PCB Tech - PCB circuit board warpage and copper foil

In the process of PCB processing, the substrate has to be subjected to heat and many kinds of chemical substances many times. For example, after the substrate is etched, it needs to be washed with water, dried and heated, and electroplating is hot during pattern electroplating.

After the green oil is printed and the logo characters are printed, it needs to be heated or dried with UV light, and the substrate is subject to great thermal shock when the hot air is sprayed on the tin. These processes may cause the PCB board to warp.

Avoid warping caused by improper printed circuit board circuit design or improper processing technology.

For example, the conductive circuit pattern of the PCB board is not balanced or the circuit on both sides of the PCB board is obviously asymmetrical, and there is a large area of copper on one side, which forms a large stress, which causes the PCB board to warp, and the processing temperature is high or hot in the PCB manufacturing process. Impact, etc. will cause the PCB board to warp.

As for the impact caused by improper storage method of superstrate,PCB factory is better to solve it, and it is enough to improve the storage environment and eliminate vertical placement and avoid heavy pressure. For PCB boards with a large area of copper in the circuit pattern, it is best to mesh the copper foil to reduce stress.

Copper foil (copper foil): a kind of cathode electrolytic material, a thin, continuous metal foil deposited on the base layer of the circuit board, which acts as the conductor of the PCB. It easily adheres to the insulating layer, accepts the printed protective layer, and forms a circuit pattern after corrosion. Copper mirror test (copper mirror test): a flux corrosion test, using a vacuum deposition film on the glass plate.

Copper foil is made of copper and a certain proportion of other metals. Copper foil generally has 90 foil and 88 foil, that is, the copper content is 90% and 88%, and the size is 16*16cm. Copper foil is the most widely used decorative material. Such as: hotels, temples, Buddha statues, golden signs, tile mosaics, handicrafts, etc.

Copper foil has low surface oxygen characteristics, can be attached to various substrates, such as metals, insulating materials, etc., and has a wide temperature range. Mainly used in electromagnetic shielding and anti-static. The conductive copper foil is placed on the surface of the substrate and combined with the metal base material. It has excellent conductivity and provides electromagnetic shielding effect. Can be divided into: self-adhesive copper foil, double-conducting copper foil, single-conducting copper foil, etc.

Electronic grade copper foil (purity above 99.7%, thickness 5um-105um) is one of the basic materials of the electronics industry. The rapid development of electronic information industry, the use of electronic grade copper foil is increasing, and the products are widely used in industrial calculators, Communication equipment, QA equipment, lithium-ion batteries, civilian televisions, video recorders, CD players, photocopiers, telephones, air conditioning, automotive electronic components, game consoles, etc. The domestic and foreign markets have an increasing demand for electronic grade copper foil, especially high-performance electronic grade copper foil. Relevant professional organizations predict that by 2015, China's domestic demand for electronic grade copper foil will reach 300,000 tons, and China will become the world's largest manufacturing base for printed circuit boards and copper foils. The market for electronic grade copper foil, especially high-performance foil, is optimistic. .

Industrial copper foil can be commonly divided into two categories: rolled copper foil (RA copper foil) and point solution copper foil (ED copper foil). Among them, rolled copper foil has good ductility and other characteristics, which is used in the early soft board process. Copper foil, while electrolytic copper foil has the advantage of lower manufacturing cost than rolled copper foil. Since rolled copper foil is an important raw material for flexible boards, the improvement of the characteristics of rolled copper foil and price changes have a certain impact on the flexible board industry.