JPS6038870B2 - Wire bonding method for semiconductor devices - Google Patents

Abstract

PURPOSE:To perform connection of high quality by setting a common length between the contact points of leads inside a package corresponding to the electrodes of semiconductor chips, by restricting the movable range of a block within the length, and by compensating the length between the two points. CONSTITUTION:The coordinates of the internal electrode 2 of the package 1 corresponding to the electrode 6 of the chip 4 are decided by the amount of movement of an XY block from the origin E, a certain common length la allowing linear junction is measured actually with respect to a standard chip and package, the result is stored in an electronic computer, and thereby a sequence program to control a joining device is prepared. The package 1 is rotated according to a position compensating information, and when the distance between junction points Px and Lx is excessive or deficient to the prescribed value la, the length lx is compared by the computer, the point Lx is moved in parallel along the axis Y so that lx equals to la and the linear junction is performed through automatical uniformalization. By this constitution, the connection is free from bending or stretch and thus the linear junction of high quality can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire bonding method for semiconductor devices, which connects semiconductor chips mounted in a package with thin metal wires.

A semiconductor device in which a semiconductor chip is attached to a package and wire bonding has been completed is shown in a perspective view and a front sectional view in FIGS. 1 and 2.

A package 1 made of ceramic or the like is provided with internal leads 2 and external leads 3 of a lead frame. A semiconductor chip 4 is placed in the recess la of the packaging box.
is mounted, and each internal lead 2 is connected to a metal pongee wire 5 by ultrasonic wire bonding. Recently, automatic machines have been used for this wire bonding, and it has become difficult to manually adjust the shape of the fine metal wires after bonding.
Note that although the tips of the external leads 3 are connected to each other in the figure, they will be separated later. Wire bonding between the semiconductor chip 4 and the internal leads 2 using ultrasonic waves is performed as shown in the explanatory diagram of FIG.

The capillary chip 7 of the ultrasonic wire bonding device descends from position A to position B and presses the metal wire 5 against the aluminum electrode 6 of the semiconductor chip 4 which is tar-bonded to the housing recess la of the package 1, thereby generating ultrasonic vibration. Add and join. Next, the capillary chip 7 is raised and moved to the position C above the corresponding internal lead 2. The capillary IJ tip 7 is then lowered to the D position, and the metal pongee wire 5 that has been fed out is pressed against the internal lead 2 and ultrasonic vibration is applied to join it. The capillary chip 7 is moved in the horizontal direction by moving an XY table (not shown) supporting the capillary chip 7 in the X-axis and Y-axis directions. This wire bonding method using an automatic machine is performed as follows.

The package 1 with the semiconductor chip 4 mounted thereon is vacuum suctioned onto a vacuum chuck stand (not shown) which is capable of minute angle rotation adjustment using a pulse motor. FIG. 4 is an explanatory diagram showing the positional relationship between each aluminum electrode 6 of the semiconductor chip 4 and the corresponding internal lead 2. Let the bonding points of some of the aluminum electrodes 6 be P, , P2, and the corresponding bonding points of the internal leads 2 be L, , L
shall be. The rotational center point of the vacuum chuck table is set as the coordinate origin E, and the X-Y line and Y-Y line are assumed. X and Y axes are XY
It is parallel to the movement direction of the table in the X direction and the Y direction.
Here, the distance between each coordinate of P, -L,, P2 -L2 is 1,
, 12. For the X and Y axes, the P point is at the coordinate points of Px and Py, the P2 point is at the coordinate points of Px2 and Py2, and the L point is at the blind point of Lx and Ly. L
The point is at the coordinate point of Lx2 and Ly2. Each aluminum electrode 6
The bonding points of each internal lead 2 corresponding to the above are stored in an electronic computer such as a microcomputer.

The method will be explained with respect to the coordinates of points P,,P2,L,,L2. The capillary chip 7 of the wire bonding device is moved and adjusted by moving the XY table in the x-axis and y-axis directions. The XY tables are each driven by a pulse motor and are moved at minute pitches. Therefore, the coordinates of points P, , P2, L, , L2 are determined by moving the XY table due to the disturbance of the pulse motor and sequentially aligning the capillary tip 7 with each coordinate point from the coordinate origin E. Coordinates from the axes are determined and stored in an electronic computer.

Memory in this electronic computer is first stored on the semiconductor chip 4.
For the similar standards of package 1 and package 1, proceed as described above. The actual package 1 is suctioned onto a vacuum chuck table with misalignment with respect to the coordinate origin E and rotational deviation with respect to the X and Y axes. Furthermore, the semiconductor chip 4 is mounted on the package with some positional or rotational misalignment. These modifications are performed on the individual packages 1 and their semiconductor chips 4 that are sucked onto the vacuum chuck table.
By aligning the capillary chip 7 with each bonding point of each internal lead 2 corresponding to each aluminum electrode 6, the coordinates are entered into a computer and corrected with respect to the standard coordinates previously stored. . Through this correction and control from an electronic computer, rotational deviations can be corrected.
The vacuum chuck table was rotated and corrected, and the positional deviation was
This is done by modifying the movement of the Y table. Therefore, a sequence program is created using each coordinate point stored in the computer and its correction, and the XY table is moved to automatically bond the thin metal wire 5 with the capillary chip 7 as shown in Fig. 3. . However, if the thin metal wire 5 is an aluminum wire, as shown in FIG.
The vacuum chuck table is rotated so that a line connecting a bonding point, for example, Px, and a bonding point, for example, Lx, of a corresponding internal lead is bonded after the vacuum chuck table is rotated so as to be parallel to the Y axis. These operations are automatically performed under program control by an electronic computer. In the following method, since bonding is performed at Lx with respect to the coordinate point Px, the lengths of the bonded thin metal wires 5 are not uniform. The shape of the thin metal wire 5 from the aluminum electrode 6 to the internal lead 3 after wire bonding in this manner depends on the distance between these two points and the amount of feed of the thin metal wire 5.

In particular, the distance between these two points is different for each semiconductor chip 4, and it is not easy to form the ideal uniform shape into a gentle mountain shape. Various shapes of the wire-bonded metal pongee wire 6 are shown in longitudinal cross-sectional views in FIGS. 5 to 7. FIG. 5 shows an ideal shape in which the thin metal wire 5 has a loose mountain shape. The metal pongee wire 5 has an extremely small diameter, and in the case of aluminum wire in particular, various problems will occur unless the wire has a loose chevron shape. However, in the conventional method, as described above, each bonding point between each aluminum electrode 6 and each corresponding internal lead 2 and its modification are stored in an electronic computer.
Under this control, both corresponding bonding points are sequentially bonded with the thin metal wire 5, which causes the following inconvenience.

A metal pongee wire 5 is bonded to a certain aluminum electrode 6, and the capillary IJ chip 7 rises and descends to the bonding point of the corresponding internal lead 2 for bonding.

In this case, the rising height of the capillary tip 7 is constant,
The distance between each aluminum electrode 6 and the bonding point of the internal lead 3 is different. For this reason, the pulled out thin metal wire 5 is too long in places where the distance between two points is short, resulting in a large slack shape as shown in Figure 6, and the length is too long in places where the distance between two points is long. was insufficient, resulting in a stretched shape as shown in Figure 7. The thin metal wire 5 has an extremely small diameter,
If it sag as shown in Fig. 6, it may hit the lid bonded to the package 1 or the adjacent thin metal wires 5 may come into contact with each other, and if it is stretched as shown in Fig. 7, it may break or the joint may be damaged. It may come off. In order to make the shape of the bonded metal pongee wire 5 as shown in FIG. 5, it is sufficient to make the distances between each aluminum electrode 6 and each corresponding internal lead 3 the same, but this is structurally difficult. Further, although the amount of the thin metal wire 5 to be drawn out may be finely adjusted depending on the distance between two points, this also requires a complicated mechanism and is difficult to realize. This invention sets a common wire bonding distance between each aluminum electrode of a semiconductor chip and each corresponding internal lead of a package, stores this set length in a computer, and The wire is bonded to the corresponding inner lead bonding point and the wire is bonded to the set length above the bonding point.The shape of each bonded metal pongee wire is made into a loose chevron shape to eliminate large sag and tension, and to improve quality. It is an object of the present invention to provide a method for wire-bonding semiconductor devices with improved performance.

In the present invention, a common length la is measured and set in advance for a standard semiconductor chip and package to maintain a constant wire bonding distance between each electrode of the semiconductor chip 4 and each corresponding internal lead. , stored in a computer, and for its standard products,
As shown in FIG. 4, the coordinate data of each bonding point from each coordinate origin E is stored in an electronic computer, and a sequence program for controlling the bonding apparatus is created.

Thus, a corresponding internal lead 2 from each aluminum electrode 6
The bonding distance to
The movable range of the Y table is limited to la to keep it constant. Figure 9 shows the set common length l
a' is an explanatory diagram showing the relationship between aluminum electrodes and internal leads, in which any aluminum electrode 6 of the semiconductor chip 4 is
Point.

The distance between coordinates from a certain coordinate origin E to point P3 is Py3
, P are also assumed to be. First, drive the pulse motor to
The table is moved, and the cavity chip 7 mounted on the table is moved from the coordinate origin E to point P3.

This amount of movement is stored in a computer. Here, if the temporary coordinate origin is set to point P3, then the XY
The movable range of the table is a radius la with point P3 as a circle. Therefore, the movable range of the XY table on the internal lead 2 corresponding to point P3 can be expressed by the area S3,
In this case, the target is the coordinates of the locus of point F drawn with radius la on the coordinates. The operator finds the locus of this point F and the corresponding contact point on the internal lead 26.
, the coordinates may be stored in the computer of the device. By performing such operations, the L of the corresponding internal lead 2 can be adjusted from the Pn point of any aluminum electrode 6 of the semiconductor chip 4.
The distance to point n can be made uniform for each aluminum electrode 6 and each corresponding internal lead 2. However, in reality, the semiconductor chip 4 only needs to be mounted within the mounting range within the accommodation recess la of the package, and it is not possible to position and mount the semiconductor chip 4 with high precision so that there is no angular shift or horizontal position shift. Have difficulty. Therefore, based on the data stored in the above operation, the positional deviation and angular deviation of the semiconductor chip 4 are detected in the same manner as in the case of correction explained above, and the data is input into a computer, and by the control thereof, it is used as a reference. On the other hand, the angular deviation is corrected by rotating the vacuum chuck table, and the positional deviation is corrected by correcting the amount of movement of the XY table. Move the side bonding points.

This operation will be further explained with reference to FIG.

Figure A shows the X of package 1 attracted on the vacuum chuck table.
, the Y-axis position, Px is the bonding point of a certain aluminum electrode 6, and Lx is the reference bonding point of the corresponding internal lead 2. The input of the data for the position correction of the semiconductor chip 4 and the position correction of the package to the electronic computer has been completed. The package 1 is rotated by a vacuum chuck so that each bonding point between the aluminum electrode 6 and the internal lead 2 is parallel to the Y-axis direction (the direction in which the capillary chip moves along the Y-axis), as shown in Figure B. In order to make it parallel to the Y axis in this way, the thin metal wire 5 is an aluminum wire.
If the distance from the position-corrected bonding point Px of the aluminum electrode 6 of the semiconductor chip 4 to the bonding point Lx of the internal lead 2 is more or less than the length la, the bonding point of the internal lead 2 is automatically displaced. I'm trying to make it the length of a.

In other words, after the Px point of the aluminum electrode 6 and the Lx point of the internal lead 2, whose position has been corrected, are determined, the values of the lengths la and lx are compared by a computer, and the lengths are lengthened until lx becomes la.
Move the x point parallel to the Y axis. (Due to the movement of the capillary tip 7 by the XY table.) In this way, the point La is reached,
Bonded. With this operation, wire bond 2
The distances between points are automatically equalized. In this way, in order to make the distance between the two wire bond points between each aluminum electrode 6 and the internal lead 2 constant, the value of the length la to be made uniform is set in advance, and the movable range of the XY table is adjusted. A sequence program is created to limit the length to la and compensate for any excess or deficiency in the length between two wire bond points with respect to la.

In the above embodiments, the electrodes of the semiconductor chip 4 are aluminum electrodes, but electrodes of other conductive layers can also be used.

As described above, according to the present invention, the wire bond between each electrode of a semiconductor chip and each internal lead is formed into a shape of a metal ponytail wire with a constant length and a moderate height, thereby preventing large sag. This eliminates tension and improves the quality of semiconductor devices.

Brief explanation of the drawings Figure 1 is a perspective view of a semiconductor device in which a semiconductor element is attached to a package and wire bonded.
The figure is a sectional view taken along the row 0 line in Figure 1, Figure 3 is an explanatory diagram showing the state in which the semiconductor element in Figure 1 is wire-bonded with a capillary chip, and Figure 4 is the inside of the semiconductor chip electrode and package. Explanatory drawings showing the coordinate system with the lead. Figures 5 to 7 show the shape of the wire-pounded metal pongee wire. Figure 5 shows the ideal shape, and Figures 6 and 7 show the defective shape. FIG. 8 is an explanatory diagram showing the conventional method in which the bonding point between the electrode and the internal lead in FIG. 4 is parallel to the Y axis, and FIG. An explanatory diagram showing the relationship between the movable range of the XY table and the bonding points with aluminum electrodes and internal leads according to the average length between two bonding points set by the method, FIG. 10 is an explanatory diagram showing the bonding method according to the present invention, A shows the semiconductor chip and package that have undergone position correction processing,
B shows a state in which the package is rotated so that the two bonding points are aligned in the Y-axis direction.

1...Package, 2...Internal lead, 4...Semiconductor chip, 5...Metal thin wire, 6...Aluminum electrode, 7...Capillary chip.

Note that the same reference numerals in the figures indicate the same or equivalent parts. Figure 1 Figure 2 Figure 3 Figure 5 Figure 6 Figure 7 Figure 4 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] 1. A package equipped with an internal lead leading to the outside and equipped with a semiconductor chip is adsorbed onto a vacuum chuck stand, and a capillary chip is installed on an XY table that is movable in the X-axis and Y-axis directions for minute dimensions A bonding device is installed, the coordinates of the bonding points of each electrode of the semiconductor chip and the corresponding internal leads are stored in an electronic computer, and the rotation of the vacuum chuck and the XY axis are controlled by a control program by the computer. In the method of wire-bowing a fine metal wire between each of the electrodes and two points of each internal lead by moving the table, the capillary chip is used to wire a wire between two bonding points of each of the internal leads corresponding to each of the electrodes. The length is set, stored in the electronic computer, and a control program is created, and in bonding using the capillary chip, there is an excess or deficiency of the above-mentioned coordinates of the bonding point of the internal lead with respect to the bonding point of each electrode with respect to the common set length. and a wire bonding method for a semiconductor device in which the capillary chip performs bonding by corrective movement, and the thin metal wire between the two bonded points is made uniform to the constant common length and formed into a gentle mountain shape.