Flip Chip Flux Dotting to Prevent Evaporation
Solution Overview
Problem
Conventional methods for manufacturing flip chip packages face challenges with the evaporation of flux during the attachment process, leading to insufficient adhesion strength between conductive bumps, which can result in improper electrical connections.
Innovation Solution
A method and apparatus that dot flux directly onto preliminary bumps of a package substrate immediately before attaching semiconductor chips, using a flux-dotting unit and chip-attaching unit to prevent flux evaporation and ensure timely attachment, followed by reflow processes to form conductive bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flux is coated on the entire surface of the package substrate before attaching semiconductor chips, then the flux coating process is simple, but the flux evaporates during the attachment process leading to insufficient adhesion strength
Solution Approach 1:
The patent divides the flux coating process into two stages: first coating flux on the entire package substrate surface, then adding additional flux only on preliminary bumps that have not yet been attached to semiconductor chips. This segmentation ensures that unattached bumps receive fresh flux while already-attached bumps are not affected, preventing flux evaporation issues and maintaining sufficient adhesion strength throughout the multi-chip attachment process.
2Measurement precision
If the chip-attaching unit holds the semiconductor chip between the chip position and flux reservoir, then the chip can be positioned accurately, but the coating time becomes too long
Solution Approach 1:
The patent performs preliminary flux coating on the entire package substrate surface before the semiconductor chip attachment process begins. This preliminary action ensures that flux is already present on the substrate, eliminating the need for time-consuming flux coating operations during chip attachment. The chip-attaching unit can then focus solely on precise chip positioning and attachment without waiting for flux coating, significantly reducing overall processing time while maintaining positioning accuracy.
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 enhances the adhesion strength between semiconductor chips and package substrates, improving electrical connections by ensuring a sufficient amount of flux is retained during the attachment process.
Implementation Method 1
The flux may include an adhesive, an oxide remover, etc. The oxide remover may remove a native oxide layer on the preliminary bumps.
Implementation Method 2
The flux may include an adhesive, an oxide remover, etc. The adhesive may attach the preliminary bumps to each other.
Implementation Method 3
The conductive bump may be formed by a reflow process on preliminary bumps of the semiconductor chip and the package substrate.
Data Source
AI summary
A method and apparatus to manufacture a flip chip package includes dotting a flux on a first preliminary bump of a package substrate, attaching a preliminary bump of a first semiconductor chip to the first preliminary bump of the package substrate via the flux, dotting a flux on a second preliminary bump of the package substrate, and attaching a preliminary bump of a second semiconductor chip to the second preliminary bump of the package substrate via the flux. Accordingly, an evaporation of the flux on the preliminary bump of the package substrate may be suppressed.