KR20000018709A - Wire bonding device for ball grid array package and wire bonding method - Google Patents

Abstract

PURPOSE: A wire bonding device for a ball grid array(BGA) directly checks a good bonding or fail bonding in a wire bonding time point at which a bonding pad formed in a chip of BGA package and a pattern of PCB are bonded. CONSTITUTION: A wire bonding device for BGA includes a capillary mounted to XY table in order to perform a wire bonding about PCB pattern and a bonding pad, a heater block body(65), a heater block adapter(69), a bonding temperature regulator, and a pattern recognition device and a control unit(10). The heater block body is fixed to a working table in order to heat the PCB with a proper temperature for the wire bonding. The heater block adapter is connected to a heater block body(65), and fixes the PCB by a suction. The bonding temperature regulator includes the heater block body and the heater block adapter. A pattern recognition device and control unit recognize a PCB pattern and a chip pattern. Each solder ball pad is grounded by a grounding part mounted to the heater block adapter. The solder ball pad is formed on a back side of the PCB in order to achieve an electrical connection of the PCB formed on its front side. Thereby, the wire bonding device immediately checks a good bonding or fail bonding in a wire bonding.

Description

Wire Bonding Fixtures and Wire Bonding Methods for Ball Grid Array Packages

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding facility and a wire bonding method for a ball grid array (BGA) package, and more particularly, to wire-bond patterns of external bonding pads and printed circuit boards formed on a chip in a BGA package. The present invention relates to a wire bonding facility and a wire bonding method for a ball grid array package capable of immediately checking whether the wire bonding succeeds or fails.

Recently, with the development of high-density chips due to the development of semiconductor thin film technology, the existing QFP (Quad Plat Package) alone is facing the limitation of packaging to accommodate high-density chips. The limitations of this packaging technology are mainly due to the increase in inductance caused by leads having smaller cross-sectional areas in response to the narrower lead pitch spacing and the noise generated during high-speed operation, which is the advantage of high density chips.

In order to secure such a problem, a fine printed circuit pattern formed by an etching method is formed on the front side, and a solder ball pad connected to the printed circuit board is formed on the rear side, and then the fine printed circuit pattern and the bonding pad of the high density chip are gold, silver, A BGA package has been developed in which a wire of suitable material is selected and wire-bonded and then solder ball attached to a solder ball pad.

However, the BGA package, which has many advantages over wire bonding the bonding pad of the chip to the inner lead of the conventional lead frame with the bonding wire, does not know immediately whether the wire bonding succeeds / fails while performing wire bonding and does not have a separate follow-up inspection. Only through the process can the wire bonding be determined to be successful or unsuccessful.

When bonding the bonding pad of the chip to the inner lead of the conventional lead frame with the bonding wire, the capillary-bonding wire when the wire bonding is correctly performed to the grounded inner lead while a predetermined voltage is applied to the capillary and the bonding wire. Although the inner lead is closed, the wire bonding momentary current flows, and the wire bonding equipment detects whether the current flows, thereby determining the success / failure of the wire bonding moment, but die-attach to the printed circuit board of the BGA package. When wire bonding the bonding pattern of the chip and the circuit pattern of the printed circuit board by the bonding wire, the solder ball is not attached yet. Therefore, it is impossible to determine whether the wire bonding succeeds or fails by the method described above. .

This problem has a big impact on package yield.

For example, failure of wire bonding caused by mechanical errors that occur only once in a few hundred to tens of thousands is not a major problem, but wear, damage and transfer of certain parts of the wire bonding facility, such as capillaries If the wire bonding continues to fail due to damage to the device, the wire bonding process will fail continuously until the problem is found, resulting in mass defects of the package.

Accordingly, the present invention has been made in view of such a conventional problem, and an object of the present invention is to be able to confirm the success / failure of wire bonding at the moment of wire bonding a chip and a printed circuit pattern of a BGA package.

Other objects of the present invention will become more apparent in the following detailed description of the invention.

1 is a block diagram of a wire bonding facility for a ball grid array package according to the present invention.

Figure 2 is a perspective view showing a bonding temperature control device of the wire bonding equipment for ball grid array package according to the present invention.

Figure 3 is a perspective view showing a part of the heater block adapter of the bonding thermostat according to the present invention.

4 is a cross-sectional view taken along line BB ′ of FIG. 3.

Figure 5 is a perspective view showing that the wire bonding is performed by the capillary in a state in which the BGA printed circuit board is seated on the heater block body according to the present invention.

6 is a conceptual diagram illustrating wire bonding of a bonding pad and a printed circuit pattern of a chip by a capillary according to the present invention;

FIG. 7A is a graph showing the current flow in the capillary when wire bonding is successful, and FIG. 7B is a graph showing the current flow in the capillary when wire bonding fails.

8 is a flowchart illustrating a wire bonding method according to the present invention.

In order to achieve the object of the present invention, the wire bonding apparatus for the ball grid array package is connected to a printed circuit pattern formed on the front surface of the printed circuit board for the ball grid array package. When wire bonding a bonding pad and a printed circuit pattern of a chip attached to the front surface of a printed circuit board by an applied capillary, the current may or may not flow in the capillary according to the success / failure of wire bonding. The failure is immediately recognized when the wire bonding ends.

Hereinafter, the wire bonding facilities for the ball grid array package of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a block diagram of a wire bonding facility.

Referring to the accompanying drawings, the wire bonding equipment 100 includes a control unit 10 for controlling a wire bonding process required for wire bonding, a data input device 20 for the operator to control the equipment, operating software and equipment data. A pattern recognition device 40 for recognizing the stored memory device 30 and the printed circuit pattern of the BGA printed circuit board to be bonded and the bonding pad of the chip, and transferring the bonding head 55 to the bonding pad and the printed circuit pattern of the chip. XY table 50, the bonding temperature control device 60 for heating the BGA printed circuit board to the temperature required for bonding.

At this time, the flow of data among the above-mentioned components is performed by the data bus 70, the flow of control is performed by the control bus 80, in particular, the bonding head 55 is a digital that can recognize the flow of current The ammeter 52 and the power applying device 53 are connected.

2 illustrates a bonding temperature controller 60 capable of confirming wire bonding success / failure, which may confirm success / failure of wire bonding when wire bonding is performed.

As such, the bonding temperature adjusting device 60 having the function of checking the bonding / success of the wire bonding and adjusting the bonding temperature is a workbench of the wire bonding facility 100 having a rectangular parallelepiped shape in which three hollows 65a, 65b, and 65c are formed. It is coupled to the heater block body (65) and the heater block body (65) installed in (1), and it is possible to check the success / failure of wire bonding while adsorbing the portion to be wire bonded in the BGA printed circuit board by vacuum pressure. In order to control the heater and the heater inserted in the hollow 65a of the heater block body 65 to heat the BGA printed circuit board fixed to the heater block adapter 69 and the heater block adapter 69 to a predetermined temperature. It consists of a thermocouple (not shown) inserted into another hollow 65b.

The other hollow 65c formed in the heater block body 65 is a vacuum hole 65c for generating a vacuum pressure in the heater block adapter 69.

3 and 4, the heater block adapter 69 includes a heater block adapter body 66, a heater block adapter through hole 66a, and a heater block to be grounded with a solder ball pad formed on a rear surface of a BGA printed circuit board. It is composed of an adapter vacuum hole 66b, a ground terminal 67, a spring 67a and a separation prevention cover 68.

More specifically, the heater block adapter body 66 has a rectangular parallelepiped plate shape, and a groove 66c having a square shape in a plane is formed on a rear surface of the heater block adapter body 66.

The groove 66c is coupled after the above-mentioned separation prevention cover 68 is inserted.

As described above, the heater block adapter body 66 having the square groove 66c having a flat surface has the same position and the same number as the solder ball pads of the BGA printed circuit board 70 shown in FIG. 5. (66a) are formed, the heater block adapter through-holes (66a) is a bonding pad of the chip 75 die-attached to the BGA printed circuit board 70 and the printed circuit pattern of the BGA printed circuit board 70 It serves as a connection terminal hole formed to confirm whether or not the wire bonding of 77 is successful or failed.

In addition to the heater block adapter through-hole 66a, the heater block adapter body 66 is provided with a heater block adapter vacuum hole 66b for adsorbing and fixing the BGA printed circuit board 70.

Meanwhile, as briefly described above, the conductive recess prevention cover 68 is inserted into the square groove 66c formed on the rear surface of the heater block adapter body 66 to close the lower end of the heater block adapter through hole 66a. So that it is engaged by fastening screws.

At this time, the portion corresponding to the heater block adapter through-hole 66a of the detachment prevention cover 68 formed conductively is blocked, but the portion corresponding to the aforementioned heater block adapter vacuum hole 66b is opened.

In this way, the heater block adapter through hole 66a of which the lower end is blocked is inserted with a spring 67a and a conductive ground terminal 67 coupled to one end of the spring 67a.

The conductive ground terminal 67 may have various shapes, for example, a pin shape, a ball shape, or the like, but in the present invention, a ball-shaped conductive steel ball is preferably used.

At this time, the length of the spring 67 is such that the conductive steel ball is slightly higher than the opening of the heater block adapter through hole 66a, that is, the length of the conductive steel ball slightly protrudes from the upper surface of the heater block adapter body 66.

At this time, the steel ball 67-the spring (37a)-the departure prevention cover 68 is all made of a conductive material so that the heater block adapter 69 is grounded to the earth (earth) through the heater block body (65).

As shown in FIG. 5, the bonding temperature controller 60 including the heater block body 65 and the heater block adapter 69 configured as described above, the chip 75 is die-attached as shown in FIG. 5. When wire bonding is performed by the capillary, which is the bonding head 55 with the loaded and adsorbed, the bonding head 55 and the bonding wire 53 are connected to the power supply device 53 as shown in FIG. By this, about 2 [V] power supply Vcc is applied.

The wire bonding method of the BGA package by the wire bonding facility for the ball grid array package of the present invention configured as described above will be described with reference to the accompanying flowchart and drawings.

First, a printed circuit board 77 for one BGA is bonded to the bonding temperature controller 60 using a guide rail 80 from a printed circuit board stocker in which a plurality of BGA printed circuit boards 77 are not shown. Transfer (step 10).

Subsequently, a vacuum pressure is formed in the hollow 65c formed in the heater block body 65, so that the BGA printed circuit board 77 to which wire bonding is to proceed is heated by the vacuum pressure of the heater block adapter vacuum hole of the heater block adapter body 66. At the same time, the solder ball pads 79 of the BGA printed circuit board 70 facing the conductive steel balls 67 provided on the heater block adapter body 66 are brought into contact with each other (step 20).

Subsequently, the capillary, which is the bonding head 55, is transferred to the bonding pad formed on the upper surface of the chip by the pattern recognition device 40 and the XY table 50, and the capillary is transferred downward and passes through the capillary. The ball formed at the end of one of the bonding wires is first bonded to the bonding pads by ultrasonic and high temperature heat while contacting the bonding pads (step 30).

After that, the capillary reaches the printed circuit pattern of the BGA printed circuit board while drawing the parabola so that the bonding wire is looped. After the bonding wire is secondarily bonded to the printed circuit pattern, the capillary upwards Is transferred (step 40).

At this time, the bonding wire 53 is subjected to a large tension, but the bonding wire 53 portion corresponding to the bent portion of the bonding wire 53 while being bonded to the printed circuit pattern is very vulnerable to external force due to concentrated stress. 53) If the tension is large, the vulnerable part will be broken.

At this time, when the bonding wire is exactly in contact with the designated position of the printed circuit pattern by the capillary, the control unit 10 determines whether a current flows in the capillary wire (step 50).

As a result of determination, when current flows while the wire bonding proceeds, the control unit 10 checks the printed circuit pattern and the bonding pad to which the wire bonding is to be performed using the pattern recognition device 40 or the like (step 60). If there is a printed circuit pattern to be bonded and a bonding pad, it feeds back to the start step and ends if it does not exist.

In step 50, the control unit 10 is able to determine the flow of the current is the capillary in a closed circuit if the wire bonding is performed correctly when the voltage of 2 [V] applied to the capillary wire is wire bonded The current flows through the wire, but if the wire bonding is not performed correctly, the current does not flow through the capillary wire without forming a closed circuit.

More specifically, when the bonding wire is correctly bonded to the designated position of the printed circuit pattern by the capillary, as shown in FIG. 7A, the printed circuit pattern is caused by a voltage of about 2 [V] applied to the capillary and the bonding wire. 2 [V] is applied. The voltage applied to the printed circuit pattern is applied to the solder ball pads 79 formed on the rear surface of the BGA printed circuit board along the printed circuit pattern.

Subsequently, a voltage of 2 [V] applied to the solder ball pads 79 is again applied to the conductive steel balls 67 and the springs 67a connected to the solder ball pads 79 and is prevented from being separated from the springs 67a. The voltage of 2 [V] applied to the cover 68 exits to the ground through the heater block body 65.

That is, a closed circuit having a path of capillary-bonding wire-printed circuit pattern-solder ball pad-conductive steel ball-spring-prevention cover-ground is formed so that the voltage of 2 [V] applied to the capillary is released to the ground. As the capillary wires flow, current flows.

As a result of the determination in step 50, if no current flow occurs while the wire bonding is in progress, the control unit 10 considers that the wire bonding failure has occurred and generates an alarm to notify the operator and at the same time, the wire bonding is no longer performed. The standby state is not performed (step 70).

More specifically, the current flow does not occur when the wire bonding fails, as shown in FIG. 7B when the bonding wire does not correctly contact the designated position of the printed circuit pattern by the capillary. This is because a closed circuit having a path of the bonding wire, the printed circuit pattern, the solder ball pad, the conductive steel ball, the spring, the anti-separation cover, and the ground cannot be formed.

Thereafter, the apparatus continues to wait until an error is corrected by an operator (step 75), and after determining whether a printed circuit pattern and a bonding pad exist to perform wire bonding when a wire bonding error is corrected (step 60), If there is a printed circuit pattern and the bonding pad to be bonded, the feedback is returned to A, and if there is no bonding circuit, the processing ends.

As described in detail above, when wire-bonding the printed circuit pattern formed on the BGA printed circuit board and the bonding pad of the chip, ground each solder ball pad connected to the printed circuit pattern on the back of the BGA printed circuit board and perform wire bonding. When the wire bonding is performed by applying power to the capillary wire to be performed, the success / failure of the wire bonding may be immediately confirmed by the current flow or no current flow of the capillary wire.

Claims (7)

Capillary installed on the XY table for wire bonding the printed circuit board formed on the printed circuit board on which the chip is attached and the die pad attached to the chip, and fixed to the work table for heating the printed circuit board to a temperature suitable for wire bonding. And a bonding temperature regulating device comprising a heater block body installed and a heater block adapter coupled to the heater block body to suck and fix the printed circuit board, a pattern recognition device and a control unit recognizing a pattern of a printed circuit board and a chip. Each solder ball pad formed on the back of the printed circuit board to be electrically connected to the printed circuit pattern formed on the front of the printed circuit board is grounded by a grounding means installed in the heater block adapter. Wire bonding equipment. 2. The heater block adapter of claim 1, wherein the grounding means comprises: a heater block adapter through hole provided in the heater block adapter to have the same position and the same number as the solder ball pads; A spring housed in the heater block adapter through hole; A conductive ground terminal inserted into the heater block adapter through hole into which the spring is inserted and contacting the solder ball pad; And a release preventing cover for closing the lower end of the heater block adapter through hole to prevent the spring and the ground terminal from being separated from the heater block adapter through hole. The wire bonding apparatus of claim 2, wherein the heater block adapter further includes a heater block adapter vacuum hole for adsorbing and fixing the printed circuit board in addition to the heater block adapter through hole. The cover of the separation prevention hole is formed in communication with the heater block adapter vacuum hole so that the heater block adapter vacuum hole is in communication with the heater block body vacuum hole by the cover through hole. Wire bonding equipment for ball grid array packages. 3. The wire bonding facility of claim 2, wherein the ground terminal is a conductive steel ball. The BGA printed circuit board is transferred to a heater block of a bonding temperature controller for heating to a wire bonding temperature, and each solder ball pad formed on the rear surface of the BGA printed circuit board is fixed to the heater block, and at the same time, a ground installed in the heater block. Grounding to the means; Wire bonding a printed circuit pattern formed on the BGA printed circuit board and a bonding pad formed on a chip attached to the printed circuit board by a capillary to which a predetermined power is applied; And determining the success / failure of wire bonding by determining whether current flows through the capillary, the printed circuit pattern, the solder ball pad, and the grounding means after wire bonding. According to claim 6, After the wire bonding, when the current does not flow through the capillary, the printed circuit pattern, the solder ball pad, the ground means means that the process is interrupted at the same time as the failure of wire bonding generates an alarm A wire bonding method characterized by the above-mentioned.