JPS6211502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pellet position detection device.

Generally, semiconductor pellets are obtained by adhering a semiconductor wafer to a flexible sheet and dicing the wafer. Furthermore, by heating and stretching the sheet to which the semiconductor wafer is attached, the pellets are aligned at predetermined intervals and sent to the die bonding process. In die bonding of semiconductor pellets, the pellets are detected, their positions and orientations recognized and corrected, and then placed on a lead frame using a pellet suction jig called a collect. This pellet position detecting section is composed of a movable table that holds the sheet on which the pellets are arranged, and a detecting section using an ITV or the like.

The movement of the loading table during pellet detection is generally a fixed pitch feed of the table that takes advantage of the fact that the pellets are aligned at approximately equal intervals, and then pellet recognition and accompanying slight table movement. Collet adsorption to a position where there is no problem.
The pellet position has been corrected. However, from the pellets set on the die bonder, defective pellets from the electrical check process and malformed pellets from around the wafer have been removed in the previous process, so wafers with poor yields are placed on the sheet. Absent locations occur. In the conventional method, where the defective pellets mentioned above are continuous or the absence of pellets continues continuously, such as in the peripheral sheet area outside the wafer, the table is moved by fixed pitch feed, the table is driven and moved until the next pellet is detected.
There is a drawback that a delay time due to table acceleration/deceleration operation for stopping and an extra scanning time until detection is required when ITV is used.

Die bonding is normally carried out with a takt time of about one second, so if the process from pellet detection to position correction is not carried out within the machine's tact time of one second, the equipment will stop working, resulting in inconvenience.

An object of the present invention is to eliminate the disadvantages of the conventional method when pellets are continuously absent, and to significantly shorten the travel time by moving the table continuously at high speed until the next pellet is detected.

The present invention provides a position detection device for pellets arranged on a flexible sheet, in which a camera and an irradiation means are provided above the flexible sheet, and a camera and an irradiation means are provided below the flexible sheet and at a predetermined position from the central axis of the camera. Optical sensor means is provided at a location a certain distance away, and when the sensor means detects the vicinity of the end of the pellet, the moving table on which the flexible sheet is placed is decelerated to bring the pellet into the field of view of the camera. The pellet position detecting device is characterized in that the detected pellet is stopped and the moving table is moved at high speed when no pellet is detected by the sensor means. According to this invention,
Even if the sheet is stretched so that the spacing between pellets varies, a given pellet can be reliably placed within the field of view of the camera. In addition, when continuously moving at high speed to the next pellet, if you try to use the ITV for pellet recognition to detect the presence or absence of the next pellet, you will have to take in images while moving at high speed, which will cause problems with noise and pellet images. The disadvantage is that the table moves for the screen scanning time after the pellet enters the field of view of the ITV, and the table moves from the time the pellet is detected until it slows down and stops, and the pellet cannot be stopped at the desired location and shifts backward. There is. Furthermore, image processing software is also becoming more complex.

In the present invention, a sensor preceding the ITV is provided in front of the pellet recognition unit in the image taking direction, and the sensor detects in real time the presence or absence of a pellet moving at high speed in a pellet absent area, and the ITV position at the rear can be easily and easily detected. By accurately stopping the pellets, it contributes to shortening the travel time in areas where no pellets are present and to shortening the wait time for pellet detection by the die bonder.

This will be explained in detail below using the drawings.

Figure 1 shows a conventional device, where 1 is a semiconductor pellet,
2 is a sheet to which pellets are attached, 3 is a moving table, 4 is a camera, and 5 is a pellet suction arm. The pellet 2 whose position was detected by the camera 4 is
The position is corrected on the moving table 3, and the arm 5 transfers and places it onto the lead frame.

FIG. 2 shows an example of the pellet arrangement after enlarging the sheet. Reference numeral 6 denotes a ring holding the sheet 2, and the pellets 1 are arranged at approximately equal pitches l. Therefore, the moving table 3 has a fixed pitch l.
By feeding the pellet, the camera 4 can easily and reliably capture the image of the next pellet. However, in the pellet-absent area 7 and the wafer peripheral area 8, the constant pitch feeding described above wastes the moving time, and the apparatus may have to wait for pellet detection.

An embodiment of the invention is shown in FIG. Reference numeral 9 is a lighting device, 10 is a pellet presence/absence detection sensor, and 11 is a light guide. Light guide 11 is camera 4
The left and right sensors are installed at a constant interval L on both sides of the table, and the left and right sensors are switched so that they always precede the camera 4 depending on the direction of movement of the moving table 3. sensor 10
If the pellet is moved continuously at high speed until it detects the presence of a pellet, and after detecting a pellet, it is moved by L + (the amount of deviation △L between the pellet center and the sensor) and then stopped, the pellet will be within the camera field of view without any problems in size or arrangement interval. is set to The interval L may be at least the amount of movement (overrun) required for the table to decelerate and stop after inputting a stop signal during high-speed movement of the table, and the presence or absence of pellets is detected in real time by a sensor, so there is no time delay. After detecting the presence or absence of pellets, the work is performed by moving at a fixed pitch as in the conventional method until the absence of pellets is confirmed by the pellet recognition section.

In this way, according to this embodiment, information on the presence or absence of pellets is taken in in real time by an optical sensor preceding the camera, so table movement when pellets are not present is efficient, easy and fast.
The pellet position can be detected reliably.

The present invention incorporates the advantages of both constant pitch feeding and high-speed continuous table feeding, and this function can be easily added to conventional devices. Furthermore, since high-speed feeding is possible in areas where pellets are not present, the operating rate of the die bonder is improved, contributing to improved productivity and reduced bonding costs.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional pellet detection section of a die bonder, FIG. 2 is an explanatory diagram showing the arrangement of pellets on a sheet, and FIG. 3 is a diagram of an embodiment of the present invention. In the figure, 1...semiconductor pellet, 2...
...Pellet adhesive sheet, 3...Moveable table, 4
...Camera, 5...Pellet suction arm, 6...
Sheet holding ring, 7... Pellet absent area due to defective pellets on the sheet, 8... Pellet absent area around the wafer on the sheet, 9... Lighting, 10...
Pellet presence/absence detection sensor 11... Light guide.

Claims (1)

[Claims] 1. In a position detecting device for pellets arranged on a flexible sheet in which only good pellets remain, a camera and an irradiation means are provided above the flexible sheet, and a table is located below the flexible sheet. Optical sensor means are provided at two locations equidistant from the central axis of the camera along the direction of movement of the pellet, and when the sensor means detects the vicinity of the end of the pellet, the flexible sheet decelerating the moving table on which the pellet is placed to stop the detected pellet within the field of view of the camera;
A pellet position detection device further comprising a control section for moving the moving table at high speed when the sensor means does not detect a pellet.