Backside Mold Configuration for IC Substrate Warpage Control
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Solution Overview
Problem
The shrinking thickness of packaging substrates in integrated circuits leads to warpage during manufacturing, causing electrical failures due to disconnections and oxidation of contact pads, which reduces the reliability of electronic connections.
Innovation Solution
A backside mold compound (BSMC) is deposited on the side of the packaging substrate opposite the die, adding stiffness to reduce warpage and supporting packaging connections, while a dielectric is used to pattern and expose contact pads after die attach, minimizing exposure to high temperatures and environmental damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the packaging substrate thickness is reduced to achieve smaller form factor devices, then the device size is reduced, but the substrate stiffness decreases causing warpage during manufacturing
Solution Approach 1:
The patent uses a composite structure combining the thin packaging substrate with a mold compound encapsulant. The mold compound acts as a reinforcing material that compensates for the reduced stiffness of the thin substrate, preventing warpage during solder reflow and other manufacturing processes while maintaining the small device form factor.
Solution Approach 2:
The patent applies mold compound to the backside of the substrate, adding structural support in the thickness dimension rather than increasing the planar dimensions. This allows the device to maintain its small footprint while gaining the stiffness needed to prevent warpage through vertical reinforcement.
2Volume of moving object
If the substrate is made thinner to reduce device size, then the form factor is improved, but warpage occurs during heating processes causing connection failures
Solution Approach 1:
The composite structure of thin substrate plus mold compound encapsulant provides thermal stability during heating processes. The mold compound has different thermal expansion characteristics that compensate for substrate warpage, ensuring connections remain intact during solder reflow and other high-temperature manufacturing steps.
Solution Approach 2:
The patent modifies the physical parameters of the packaging structure by introducing mold compound with specific mechanical and thermal properties. This changes the overall thermal expansion behavior and stiffness of the package, enabling thin substrates to withstand manufacturing heat without warping or connection failure.
3Ease of manufacture
If contact pads are exposed during manufacturing processes, then connections can be made, but oxidation occurs at high temperatures reducing connection reliability
Solution Approach 1:
The contact pads are exposed and connections are established before the mold compound is applied and cured. This preliminary action allows connections to be made when pads are accessible, while subsequent application of mold compound protects the exposed pads from oxidation during remaining manufacturing processes and operation.
Solution Approach 2:
The mold compound serves as a protective intermediary layer that covers and protects the contact pads and packaging connections from atmospheric exposure. This intermediary barrier prevents oxidation while allowing the connections to be established earlier in the manufacturing process when pads are accessible.
Data Source
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AI summary
A backside mold configuration (BSMC) process for manufacturing packaged integrated circuits includes applying a mold compound to a side of a packaging substrate opposite an attached die. The mold compound is deposited on a dielectric (such as photo resist). The mold compound and dielectric are patterned after coupling a die to the packaging substrate to expose a contact pad of the packaging substrate. After patterning the mold compound and dielectric, a packaging connection is coupled to contact pads through the mold compound and dielectric. The mold compound surrounding the packaging connection reduces warpage of the packaging substrate during processing. Additionally, patterning the dielectric after attaching the die improves reliability of the packaging connection.