Wire bonding: new challenges
In semiconductor packaging sector, wire bonding technique is an evergreen field. More than 75% of all IC-elements in 2018 contained primary wire-bond interconnections, which indicates the dominant and growing interest in wire-bonding technologies.
Well, that’s not a surprise. Every year, the main challenges for the global market for micro-electromechanical components and systems are miniaturization and augmented performance capabilities. If you want togive a run for one’s money in your business, you need to not only keep up with the new technologies but also understand the wire bonding process.
What modern wire bonding methods are there?
There are three main ways to connect wires to pads:
- The thermo-compression method where the bonding pad and capillary, a capillary-like tool for wire transfer, are heated and compressed for connection;
- a method of bonding, by applying ultrasonic waves to the capillary without using heat;
- and a complex method that uses both heat and ultrasonic waves at the same time — thermosonic.
The most commonly used method in the semiconductor process is the thermosonic method, which combines the advantages of the thermos-compression method and the ultrasonic method. Since the bonding strength is more important than the cost in the semiconductor back-end process, the thermosonic method using gold wires is mainly adopted despite the high cost.
The material of wires is determined by combining the most suitable methods, considering various parameters for bonding. Typical wire materials include gold (Au), aluminum (Al), and copper (Cu). Among them, gold is mostly used for semiconductor packaging.
However, a lot depends on the needs. For example, compared to aluminum wedge bonding, gold ball bonding is significantly faster due to being non-directional, resulting in its widespread use in plastic packaging.
ABC Assembly semiconductor packaging capabilities include a large range of processes: precise dispensing, die placement, gold ball bonding, gold or aluminum wire or ribbon wedge bonding with tight control of pull and shear parameters.
How to stay out of trouble?
Just like soldering, wire bonding appears to be a simple process and is frequently taken for granted. Layman tends to think all that is required to have a high-quality bonding process is a simple wire pull test to monitor and control the process. But it’s deeper than that.
And so that your equipment does not suffer from corrosion, short circuit or combustion, it is better to check the quality in advance, using tests.
For example, we at ABC Assembly use the following tests:
- Pull Test
The wire pull test is used to measure the strength and failure mode of the wire bond. Pull Test is a destructive test & it’s a Statistical Process Control monitor at all of National Semiconductors’ Assembly sites.
- Ball Shear Test
Ball shear test is another method for evaluating the quality of a ball bond. The bond strength and failure mode are measures of the ball bond quality.
A correct understanding of the conditions of use and metallic systems are often the most important factors in improving the reliability of the wire connection and for the success of your electronics.