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THE PCB MANUFACTURING PROCESS
MODERN DAY PRINTED CIRCUIT BOARD MANUFACTURING PRODUCTION FACILITY SHOWING THE PROCESSES YOUR DESIGN WILL GO THROUGH BEHIND THE SCENES COMPLIMENTS OF THE JLCPCB FACTORY.
Drilling is the most expensive and time-consuming process in PCB manufacturing. The PCB drilling process must be carefully implemented since even a small error can lead to a great loss. The drilling process is considered the most critical and bottleneck of printed circuit board manufacturing.
The first step in the plating process is the chemical deposition of a very thin layer of copper on the hole walls. The operator clamps the production panels into the jigs. The line is fully computer controlled and the panels are carried through a series of chemical and rinsing baths by the overhead crane. Almost all PCBs with 2 or more copper layers use plated through holes to connect the conductors between the layers. A good connection needs about 25 microns of copper on the walls of the holes. This thickness must be electroplated, but the walls of the holes are non-conductive glass cloth and resin. So the first step is to deposit a conductive layer over the hole walls. We use electroless copper, that is we deposit chemically a layer of copper about 1 micron thick over the walls of the hole (and incidentally across the whole panel). This is a multi-stage process as you see from the video with washing steps between the stages. We pre-treat the panel, then we seed the hole wall with micro-particles of palladium, and finally deposit the copper
We image the outer layers in a clean room to make sure that no dust gets onto the panel surface where it could cause a short or open circuit on the finished PCB.
The panel is first coated with a layer of photosensitive film, the photoresist, which is hot-rolled onto the copper using a cut-sheet laminator.The laminated panels are collected by an automatic rack.The clean room uses yellow lighting as the photoresist is sensitive to UV light.
The first step in the plating process is the chemical deposition of a very thin layer of copper on the hole walls. The operator clamps the production panels into the jigs. The line is fully computer controlled and the panels are carried through a series of chemical and rinsing baths by the overhead crane. Almost all PCBs with 2 or more copper layers use plated through holes to connect the conductors between the layers. A good connection needs about 25 microns of copper on the walls of the holes. This thickness must be electroplated, but the walls of the holes are non-conductive glass cloth and resin. So the first step is to deposit a conductive layer over the hole walls. We use electroless copper, that is we deposit chemically a layer of copper about 1 micron thick over the walls of the hole (and incidentally across the whole panel). This is a multi-stage process as you see from the video with washing steps between the stages. We pre-treat the panel, then we seed the hole wall with micro-particles of palladium, and finally deposit the copper
AOI for a bare PCB board inspection may detect these features:
- Line width violations
- Spacing violation
- Excess copper
- Missing pad – a feature that should be on the board is missing
- Short circuits
- Gold Finger damage
- Cuts
- Hole breakage – a drilled hole (via) is outside of its landing pad
- Wrong mounting components identified
The triggering of a defects report may be either rule-based (e.g. no lines on the board should be smaller than 50μ) or CAD based in which the board is locally compared with the intended design.
This inspection is much more reliable and repeatable than manual visual inspection.
In many cases, smaller circuit board designs are driving up the demand for AOI vs in-circuit testing.[ci
Solder mask or solder stop mask or solder resist is a thin lacquer-like layer of polymer that is usually applied to the copper traces of a printed circuit board (PCB) for protection against oxidation and to prevent solder bridges from forming between closely spaced solder pads.
Here is a step-by-step process of PCB board assembly:
Step 1: Apply solder paste to the circuit board Place the thin, stainless steel stencil over the board using a mechanical fixture. Solder paste should be applied evenly to the circuit board in the exact locations needed.
Step 2: Pick and place the machine SMDs, or surface mount components, should be placed on a prepared PCB by a robotic device. Then, the components need to be soldered onto the circuit board surface.
Step 3: Let the solder paste solidify In order to adhere the components to the PCB, the solder paste needs to reflow and remain in place for an extended period of time.Step 4: Inspect the PCB assembly After the reflow process is complete and the mount components are soldered into place, comes the PCB inspection. The assembled board should be tested and inspected for functionality. Ways to check the PCBA for quality control include:
Manual checks:A visual inspection done in person by a designer to ensure the quality of a PCB.Automatic optical inspection:An inspection method more appropriate for larger batches of PCBAs. An automatic optical inspection machine, or AOI machine, uses high-powered cameras, set at different angles to view the solder connections.X-ray inspection:An inspection used for more complex PCBs by examining the layers of the PCB and identifying potential problems.
5: Insert the plated through-hole component A plated through-hole, or PTH, component is a hole in the PCB that is plated through the board. Rather than soldering paste, more specialized soldering method is required for PTHs.
Manual soldering:nbsp;A manual, through-hole insertion.Wave soldering:nbsp;The automated version on manual soldering where a wave of molten solders all the holes in the bottom of the board at once.Note: A solder paste applier, pick-and-place machine, high-speed chip shooter, and infrared oven inserted in a conveyor configuration can apply solder, pick-and-place, and solder 50,000 parts or more in an hour.Step
6: Complete a final inspectionOnce the soldering process of the PCB board assembly is complete, it is time to do a final inspection and functional test. Run power and simulated signals to test the PCBs electrical characteristics. A sign that the PCB has failed is when it shows the fluctuation of electrical signals during the test. If the PCB fails the final inspection, it should be scrapped. And the process begins all over until a successful PCB is produced.