Analysis of Aluminum Foil Pouch Layers
Recently, many PCB manufacturers have inquired about the number of layers in aluminum foil bags and potential air leakage during storage. Currently, the industry predominantly uses four-layer aluminum foil bags, though some suppliers opt for three-layer structures. Below, we’ll focus on explaining the standard layer composition of a four-layer aluminum foil bag.
HUAZHONG’s Four-Layer Aluminum Foil Bag Structure:
1. PET (Layer 1)
2. PA (Layer 2)
3. Aluminum Foil (Core Barrier Layer, Layer 3) – This critical layer provides high-efficiency moisture and oxygen barrier properties. To meet the stringent requirements for 5G communications, AI servers, and high-layer-count PCBs (with a water vapor transmission rate of ≤0.03g/m²·24h and oxygen transmission rate of ≤0.03cm³/m²·24h·0.1MPa), the aluminum foil must be at least 7μm thick to minimize pinholes and achieve optimal barrier performance.
4. PE Heat-Seal Layer (Layer 4) – HUAZHONG uses a proprietary high-strength PE composite film, which offers excellent heat-seal strength, flexibility, and toughness, ensuring a tight seal to protect the inner aluminum foil layer.
Key Clarification:
Some manufacturers misleadingly refer to the number of screw barrels in a film blowing machine as "multiple layers," but this is entirely different from the dry lamination process’s definition of "layers." These should only be classified as part of the PE layer, not true multilayer composites.
Industry Comparison:
Most manufacturers position the aluminum foil as the second layer (PET+AL+PA+PE). However, this design has a critical flaw: during vacuum sealing, the aluminum foil is prone to fracturing, increasing the risk of air leakage over time.
HUAZHONG’s Superior Design:
To better protect the core aluminum foil barrier and prevent breakage during vacuum sealing—ensuring long-term moisture and oxygen resistance—we place the aluminum foil as the third layer (PET+PA+AL+PE). This structure significantly enhances the foil’s durability, guaranteeing superior product stability for extended storage.