JPH09223728A - Pickup method of pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the pickup operation of a pellet on a wafer sheet, by beginning to pickup from a pellet positioned in the outermost periphery and continuing to pickup as far as a pellet positioned at the center, in the sequence forming a spiral. SOLUTION: On a pellet 5, figures from 1 to 40 are assigned. According to the figures, pickup is performed until the 40th pellet 5, in the order of 1, 2, 3,.... On and after the 41st pellet, pickup is continued as far as the last pellet 5 at the center, in the sequence shown by arrows. The pickup starts from the pellet 5 positioned in the outermost periphery, and continues as far as the pellet 5 positioned at the center, in the sequence forming a spiral. Hence the locus of pickup is made approximate to a concentric circle type tension distribution, and the change amount of tension of the pellet 5 to be picked up becomes gentle. Thereby the pickup operation of the pellet 5 on a wafer sheet 13 can be stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for picking up pellets on a wafer sheet.

[0002]

2. Description of the Related Art In the field of semiconductors, the importance of packaging technology has been highlighted as semiconductor devices have become more sophisticated and have larger capacities. Here, the mounting technique is a joining technique (a technique for connecting two components or two electrodes,
Further, it is considered to be divided into a semiconductor mounting technology and a lead bonding technology) and a circuit board technology (technology related to a wiring board for mounting a semiconductor device). In the semiconductor mounting technology, which is one of the bonding technologies, in the conventional wire bonding, not to mention TAB and LOC, which directly and collectively bond the pellet and the plurality of inner leads through the bonding pad, the fine pitch is used. For high quality bonding below, it is important that the pellet be properly mounted in place on the leadframe. And for that purpose, it is a premise that the pellets on the diced wafer sheet are properly picked up.

Here, a method of picking up the pellets is such that the pellets are pushed up from the back side by a needle and held by a transfer jig standing by above. It is generally considered that the pick-up order is to start from one of the pellets arranged in a grid and proceed in the order, that is, in the horizontal direction or the vertical direction.

As an example in which the die bonding technology for mounting pellets on a lead frame is described in detail, for example, "VLSI packaging technology (bottom)" issued by Nikkei BP (issued May 31, 1993), P17 ~
There is P22.

[0005]

The wafer sheet to which the pellets are attached is pulled from the outer periphery by a wafer ring holding the wafer sheet in an annular shape and an annular expander located inside the wafer ring. It is stretched and tensioned. Therefore, the tension becomes smaller toward the center of the wafer sheet. That is, the tension has a distribution in which it spreads concentrically from the pellet in the center and increases.

Even if the tension has such a distribution, if the pellets are picked up in the above order ignoring this distribution, the amount of change in the tension becomes steep and the pickup operation becomes unstable. Then, especially in the pellets in the central portion, there is a concern that, for example, a phenomenon in which the wafer sheet follows and is not peeled off from the pellets, or a phenomenon in which the pellets come into contact with adjacent pellets and the edges are chipped. Further, it is assumed that such a phenomenon becomes more remarkable because the change width of the tension becomes larger as the diameter of the semiconductor wafer becomes larger as in the present trend.

[0007] It is conceivable that the data of non-defective products and defective products based on the result of the electrical test of pellets carried out in advance is stored in a floppy disk or the like, and only non-defective products are picked up according to this data. The change in tension becomes sharper, which is not preferable.

[0008] Therefore, an object of the present invention is to provide a technique capable of stabilizing the pickup operation of pellets on a wafer sheet.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0010]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the pellet pick-up method according to the present invention is a pellet pick-up method of picking up a plurality of pellets on a wafer sheet which are individually separated by dicing and mounting them on a predetermined position of the lead frame. It is characterized in that the pellets located at the center are picked up in the order of forming a spiral shape starting from the pellets.

In this method of picking up pellets, the tension of the wafer sheet may be increased toward the pellet located at the center so that the tension of the pellets picked up becomes uniform. The tension can be changed by moving at least one of a wafer ring that holds the wafer sheet in an expanded state and an expander that is located inside the wafer ring and applies tension to the wafer sheet.

Further, in the above-mentioned pellet pick-up method, in the needle which pushes up the pellet from the lower side of the wafer sheet, the first operating condition in which the push-up height is increased toward the centrally located pellet, and At least one of the second operating conditions for increasing the push-up speed toward the located pellet.
You may make it apply one operating condition.

In these pellet pick-up methods, only non-defective pellets may be selectively picked up.

According to this, the trajectory of the pickup approximates the concentric circular tension distribution, and the amount of change in the tension of the pellet to be picked up becomes gentle, so that the pickup operation of the pellet on the wafer sheet can be stabilized. it can. Then, it becomes possible to selectively pick up only non-defective products based on the electrical test data.

Further, if the tension of the wafer sheet is increased toward the pellet located at the center or the push-up height and push-up speed are raised toward the pellet located at the center, a more stable pickup operation is realized.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments, the same members are denoted by the same reference numerals, and a repeated description thereof will be omitted.

(Embodiment 1) FIG. 1 is a perspective view showing a die bonder in which a pellet pick-up method according to an embodiment of the present invention is executed, and FIG. 2 is an explanation showing a pellet pick-up order in the die bonder of FIG. It is a figure.

The die bonder shown in FIG. 1 has a feeder section 2 for conveying the lead frame 1 in the lengthwise direction thereof, a loader section 3 for supplying the lead frame 1 to the feeder section 2, and leads which are conveyed at a predetermined pitch. The pellet 5 adsorbed by the collet 4 against the die pad 1a of the frame 1
A bonding head section 6 for mounting the pellets, a pellet loading section 7 for supplying the pellets 5 to the bonding head section 6, and an unloader section 8 for accommodating the lead frame 1 on which the pellets 5 are mounted.

A positioning stage 9 is installed on the path from the pellet loading section 7 to the bonding head section 6. The pellet 5 is positioned by the gauge 9a of the positioning stage 9 and then sucked by the collet 4. It has become. Further, a paste supply unit 10 for supplying a paste made of, for example, an epoxy-based or polyimide-based thermosetting resin to the lead frame 1 loaded in the feeder unit 2 is installed in front of the bonding head unit 6 in the transport direction, and a paste dispenser is provided. The paste from 11 is dropped from the nozzle 12 onto the die pad 1a. The pellet 5 is the lead frame 1.
After being adhered to, the paste is cured by heating it. However, the pellet 5
You may use the eutectic joining method which heat-bonds the back surface of Au and the Au plating surface of the lead frame 1, and the solder joining method which heat-melts and joins Pb-Sn type preform in an inert gas.

The pellet loading unit 7 holds a wafer ring 14 (see FIG. 2) for holding the wafer sheet 13 to which the pellets 5 individually separated by dicing are adhered in an unfolded state (see FIG. 2). The stage 15 to be placed and the pellets 5 are picked up one by one from the wafer sheet 13, and the positioning stage 9 is described above.
It comprises a transfer jig 16 for transferring to, and a camera 18 which captures images of both for picking up the pellet 5 to be picked up and the transfer jig 16 and displays the images on the monitor 17. In addition, as shown in Embodiments 2 and 3 described later and FIGS. 3 and 4 corresponding to the drawings, a needle 19 for penetrating the wafer sheet 13 and moving up and down is provided below the wafer sheet 13. The pellet 5 to be bonded is transferred to the transfer jig 1
6, the expander 20 is located inside the wafer ring 14 to apply tension to the wafer sheet 13.

In the die bonder having such a structure,
The pellets 5 are picked up in the order shown in FIG. More specifically, in FIG.
Numbers up to 0 are given, but the pickup is centered in the order of 1, 2, 3 ... up to the 40th pellet 5 according to this number, and from 41st onwards in the order shown by the arrow. To the last pellet 5 in the position is carried out. That is, in the present embodiment, the pickup is started from the pellet 5 located at the outermost periphery and is sequentially picked up to the pellet 5 located at the center in the order of forming a spiral shape. Here, the pellet 5 that is first picked up may be any pellet 5 as long as it is located at the outermost periphery (in FIG. 2, the pellet 5 is numbered from 1 to 36). However, as shown by hatching in FIG. 2, the pellet 5 does not include a portion that does not have the entire shape. Further, it is possible that the pellet 5 at the last picked-up position differs depending on which pellet 5 is picked up first.
The last pellet 5 may be the last one picked up in a spiral shape, and does not need to be physically located at the center of all the pellets 5. In addition, including the cases of Embodiments 2 and 3 described below, data of a good product and a defective product determined in an electrical test of the pellet 5 performed before die bonding is stored in a storage device such as a floppy disk. Alternatively, only non-defective products may be picked up in the above-mentioned spiral shape.

The bonding operation of the die bonder shown in this embodiment is as follows.

First, the lead frame 1 supplied from the loader section 3 to the feeder section 2 is pitch-fed and the paste supply section 10 drops the paste onto the die pad 1a. On the other hand, the pellets 5 on the wafer sheet 13 are picked up by the transfer jig 16 and aligned by the positioning stage 9.

As described above, the pickup is carried out in the order of starting from the pellet 5 located at the outermost periphery to the pellet 5 located at the center while forming a spiral shape. The tension of the wafer sheet 13 held in the expanded state by the wafer ring 14 has a concentric distribution in which the outer peripheral portion has the largest tension and gradually decreases toward the center portion. Therefore, in the present embodiment, the trajectory of the pickup by the transfer jig 16 (spiral shape) approximates to the tension distribution (concentric shape) of the wafer sheet 13. As a result, even if only good products are selectively picked up, the amount of change in the tension of the pellets 5 picked up becomes gentle, and a stable pickup operation can be realized, and a pickup error such as peeling failure or chipping occurs. Are prevented by.

The pellets 5 aligned by the positioning stage 9 are adsorbed by the collet 4 and conveyed to the bonding head portion 6 where they are bonded to the die pad 1a coated with the above-mentioned paste. After the bonding, it is stored in the unloader unit 8.

(Embodiment 2) FIG. 3 is an explanatory view showing a change in tension of a wafer sheet in a die bonder in which a pellet pickup method according to another embodiment of the present invention is executed.

In the present embodiment, in addition to the contents described in the first embodiment, the spiral pellets 5 are added.
Is picked up, the tension of the wafer sheet 13 is increased toward the pellet 5 located at the center, and the tension in the pellets 5 to be picked up is made uniform.

That is, the tension of the wafer sheet 13 is applied by the expander 20 located inside the wafer ring 14 which holds the wafer sheet 13 in an expanded state, and the outer peripheral portion is the largest and the central portion is located at the central portion. It is getting smaller gradually. Therefore, the tension of the wafer sheet 13 is minimized when the pellets 5 on the outer periphery are picked up as shown in FIG. 3A by moving the expander 20 in the direction opposite to the wafer ring 14. As shown in FIG. 3B, the tension of the pellets 5 to be picked up is made uniform by gradually increasing toward the center. Note that either the expander 20 or the wafer ring 14 may be moved. The tension control is not limited to the movement of the expander 20 and the wafer ring 14.

As described above, in the present embodiment, the tension of the wafer 5 is gradually increased to equalize the tension of the pellets 5 to be picked up, so that a more stable pickup operation can be realized. .

(Embodiment 3) FIG. 4 is an explanatory view showing a change in needle push-up height in a die bonder in which a pellet pick-up method according to still another embodiment of the present invention is executed.

In this embodiment, the first embodiment described above is used.
In addition to the contents described in (1), when the pellets 5 are picked up in a spiral shape, the needles 19 operate so that the height of the needle 19 is increased toward the centrally located pellets 5 (first operating condition). ).

As described above, the tension of the wafer sheet 13 is largest at the outer peripheral portion and gradually becomes smaller toward the central portion. Therefore, when the needle 19 is pushed up,
The pellet 5 on the outer peripheral portion is peeled off from the wafer sheet 13 with a relatively low push-up height and held by the transfer jig 16. However, in the case of the pellet 5 in the central portion where the tension of the wafer sheet 13 is small, the phenomenon that the wafer sheet 13 does not easily separate from the pellet 5 when pushed up at the same height as the outer peripheral portion, and further, due to this, A phenomenon occurs in which an edge is chipped due to contact with an adjacent pellet 5.

Therefore, the thrust height of the needle 19 is
As shown in FIG. 4 (a), when the pellet 5 on the outer periphery is picked up, it is set to the lowest, and as shown in FIG. 4 (b), the tension is lowered to be picked up by gradually increasing the height toward the center. Pellets 5
The wafer sheet 13 that follows the sheet is forcibly peeled from this. Therefore, even if the tension of the wafer sheet 13 changes, a more stable pickup operation can be realized.

The force for peeling the pellets 5 from the wafer sheet 13 is not only to increase the height of pushing up the needle 19 as described above, but also to increase the speed of pushing up the needle 19 (second operating condition). Can also be controlled by. Therefore, even if the push-up speed of the needle 19 increases toward the pellet 5 located at the center, the first operating condition of the push-up height control and the second push-up speed control of the second push-up speed control.
Even when the operating conditions of (1) and (2) are used together, it is possible to realize a more stable pickup operation.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the embodiment, and various modifications may be made without departing from the gist of the invention. It goes without saying that it is possible.

For example, in the present embodiment, an example in which the pellet 5 is mounted on the lead frame 1 having the die pad 1a is disclosed. However, in a lead frame having no die pad 1a, for example, of a COL (Chip On Lead) structure. In some cases, the pellet 5 is mounted in a predetermined position. Thus, the pellet 5 including the lead frame without the die pad is mounted at a predetermined position of the lead frame.

In order to adjust the tension of the wafer sheet 13 and the height of the needle 19 to be pushed up, any mechanical means such as a cam mechanism or electrical means such as a step motor may be employed. You can

[0039]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) That is, according to the pellet pick-up technique of the present invention, the pellets located at the outermost periphery on the wafer sheet are picked up in the order from the center to the center while forming a spiral shape. The amount of change in tension of the pellet picked up becomes gentle as the trajectory approximates to a concentric circular tension distribution. As a result, the pickup operation of the pellets on the wafer sheet can be stabilized.

(2) Therefore, even in the case of pellets obtained by dicing a large-diameter semiconductor wafer, the range of change in tension is small, and stable pickup is possible.

(3) Further, since the amount of change in tension becomes gentle, it becomes possible to selectively pick up only non-defective products according to the data of the electrical test.

(4) If the tension of the wafer sheet is increased toward the pellet located at the center, the tension in the pellets to be picked up is made uniform and a more stable pickup operation is realized.

(5) Further, even if the push-up height and push-up speed are increased toward the pellet located in the center, the tension is reduced and the wafer sheet following the picked-up pellet is forcibly peeled off. So
As in the case of (4) above, more stable pickup operation is realized.

[Brief description of drawings]

FIG. 1 is a perspective view showing a die bonder in which a pellet pickup method according to a first embodiment of the present invention is executed.

FIG. 2 is an explanatory view showing a pickup order of pellets in the die bonder of FIG.

3 (a) and 3 (b) are explanatory views showing changes in the tension of a wafer sheet in a die bonder in which the pellet pickup method according to the second embodiment of the present invention is executed.

4 (a) and 4 (b) are explanatory views showing changes in needle push-up height in a die bonder in which the pellet pick-up method according to the third embodiment of the present invention is executed.

[Explanation of symbols]

 1 Lead Frame 1a Die Pad 2 Feeder Part 3 Loader Part 4 Collet 5 Pellet 6 Bonding Head Part 7 Pellet Loading Part 8 Unloader Part 9 Positioning Stage 9a Gauge 10 Paste Supply Part 11 Paste Dispenser 12 Nozzle 13 Wafer Sheet 14 Wafer Ring 15 Stage 16 Transfer Jig 17 Monitor 18 Camera 19 Needle 20 Expander

Claims (5)

[Claims] 1. A method of picking up a plurality of pellets individually separated by dicing on a wafer sheet and mounting the pellets on a predetermined position of a lead frame, starting from the pellets located at the outermost periphery. A method of picking up a pellet, characterized in that the pellets located at the center are picked up in the order of forming a spiral shape. 2. The method for picking up pellets according to claim 1, wherein the tension of the wafer sheet is increased toward the pellet located at the center so as to equalize the tension in the pellets to be picked up. Characteristic pellet pick-up method. 3. The pellet pick-up method according to claim 2, wherein the tension of the wafer sheet holds the wafer ring in an unfolded state, and the wafer sheet is positioned inside the wafer ring. A method for picking up pellets, which comprises moving and changing at least one of expanders that gives tension to the. 4. The method for picking up pellets according to claim 1, wherein a needle that pushes up the pellets from below the wafer sheet increases the push-up height toward the pellets located at the center. A pellet pick-up method, characterized in that at least one of operating conditions and a second operating condition of increasing a push-up speed toward the pellet located at the center is applied. 5. The method for picking up pellets according to claim 1, 2, 3 or 4, wherein only the good pellets are selectively picked up.