What is C4
In the context of the PCB industry, C4 has multiple meanings depending on the specific context. One interpretation of C4 is as standard IBM solder balls used in flip-chip bonding. These C4s come in various sizes and pitches, with examples being “3 on 6” (mil) and “4 on 8”. They serve as on-chip electrodes that are compatible with the standard CMOS process, requiring minimal post-processing and offering low cost and high yield. C4s are crucial for flip-chip bonding, enabling the integration of penetrating electrodes with the presented IC for single unit recording.
Another interpretation of C4 relates to its use in impedance analysis and measurement. In this context, C4 represents a specific electrode or component used in the PCB industry. It is associated with the MINS chip and is wired to external pads for separate access. Impedance characteristics of the C4 electrodes are analyzed using low-frequency signal generators and transimpedance op-amps. The obtained values of resistance (R) and capacitance (C) provide a model for a single C4.
Additionally, C4 can also refer to the controlled collapse of chip connection in the BGA packaging process. It involves depositing solder bumps on chip pads, mounting the chip to external circuitry through a substrate, and then flipping the chip over to complete the connection process. C4 is a well-proven and widely used technology in BGA assemblies, offering a cost-effective alternative to other methods like C2.
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