What is wet lamination of circuit boards

pcbaPCB manufacturers in the substrate copper foil surface due to production, shipping, cutting, pretreatment and other processes will always be more or less scuffed, or copper foil itself there are pinholes, pockmarks, pits, scratches and glass fabric weave caused by copper foil surface unevenness and other defects, the use of dry film, it will cause the dry film and the substrate copper foil surface anastomosis adhesion is not firm, the formation of interfacial air gaps, cavities, and so on.pcbaWhen etching, the etching solution may cause broken wires, nicks or depressions in the thickness of the wire once it enters the void. In order to improve the adhesion of the dry film and to eliminate the air bubbles trapped between the copper foil surface and the dry film interface, some dry film manufacturers have developed a wet lamination process and the equipment and dry film to be used with it. The so-called wet lamination is to apply a layer of water film on the copper foil surface of the substrate before lamination, when the substrate passes through the hot press roller, part of the water will be evaporated and the remaining water will be absorbed by the dry film, thus forming a vacuum on the original irregular or depressed surface. firmly cohesive with the copper surface.

 pcbaThe traditional water-soluble dry film is not suitable for wet lamination in the laminating factory, when there are water stains on the copper surface, the dry film will be "locked" after the general dry film is applied (Lock InThe residual glue phenomenon occurs on the copper surface after the development, between the film and the development. pcbaProduction if dry film stagnation time (Hold TimeThe longer the film is applied, the more serious the "locking" problem will be and the more residual glue will remain. Wet lamination often uses special dry film, which is compatible with water and is almost unaffected by stagnation time, and does not have the problem of "locking".      

Wet lamination not only improves the adhesion of dry film, but also overcomes the roughness and unevenness of the glass fiber and the various problems that exist on the copper surface. In general, the finer the wire, the better the wet lamination will be for the improvement of the qualification rate.pcbaprocessors use. However, the wet lamination method has its limitations, as it is only applicable to the production of wire patterns on undrilled inner laminates. For the production of wire patterns on the surface of drilled double-sided and multilayer boards, the method is not suitable for substrates with metalized holes because the inflow of wet water into the holes can cause serious oxidation of the copper wall surface and affect the process quality of the subsequent processes. In order to overcome the defects of wet lamination, liquid photopolymer ink has emerged in recent years to be directly coated on the substrate to be laminated, forming a photoresist layer with the same effect as wet lamination, and is suitable for all rigid substrates with or without metallization holes, which can replace dry and wet lamination..