PCB Design and Layout
The beginning step of any PCB manufacture is, of course, the design. To design the PCB layout in any simulator that is readily available.PCB manufacture and design always start with a plan: the designer lays out a blueprint for the PCB that fulfills all the requirements as outlined.
You have to take care of certain things while designing the PCB layout such as the width of the routes, connecting different elements, and placing vias of the specific size.
Prototype circuit boards should be rigorously compatible with, the designer creates a PCB layout using PCB design software.
NOTE: Before PCB fabrication, designers should inform their contract manufacturer about the PCB design software version used(Commonly-used PCB design software includes Altium Designer, OrCAD, Pads, KiCad, Eagle etc. ) to design the circuit, it helps avoid issues caused by discrepancies.
Different PCB design software possibly calls for different Gerber file generation steps(we provide knowledge about how to generate Gerber files in Altium and Eagle), they all encode comprehensive vital information including copper tracking layers, drill drawing, apertures, component notations, and other options.
So it needs a thorough examination, designers forward PCB file to PC Board Houses for manufacturing.
To ensure the design fulfills requirements for the minimum tolerances during the manufacturing process, almost all PCB Fab Houses run Design for Manufacture (DFM) check before circuit boards fabrication.
After all the checks are complete, the PCB design can be printed.
The customer sends us a document; it is submitted to the engineer for review and accurate quotation again; help confirm whether the production documents are missing or wrong; also determine the process steps and associated checks. Then start to arrange production after confirmation
Cutting and laminating according to the size of the finished board or the size of the panel;
The main purpose of drying is to remove the moisture in the board and prevent it from warping during processing. Generally, it is dried at 150℃ for 3-4 hours.
Inner Layer Imaging
A dry film is applied to the bare copper core board, and all photoimaged reactions are performed on the dry film.
Inner layer development
The exposed core plate is developed, and the unexposed dry film is developed to reveal the original copper skin, and the exposed dry film is retained.
Photo-imaging is the main process of open and short circuit. Therefore, the environmental sanitation requirements are very high. Personnel entering must be cleaned by air shower door. All operators need to wear anti-static clothing.
Inner Layer Etching
Through the etching line, the copper skin covered by the dry film is protected, while the copper skin not protected by the dry film is etched away.
The line pattern that needs to be retained at this time will be displayed by etching.
Unloading the film
Retreat the dry film of the copper sheet on the core board, and the line pattern to be retained is finally formed.
Inner Layer AOI
This is an automatic optical inspection to check whether the core plate after etching has open or short circuit, and the etching is clean or not.
According to the copper foil, it is pressed to one board through an insulating medium (PP) between the layers.
Drilling the laminated plate. At this time, there is no metal in the hole, that is, the layer cannot be connected to the layer.
Electroless copper deposition
Through the chemical reaction, the hole is coated with a very thin layer of copper, about 2-3 um.
Horizontal Electrolytic Plating
Since there is already a thin layer of metallic copper in the hole, the copper in the bare plate and the copper in the hole can be thickened to 5-8um by electron transfer reaction.
Outer Layer Imaging
Outer Layer Film
A dry film is applied to the bare copper core board, and all photoimaged reactions are performed on the dry film.Unlike the inner layer film, the hole has been drilled on the plate now, the dry film is attached to the plate to protect the hole.
Outer Layer Exposure
Outer layer development
This step is different from the Inner layer development because after the inner layer is developed, the copper under the dry film is the last copper to be retained: after the outer layer is developed, the copper of the dry film is the last copper to be etched, and the copper that needs to be preserved is exposed at this time.
Thick copper plating
The bare copper (that is, the copper that needs to be retained at the end) is plated to the finished copper thickness. Generally, the copper plating thickness is 18-25 um. At this time, the surface copper thickness and the copper thickness in the hole are plated together to reach the finished copper and holes copper thickness requirements.
The surface of the copper has been thickened with a layer of white metallic tin to protect the copper foil.
Getting rid of the film
The dry film attached to the board is removed. At this time, the copper under the dry film will be exposed (it will be etched away), and the copper that needs to be retained will be protected by tin underneath.
Outer Layer Etching
The tin protects the desired copper during this stage. By etching the line, the exposed copper will be etched away, while the copper protected by tin will remain.
The tin used to protect the copper is removed. At this time, the copper that needs to be preserved will be exposed. Up to now, all the outer circuit patterns have been completed.
Coat the entire panel with a liquid solder mask. The board is then exposed to high-intensity UV light. Solder mask is applied to achieve the following: Protect copper circuitry from oxidation, damage, and corrosion.
WellPCB prints the solder mask under customers’ requirements and do not have an extra charge.
Silkscreening is a vital step since this process is what prints important information onto the board. Then PCB finally passes onto the coating and surface finishing process.
This step is to enable protection of the surface and good solderability. Common surface finishes include such as Electroless Nickel Immersion Gold, Hot Air Solder Leveling(HASL), Lead-Free HASL, Immersion Silver, OSP( anti-oxidation), etc.
Following the implementation of the Rohs directive in the EU, all products containing lead and bromine will not be allowed to enter the EU market; therefore, the traditional pewter process will be gradually replaced.
WellPCB defaults to the lead-free HASL for our customers If you need any other way to deal with it, please check the box when you place the order.
The engineering department creates a shape program based on the border provided by the customer.
The shape process is based on the engineering department to provide milling
Other Surface Finishing Process
Such as V-CUT, gold finger beveling will be done after the profile process.
This is the process of cutting the manufac-turing panels into specific sizes and shapes based upon the customer design as defined within the gerber data.
The method employed either centers on using a router or a v-groove. A router leaves small tabs along the board edges while the v-groove cuts diagonal channels along both sides of the board. Both ways permit the boards to easily pop out from the panel.
Primarily, PCB connection points are subject to constant plugging and unplugging owing to their nature of interconnecting PCBs. Hence, without a strong contact edge, they are prone to wear-and-tear that can cause device malfunctioning. The act of plaiting the connectors with other metals (in this case gold) is done to enhance the durability of the edge connectors.
So far, the board production has been basically completed, but another important thing is to conduct electrical testing to ensure functionality. The main tests that are performed are the circuit continuity and isolation tests.
Basic electrical reliability testing, used for checking the integrity of the tracks and the through hole interconnections-checking to ensure there are no open circuits or no short circuits on the finished board. WellPCB using Flying Probe Testing which depends on moving probes to test electrical performance of each net on a bare circuit board. We check each net to ensure that it is complete (no open circuits) and does not short to any other net, to ensure optimum performance and quality.
Final Visual Inspection(FQA、FQC)
This is the final step in PCB fabrication process. The professional quality control team will perform the final inspection of each PCB.Including: visual inspection, finished product size inspection, aperture hole number measurement, warpage measurement, etc. If the inspection is qualified, we will print a test report for customer reference.
After inspection, the PCBs are vacuum-sealed to keep out dirt and moisture. securely boxed, sealed and shipped off to the customers all over the world by courier. WellPCB suggest DHL and FEDEX which are more convenient and fast – generally 1-4 Days so you can receive the board as soon as possible and start your project soon.
I believe that you have a general understanding of the fabrication process of pcb after reading this guide. If you are ready with your pcb design and want to try to implement it for your project; try using our quotation system and upload your CAD or Gerber files. And our experienced professionals are available for consultation and to advise you when needed.
If you want to learn more about the details of pcb manufacturing steps or problems encountered in file generation, you can contact us. We are always at your service.