RDL-First Packaging Process for Semiconductor Alignment
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Solution Overview
Problem
In the packaging of semiconductor chips, the formation of Redistribution Lines (RDLs) after molding processes leads to alignment issues and stress-induced shifts, making it difficult to achieve fine-line RDLs without overlay misalignment.
Innovation Solution
Forming front-side RDLs before the molding process to avoid stress-induced shifts and improve alignment, followed by flip-chip bonding of device dies and subsequent packaging steps, including the formation of through-vias and solder regions, to enhance package integration and alignment precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If RDLs are formed after molding process, then packaging process can proceed in conventional sequence, but alignment precision deteriorates due to stress-induced shifts
Solution Approach 1:
The patent applies preliminary action by forming the Redistribution Lines (RDLs) before the molding process instead of after. This sequence reversal allows the RDLs to be established on the carrier substrate while stress-free, preventing subsequent stress-induced alignment shifts that would occur if RDLs were formed after molding. The RDLs are created, patterned, and cured in advance, then the molding compound is applied, eliminating the alignment precision problem entirely.
2Device complexity
If RDLs are formed after molding process, then process sequence remains simple, but overlay misalignment occurs due to stress
Solution Approach 1:
The invention resolves the overlay misalignment issue by performing the RDL formation action preliminarily, before the molding process introduces stress. The RDLs are completely formed, patterned, and cured on the carrier substrate before the molding compound is applied. This preliminary completion of RDL formation ensures that no subsequent stress from molding can cause overlay shifts, while the overall process complexity remains manageable through this sequence optimization.
Data Source
AI summary
A method includes forming a first plurality of Redistribution Lines (RDLs) over a carrier, and bonding a device die to the first plurality of RDLs through flip-chip bonding. The device die and the first plurality of RDLs are over the carrier. The device die is molded in a molding material. After the molding, the carrier is detached from the first plurality of RDLs. The method further includes forming solder balls to electrically couple to the first plurality of RDLs, wherein the solder balls and the device die are on opposite sides of the first plurality of RDLs.