Table of Contents
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 1):
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 |
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) 1) 2) | 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 3), 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 4) 5) 6), 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
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 |
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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 | ||
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
1)
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