Circuit board proofing (PCB proofing) refers to the trial production of printed circuit boards before mass production. The main application is the process of small-scale trial production by the electronics engineer after designing the circuit and completing the drawing of the PCB to the circuit board factory. Proof for board (PCB proofing).

Circuit board proofing manufacturer production process

First, contact the manufacturer

First of all, you need to tell the manufacturer the documents, process requirements, and quantity.

Second, the material

Purpose: According to the requirements of the engineering data MI, cut into small pieces of production plates on large sheets that meet the requirements. Small pieces of sheet that meet customer requirements.

Process: large sheet material → cutting board according to MI requirements → slab board → beer round corner edging → exit board

Third, drilling

Purpose: According to the engineering data, the required hole diameter is drilled at the corresponding position on the sheet of the required size.

Process: stacking pin → upper plate → drilling → lower plate → inspection and repair

Fourth, sink copper

Purpose: Copper is deposited by chemically depositing a thin layer of copper on the walls of the insulating holes.

Process: coarse grinding → hanging board → copper-plated automatic line → lower board → dip 1% diluted H2SO4 → thick copper

Five, graphics transfer

Purpose: Graphic transfer is the transfer of images on the production film to the board

Process: (blue oil process): grinding board → printing the first side → drying → printing the second side → drying → explosion → shadowing → inspection; (dry film process): hemp board → laminating → standing → right Bit → Exposure → Rest → Shadow → Check

Sixth, graphic plating

Purpose: Graphic plating is to deposit a layer of copper to the required thickness and a layer of gold or tin of the required thickness on the bare copper or the wall of the line pattern.

Process: upper plate → degreasing → water washing twice → micro-etching → water washing → pickling → copper plating → water washing → pickling → tin plating → water washing → lower plate

Seven, unwinding

Purpose: Retreat the anti-plating coating layer with NaOH solution to expose the non-line copper layer.

Process: water film: inserting → soaking alkali → washing → scrubbing → passing machine; dry film: placing board → passing machine

Eight, etching

Purpose: Etching is the use of chemical reaction to corrode the copper layer in non-line parts.

Nine, green oil

Purpose: Green oil transfers the pattern of green oil film to the board to protect the line and prevent tin on the line when soldering parts.

Process: grinding plate → printing photosensitive green oil → 锔 plate → exposure → shadow; grinding plate → printing the first side → baking sheet → printing the second side → baking sheet

Ten, characters

Purpose: Characters are an easy-to-identify markup

Process: After the end of green oil → cool and cool → adjust the network → print characters → after 锔

Eleven, gold plating

Finger purpose: Plating a layer of nickel gold with a required thickness on the plug finger to make it more wear-resistant. Process: upper plate → degreasing → water washing twice → micro-etching → water washing twice → pickling → plating Copper → water wash → nickel plating → water washing → gold plating.

Tin plate? (Parallel process) Purpose: Spray tin is sprayed with a layer of lead tin on the bare copper surface not covered with the solder resist oil to protect the copper surface from oxidation and oxidation to ensure good soldering performance. Process: micro-etching → air drying → preheating → rosin coating → solder coating → hot air leveling → air cooling → washing and drying

Twelve, molding

Purpose: Through the die stamping or CNC machine to cut out the shape forming method required by the customer, organic enamel, beer board, handcuffs, hand cut.

Note: The accuracy of the data board and the beer board is higher, and the handcuffs are second. The hand cutting board can only make some simple shapes.

Thirteen, testing

Objective: Through the electronic 100% test, it can detect the open circuit and short circuit that are not easily seen by the visual system.

Process: upper mold → release board → test → qualified → FQC visual inspection → unqualified → repair → return test → OK → REJ → scrap

Fourteen, final inspection

Purpose: Through 100% visual inspection of the appearance defects of the board and repair of minor defects to avoid problems and defective board outflow.

Specific work flow: incoming materials → view data → visual inspection → qualified → FQA random inspection → qualified → packaging → unqualified → processing → check OK.

Board composition

The circuit board is mainly composed of pads, vias, mounting holes, wires, components, connectors, filling, electrical boundary circuit board industrial area, etc. The main functions of each component are as follows:

Pad: A metal hole used to solder the component leads.

Via: There are metal vias and non-metal vias, where metal vias are used to connect the component leads between layers.

Mounting hole: used to fix the board.

Wire: An electrical network copper film used to connect component leads.

Connector: A component used to connect between boards.

Filling: Copper for the grounding network can effectively reduce the impedance.

Electrical Boundary: Used to determine the size of the board, and all components on the board must not exceed this boundary.

Main board classification

Board systems are classified into the following three types:

Single panel

As we just mentioned, on the most basic pcb, the parts are concentrated on one side and the wires are concentrated on the other side. Because the wire only appears on one side, we call this pcb a single-sided. Because single-panel has many strict restrictions on the design line (because there is only one side, the wiring can not be crossed * and must be around the original path), so only the early circuit used this type of board.

Double panel

There are wiring on both sides of the board. However, to use the wires on both sides, it is necessary to have proper circuit connections between the two sides. The “bridge” between such circuits is called a via. The via hole is a small hole filled or coated with metal on the pcb, which can be connected to the wires on both sides. Because the area of ​​the double panel is twice as large as that of the single panel, and because the wiring can be interlaced (can be wound around the other side), it is more suitable for circuits that are more complex than single panels.

Multilayer board

[Multilayer board] In the case of more complicated application requirements, the circuit can be arranged in a multi-layer structure and pressed together, and a through-hole circuit is connected between the layers to connect the layers of the circuit.

Inner line

The copper foil substrate is first cut into a size suitable for processing. Before the substrate is pressed, the copper foil on the copper surface is usually roughened by brushing, micro-etching, etc., and the dry film photoresist is closely adhered to it at an appropriate temperature and pressure. The substrate with the dry film photoresist is sent to an ultraviolet exposure machine for exposure, and the photoresist is polymerized after being irradiated with ultraviolet rays in the light transmitting region of the film (the dry film in the region will be in the later development and copper etching step). It is retained as an etch resist) and the line image on the film is transferred to the dry film photoresist on the board. After the protective film on the film surface is peeled off, the unexposed area on the film surface is developed and removed with an aqueous solution of sodium carbonate, and the exposed copper foil is etched away with a mixture solution of hydrochloric acid and hydrogen peroxide to form a line. Finally, the dry film photoresist that has been retired is washed away with an aqueous solution of sodium hydroxide. For the inner layer circuit board of six or more layers, the riveting reference hole of the interlayer line is punched out by the automatic positioning punching machine.

In order to increase the area that can be wired, the multilayer board uses more single or double-sided wiring boards. The multi-layer board uses several double-sided panels and is adhered (pressed) after placing an insulating layer between each layer. The number of layers in the board represents several separate layers of wiring, usually with an even number of layers and containing the outermost two layers. Most of the motherboards are 4 to 8 layers of structure, but technically can achieve nearly 100 layers of pcb boards.

Large supercomputers mostly use quite a few multi-layer motherboards, but because such computers can already be replaced by clusters of many common computers, super-multilayer boards have gradually disappeared. Because the layers in the pcb are tightly coupled, it’s not easy to see the actual number, but if you look closely at the motherboard, you might see it.

The automatic detection technology of the circuit board is applied with the introduction of surface mount technology, and the packaging density of the circuit board is rapidly increased. Therefore, even for a board of low density and a general number of boards, automatic detection of the board is not only basic but also economical. In complex board inspection, two common methods are the needle bed test and the double probe or flying probe test.

Board maintenance

The board should be serviced regularly during use to ensure that the board is in good working order and reduces board failure rates. The maintenance of the board in use is divided into the following cases:

1, half year maintenance:

(1) Clean the dust on the circuit board every quarter, and clean it with the special cleaning liquid of the circuit board. After the dust on the circuit board is cleaned, blow the circuit board with a hair dryer.

(2) Observe that the electronic components in the circuit have not passed the trace of high temperature, and the electrolytic capacitor has not swelled and leaked, and should be replaced if necessary.

2, annual maintenance:

(1) Clean the dust on the board.

(2) Sampling the capacity of the electrolytic capacitor in the circuit board. If the capacity of the electrolytic capacitor is less than 20% of the nominal capacity, it should be replaced. Generally, the life of the electrolytic capacitor should be replaced after working for about ten years to ensure the operation of the circuit board. performance.

(3) For high-power devices coated with heat-dissipating silicone grease, check whether the heat-dissipating silicone grease is dry. For dry-drying, the dry heat-dissipating grease should be removed and coated with new heat-dissipating grease to prevent the board from being damaged. The high-power devices burn out due to poor heat dissipation.