Some customers are interested in PCB fabrication process, and Linked Electronics will make a brief introduction about how PCB board is made.
Though PCB board is really small, but it involves a lot of compliated process to make a this tiny printed circuit board
Let's come to Multilayer PCB steps first.
Most PCB process is manufacturing under dirt-free and constant temperature environment.
We will creat the substrate for the working panels our engineer designs, and bake the substrate before continuing the following steps.
Inner layer Imaging
First A dry film with the traces is applied to the FR4 board. The copper area covered by the dry film is protected, and unwanted copper on the substrate will be etched away. The dry film will be unloaded and traces pattern is formed.
The patterns on the circuit boards are scanned by a camera and will compare to the data provided.It could monitor any small defects for the traces error such as open or short circuits, shorts and other issue.
Before Lamination, the inner layer will be black oxidized first. The purpose of black oxide on Cu in the PCB process is to provide a rough surface in preparation for the lamination process. Black oxide coatings create much the same roughness on a smooth copper surface. This enables the PCB layer to laminate more effectively
For double sided PCB, it begins from following steps. And multilayer PCB boards will contiune the following process to complete the boards
Holes are drilled into the PCB by a drilling machine.
Plating the holes
After drilling, PTH holes will be plated so as to create circuit conduction. We use some chemicals so that the PCB panel will be covered with a thin copper layer which will then go into the holes.
After PTH, the copper inside the holes is very thin, which cannot meet IPC Class 2 standar. And according to IPC class 2 standard. Minimum hole copper thickness is 18um, but at Linked Electronics, we have stricter manufacturing standard, that is minimum 20um, average 25um.
This comes to what we do to the inner layer imaging again. We use the film and create the traces pattern on the substrate for the printed circuit board.
This is exactly the same as we do for the first plating. Due to a thin layer of copper on the substrate, always 17um, it will be plated to meet the customer requirement such as 1oz or more.
Tin will cover the protective area, unwanted copper without tin will be etched. And final pattern is now created.
Soldermask step is like other PCB manufacturing, it must be done under dirt-free environment. Before that PCBs will be cleaned. PCB boards is covered by soldermask mask for the whole panel, and then exposed to high intensity UV lighted. Unwanted area of soldermask is removed and the soldermask wanted is baked on to the board.
At Linked Electronics, we use the most advanced method to prints the silkcreen onto the PCB boards, silkprinter, which is much more clear and faster than traditional printer method.
Surface finish will add a coating to protect the copper and provide extra solder ability.
At Linked Electronics, there are different options for the surface treatment. HASL Lead Free, ENIG Rohs, Immersion Silver, Immersion Tin, OSP, Hard Gold etc. And customer could choose they preferred surface treatment.
This step is outline, which includes outline and v-cut. Our engineer set the machine on the numerical routing machine and v-cut machine. It will be done automatically. Our staff will check the first article when outline step is finished
There are two way to perform e-test. One is flying probe, and the other is fixture.
Flying probe is relatively price competitive for PCB prototyping, but it takes longer time to complete. But for mass production, it will be expensive compared with fixture.
Fixture is fast and price is charged once only! But if there is any modifications to the PCB, fixture cannot be used any more.
This is the most critical step for PCB board at Linked Electronics. Following will be checked,
board thickness, PCB board twist and warp, any scratch, microsection report, holes size etc.
And PCBs will be packed by vacuum package, and put into a carton box for shipment.
PCB manufacturing process takes so many process, you might have a clear idea why the lead time is at least 5 working days for standard turn.
If you have any more questions regarding the PCB boards manufacturing, contact our team for more information.
Contact Person: Mr. Jonathan
Tel: +86 755 2553 8256