Process and apparatus for coating printed circuit boards

An apparatus for applying a coating that is crosslinkable by electromagnetic radiation to at least one printed circuit board, said apparatus comprising:

• along a conveyor belt for the at least one printed circuit board, at least one coating station for applying the coating to a surface of the at least one printed circuit board;
• a device for adjusting a temperature of the surface of the at least one printed circuit board to a temperature that is greater than or equal to room temperature;
• a first coating station that is arranged for at least one-sided application of a first layer of a meltable, low-molecular-weight first coating composition that has a molecular weight of approximately from 500 to 1500 and that is highly viscous at room temperature;
• and
• a second coating station for application, over the first layer, of a second layer of a high-molecular-weight, second coating composition having a molecular weight of approximately from 2000 to 10000, wherein the temperature-control device for the surface of the at least one printed circuit board is arranged at least one of upstream of the first coating station and as a part of the first coating station;
• wherein the first coating station has at least one curtain pouring coating device that comprises a storage container for the first coating composition and at least one of a heatable run-off plate and a heatable knife that is connected to the storage container, extends obliquely downwards in a direction of transport of the at least one printed circuit board and ends just above a transport plane of the at least one printed circuit board, as well as heating devices, arranged above the at least one of a run-off plate and knife, by which the first coating composition flowing over the at least one of a run-off plate and knife is brought to pouring temperature and pouring viscosity immediately before it is coated on to the surface of the at least one printed circuit board.

A coated printed circuit board, comprising:

• a first surface;
• a first layer of meltable, low-molecular-weight coating composition that has a molecular weight of approximately from 500 to 1500 and that is highly viscous to solid at room temperature in a thickness of approximately 10 .mu.m to 200 .mu.m formed on said first surface;
• and
• a second layer of a high-molecular-weight composition having a molecular weight of approximately from 2000 to 10000 in a thickness from 2 .mu.m to 20 .mu.m formed over the first layer.