Full Analysis of TGV Chip Advanced Packaging Carrier Coating

The coating on the advanced packaging carrier of TGV (Through Glass Via) chip is a multi-layer composite system, mainly including insulation/passivation coating, adhesion/barrier layer, metal seed layer, stress buffering coating and thermal management coating, which together provide electrical isolation, mechanical enhancement, thermal management and environmental protection for high-density interconnection.

Core coating material system

Insulation/passivation coating (basic guarantee)
-Silicon oxide (SiO ₂): PVD/CVD deposition, thickness 0.1-2 μ m, providing electrical isolation and moisture barrier
-Silicon nitride (Si ∝ N ₄): dense (<1nm pores), blocks water vapor and ions, enhances mechanical strength -Polyimide (PI): coating curing, insulation temperature resistance (>250 ℃), flexibility, suitable for stress buffering
-Aluminum oxide (Al ₂ O3): ALD deposition (50-200nm), atomic level uniformity, high-frequency insulation and passivation

Adhesive/Barrier Layer (Interface Bridge)
-Metal oxides: such as TiO ₂ ZnO(8–9nm)， Form chemical bonds with glass to enhance adhesion with metals (>6N/cm)
-Ti/Cu or Cr/Cu: Sputtering (50-200nm) as a barrier layer to prevent Cu diffusion and improve bonding strength
-PI: Coating on the interface, balancing adhesion and stress relaxation

Metal seed layer (conductive foundation)
-Ti/Cu or Cr/Cu: Sputtering deposition provides a conductive substrate for electroplating
-Ni-P alloy: chemical plating, uniformly covering high aspect ratio (10:1) through holes, high adhesion strength

Stress buffering coating (reliability critical)
-Low modulus PI: coated on the edge of TGV (5-10 μ m) to alleviate stress concentration caused by the CTE difference between Cu (17ppm/℃) and glass (3ppm/℃)
-Composite buffer layer: PI/SiO ₂ alternating, balancing insulation and flexibility to prevent glass cracking

Thermal management coating (performance optimization)
-Graphene/carbon nanotube coating: high thermal conductivity (~1500W/m · K), achieving rapid in-plane thermal diffusion
-Metal heat dissipation layer: Cu/Al thin film (1-5 μ m), expands the heat dissipation area and reduces thermal resistance
-Diamond coating: nano bonded with glass, thermal conductivity increased to 500W/m · K, significantly reducing chip junction temperature

The Five Core Functions of Coatings

Electrical Insulation and Circuit Protection
-Isolate adjacent TGVs from surface circuits to prevent leakage and short circuits
-Shielding electromagnetic interference to ensure high-speed signal integrity (loss)< 0.3dB@220GHz )
-As an insulation barrier between chips and metal interconnects, it prevents electrochemical corrosion

Metalization and Interconnection Enhancement
-The seed layer provides a conductive substrate for electroplating, ensuring uniform filling of TGV with metals such as Cu
-Enhance the adhesion between glass and metal (>1.0kN/m) to prevent interface delamination
-Realize conformal coverage in deep holes (depth to diameter ratio>10:1) to ensure defect free metallization

Thermal management optimization
-Build efficient heat dissipation channels and control chip temperature (<70 ℃)
-Relieve heat concentration caused by low thermal conductivity (1.1W/m · K) of glass
-Reduce thermal stress and prevent structural failure caused by temperature fluctuations

Mechanical reinforcement and environmental protection
-Passivation layer enhances bending strength (>50MPa) and prevents microcrack propagation
-Sealed structure blocks water vapor (WVTR<0.01g/m ² · day) and oxygen, extending lifespan (>10 years)
-As a physical barrier, it prevents chemical erosion and mechanical damage

Signal integrity enhancement
-Glass substrate with low dielectric constant (about 3.8, silicon about 11.9) and low loss factor significantly reduces signal loss
-Coating optimization impedance matching, reducing reflection and crosstalk, supporting 5G/6G RF and high-speed digital applications

Coating synergy: working mechanism of multi-layer composite systems

TGV coating forms a “multi-layer composite protective network”, and each layer works together:
1. Bottom insulation layer: SiO ₂/Si ∝ N ₄, providing basic electrical isolation
2. Intermediate functional layer: adhesive layer+seed layer+conductive metal (Cu), achieving vertical interconnection
3. Stress relief layer: low modulus materials such as PI to alleviate interfacial stress
4. Surface protective layer: Si ∝ N ₄/PI composite passivation, balancing environmental and mechanical protection

Summary

The advanced packaging carrier coating of TGV chips is not a single material, but a multi-layer composite system that works together, serving as an “invisible guardian” for the interconnection between glass substrates and metals. They work synergistically in electrical insulation, metallization enhancement, thermal management, mechanical protection, and signal integrity, making TGV technology a key support for the next generation of advanced packaging, particularly suitable for high-performance applications such as 2.5D/3D integration, AI acceleration chips, and optoelectronic co packaging (CPO). With the development of technology, coating materials are evolving towards ultra-thin, high thermal conductivity, and high integration to meet the demand for higher performance chip packaging in the future.

Ultrasonic spraying is the core preparation process for advanced packaging carrier coatings of TGV chips, accurately matching their high-density integration and high reliability requirements. This process can uniformly deposit insulating passivation materials such as SiO ₂, Si ∝ N ₄, PI, etc., forming a dense protective layer to achieve circuit isolation and water oxygen barrier; Suitable for low modulus stress buffering coatings, effectively alleviating stress concentration caused by the difference in CTE between glass and metal, and avoiding substrate cracking. Its atomization accuracy is excellent, with a coating thickness deviation of less than ± 5%. It can form conformal coverage on the surface of high aspect ratio TGV through holes, with strong adhesion and low porosity. The low-temperature process does not damage the glass substrate, ensuring high-speed signal integrity and heat dissipation efficiency, providing stable coating support for high-end scenarios such as 2.5D/3D integration, AI acceleration chips, CPO, etc., helping the carrier board achieve high interconnect density and long life.

About Cheersonic

Cheersonic is the leading developer and manufacturer of ultrasonic coating systems for applying precise, thin film coatings to protect, strengthen or smooth surfaces on parts and components for the microelectronics/electronics, alternative energy, medical and industrial markets, including specialized glass applications in construction and automotive.

Our coating solutions are environmentally-friendly, efficient and highly reliable, and enable dramatic reductions in overspray, savings in raw material, water and energy usage and provide improved process repeatability, transfer efficiency, high uniformity and reduced emissions.

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