BCB Bonding Layer for Moisture-Resistant Chip Packages
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Solution Overview
Problem
Chip packages in optics face issues such as moisture damage due to hygroscopic polymer layers, film warpage from unspecific film thickness, and electrostatic stress from poorly designed dummy pads, which compromise product reliability.
Innovation Solution
A chip package design featuring a Benzocyclobutene (BCB) bonding layer between substrates to prevent moisture ingress, combined with a transparent conductive layer and anti-reflection layers to manage stress, and strategically placed conductive pads to mitigate capacitance and electrostatic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polymer layer with hygroscopic property is used to bond the chip with the lower translucent film, then bonding strength is improved, but moisture is absorbed in the cavity causing damage to the chip package
Solution Approach 1:
The patent changes the material parameter of the bonding layer from hygroscopic polymer to non-hygroscopic BCB (Benzocyclobutene) material, eliminating moisture absorption while maintaining bonding functionality. This parameter change resolves the contradiction by preserving bonding strength without the harmful moisture absorption effect.
Solution Approach 2:
The patent uses a composite structure where the BCB bonding layer is integrated with the chip and translucent films. The BCB material provides both bonding function and moisture barrier properties, combining multiple functions into a single material layer that resolves the contradiction between bonding strength and moisture resistance.
2Ease of manufacture
If the translucent film thickness is not specifically designed, then manufacturing simplicity is maintained, but film warpage occurs due to film stress
Solution Approach 1:
The patent establishes specific thickness parameters for the translucent film (first translucent film: 50-200 μm, second translucent film: 50-200 μm) to control film stress and prevent warpage. By defining precise thickness ranges, the patent maintains manufacturing simplicity while ensuring film stability and flatness.
3Adaptability or versatility
If the dummy pad location is not specifically designed, then design flexibility is maintained, but capacitance effect and electrostatic stress deconstruct the chip package
Solution Approach 1:
The patent specifies that the dummy pad must be located at a distance of 10-50 μm from the edge of the chip. This localized positioning requirement ensures that the dummy pad is placed in a specific region that minimizes capacitance effects and electrostatic stress concentration, thereby protecting chip package integrity while maintaining overall design flexibility.
4Volume of stationary object
If a hollow structure is created in the bonding layer, then cavity formation is achieved, but moisture accumulation damages the chip package
Solution Approach 1:
The patent eliminates the hollow cavity structure in the bonding layer by using BCB material that can be deposited as a solid, non-porous layer. This parameter change in the bonding layer structure removes the space where moisture could accumulate, preventing moisture damage while maintaining the necessary bonding function and optical transparency.
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 effectively prevents moisture entry, reduces warpage, and enhances reliability by using a non-water-absorbing BCB bonding layer and carefully designed substrate thicknesses, along with anti-reflection and conductive layers to manage stress and electrical interference.
Implementation Method 1
The bonding layer is located between the lower substrate and the first silicon nitride substrate, and made of a material comprising Benzocyclobutene (BCB)... the bonding layer may not only be formed on the lower substrate and/or the first silicon nitride substrate by coating, but also fill up the space between the lower substrate and the first silicon nitride substrate after bonding. Moreover, the bonding layer is not water-absorbing.
Implementation Method 2
A chip package design featuring a Benzocyclobutene (BCB) bonding layer between substrates to prevent moisture ingress, combined with a transparent conductive layer and anti-reflection layers to manage stress
Implementation Method 3
The location of the dummy pad of the chip package is also not specifically designed. This may cause a capacitance effect, and electrostatic and electrical stress may deconstruct the chip package
Data Source
AI summary
A chip package includes a lower substrate, a first silicon nitride substrate, a bonding layer, an upper substrate, a first functional layer, a transparent conductive layer, an isolation layer, and a first conductive pad. The supporting layer is located between the lower substrate and the first silicon nitride substrate, and is made of a material including Benzocyclobutene (BCB). The upper substrate is located on the first silicon nitride substrate. The first functional layer is located between the upper substrate and the first silicon nitride substrate. The transparent conductive layer is located on the upper substrate. The isolation layer covers the upper substrate and the transparent conductive layer. The first conductive pad is located in the isolation layer and in electrical contact with the transparent conductive layer.