1. Warehouse
The CCL(copper clad laminate) sheets are store here and IQC engineers inspect them with accordance of PO(Purchase Order), part number and quantities, if everything is OK, then IQC will log them in the ERP system, update the status with both production division and sales division.
2. CCL Sheet Preparation
This process cut the sheet into prefered dimension, grinds the sheets edge and corners, remove the sharp edge and burrs, prepare for subsequent processes.
3. Inner Layer Imaging
This process transfers the designed circuit pattern onto the copper surface with high precision, by the imaging process, phototool exposure.
4. Inner Layer Etching
At this process, it removes unwanted copper, leaves the circuit pattern and circuit traces, by according to the imaging process, that connects electronic components.
And next step will strip off the photoresist afterward, then inspect the circuit pattern at next stop, AOI.
5. AOI – Automated Optical Inspection
At AOI station, it inspects the circuits by comparing against the reference images, detect and identify are there defects or flaws on the circuits, such as opens, shorts, missing features, and unwanted copper.
6. Lay-up and Lamination
Lamination process is applied for multilayer boards and not for 2 layers PCBs.
For multilayer boards, inner layer cores will be stacked up with insulating prepreg and copper foil, according to the required stack-up. Press them with certain temperature and pressure, melt the pregreg and bond the layers together.
7. Drilling
CNC drilling creates holes and vias.
Blind and buried vias are mainly for HDI PCB boards.
The location and diameter of holes must meet the required specifications.
The holes dictates the assembly the THT/DIP components, and some of them are critical for electrial connections between copper layers.
8. Desmear and Copper Plating
This process cleans the hole walls, remove drilling residue and prepare for next step: metallization, or in other word: copper plating.
A conductive copper layer is deposited and built up, by the plating process.
Copper plating creates conductive paths through the holes, allowing signals and electrical power to pass through them, between the layers.
9. Outer Layer Imaging and Etching
This process is only for multilayer boards, per PCB only has 2 layers, no need to go through this process.
The outer copper layers go through imaging, pattern formation, and etching, as previous step, to produce the required circuits.
The precise sequence depends on the factory’s pattern plating or panel plating process.
10. Solder Mask
Solder mask is a coating which cover up the PCB, protects copper traces from oxydation and physical damage, it also prevents solder bridging during component assembly, such as the solder mask dam between solder pads.
11. Surface Finish
Common surface finishes are Lead-Free HASL, ENIG, and OSP, apply onto the solder pads and protect them from oxydation and it also improve the solderability for assembly, when go to SMT assembly process, the solder paste will be printed on them, to mount components.
12. Silkscreen Printing
As for silkscreen, also call as legend printing, this process prints component designators and logos, so as other markings on the PCB, to identify components and board information.
13. Routing and Profiling
Routing, also called as profiling, it shapes the boards to the required frame and dimensions.
14. Testing: Flying Probe Testing and Fixture Testing
This is electrical testing process, all completed PCB boards will be tested here by flying probe or fixture, to confirm their electrical connection, make sure all circuits are well connected and PCBs are fabricated.
15. Final Inspection
This is final inspection, also called in short as FQC, at this stage, QC inspects all PCB boards by visual, to check are there residues, scratches, messy solder mask, bubble under solder mask, silkscreen flaws, are the solder pads well and edge damages.
16. Package and Shipment
The PCB boards will be packed here by vacuum and plastic sheets, to protect them and isolate from dust & humidity. The order information will be printed on the label, such as project code, order number and quantities, then ready for shipment.
