# Manufacturing processes of multilayer Printed Circuit Boards (PCB) This page is dedicated to explaining the process flow of multilayer PCB manufacturing. The image gives an overview of this flow [(https://www.ncabgroup.com/wp-content/uploads/2015/10/02-NCAB_Group_Seminars_How-to-make-a-PCB_2_0_150925.pdf)]: {{:capture_d_ecran_2026-04-08_113838.png?direct&400}} It is important to note that this flow is adapted depending on the type of PCB (single sided, double sided, or multilayer). --------------------------------------- t ## 0. substrate/board fabrication ## 1. board cutting ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | sharp edge removal| soften the edges of the board | CCL sheet (copper sheets + glass fiber impregnated by resin), energy for equipment functionning | | | cutting | cut the CCL sheet to the required size | | | --------------------------------------- ## 2. inner layer printing and etching ### 2.1 pre-treating ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | cleaning | remove impurities and increase copper roughness | acidic cleaners, water | acidic cleaners mixed with water | | drying| blow dry | N2 gas | N2 gas | g ### 2.2. dry photosensitive film lamination ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | resist film application on the panel | lamination in clean room environment | liquid photoresist on PET film and covered by a PE film, water (+ other chemicals to improve pattern clarity and enhance stability of the film) ((Pour coller en dehors de Nextcloud Office, veuillez d'abord cliquer sur le bouton « télécharger »)) ((https://www.nokgrp.com/en/assets/images/sustainability/archive/2022/esg_databook_2022_en.pdf)) | N-butyl acrylate and other chemicals | l ### 2.3. UV ray exposure ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | resist exposure | exposition of some part of the phooresist through a photomask | UV light ((https://eshop.dpsk.sk/files/riston200.pdf)), photomask (optical-grade quartz or soda-lime glass with sputtered chrome layer, silver-halide emulsion-coated polyester film) | TBA | k ### 2.4. developpment ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | removing unexposed photosensitive film | | Potassium carbonate K2CO3 aqueous solution sprayed onto the substrate or sodium carbonate Na2CO3 (the latter one seems the most used one). Or sodium metasilicate Na2SiO3 CAS6834-92-0 ((https://eshop.dpsk.sk/files/riston200.pdf)) ((http://pcbfab.com/developing)) ((https://www.dakenchem.com/photoresist-dry-film/)), DI water| | m ### 2.5. etching ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | etching | removing the unwanted copper around parts protected by the photosensitive film | amonia or chloride based etchants | TBA | m ### 2.6. stripping ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | stripping | removing remaining photosentsitive film parts | sodium hydroxide solution | TBA | -------------------------------------- - ## 3. optical inspection checking the conformity of the internal layer traces with the virtual design using optical system --------------------------------------- ## 4. lamination ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | oxidating | roughing and passivating copper | | | | stacking up | stack up core layers together, copper foil and pre-preg | | | | laminating | laminating all layers together | Prepreg, Copper foil, Aluminium plate | | | cooling | | | | | drilling position checking | checking drilling position to avoid misalignment | | | | edge routing | removing resin or copper foil that sticks out the board | | | | edge milling | remove rough edges | | | | visual checking | | | | --------------------------------------- ## 5. drilling ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | drilling a location hole | drilling a hole to fix the board for further drilling and ensure allignment | Aluminium sheet, Base sheet | TBA | | inserting pins | pins to maintain boards together | TBA | TBA | | drilling holes | | Aluminium sheet, Base sheet | TBA | | inspection | checking the alignment and the correct position of holes | TBA | TBA | -------------------------------------- - ## 6. electroless copper deposition ^ Process steps ^ Process description ^ Inputs ^ Outputs ^ | cleaning | successive steps to remove dust, smear from drilling, etc. | | | | etching | pepare the surface for plating by modifying its surface properties ||| | activation | immersing the surface in catalyst colloid to attach it to the surface sites | | | --------------------------------------- ## 7. plating (optional) --------------------------------------- ## 8. back-drilling (optional) --------------------------------------- ## 9. outer layer imaging --------------------------------------- ## 10. plating --------------------------------------- ## 11. outer layer etching --------------------------------------- ## 12. optical inspection --------------------------------------- ## 13. solder mask --------------------------------------- ## 14. legend --------------------------------------- ## 15. surface finish --------------------------------------- ## 16. profile --------------------------------------- ## 17. tests and inspection ## References ~~REFNOTES~~