JPH0423340A - Wire bonder - Google Patents

Abstract

PURPOSE:To obtain a uniform bonding state even when a temperature is changed suddenly by the movement of the surrounding air at a bonding operation by a method wherein a means to monitor the temperature at a wire bonding face is provided and at least one parameter out of the ultrasonic output, the ultrasonic application time and the load is corrected. CONSTITUTION:The ultrasonic output, the ultrasonic application time and the load which are applied to a capillary 7 as wells as the temperature which heats a work stage are set initially to optimum set values by using respective parameter setting dials 8, 10, 12 and 14. However, there are cases where the temperature of the work stage is changed suddenly by the movement of the surrounding air at a bonding operation. In order to be able to always obtain a uniform bonding state even with a temperature change, the temperature of a bonding face is monitored successively by using a temperature sensor 16, and at least one parameter out of the ultrasonic output, the ultrasonic application time and the load can corrected, on the basis of the monitored temperature, by using a microcomputer 17 which is installed inside a wire bonder 5.

Description

[Detailed Description of the Invention] [Summary] Regarding a wire bonder for bonding bonding wires, the purpose of this invention is to obtain a uniform bonding state even if the temperature changes rapidly due to the movement of air around the bonding area. Means is provided for monitoring the temperature of the bonding surface and configured to correct at least one parameter of ultrasound output, ultrasound application time, and load in response to a change in the monitored temperature.

[Industrial application field]

The present invention relates to a wire bonder for bonding a bonding wire to an electrode of an IC chip.

[Conventional technology]

Normally, with a wire bonder, the bonding wire is placed on a pad of an IC chip placed on a work stage heated to a predetermined temperature, or on a predetermined electrode of a package lead or printed circuit board to which the pad is connected. The bonding wires are bonded by applying a predetermined load using a capillary provided in the wire bonder and performing thermocompression bonding. Here, during the thermocompression bonding, by applying a predetermined ultrasonic output to the capillary to cause the capillary to vibrate slightly in a horizontal direction (a direction parallel to the bonding surface), it is possible to bond the bonding wire at a lower temperature. Therefore, bonding of the bonding wire is usually performed by a thermocompression bonding method combined with ultrasonic waves.

When bonding wires using such a thermocompression bonding method combined with ultrasonic waves, ■Ultrasonic output■
The bonding state is determined by the ultrasonic application time, load, and temperature. However, the temperature mentioned in (■) above may change rapidly due to the movement of air around the bonding process.
At that time, the bonding conditions have changed, and there is a problem that a uniform bonding state cannot be obtained.

[Problem to be solved by the invention]

The present invention was made to solve such problems,
Monitor the bonding surface temperature (temperature of the pad or printed circuit board electrode, etc.) that corresponds to the temperature in (■) above, and change the parameters in (2) to (3) above according to this temperature change to always maintain a uniform bonding state in wire bonding. It was designed so that it could be obtained.

Now monitor the temperature mentioned in ■ above and adjust accordingly.
The reason for correcting the parameters of (1) to (2) is that if the temperature changes rapidly due to the movement of surrounding air, it is difficult to instantly return the temperature to the predetermined set temperature.

[Means to solve the problem]

In order to solve this problem, the present invention includes a means for monitoring the temperature of the wire bonding surface, and adjusts at least the ultrasonic output, the ultrasonic application time, and the load according to the monitored temperature change. A wire bonder is provided that allows correction of one parameter.

[For production]

According to the above configuration, even if there is a sudden change in the temperature of the bonding surface, by correcting at least one of the parameters described above accordingly, it is possible to maintain a uniform bonding state in wire bonding.

〔Example〕

FIG. 1 shows a wire bonder as an embodiment of the present invention and a bonding state of a bonding wire bonded by the wire bonder. That is, a predetermined substrate 2 (for example, a printed circuit board, etc.) and an IC chip 3 are provided on a work stage 1.
a predetermined pad on the top and the substrate 2 to be the counterpart of the pad.
A predetermined electrode on the top is connected by a bonding wire 4, and the wire bonder 5 is shown waiting to perform the next wire bonding.

The wire bonder 5 is provided with a capillary 7 via a horn 6, and as described above, the bonding wire is placed on a predetermined bonding surface (for example, a pad of an IC chip or an electrode on a substrate to be mated with it). It is pressed by the capillary 7. At that time, the wire bonder 5
Temperature setting dial 14 and temperature setting device 1 provided on the side
5, the work stage 1 is heated to a predetermined set temperature (here, 1M), and the setting dial 8
A predetermined ultrasonic output (here, P) is applied to the capillary 7 via the ultrasonic output setting device 9, and the ultrasonic application time (here, T) is applied to the capillary 7. ) is set in the ultrasound application time setting device 11 using the setting dial 10. Furthermore, a predetermined load (here F
) is applied to the capillary 7 via the load setting device 13. In this way, a predetermined ultrasonic output is applied to the capillary 7 for a predetermined time during wire bonding, and as a result, the capillary 7 vibrates slightly parallel to the bonding surface downward, as described above. The bonding wire is pressed against the bonding surface by a predetermined applied load to bond it by thermocompression (
The heat at that time is transferred from the work stage heated to a predetermined temperature), thereby performing bonding of the bonding wire by the so-called ultrasonic thermocompression bonding method described above. Although not shown, the wire wound on a reel is supplied from above the capillary 7 through the pores provided in the capillary 7, and the wires that are sequentially unwound in this way are supplied from above the capillary 7. When the bonding between the pad of the IC and the mating substrate electrode, for example, is completed, the wire is held by a clamp (not shown) and pulled up to cut the wire. , the following bonding is performed.

As mentioned above, the ultrasonic output, ultrasonic application time, and load applied to the Kimapillary 7, as well as the temperature for heating the work stage, are initially set to optimal settings using the respective parameter setting dials 8, 10, 12, and 14. (
P, T, F, and tx), but the temperature of the work stage (and therefore the temperature of the bonding surface) may change rapidly due to the movement of air around the bonding process, so this temperature cannot be set instantly. It is difficult to return to temperature.

Therefore, in the present invention, the temperature of the bonding surface is successively monitored by the temperature sensor 16, and the wire bonder is 5
At least one parameter among the ultrasonic output, the ultrasonic application time, and the load is corrected by a microcomputer 17 provided therein.

For this purpose, a map as shown in FIG. 2 is stored in the memory 18 provided in the wire bonder 5, and the map is stored in the memory 18 according to the bonding surface temperature (temperature detected by the temperature sensor 16) at that time. The microcomputer 17 reads and compares the corrected parameters. In the map shown in FIG. 2, the optimum values of the above parameters (ultrasonic output, ultrasonic application time, load) for the normal bonding temperature (set temperature) tx are respectively P, T, and F, and the bonding Temperature t. The bonding temperature is the lower limit temperature at which parameter correction is possible centering on 11. (The lowest temperature at which good bonding cannot be guaranteed even if the parameters are corrected if the bonding temperature falls further) to the upper limit temperature t at which parameter correction is possible. The above parameters (ultrasonic output, ultrasound application time, and load) change from (P+α) to (maximum temperature that cannot be compensated for).
P-α), (T+β) to (T-β), and (F+r) to (F-r). That is, α
, β, and r are correction coefficients for each of the above parameters. Therefore, for example, when the bonding temperature (temperature detected by a temperature sensor) drops to tL, each of the parameters of the ultrasonic output, ultrasonic application time, and load becomes (P+α).

(T+β) and (F+γ), the microcomputer 17 reads these increased parameters, and changes the above parameters (ultrasonic output, ultrasonic application time, and load) to the above through the control system shown by the dotted line in Figure 1. Each parameter setting device 9.11.13 is controlled so that the parameter setting device 9.11.13 increases to a predetermined value. Conversely, when the bonding temperature rises to tH, each of the above parameters becomes (P-α) and (
The microcomputer 17 controls each parameter setting device 9.1L13 so as to decrease the parameters to T-β) and (F-7).

Note that in the map shown in Figure 2 above, the above three parameters (ultrasonic output, ultrasonic application time, load) are corrected according to the temperature detected by the temperature sensor, but in some cases the above three parameters may be corrected. At least one of the three parameters may be corrected.

FIG. 3 is a flowchart showing the processing procedure of the microcomputer. In step 2, the temperature of the bonding surface is detected via a temperature sensor, and the temperature of the bonding surface reaches t. If they are equal to each other, predetermined set values P, T, and F are output as each of the above-mentioned parameters. (Step 7) On the other hand, if the detected temperature of the bonding surface is greater than 1M, the process proceeds to step 3, where it is detected whether or not it is greater than the upper limit temperature t)I. The output is stopped as it is, and conversely the output is lower than the tH (i.e. tM
and tH), in step 6, the parameters are corrected (P-P-α, T-T-β, F
to F-7-) and outputs each of the corrected parameters (step 7). On the other hand, if the detected temperature of the bonding surface is lower than tX, step 4
It is detected whether or not the temperature is lower than the lower limit temperature tL, and if it is lower than tL, the output is directly stopped in step 5, and conversely, the temperature is higher than tL (that is, between 1M and t).
If so, in step 6, perform parameter correction (correction between P-P+α, T-T+β, and F-F+7) according to the above-mentioned predetermined map, and convert each of the corrected parameters into 8
(Step 7). In this way, the same processing procedure is repeated until all bonding is completed (step 8).

〔Effect of the invention〕

According to the present invention, even if the temperature of the bonding surface changes suddenly, wire bonding can be performed in a uniform bonding state regardless of the sudden change in temperature of the bonding surface.

[Brief explanation of the drawing]

1 is a diagram showing the overall configuration of a wire bonder as an embodiment of the present invention; FIG. 2 is a diagram illustrating the relationship between the bonding temperature and various parameters stored as a map in the memory of FIG. 1; FIG. 3 is a flowchart showing the processing procedure of the microcomputer in FIG. 1. (Explanation of symbols) 1... Work stage, 4... Bonding wire, 5... Wire bonder, 6... Horn, 7... Capillary, 8, 10, 12. 14... Parameter setting dial ,
16... Temperature sensor, 17... Microcomputer, 18... Memory. Diagram

Claims (1)

[Claims] 1. A means for monitoring the temperature of the wire bonding surface is provided, and an ultrasonic wave is output in response to a change in the monitored temperature.
A wire bonder characterized in that at least one parameter of ultrasonic application time and load is corrected.