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# 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). 


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## 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 |  |  |


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## 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 |
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### 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   |

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### 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  |

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### 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| |
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### 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  |
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### 2.6. stripping

^ Process steps ^ Process description ^ Inputs ^ Outputs ^
|  stripping  |  removing remaining photosentsitive film parts  |  sodium hydroxide solution  |   TBA  |


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## 3. optical inspection
checking the conformity of the internal layer traces with the virtual design using optical system

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## 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  |  |  |  |
 

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## 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  |



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## 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  |  |  |

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## 7. plating (optional)


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## 8. back-drilling (optional)


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## 9. outer layer imaging


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## 10. plating


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## 11. outer layer etching


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## 12. optical inspection


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## 13. solder mask 


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## 14. legend


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## 15. surface finish 


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## 16. profile


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## 17. tests and inspection

## References

~~REFNOTES~~