Flip Chip Packaging Flux Head Design for PCB Pad Pre-Fluxing
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Solution Overview
Problem
The conventional flip chip packaging process is hindered by the increased tact time due to the pre-coating of die bumps with flux, which decreases productivity as the process becomes more labor-intensive, especially with smaller PCBs and pads.
Innovation Solution
Implementing a pre-fluxing process where flux is printed onto the PCB pads before flip chip bonding, eliminating the need for die bump coating and enhancing productivity, along with a flux head manufacturing method using a polydimethylsiloxane (PDMS) mold with glass fiber sheets to create a flux head capable of precise flux application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bump of the die is coated with flux before mounting, then the bonding process can be completed, but the tact time increases and productivity decreases
Solution Approach 1:
Instead of coating the die bump with flux before mounting (conventional method), the patent inverts the process by pre-coating the PCB pad with flux before the die is mounted. This reversal eliminates the need for separate die handling and flux coating steps, reducing tact time while ensuring proper flux application for bonding.
Solution Approach 2:
The flux is applied to the PCB pad in advance (pre-fluxing) before the die mounting process. This preliminary action prepares the bonding surface beforehand, eliminating the need for on-demand flux application during the mounting process, thereby reducing overall process time and improving productivity.
2Reliability
If the die bump is coated with flux manually, then the bonding can be achieved, but the process becomes labor-intensive and less efficient
Solution Approach 1:
The patent replaces manual mechanical flux application with an automated flux printing system. The flux printing apparatus uses controlled dispensing mechanisms to apply flux precisely to the PCB pad, eliminating manual labor while ensuring consistent and reliable flux application for bonding.
Solution Approach 2:
The system enables self-service by integrating flux application directly into the PCB preparation process. The flux is automatically printed onto the pad during PCB processing, eliminating the need for separate manual flux coating operations on the die, thereby simplifying the overall manufacturing process.
3Area of stationary object
If conventional flux application methods are used, then flux can be applied to larger areas, but precise flux application on smaller PCBs and pads becomes difficult
Solution Approach 1:
The flux printing apparatus applies flux with local quality by precisely controlling the flux deposition location and amount. The system can adapt its application parameters to match the specific size and requirements of each PCB pad, ensuring optimal flux coverage whether the pad is large or small, thereby achieving both area coverage and precision.
Solution Approach 2:
The flux printing system is dynamic and adaptable, capable of adjusting its operation based on real-time conditions. The apparatus can modify flux application parameters (such as dispensing rate, positioning, and pattern) to accommodate varying pad sizes, ensuring precise flux application on smaller PCBs while maintaining effectiveness on larger areas.
Data Source
AI summary
Flip chip packaging methods, and flux head manufacturing methods used in the flip chip packaging methods may be provided. In particular, a flip chip packaging method including printing flux on a pad of a printed circuit board (PCB), mounting the die in a flip chip manner on the PCB such that a bump of the die faces the pad of the PCB, and bonding the bump of the die to the pad of the PCB using the flux may be provided.