JPH0810714B2 - Wire bonding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wire bonding method.

[Background Art] When manufacturing a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI), as shown in FIG.
After positioning the lead frame LF attached to the table T on the table T, the tool holding the wire W is relatively displaced with respect to the lead frame LF and the semiconductor pellet S, so that the lead W provided on the lead frame LF is provided. The post LP and the pad SP of the semiconductor pellet S are respectively led and bonded. The experimental bonding points of the lead frame LF and the pellet S positioned on the table T are generally deviated from the regular bonding points which are predetermined as coordinates on the XY table. As a method of correcting the position of the displacement of the bonding point, there is a method of previously determining two fixed points of the lead post and calculating the actual positional displacement of the two fixed points to calculate the actual bonding positions of the respective points of the lead post. However, variations in the relative positions of the lead posts LP on the lead frame LF are not considered. Therefore, in this method, in a multi-pin IC having a large number of lead posts, the variation in the relative position becomes large, so that the bonding cannot be performed automatically.

As a means for correcting the relative position of the lead post LP, the one shown in JP-A-56-8830 is known.

In this conventional example, a detection range is created so that an optimum detection range can be obtained for one lead post LP, and a bondable range corresponding to each lead post is set to perform position correction. Is.

That is, when bonding to one lead post LP extending in the vertical Y direction as shown in FIG. 8, a position I indicated by a chain double-dashed line is set as a regular position of the lead post LP at the time of bonding, and a regular bonding point is set. Be A. The coordinate A of this regular bonding point is previously set as a coordinate on the XY table by the microcomputer to the lead post.
It is input to find the center of LP. However, since the point A1 at the position II shown by the solid line is the actual position of the lead post LP, it is necessary to detect the displacement amount between AA1 and correct the displacement of the bonding point. In this case, the bonding point may be within the predetermined range on the lead post LP, and is not necessarily the fixed point A1. Therefore, the detection range B is established so as to be within the predetermined range on the lead post. When all of the setting range B is within the lead post LP, it is determined that bonding is possible, and the center A of the detection range at this time is determined as the bonding point. Also,
When trying to set the detection range corresponding to each lead post LP, each lead post LP is set so that the optimum detection range is obtained according to the shape and position of the lead post LP as shown in FIG. The detection range B1, B2, ... B8 is changed and set.

[Problems to be Solved by the Invention] However, in the conventional wire bonding method, the position of the lead post LP is corrected by variably setting the optimum detection range according to the shape of each lead post of the lead post LP. It takes time to set the detection range. Moreover, in this method, the effective areas of the lead posts are calculated, the detection range is determined, and the image is displayed on the monitor. Therefore, when there are a large number of lead posts, there is a drawback that the positional relationship of where the next lead post to be corrected is located cannot be known. Moreover, when there are many lead posts such as a multi-pin IC, it takes a lot of time because the XY table is moved and detected for each lead post.

The present invention has been made in view of the above-mentioned drawbacks of the prior art,
An object of the present invention is to provide a wire bonding method capable of automatically correcting the relative displacement of a plurality of lead posts together even in a multi-pin lead frame and automatically performing bonding.

[Means for Solving the Problems] According to the present invention, a lead frame to which a semiconductor pellet is attached is arranged on a positioning table, and a tool holding a wire is relatively displaced with respect to the lead frame and the semiconductor pellet. In a wire bonding method in which the wire is guided to a lead post provided on the lead frame and a pad on the semiconductor pellet respectively, and bonded, the lead post imaged by a camera can be binarized and then processed in one screen. The number of lead posts is determined by the determining means, and the detection range, the fixed point, and the detection range between the lead posts located at both ends of the lead posts 2 included in one screen of the lead posts determined by the determining means are determined. A regular detection point of each lead post is set in advance, and the relative positional relationship between each lead post is determined from the detection point. Alternatively, the shift amount is calculated, and based on the calculated data, the coordinates of the regular bonding point which is previously input to the control means are corrected,
The lead post is bonded based on the corrected coordinates.

EXAMPLES Next, the present invention will be described in detail with reference to the drawings.

 FIG. 1 shows a detection device used in the method of the present invention.

In FIG. 1, the timing circuit 2 is composed of an oscillation circuit 1a that generates a predetermined reference signal and a synchronization signal generation circuit 1b that generates constant horizontal and vertical synchronization signals, and this synchronization signal is input to the camera 3. . The camera 3 is mounted on the XY table drive mechanism 9 and images the lead frame LF and the pellet S on the table T. The output of the camera 3 is input to the binarization circuit 5 through the amplifier 4. In this binarization circuit, for example, the portion of the lead post LP that is lightened and read is set to "1", and the other portions are darkened and read as "0" and digitized. It is composed. The binarized signal is input to the monitor 6 and the determination circuit 7. The determination circuit 7 determines the detection range of the plurality of lead posts LP and, at the same time, calculates the deviation amount between the regular detection points of the lead posts LP and the actual bonding points. This determination result is output to the control circuit 8 to correct the proper bonding point, and then the XY table drive mechanism 9 performs bonding.

FIG. 2 is a diagram for specifically explaining the determination method of the determination circuit 7 shown in FIG. 1 in the apparatus having the above configuration. In FIG. 2, a plurality of lead posts LP (hereinafter referred to as leads) a, b ... D, e are arranged on the positioning base of the table T. The coordinates of each lead are obtained as Ax, Ay for the lead a and Bx, By for the lead b, and are stored in the memory circuit as coordinate points of each lead in the control circuit 8 including a microcomputer.

Next, a method of determining the number of lead posts that can be processed on one screen will be shown.

In the present invention, the range that can be processed by one screen is set as shown in FIG. 2 (b) by the mouths W1 W2 W3 W4.
The lengths of the sides Wx and Wy defined by the mouths W1 W2 W3 W4 are set within a range in which at least one lead is inserted. Also,
This range may be set using the range projected by the camera 3 or a part thereof.

This detection method will be described with reference to the flowchart of FIG. 3. In step 1 (S1), it is first determined whether the leads a and b are within one screen (whether or not they can be processed). In the embodiment of FIG. 2, since it is within one screen, it is determined that processing is possible, and the process proceeds to step 2 (S2). Here, the leads a, b, and c are also included in the determination, and since the processing can be performed in the same manner as in step 1, the process proceeds to step 3 (S3). In this step 3, the determination is made by adding d to the leads a, b, c, but since it cannot be processed, the range up to step 2 is determined to be processable and processed. Step 4 (S
In 4), using the above method, repeat for leads d, e.

Since the leads a, b, and c can be processed by this determination, the mouths sW1 sW2 sW3 sW4 are formed as shown in FIG. 4, and the midpoint thereof is obtained. This coordinate point is easily calculated as coordinates on the XY table, that is, X = (Ax + Cx) / 2, Y = (Ay + Cy) / 2. The relative positional relationship with each lead is calculated at the same time using the midpoint S as a base point, and set as a normal detection point.

This completes the condition setting (self-teaching) necessary for lead detection.

 Next, a method for detecting the position of the lead post will be described.

As shown in step 5 (S5) of the flowchart of FIG. 6, the determination circuit 7 takes in the processed image once. Judgment circuit 7
The control circuit 8 instructs the XY table drive mechanism 9 by the output signal from the XY table to move the XY table to the next detection point (step 6).

The amount of deviation (Δx _a , Δy _a ), (Δx _b , Δy _b ), from the normal detection point of the lead shown by the chain double-dashed line in FIG. 2 (c),
Calculate (Δx _c , Δy _c ). The process steps are shown in steps 7, 8 and 9. If the image is captured in the process, the XY table can be moved.
At 10, determine whether the XY table is stopped and move to the next detection point.

According to this embodiment, not only the relative positional relationship of a plurality of leads can be determined at the same time, but also the XY table can be moved to the next detection screen by the determination signal, so high-speed processing is possible. be able to.

Although the determination circuit and the control circuit of the detection device have different configurations in this embodiment, they can be appropriately changed as long as they have the same function.

As described above, according to the present invention, not only the relative positional relationship of a plurality of leads can be determined at the same time, but also the XY table is moved to the next detection screen by the determination signal. Therefore, it can be processed at high speed. In addition, since it is possible to simultaneously determine the relative positional relationship between the lead posts and correct the position of these deviation amounts, there is an effect that it does not take time. Moreover, according to the present invention, since the relative positional relationship between the lead posts can be confirmed, there is an effect that it is easy to confirm the lead post to be corrected next. Further, there is also an effect that the cost is low because a special detection circuit or the like is not required for setting the lead post detection range.

[Brief description of drawings]

FIG. 1 is an embodiment of the present invention, showing a detection device used in the method of the present invention, FIGS. 2 and 4 are explanatory views for explaining the detection method of the present invention, and FIG. FIG. 2 is a flow chart of the method, FIGS. 5 and 6 are diagrams showing another embodiment of the present invention and their flow charts, and FIGS. 7, 8 and 9 are diagrams showing a conventional wire bonding method. is there. LF ... lead frame, LP ... lead post, W ... wire, S ... pellet, SP ... pad, 1a ... oscillation circuit, 1b ... synchronous signal generation circuit, 2 ... timing circuit,
3 ... Camera, 4 ... Amplifier, 5 ... Binarization circuit, 6 ...
... Monitor, 7 ... Judgment circuit, 8 ... Control circuit, 9 ... XY
Table drive mechanism.

Claims (1)

[Claims] 1. A lead frame to which a semiconductor pellet is attached is arranged on a positioning table, and a tool for holding the wire is relatively displaced with respect to the lead frame and the semiconductor pellet to provide the wire on the lead frame. In the wire bonding method, in which the lead posts and the pads on the semiconductor pellet are respectively guided and bonded, after binarizing the lead posts imaged by the camera, the number of lead posts that can be processed in one screen is determined by the determination means. The detection range, the fixed point, and the regular detection point of each lead post within the detection range are determined in advance between the lead posts located at both ends of the lead post included in one screen of the lead post determined by the determination means. The relative positional relationship or the amount of deviation between the lead posts is calculated from the detection points, and the calculated Signal by the control unit the wire bonding method is characterized in that so as to move start to lead posts adjacent the XY table to the detected screens.