Detailed explanation of the PCB circuit board in the factory production processing flow

How does the processing flow of circuit board manufacturers? This is a lot of customers in the procurement of circuit board manufacturers want to know and understand how to choose the first issue of the circuit board manufacturers, now Jubao circuit board manufacturers small make up to take you to analyze the PCB circuit boards in the factory's processing process is how the

Categorized by Circuit Configuration

The printed circuit board is a key component in an electronic assembly. It carries other electronic parts and connects circuits to provide a stable circuit working environment. Circuit configurations can be categorized into three types:

[Single-sided board] Metal circuits that provide connections to parts are arranged on an insulated substrate material that also serves as a support carrier for mounting the parts.

[Dual Sided Boards] When single-sided circuits are not sufficient to provide electronic component connections, circuits are arranged on both sides of the substrate and through-hole circuits are built into the board to connect the circuits on both sides of the board.

[Multilayer boards] For more complex applications, circuits can be arranged in multiple layers and pressed together, with through-hole circuits built between the layers to connect the circuits on each layer.

Processing flow:

[The inner layer of the line] copper foil substrate first cut into size suitable for processing and production of the size of the PCB circuit board manufacturers in the substrate before pressing the film usually need to be brushed and milled, micro-etching and other methods of copper foil on the surface of the board to do the appropriate roughening, and then with the appropriate temperature and pressure will be a dry film photoresist close to the adherence of its on. The substrate with the dry film photoresist is sent into the UV exposure machine for exposure. The photoresist will have polymerization reaction after UV irradiation in the light-transmitting area of the substrate and the line image on the substrate will be transferred to the dry film photoresist on the surface of the board. After tearing off the protective adhesive film on the film surface, the first aqueous solution of sodium carbonate will be removed from the film surface of the unilluminated areas of the development, and then a mixture of solutions to remove the exposed copper foil corrosion, the formation of lines. Then the dry film photoresist with light oxidized nano aqueous solution will be washed away.

[Pressing] After the completion of the inner layer of the circuit board must be glass fiber resin film and the outer layer of the line of copper foil bonding. Before pressing, the inner layer of the board needs to be black (oxygen) treatment, so that the copper surface passivation to increase the insulating properties; and make the copper surface of the inner line roughened in order to be able to produce a good bond with the film performance. Iteration of the first six layers of the line (including) more than the inner layer of the circuit board with riveting machine riveted together in pairs. Then use the tray to put it neatly between the mirror steel plate, and send it into the vacuum laminating machine to make the film harden and bond with appropriate temperature and pressure. After pressing the circuit board to X-ray automatic positioning drilling target machine to drill target holes for the inner and outer circuit alignment of the reference hole. The edges of the boards are cut to a fine size to facilitate subsequent processing.

[Drilling] The circuit board factory workers will use CNC drilling machine to drill out the interlayer circuit conduction hole and the fixed hole for soldering parts. When drilling holes, the board is fixed to the drilling machine table with pins through the previously drilled target holes, and a flat lower pad (phenolic resin board or wood pulp board) and upper cover (aluminum plate) are added to reduce the occurrence of drilling burrs.

[Plating through-hole] After molding the interlayer through-hole, we need to build a metal copper layer on it to complete the interlayer circuit conduction. First, we clean up the hairs on the holes and the dust in the holes by heavy brushing and high-pressure rinsing, and then we soak the cleaned holes and attach tin to them.

[A copper] palladium gelatinous layer, which is then reduced to metallic palladium. The board is immersed in a chemical copper solution, and the palladium catalyzes the reduction of the copper ions in the solution and deposits them on the walls of the holes, forming through-hole circuits. The copper layer inside the through-hole is then thickened by copper bath plating to a thickness sufficient to resist subsequent processing and environmental impacts.

[Outer Layer Line Secondary Copper] The production of the line image transfer is like the inner layer line, but the etching of the line is divided into two production methods: positive and negative. Negative film is produced in the same way as the inner layer of the line, and is completed by directly etching copper and removing the film after development. Positive film production method is in the development and then plated with a second copper and tin-lead (tin-lead in the region will be retained later in the etching copper step as an etching resist), to remove the film to alkaline, copper chloride solution will be mixed to remove the exposed copper foil corrosion, the formation of the line. The tin-lead layer is then stripped off with a tin-lead stripping solution (in the early days, there was a practice of retaining the tin-lead layer and using it to cover the line as a protective layer after remelting, but it is not used now).

[Anti-soldering ink Text Printing] Earlier green paint is printed with a screen directly after hot baking (or ultraviolet irradiation) to make the paint film hardened production method. However, due to the printing and hardening process will often cause the green paint penetration into the copper surface of the line terminal joints and produce parts welding and use of trouble, now in addition to the line of simple and rugged circuit boards use, most of the circuit board manufacturers switch to photopolymerized green paint for production.

The customer's desired text, logo or part number is printed on the board by screen printing, and then heat baked (or ultraviolet irradiation) to make the text ink hardening.

[Junction Processing] The solder-resistant green paint covers most of the copper surface of the circuit, leaving only the termination point for soldering, electrical testing, and circuit board insertion. The terminals require an additional layer of protection to prevent oxidization of the anode (+) terminals during long-term use, which could affect circuit stability and cause safety concerns.

[Forming & Cutting] The circuit boards are cut into the customer's desired dimensions by CNC molding machines (or mold punching machines). During cutting, the circuit boards are fixed to the bed (or mold) with pins through previously drilled positioning holes. After cutting, the gold fingers are beveled to facilitate the insertion of the board. For multi-chip circuit boards, it is necessary to add an X-shaped break line to facilitate customers to split and disassemble the boards after insertion. Then the circuit board on the powder and the surface of the ionic pollutants wash.

[Inspection Board Packaging]  Circuit board manufacturers will be based on customer needs to choose the usual packaging PE film packaging, shrink film packaging, vacuum packaging.