PCB board fully name is called printed circuit board, it is an important electronic component. As the supporting body of electronic components, provide electrical connection of electronic components. Since it is made by electronic printing, it is called “printed” circuit board.
Although PCB board are changing with the development of technology but the same is that a complete production process is required before the electrical performance of PCB board can be realized. The following is a detailed understanding of the PCB manufacturing process.
According to the requirements of MI engineering info , cut into small pieces on the copper substrate board that meet the requirements. small material in accordance with customer requirements.
2. Inner dry film
The inner dry film is to transfer the circuit graphic using an artwork film to the PCB board surface.
In PCB production processing, we will mention the concept of graphic transfer, because the fabrication of conductive graphics is the foundation of PCB production processing. Therefore, the graphics transfer process is of great significance to PCB production. The inner dry film consists of dry film lamination, exposure and development, inner etching and so on.dry film lamination is a special photosensitive film on the surface of the copper plate, which is what we call dry film. The film will solidify in the UV light, forming a protective film on the board. Exposure and development is to laminate the film of the board for exposure, the transparent part is cured, the opaque part or dry film. and after development, the dry film that has not been cured is removed, and the plate with the cured protective film is etched. After the firm stripping then the inner circuit diagram is transferred to the board.
3. Brown oxidation
Objective: To make the inner copper surface form a microscopic rough and organic metal layer to enhance the adhesion between layers.
Passing chemical treatment produce a uniform organic metal layer structure with good adhesion properties, This structure allows controlled roughening of the surface of the inner copper layer before Lamination, which is used to enhance the lamination strength between the inner copper layer and the Prepreg.
Lamination is the process of bonding each layer of traces into a whole by virtue of the adhesion of Prepreg. The lamination process consists of placing the internal layers under extreme temperature (375 degrees Fahrenheit) and pressure (275 to 400 psi) while laminating with a photosensitive dry resist. The PCB is allowed to cure at a high temperature, the pressure is slowly released and then the material is slowly cooled.
Make the PCB board each layer connecting by through hole, so we can achieve registration to all of the the inner layer connections.
6. Plating and Copper Deposition
After drilling, the panel moves onto plating. The process fuses the different layers together using chemical deposition. After a thorough cleaning, the panel undergoes a series of chemical baths. During the baths, To thicken the board surface and the copper in the hole to 5-8um of the PCB board with just Plating, to prevent the thin copper in the hole from being oxidized and corroded before the pattern plating and from leaking base material.
Prior to this step, the interior surface of the holes simply exposes the fiber glass material that comprises the interior of the panel. then we need place PCB board in the immersed copper cylinder to occur REDOX reactions. it will cause the copper baths completely cover, or plate, the walls of the holes so that the original insulation base materials surface deposition of copper, to achieve electrical interlayer communication.
7. Outer Layer Imaging
Similar to the inner layer process (image transfer using photosensitive dry film, exposure to UV light and etching), but with one main difference – we will remove the dry film where we want to keep the copper/define circuitry – so we can plate additional copper later in the process.This step of the process is performed in a clean room.
We return to the plating process again. where the additional plating is deposited in areas without dry film (circuitry). Once the copper has been plated, tin is applied to protect the plated copper.
9. Etching outer layer
The tin protects the desired copper during this stage. The unwanted exposed copper and copper beneath the remaining resist layer undergo removal. Again, chemical solutions are applied to remove the excess copper. Meanwhile, the tin protects the valued copper during this stage. The conducting areas and connections are now properly established.
10. Solder Mask
Solder mask, also known as anti-soldering, it is one of the most critical processes in the production of printed boards, mainly through printing or coverd an epoxy solder mask ink, on the surface of the board printed with solder mask, through exposed and development process, exposing the solder pad and hole to be soldered, other areas on the cover of solder mask to prevent PCB shorting in soldering process
The nearly completed board receives ink-jet writing on its surface, used to indicate all vital information pertaining to the PCB. The PCB finally passes onto the last coating and curing stage. UETPCB used Automatic silkscreen printor for printing silkscreen on the PCB board. so we printed silkscreen more clear.
12. Surface finish
Bare copper itself has good solderability, but it is easy to be exposed to moisture and oxidized in the air for a long time. It tends to exist in the form of oxide and is unlikely to remain as the original copper for a long time. Therefore, various surface finishes of copper surface is needed. The most basic purpose of surface finish is to ensure good solderability and electrical performance.
Common surface finsh: HALS/HALS lead free, Immersion gold, OSP, Hard Gold, ENEIG, Immersion sliver, etc
13. Profiling and V-Scoring
Different boards are cut from the original panel. 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.
14. Electrical test
As a final precaution, a technician performs electrical tests on the PCB. checking to ensure there are no open circuits or no short circuits on the finished board. There are two test methods, flying probe for smaller volumes and fixture based for volumes.We electrically test every multilayer PCB against the original board data. Using a flying probe tester we check each net to ensure that it is complete (no open circuits) and does not short to any other net.