With the widespread use of multi-layer boards and HDI boards, PCB manufacturers have gradually realized a key auxiliary material that has been neglected for a long time - the cushion pad, in the process of improving the compression yield. Especially when facing complex structures such as high-order blind buried hole plates, thick copper plates, and rigid flex joint plates, pressing problems occur frequently, such as warping, bubbling, copper surface pressure damage, resin accumulation, etc. Then, how to choose the most suitable cushion pad for your product and process?

Rubber based cushioning pads, especially high-temperature neoprene rubber, are widely used in high-order HDI boards and multiple compression structures due to their excellent elasticity, pressure resistance, and thermal stability.

Advantage features: high elasticity recovery: can withstand repeated compression pressure, not easily permanently deformed; Strong shear resistance: suitable for HDI multi-stage lamination with complex blind hole structures; Stable high temperature resistance: suitable for hot pressing process at 180-220 ℃; Reusable: High cost-effectiveness, suitable for mass production lines to save costs.

Applicable scenarios: HDI blind hole pressing; Embedded copper structural plate (uneven copper thickness); High frequency hybrid structure (sensitive to changes in dielectric constant)

Attention: The rubber surface is slightly rough and needs to be used with release cloth; After long-term use, it is necessary to check for aging and cracks to prevent damage to the finished board; Not recommended for use in process environments with extremely high cleanliness (may release trace amounts of volatile compounds). Recommended thickness: 0.6~1.5mm, specific to match the product stacking thickness and pressure window.

Aramid Fiber Pad is a cushion pad made of aramid fiber as the base material, which is compressed and compounded. It has excellent thermal stability and mechanical cushioning properties, and is currently one of the most widely used cushion pads in the PCB industry.

Advantages and characteristics: Medium elasticity, good buffering, suitable for the vast majority of ordinary pressing needs; Low thermal expansion rate and good dimensional stability during the compression process; The surface is flat and does not damage the board, and there is no impact of indentation on the copper foil circuit; Easy to process and cut, suitable for various sizes and structural plates.

Applicable scenarios: 6-12 layer multi-layer PCBs; high-frequency high-speed board;

Attention: Elasticity is not as good as rubber, and if used for products with significant structural differences, the buffering capacity may be slightly insufficient; Long term use at high temperatures may result in slight delamination or pulverization, and regular replacement is recommended; For structurally complex HDI boards, it is recommended to use flexible release cloth or composite materials. Recommended thickness: 0.4~1.0mm, recommended regular thickness is 0.6mm

PI composite pad is a composite of polyimide film and polymer buffer materials (such as silicone and non-woven fabric), which combines high temperature stability, flexibility, thermal conductivity, and pressure compatibility, and is particularly suitable for high-precision compression processes.

Advantages: High temperature resistance up to 260 ℃ or above, suitable for high-speed materials/rigid flex compression bonding; The surface is super smooth, with extremely low particle size, and no pressure damage to micro line width circuits; Excellent thermal conductivity, can promote resin flow and consistent curing; Good exhaust performance, breathable but not hygroscopic, effectively preventing foaming.

Applicable scenarios: Precision HDI board (fine line width/fine aperture); High frequency high-speed communication board (such as 5G antenna); Rigid-flex board

Attention: Relatively high cost, suitable for products with high value density; Generally, it is a disposable material and the cost per use needs to be considered; The material needs to be stored against moisture to avoid performance degradation after moisture absorption. Recommended thickness: 0.3~0.8mm, for precision HDI, it is recommended to use within 0.5mm.