Interconnection technology and process of insulating coating bonded copper wire

1. Introduction

Analyze various technical difficulties in the interconnection of Stand-off Stitch Bond (SSB) bonded with insulating coating bonding and copper wire bonding in lead frame packages, and study and validate solutions. From the aspects of chips, tools, materials, and processes, the key influences of chip surface quality, bonding fixtures, and bonding splitting knives on the SSB process of insulating coating bonded copper wire were analyzed. The stability of the size of the airless ball (FAB) under different shielding gases and the stability of the shape of the FAB in different protection devices are studied, as well as the technology to prevent damage to the SSB-bonded pads of insulating coating-bonded copper wires and to control "aluminum extrusion". The key points and improvement methods of SSB process control are determined, and the effectiveness of the measures and methods is confirmed by experiments.

The wire bonding process is dominant in integrated circuit lead frame packaging technology. Due to the advantages of insulating coating bonded copper wire in terms of cost, electrical properties, mechanical properties and reliability, the bonding technology of insulating coating bonded copper wire has become the main welding process technology. SSB (Stand-off Stitch Bond) bonding of insulating coating-bonded copper wire is a process method in insulating coating-bonded copper wire bonding, that is, first planting a solder ball at the chip or pin position, and then performing a normal welding wire, and welding the second solder point of the normal solder wire to the ball implantation point, so as to complete the entire welding process. The SSB process is used in the interconnection of multiple chip functions, with the aim of enabling multiple chips to be integrated in a single package to achieve complete connection and output of functions.

Due to the high hardness and easy oxidation characteristics of insulating coating bonded copper wire, the SSB bonding process of insulating coating bonded copper wire is difficult. With the rapid development of the application of insulating coating bonded copper wire technology, the number of products that require chip interconnection such as multi-chip, stacked chip, multi-layer wiring and so on is increasing, in order to make the packaging technology such as insulating coating bonded copper wire interconnection process be rapidly applied, and the quality and reliability are sufficiently guaranteed, the difficulties and process control of insulating coating bonded copper wire SSB interconnection technology are studied.

2. Analysis of principles and technical difficulties

1. The SSB process is mainly used in multi-chip components or stacked chip products, and the insulating coating bonded copper wire SSB process is shown in Figure 1. SSB soldering wire mainly includes three types of wiring methods: 1) inter-pad wiring between chips, that is, from one chip to another; 2) Wiring between pads of the same chip, that is, connecting between 2 or more pads on the same chip; 3) Reverse line from the frame carrier or inner tube pin to the pad of the chip, first plant the ball on the chip, and then line the ball planting point on the chip from the frame carrier or inner tube foot.