JPH07114228B2 - Wire bonding defect detection method and apparatus used therefor - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a bonding failure detection method in a wire bonding process for manufacturing electronic components and an apparatus used therefor.

[Prior art]

For example, wire bonding in the manufacturing process of a small signal transistor is performed only by bonding two gold wire wires between the upper surface of the pellet and the frame land for the emitter and between the upper surface of the pellet and the frame land for the base in the unit transistor. It is called a ball-to-ball method as described below, instead of the general bonding method in which both of the first bond for bonding one end of the wire to the pellet and the second bond for bonding the other end of the gold wire to the frame are performed by capillary pressure welding. A simple bonding method may be adopted. First, when the pellet 2 on the lead frame 1 fed stepwise reaches the first stage, as shown in FIG. 3 (a), two gold wires fast-bonded on the pellet 2 by the pressure contact of the capillary are erected. Set up. The upper ends of the gold wires 3 and 4 are melted when cutting with the hydrogen torch T and balls 5 and 6
Is made. Then sent to the second stage, each gold wire 3,
The sorting bar 7 inserted between the four moves left and right, and the gold wires 3 and 4 are bent left and right as shown in FIG. 3 (b). The tips of the bent gold wires 3 and 4 extend so as to overlap the emitter frame lands 8 and the base frame lands 9 located on the left and right of the pellet bonding land in plan view, and the subsequent third stage As shown in FIG. 3 (c), the balls 5 and 6 are pressed against the frame lands 7 and 8 by the vertically moving pressure contact rod 10, and the second bond is completed. Such an operation is sequentially performed, and wire bonding is performed on all the pellets 2 on the lead frame. According to this bonding method, the horizontal movement of the capillaries C is small, so that the bonding speed is greatly increased and the manufacturing efficiency is increased as a whole. Moreover, since the movement of the capillary C, the sorting rod 7, and the pressure contact rod 10 is simple, the device becomes simple. By the way, whether or not the first bond was made reliably and accurately can be confirmed by performing a ground check through the gold wire connected to the capillary at the moment of the first bond,
It is not possible to confirm by a similar method whether or not the second bond is surely made. Particularly, in the wire bonding by the ball-to-ball method described above, since the tip balls 5 and 6 of the gold wire distributed by the distribution bar 7 are pressed against a predetermined lead at high speed by a pressure contact bar 10 which is different from the capillary. ,
For example, it is possible that the second bond is not completely performed due to a slight deviation of the distribution rod 7. In this case, it is extremely difficult to apparently determine whether or not the bonding is completely performed electrically or positionally. Therefore, even if it seems that the tip of the gold wire is bonded to a predetermined lead, it is conceivable that a large number of defective products with incomplete electrical connection may actually occur. It was The present invention has been conceived under the circumstances described above, and provides a method for easily and surely detecting a substantial defect in wire bonding in the manufacturing process of a semiconductor device, and an apparatus used therefor. The task is to do.

[Means for solving problems]

The wire bonding failure detection method of the present invention for solving the above-mentioned problem is to sequentially bond wires to pellets bonded on the surface of the lead frame that is sequentially fed, and then to the bonding wire, on the back surface side of the lead frame. It is characterized in that a gas flow ejected from the arranged nozzle is applied, the wire with defective bonding is raised by the dynamic pressure of this gas flow, and the defective bonding wire thus raised is detected by the detecting means. A wire bonding defect detecting device for performing the above-mentioned wire bonding defect detecting method is arranged below the lead frame in the downstream of the wire bonding station in the lead frame transport path, and ejects an upper gas flow to discharge the upper gas. It is characterized by further comprising a nozzle for applying a flow to the bonding wire from below, and a detection means for detecting an object existing at a position higher than a predetermined height with respect to the pellet in a flow downstream of the nozzle.

[Action]

If there is a bonding failure in either the first bond to the pellet or the second bond to the frame land, that is, if the connection force is insufficient, the connection failure part of the wire to which the upper airflow injected from the nozzle is applied peels off. And is forced to rise by the dynamic pressure of the upper air stream. On the other hand, if the first bond and the second bond are reliable and the connecting force is sufficient, the bonding portion of the wire will not be peeled off even if the upper space is hit. Wires with reliable bonding form a chevron-shaped loop, and the upper and lower positions of the upper end of the loop do not change much even when hit by an upward gas flow, but the upper end of a poorly-bonded wire raised as described above is , Above the top of the normal wire loop above. Therefore, the wire with the defective bonding that has been raised is easily detected by the detection unit that can detect an object existing at a predetermined height with respect to the pellet, that is, slightly above the upper end of the loop of the normal wire.

【effect】

As described above, according to the wire bonding failure detection method and apparatus of the present invention, it is possible to reliably detect the wire bonding failure in the manufacturing process of the semiconductor device. Moreover, since the upper gas flow ejected from the nozzle arranged below the lead frame is used to peel off the defective bonding portion, there is no damage to the normally bonded wire,
Since the gas flow ejected from the nozzle can be locally applied to a required place, an unreasonable force, for example, on a chip other than the bonding wire is not applied to cause defective chip bonding. Further, the wire that is normally bonded and forms a loop from the first bonding position to the second bonding position is also subjected to the upward gas flow, and the dynamic pressure improves the loop shape to an ideal shape, which results in the resin. There is also an additional effect of preventing the occurrence of defects such as contact between the wire and the pellet in the mounting process.

[Explanation of Examples]

An embodiment of the present invention will be specifically described below with reference to FIG. In these figures, the same parts as those in FIGS. 2 to 3 are designated by the same reference numerals. The wire bonding failure detection device of the present invention can be attached to a wire bonder. Usually, this wire bonder is provided with a conveying means (not shown) for feeding the lead frame 1 by pitch, and while being conveyed on this conveying means,
As described above, the wire bonding process including the first stage to the third stage is performed. In the present invention, first, as shown in FIG. 1 (b), the nozzle 11 faces upward under the lead frame 1 in the lead frame conveying direction downstream of the above-mentioned conveying means after the wire bonding process is completed. Blowing means 12 is provided which can apply an upper air flow ejected from 11 to the wires 3 and 4 from below. The blowing means 12 may eject air upward or may eject other inert gas. The flow rate and flow velocity of the gas ejected by this are taken into consideration when the bonding of both ends of the gold wire wires 3 and 4 is incomplete, and this part can be separated by the gas dynamic pressure and can be started up. And set appropriately. Next, in the further downstream of the blowing means 12, as shown in FIG. 1 (c), above the predetermined height from the pellet 2, that is, above the height slightly above the upper end of the loop L formed by a normal wire. Detecting means (13) capable of detecting an object existing in is arranged. The detection means 13 is, for example, two optical fibers, which are generally called a fiber sensor, an optical fiber 14a whose base end is connected to a light emitting element and an optical fiber 14b whose base end is connected to a light receiving element. It is easy to adopt the device in which the terminals are arranged so as to face the direction to be detected. On the other hand, if the wires 3 and 4 after wire bonding have a connection failure as shown in FIG. 1 (a), when the wire 3 or 4 passes above the blow means 12, as shown in FIG. Are separated and activated by the dynamic pressure of the upper gas flow from the nozzle 11. Since the end of the wire 3 thus raised is located above the upper end of the normal wire loop L, it is detected by the detection means 13 described above. When the above fiber sensor is used as the detection means 13, specifically, the optical fiber 14
The light emitted from the terminal a is reflected by the raised defective wire 3 and is received by the terminal of the optical fiber 14b, and this reacts the light receiving element to detect the presence of the defective wire 3 as a result. The detection unit 13 may have any specific configuration, such as a light-emitting element and a light-receiving element that are arranged to face each other. When a wire bonding defect is detected in this way, the wire bonder operation is automatically stopped, an alarm is issued at the same time to prompt the wire bonder inspection, and the bonding defect is stored in correspondence with the order of pellets on the lead frame. , The defective data can be excluded later by the data. Of course, the scope of the present invention is not limited to the above-described embodiments, and the wire bonding method is not particularly limited.

[Brief description of drawings]

FIG. 1 is an explanatory view of a position embodiment of the method of the present invention, FIG. 2 is a partial plan view of a lead frame after wire bonding, and FIG. 3 is a view for explaining an example of a wire bonding method. It is a figure corresponded to the III-III line expanded cross section of a figure. 1 ... Lead frame, 2 ... Pellet, 3, 4 ... (gold wire) wire, 12 ... Blowing means, 13 ... Detection (detection) means.

Claims (2)

[Claims] 1. After sequentially wire-bonding pellets bonded on the front surface of a lead frame which is sequentially fed, a gas flow ejected from a nozzle arranged on the back surface side of the lead frame is applied to the bonding wire, and this gas is injected. A wire bonding failure detection method, wherein a defective bonding wire is raised by a dynamic pressure of a flow, and the defective bonding wire thus raised is detected by a detecting means. 2. A nozzle, which is arranged below the lead frame in the downstream of the wire bonding station in the lead frame transport path, ejects an upper gas flow and applies the upper gas flow to the bonding wire from below, and a nozzle of this nozzle. A wire bonding failure detection device further comprising a detection means for detecting an object existing at a position higher than a predetermined height with respect to the pellet in a downstream flow.