JPS624331A - Wire bonding method - Google Patents

Abstract

PURPOSE:To improve junction strength by covering the bonding wire junction part on a substrate side with solder. CONSTITUTION:Solder paste is applied to a conductor pad 2 formed on an insulating substrate 1 out of gold, Ag/Pd, copper or the like except a bonding wire junction part. After a semiconductor chip 5 is die-bonded on a die-bonding pad 4, ends of a bonding wire 7, made of solderable metal such as gold, are brought into contact with the bonding pad 6 on the chip 5 and the corresponding conductor pad 2 and contact bonding is carried out by applying heat or ultrasonic wave. Then solder 8 on the pad 2 is heated to melt so as to cover the junction part of the pad 2 and the wire 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a wire bonding method that improves the bonding strength between a conductor pad and a bonding wire.

[Technical Background of the Invention] In recent years, hybrid integrated circuits have been increasingly used to make electronic devices smaller and lighter. Methods for mounting ICs in this hybrid integrated circuit include a mounting method using a plastic package and a wire bonding method in which a semiconductor chip is mounted on a circuit board using bonding wires.

Among these methods, the wire bonding method has conventionally been carried out using the following procedure.

That is, as shown in FIG. 4, gold and silver are deposited on the insulating substrate 1.
A semiconductor chip 5 is bonded using a conductive adhesive or the like onto a die bond pad 4 on a circuit board 3 formed with a conductor circuit and a conductor pad 2 made of palladium (A!II/Pd), copper, etc., respectively. After that, the bonding pads 6 on the semiconductor chip 5 and the corresponding conductor pads 2 are bonded using the bonding wire 7 and heat or ultrasonic waves are applied thereto to cause in-phase diffusion between the phases.
An electrical connection is being made.

And the 5th r! As shown in 11, active electronic components 8 such as capacitors and resistors are mounted on a circuit board 3 together with a semiconductor chip 5 to produce a hybrid integrated circuit. Code 9 in the figure
1 is a fixed solder for the electronic component 7, and 10 is a sealing resin. The method for manufacturing this hybrid integrated circuit is as shown in the flowchart of FIG. 6. After printing and applying solder paste to a predetermined portion of a circuit board, mounting active electronic components and joining them by reflow soldering, The semiconductor chip is die-bonded by applying a conductive adhesive onto the die-bonding pad, then the bonding wire is connected to perform wire bonding, and finally the outside of the semiconductor chip is sealed with a sealing resin.

[Problems with the Background Art] However, in conventional wire bonding methods, gold wire is usually used as the bonding wire 7, so if the conductor pad 2 is made of gold, the bonding reliability is high but the cost is high. was there.

Furthermore, when the conductor pad 2 is made of a low-cost material such as Aa/Pd or copper, solid phase diffusion between the two phases due to heat or ultrasonic waves does not occur sufficiently, and the bonding strength of the bonding wire 7 is low. There was a problem.

[Object of the Invention] The present invention was made to solve such problems, and an object of the present invention is to provide a wire bonding method that is low in material cost and has high reliability in electrical connection of bonding wires. .

[Summary of the Invention] That is, the wire bonding method of the present invention involves die-bonding a semiconductor chip to a predetermined position on a circuit board, and connecting bonding pads on the semiconductor chip and corresponding conductor pads on the circuit board with bonding wires. In this method, solder is applied to the surface of the conductor pad except for the bonding wire joint, and the end of the bonding wire that can be soldered is placed on the joint of the bonding pad and the conductor pad. The bonding strength between the conductor pad and the bonding wire is improved by applying heat or ultrasonic waves to each, and then heating and melting the solder.

[Embodiment of the Invention] An embodiment of the present invention shown in the first vA will be described below. In FIG. 1, parts common to those in FIG. 4 are designated by the same reference numerals, and their explanations will be omitted.

First, as shown in FIG.
After applying the paste and die-bonding the semiconductor chip 5 onto the die-bonding bat 4, the bonding pads 6 on the semiconductor chip 5 and the corresponding conductor pads 2 are bonded.
The end portions of bonding wires 7 made of metals that can be soldered, such as gold, are brought into contact with each other, and heat or ultrasonic waves are applied thereto to compress them.

Next, as shown in FIG. 1(b), the solder 8 on the conductor pad 2 is heated and melted, and the joint between the conductor pad 2 and the bonding wire 7 is covered with the solder 8.

As described above, according to the method of the present invention, the joint between the conductor pad 2 and the bonding wire 7 is covered with the solder 8, and the joint is reinforced with the solder 8, so that A! Even when using II/Pd or copper, the electrical connection is highly reliable. Furthermore, as shown in Figure 2, the bonding strength between wire bonding using the method of the present invention and conventional bonding methods using only heat or ultrasonic waves is clear from a comparison of the strength distribution. In this way, the method of the present invention is superior.

Furthermore, in general, when crimping the bonding wire 7 using heat, it is necessary to preheat the circuit board 3 in advance, but in the method of the present invention, this heating temperature is set to a temperature of 150° C. or lower at which the solder 8 does not melt. However, by making this heating also serve as preheating during soldering of active electronic components other than the semiconductor chip 5, the process can be shortened.

FIG. 3 shows a process of fabricating a hybrid integrated circuit by mounting the semiconductor chip 5 and simultaneously mounting active electronic components on the circuit board 3 according to the method of the embodiment.

[Effects of the Invention] As is clear from the above description, according to the wire bonding method of the present invention, bonding strength can be improved by covering the bonding wire bonding portion on the substrate side with solder. Furthermore, in the fabrication of hybrid integrated circuits, active electronic components such as capacitors and resistors can be mounted in the shortest process steps without adding any extra steps.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the wire bonding method of the present invention, and FIG. 2 is a comparison of the tensile strength distributions of joints obtained by the wire bonding method of the present invention and the conventional wire bonding method. 3 is a flowchart showing the process of manufacturing a hybrid integrated circuit using the wire bonding method of the present invention, FIG. 4 is a cross-sectional view showing the conventional wire bonding method, and FIG. FIG. 6 is a cross-sectional view of the wire bonding method of FIG. 1......Insulating board 2...Conductor pad 4...
・・・・・・Die bond pad 5・・・・・・・・・・・・
...Semiconductor chip 7...Bonding wire 8...Solder applicant Toshiba Corporation

Claims (1)

[Claims] (1) In a method in which a semiconductor chip is die-bonded to a predetermined position on a circuit board, and a bonding pad on the semiconductor chip and a corresponding conductor pad on the circuit board are electrically connected by a bonding wire, the conductor pad After applying solder to the surface of the bonding wire except for the joint part thereof, the ends of the solderable bonding wire are bonded by applying heat or ultrasonic waves to the joint part of the bonding pad and the conductor pad, respectively, and then A wire bonding method characterized in that the solder is heated and melted to bond the conductive pad and the bonding wire to improve the bonding strength between the two.