Short answer: PCB kraft paper is a dense, high-purity kraft fibre sheet. In drilling it is the base material of phenolic backup boards (PHE grade), where the kraft is saturated with phenolic resin and cured into a rigid, flat sheet that supports the drill bit on exit, controls burr and protects the drill on breakout. In lamination it is used as press packing paper between stacked booklets. It is the high-temperature kraft base behind clean exit and low burr on paper-backed (phenolic) backup boards. For the stack decision it feeds into, the PCB backup board selection guide starts from hole size.
What is PCB kraft paper
PCB kraft paper is a dense, high-purity kraft fibre sheet. In drilling it is the base material of phenolic backup boards (PHE grade): the kraft is saturated with phenolic resin and cured into a rigid, flat sheet that supports the drill bit on exit, controls burr and protects the drill on breakout. In lamination it is used as press packing paper between stacked booklets.
Typical properties
| Base fibre | High-density kraft paper |
|---|---|
| Impregnation | Phenolic resin (cured) |
| Heat resistance | Rated for sustained drilling spindle heat |
| Typical thickness | 0.5 – 2.5 mm (as backup board) |
| Exit burr (PHE board) | ≤ 0.05 mm below Ø0.10 mm holes |
| Compliance | RoHS / E1 |
Because kraft is the base of the phenolic grade and the base of the coated wood grades, it sits at the bottom of the family tree. the backup board range explained shows how the whole range is built from it.
Where PCB kraft paper is used
- Drilling backup board base — phenolic-impregnated kraft becomes the PHE backup board for IC substrate and fine-pitch drilling.
- Lamination packing — kraft paper cushions booklets in the press for even pressure and surface finish.
- General PCB manufacturing — packing, separation and protective layers in fab handling.
Kraft paper vs phenolic backup board
Kraft paper is the raw base fibre; a Phenolic PHE Backup Board is that kraft paper saturated and cured into a rigid drilling sheet. The resin gives the board its hardness, heat resistance and flatness. For production drilling the cured phenolic kraft board is the choice; loose kraft is used for lamination packing. Both work alongside HDF, UV melamine and wood backup boards depending on the hole size and substrate.
PCB kraft paper FAQ
What is PCB kraft paper? PCB kraft paper is a high-density kraft fibre sheet used as the base material for paper-backed (phenolic) PCB backup boards. It sits under the drilling stack to support the drill on exit, control burr and protect the bit.
What is PCB kraft paper used for? It is used in PCB drilling as the cushioning base of backup boards, and in lamination as press packing paper. In drilling it reduces exit burr, improves hole-wall quality and lowers bit breakage on breakout.
Is PCB kraft paper heat resistant? Yes. Drilling-grade kraft paper is phenolic-impregnated and rated for the heat and friction of high-speed drilling. High-temperature grades stay stable through sustained spindle heat without delaminating or charring.
What is the difference between kraft paper and a phenolic backup board? Kraft paper is the raw base fibre; a phenolic backup board is that kraft paper saturated with phenolic resin and cured into a rigid, flat sheet. The resin gives the board its hardness, heat resistance and dimensional stability for drilling.
Can kraft paper be used directly as a PCB backup board? Loose kraft paper is not used directly; it is converted into a phenolic-impregnated backup board. For most HDI and multilayer drilling, the cured phenolic kraft backup board (e.g. our PHE grade) is the production choice, while raw kraft is used as lamination packing paper.