1. The fr-4 we often choose is not the name of a material.
We often refer to "FR - 4" is a kind of code of fire resistant material level, it represents the meaning of the material is resin after combustion state must be able to put out a material specification, it is not a material name, but a level of material, so the general FR - 4 grade materials used in the circuit board has a lot of kinds, but most are based on the so-called four functions (Tera - Function) of epoxy resin and Filler (Filler) and glass fiber made of composite materials.
Our company is now doing the fr-4 fiberglass fiberglass board, which has the functions of high temperature, insulation and flame retardant.
Flexible Printed Circuit Board (FPC) is also called Flexible Printed Circuit Board, or Flexible Printed Circuit Board.Flexible printed circuit boards are designed and produced on flexible substrate by way of printed circuit.
There are two main types of printed circuit board base materials: organic substrate materials and inorganic substrate materials, and most of them are organic substrate materials.Different layers of PCB are different, for example, 3 ~ 4 layers are made of prefabricated composite materials, and the two panels are mostly made of glass-epoxy resin.
2. Select the board, we need to consider the impact of SMT.
Utilizing electronics assembly process, due to temperature increase, a greater degree of printed circuit boards, bends when heated, therefore, in the SMT requirement as far as possible use small bending degree of plank, types of substrates such as FR - 4.Because of substrate after heat stress on the impact of component, will cause the electrode and reduce the reliability, therefore, when select material should also pay attention to material expansion coefficient, especially when the component is greater than 3.2 x 3.2 mm pay special attention to.
Surface mount technology is used in PCB for high thermal conductivity, excellent heat resistance (150 ℃, 60 min) and weldability (260 ℃, 10 s), high (more than 1.5 x 104 pa) copper foil adhesive strength and bending strength (25 x 104 pa), high conductivity and dielectric constant, good cutting precision (+ / - 0.02 mm) and the compatibility with cleaner, additional requirements appearance smooth level off, not warp, crack, scars and rusty spot, etc.
3. Thickness selection of PCB.
Printed circuit board thickness is 0.5 mm, 0.7 mm and 0.8 mm, 1 mm and 1.5 mm, 1.6 mm (1.8 mm), 2.7 mm (3.0 mm), 3.2 mm, 4.0 mm and 6.4 mm, 0.7 mm and 1.5 mm thickness of the PCB with the belt gold finger double panel design, 1.8 mm and 3.0 mm for non-standard sizes.Printed circuit board size in terms of production, minimum veneer should not be less than 250 x 200 mm, general manager and want to size for (250 ~ 350 mm) x (200 x 250 mm), for the long side is less than 125 mm or edge is less than 100 mm wide PCB, easy to use makeup.The surface assembly technology has the requirement that the bending amount of 1.6mm substrate is less than 0.5mm, and the bottom warp is less than 1.2mm.
Generally, the allowable bending rate is divided into 3 types according to the metal material according to the metal material, as shown in the typical PCB.According to the structure soft and hard into 3 kinds, electronic plug-in also to the high foot number, miniaturization, SMD and complicated development.The electronic plug-in is mounted on the circuit board and welded to the other side of the circuit board, which is known as the THT (ThroughHoleTechnology) plug-in technology.In this way, the PCB board should be drilled for each foot, indicating the typical application mode of PCB.
With the high speed development of SMT patch technology, it is necessary to guide the multi-layer circuit board, and the electroplating after drilling is required to ensure that all kinds of drilling equipment are required.In order to meet the above requirements, at present, different performance of PCB CNC drilling equipment is introduced at home and abroad.
The production process of printed circuit board is a complicated process. It involves a wide range of processes, including photochemistry, electrochemistry and thermochemistry.The process involved in the manufacturing process is also more, the hard multilayer circuit board as an example to illustrate the process.
Drilling is very important in the whole process working procedure, hole processing, with the longest holding time is also the location precision of hole and the hole wall quality directly affect the subsequent hole metallization and SMT process, also directly affect the machining quality and the cost of printed circuit board nc drilling machine principle, structure and function on the PCB drilling method is often used with CNC machinery drilling method and laser drilling method, etc., at this stage to mechanical drilling method most used.