Wire Bonding Scrub Settings for Aluminum Splash Control
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Solution Overview
Problem
The challenge of attaching copper bond wires to small bond pads with aluminum cap layers without causing aluminum splash, which can lead to short circuits due to the heating effect during ultrasonic bonding, especially as bond pad sizes decrease.
Innovation Solution
A method involving different table scrubbing settings during ultrasonic bonding to manage aluminum splash, where the capillary moves in the Y-direction and the table scrubs in the X-direction, with specific scrub settings for bond pads on opposing sides to minimize splash onto the passivation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper wire is bonded to bond pad using ultrasonic bonding, then electrical characteristics and cost are improved, but aluminum splash occurs causing short circuits
Solution Approach 1:
The patent applies dynamics by implementing table scrubbing motion during the ultrasonic bonding process. The table moves in a scrubbing direction (perpendicular to capillary motion) at controlled speeds and amplitudes, dynamically controlling the bonding interface to prevent aluminum splash while maintaining reliable copper wire bonding to bond pads with aluminum cap layers
Solution Approach 2:
The patent changes physical parameters by introducing table scrubbing with specific speed ranges (0.5-5 mm/s) and amplitude ranges (5-50 µm). These parameter adjustments modify the bonding process to reduce aluminum heating and splash, enabling reliable bonding to small bond pads (43 µm or less) without compromising bond reliability
2Area of moving object
If bond pad opening size is reduced, then integration density is improved, but aluminum splash increases causing short circuits
Solution Approach 1:
The patent uses table scrubbing motion to dynamically control the bonding process on small bond pads. By moving the table perpendicular to capillary motion at controlled speeds and amplitudes, the process accommodates reduced bond pad opening sizes (43 µm or less) while preventing aluminum splash that would otherwise occur on such small, confined bonding areas
Solution Approach 2:
The patent adjusts process parameters including table scrubbing speed (0.5-5 mm/s) and amplitude (5-50 µm) to specifically address bonding on small bond pads. These parameter changes reduce the heating effect on aluminum cap layers during bonding to miniaturized bond pads, preventing aluminum splash while maintaining bonding effectiveness on high-density interconnect structures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces aluminum splash, preventing bond failures and short circuits, particularly for bond pads with openings of 43 um or less, by controlling the direction and extent of splash, thereby enhancing the reliability of copper wire bonding.
Implementation Method 1
performing a table scrubbing simultaneously with the moving of the capillary. The moving of the capillary comprises performing an ultrasonic bonding process in which the capillary moves back and forth in the Y-direction
Implementation Method 2
performing a table scrubbing simultaneously with the moving of the capillary... the table scrubbing is performed in the X-direction
Implementation Method 3
the rubbing of the copper wire against the aluminum cap layer heats the aluminum and causes it to splash
Data Source
AI summary
A method of attaching bond wires to bond pads on an active surface of a semiconductor die, where the bond pads are disposed along four side edges of the die, and have aluminum top layers. The method includes attaching first bond wires to first bond pads on first and second opposing sides of the die using a first group of settings and attaching second bond wires to the bond pads on third and fourth sides of the die that oppose each other and are adjacent the first and second sides, using a second group of settings. The first and second groups of settings include first and second scrub settings that are different from each other. Employing two separate scrub settings allows for reduced splashing of the aluminum cap layer on the die pad from splashing onto passivation edges of the bond pads.