what is rigid circuit board

Rigid board: Generally refers to the ability of the material to not deform under the action of external force. Of course, it is an ideal rigid board that does not deform under the action of external force, but a material that undergoes a small amount of elastic deformation under a large external force is a rigid material.

Rigid printed circuit boards include phenolic cellulose paper copper-clad laminates, epoxide cellulose paper laminates, polyester woven glass fabric laminates, and epoxide woven glass fabric   laminates. The flexible circuit board is a printed circuit board with high reliability and high bending performance, which is made of polyimide or polyester film as the base material.

Inner circuit of rigid board

The copper foil substrate is first cut to a size suitable for processing and production. Before the substrate is laminated, the copper foil on the surface of the board should be roughened properly by brushing, micro-etching, etc., and then the dry film photoresist should be attached to the dry film at an appropriate temperature. Take the substrate with the dry film photoresist into the UV exposure machine for exposure. The photoresist will undergo polymerization after being irradiated with ultraviolet light in the transparent area of the negative film (the dry film in this area will be exposed in the later development and copper etching steps Keep it as an etch resist), and transfer the circuit image on the negative film to the dry film photoresist on the board. After tearing off the protective film on the film surface, first remove the wet shadow of the unexposed area on the film surface with an aqueous solution of sodium carbonate, and then corrode and remove the exposed copper foil with a mixed solution of hydrochloric acid and hydrogen peroxide to form a circuit. Finally, the aqueous film of sodium hydroxide is used to wash away the dried photoresist. For inner layer circuit boards with more than six layers (inclusive), use the automatic positioning punching machine to punch out the riveting reference holes for the alignment of the lines between the layers.

Rigid plate pressing

After completion, the inner circuit board must be bonded to the outer circuit copper foil with glass fiber resin film. Before lamination, the inner layer board needs to be blackened (oxidation) to increase the insulation of the copper surface; the copper surface of the inner layer circuit should be roughened to produce good bonding performance with the film. When laminating, the six-layer circuit (including the inner layer circuit board above) is riveted in pairs with a rivet machine. Then use a platter to place it neatly between the mirror steel plates and send it to a vacuum laminator to harden the film with appropriate temperature and pressure. The circuit board after pressing is locked by X-ray automatic positioning lock, and the hole is used as the reference hole for the alignment of the inner and outer layers. The edges of the board should be properly cut to facilitate subsequent processing.