed control circuit, 17...Motor driver circuit, 18...Timer.

Claims (1)

[Claims] 1. A bonding terminal landing detector that detects that the bonding terminal has contacted the surface to be bonded, and lowering of the vertical movement of the bonding terminal based on the detection result by the detector and the variation in the position of the surface to be bonded. A wire bonder comprising: a control section that controls speed.