Circuit Module Sealing Member Separation for Stress Relief
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Solution Overview
Problem
The existing circuit modules face reliability issues due to shear stress between flat and frame substrates caused by the shrinkage of sealing members during manufacturing and thermal expansion differences, leading to potential breakage of connection members.
Innovation Solution
A circuit module design where the sealing member is separated from the inner surface of the frame substrate, using a photo-curing resin or thermosetting resin with precise shaping, and a high-melting-point connection member to prevent shear stress and ensure reliable connections, along with an anisotropic conductive resin or Sn-based solder for enhanced electrical and mechanical bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sealing member is filled in the cavity to contact the inner surface of the frame substrate, then the sealing member definitely contacts with the frame substrate to provide sealing, but shear stress occurs between the flat substrate and the frame substrate when the sealing member shrinks during solidification or expands during reflowing, which may break the connection members
Solution Approach 1:
A resin layer is introduced as an intermediary substance between the sealing member and the frame substrate. This resin layer absorbs the stress generated by thermal expansion and contraction, preventing direct stress transmission to the connection members while maintaining the sealing function. The resin layer acts as a buffer that decouples the mechanical stress from the fragile connection members.
Solution Approach 2:
The resin layer is applied in advance on the inner surface of the frame substrate before the sealing member is positioned. This pre-applied cushioning layer anticipates and prepares for the thermal stress that will occur during subsequent heating and cooling cycles, distributing and mitigating the stress before it reaches the connection members.
2Reliability
If the coefficient of thermal expansion of the sealing member is larger than that of the frame substrate, then the sealing member expands more during reflowing to push the inner surface of the frame substrate outward, but this creates opposite shear stress that may still break the connection members
Solution Approach 1:
The resin layer serves as a stress-absorbing intermediary that prevents the direct transmission of expansion forces from the sealing member to the frame substrate. During reflowing, when the sealing member expands, the resin layer deforms to accommodate this expansion, preventing the generation of shear stress on the connection members.
Solution Approach 2:
The resin layer changes its physical parameters (viscosity, elasticity) in response to temperature changes during the reflowing process. At elevated temperatures, the resin becomes more compliant, allowing it to accommodate the thermal expansion of the sealing member without transmitting stress to the connection members.
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
The solution provides highly reliable electrical and mechanical connections between the flat and frame substrates by eliminating shear stress and ensuring the connection members do not remelt during reflowing, thereby enhancing the long-term reliability of the circuit module.
Implementation Method 1
a liquid sealing member shrinks in volume at the time when the liquid sealing member solidifies
Implementation Method 2
the coefficient of thermal expansion of the frame substrate 220 and the coefficient of thermal expansion of the sealing member 230 differ from each other
Data Source
AI summary
A circuit module includes a flat substrate, a frame substrate, a first electronic component, and a first sealing member. First connection electrodes are disposed at a peripheral portion of one main surface of the flat substrate. Second connection electrodes are disposed on one main surface of the frame substrate at locations corresponding to the first connection electrodes. Each of the first connection electrodes and a corresponding one of the second connection electrodes are connected to each other via a first connection member. The first electronic component is sealed by the first sealing member. The first electronic component and the first sealing member are disposed in a cavity defined by the one main surface of the flat substrate and an inner surface of the frame substrate. The first sealing member is separated from the inner surface of the frame substrate.