MEMS Transducer Packaging With Low-Modulus Paste
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Solution Overview
Problem
Conventional packaging methods for MEMS transducer devices, such as membrane-based speakers, using epoxy-based or polyamide-based glues/resins reduce the internal volume of acoustic cavities and cause warpage due to high Young's modulus adhesives like biadhesive tapes, leading to undesirable deformation and acoustic characteristic degradation.
Innovation Solution
A method involving a semiconductor die with a sealing layer on the back side and a paste layer between the sealing layer and the package inner surface for coupling, using a low Young's modulus adhesive paste that does not penetrate the cavities, combined with a sealing layer like biadhesive tape or dry resist to prevent volume reduction and warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy-based, polyamide-based, or acrylic-based glues or resins are used for bonding the semiconductor body to the package, then strong bonding strength is achieved, but the internal volume of the cavities is reduced and membrane warpage occurs
Solution Approach 1:
The patent segments the adhesive application into two distinct functional zones: a sealing layer that closes the cavity openings without penetrating inside, and a bonding layer that provides strong adhesion between the semiconductor body and package substrate. This segmentation allows each layer to perform its specific function optimally without interfering with the other.
Solution Approach 2:
The patent introduces a sealing layer as an intermediary element between the bonding adhesive and the cavity interior. This sealing layer acts as a barrier that prevents the bonding adhesive from penetrating into the cavities, thereby maintaining cavity volume while still allowing strong bonding to occur.
2Strength
If epoxy-based, polyamide-based, or acrylic-based glues or resins are used for bonding the semiconductor body to the package, then strong bonding strength is achieved, but membrane warpage and deformation occur due to high Young's modulus
Solution Approach 1:
The patent segments the adhesive system into a sealing layer and a bonding layer with distinct material properties. The sealing layer uses high-modulus material for structural integrity, while the bonding layer uses low-modulus material that accommodates thermal expansion differences without transmitting excessive stress to the membranes.
Solution Approach 2:
The patent changes the material parameter (Young's modulus) of the bonding adhesive to a low value (0.1-30 MPa) specifically for the bonding layer, while the sealing layer maintains higher modulus for structural function. This parameter optimization reduces stress transmission to the membranes during bonding and thermal cycling.
3Reliability
If biadhesive tapes with high Young's modulus are used for sealing, then cavity sealing is achieved, but membrane warpage occurs due to the high elastic modulus causing deformation
Solution Approach 1:
The patent separates the sealing function from the bonding function into distinct layers. The sealing layer uses biadhesive tape with high Young's modulus to provide rigid cavity closure, while the bonding layer uses low-modulus adhesive to bond the semiconductor body to the package substrate without transmitting warpage-inducing stresses to the membranes.
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
Significantly reduces membrane deformation and maintains acoustic characteristics by preventing adhesive penetration into cavities and using adhesives with low elastic modulus to avoid warpage, while simplifying the manufacturing process.
Implementation Method 1
a paste layer located between the sealing layer and said inner surface of said package for coupling the die to the package
Implementation Method 2
a biadhesive tape is used as a sealing layer to maintain cavity integrity
Data Source
AI summary
A packaged MEMS transducer device comprising: a die, including: a semiconductor body having a front side and a back side, opposite to one another in a first direction, at least one cavity extending through the semiconductor body between the front side and the back side, and at least one membrane extending on the front side at least partially suspended over the cavity; and a package designed to house the die on an inner surface thereof. The transducer device moreover includes a sealing layer extending on the back side of the semiconductor body for sealing the cavity, and includes a paste layer extending between the sealing layer and the inner surface of the package for firmly coupling the die to the package.