Gang Flipping IC Packaging Using Releasable Mount Tape
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Solution Overview
Problem
Conventional flip-chip die attach machines are expensive and less efficient compared to conventional die attach machines, limiting the ability to efficiently package solder bumped dice for applications requiring low pin counts, such as micro surface-mount devices.
Innovation Solution
A method involving a releasable mount tape to singulate and handle individual solder bumped dice, allowing their attachment to substrates using conventional die attach machines, which are faster and more cost-effective, without the need for expensive flip-chip die attach machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional flip-chip die attach machines are used, then die attachment can be performed, but the equipment cost is high and production efficiency is low
Solution Approach 1:
The process is segmented into distinct stages: mounting dice to carrier tape, forming solder bumps, singulating the carrier tape with dice, and transferring to final substrate. This segmentation allows conventional machines to handle each stage separately, avoiding the need for expensive integrated flip-chip systems.
Solution Approach 2:
A carrier tape serves as an intermediary device that holds multiple dice during processing. The tape allows conventional die attach machines to pick up and place dice individually while maintaining the flip-chip configuration, bridging the gap between conventional equipment and flip-chip requirements.
2Ease of manufacture
If solder bumps are formed after mounting to tape, then the process sequence is simplified, but the tape must be removed later adding complexity
Solution Approach 1:
Solder bumps are formed on the dice while they are still mounted on the carrier tape, before singulation occurs. This preliminary action simplifies the manufacturing sequence by eliminating the need for complex repositioning operations later in the process.
Solution Approach 2:
The carrier tape is selectively removed from the back surface of the dice after singulation, leaving the dice with exposed back surfaces. This extraction is performed using simple mechanical means rather than complex release mechanisms.
3Productivity
If the carrier tape is cut completely through during singulation, then individual dice are separated, but the dice lose support and may be damaged
Solution Approach 1:
The carrier tape is singulated in a controlled manner where cuts are made through the tape material but stop before completely separating the dice. This local quality control ensures the tape maintains sufficient structural integrity to support dice during handling while still enabling individual dice separation.
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
Enables high-speed attachment of up to 8,000 flip-chip dice per hour using conventional machines, reducing costs and improving efficiency while maintaining die registration and minimizing damage during the singulation and flipping process.
Implementation Method 1
the back surface of the wafer is mounted and adhered to a first releasable mount tape
Implementation Method 2
Solder bumps are formed on the bond pads to form a bumped wafer
Implementation Method 3
The bumped active surfaces of the singulated dice are then adhered to a second tape
Data Source
AI summary
A method of handling an IC wafer that includes a multiplicity of dice is described. Solder bumps are formed on bond pads on the active surface of the wafer. The back surface of the bumped wafer is adhered to a first mount tape. The wafer is singulated while it is still secured to the first tape to provide a multiplicity of individual dice. The active surfaces of the singulated dice are then adhered to a second tape with the first tape still adhered to the back surfaces of the dice. The first tape may then be removed. In this manner, the back surfaces of the dice may be left exposed and facing upwards with the active surfaces of the dice adhered to the second tape. The described method permits the use of a conventional die attach machine that is not designated for use as a flip-chip die attach machine.