Research On Optimizing Exposure Performance Of Large Area PCB Based On DMD

Lithography technology is the core technology of printed circuit board(PCB)platemaking.Currently,mask lithography is used in mass production of PCB,and film sheet is usually used to make mask,which is fast in production and low in cost.However,the accuracy of film mask platemaking is low,and chemical reagents will seriously affect the environment and human health.As a result,more environmentally friendly photomask lithography technology is developing rapidly.Digital micro-mirror device(DMD),as a key device of maskless lithography,has the advantages of high speed,flexibility and high resolution.Therefore,it can be used as digital mask to replace film sheet and other physical mask to realize maskless lithography.As for PCB plate-making in large scale based on DMD,the exposure performance directly affects the quality of PCB and the economic benefit of plate-making.Therefore,this paper studies two aspects of increasing exposure efficiency and exposure precision in plate making technology.A large area of PCB exposure is usually done in a stepwise lithography mode,which controls the movement of DMD from the start to the end,along an S-type path through a precise motion platform,but the path may contain coordinates that do not require exposure,resulting in redundancy of the exposure path.For PCB in large area and with uneven line density,the redundancy of path seriously affects the efficiency of exposure and production.Aiming at solving the above problems,an improved ant colony algorithm based on clustering idea is proposed.The simulation results show that the exposure efficiency of the proposed algorithm is 68.3% higher than that of the S-type path for the large-area PCB with uneven line density,and 41.8% higher than that of the ant colony algorithm.Due to device characteristics and mechanical installation errors,large-area exposure image has edge sawtooth,surface gap and splicing dislocation,which will seriously affect the precision and quality of PCB.For the presence of edge sawtooth and surface gap,results show that the error is reduced by 50% and the surface gap is completely filled when the original sawtooth size is about one pixel.For splicing misalignment,the error can be reduced by 80% when the error range of pixel center offset is within 0.1mm?0.5mm.That way,no line misalignment can be detected by low power microscope,which conforms to the inspection standard of appearance and quality of circuit board.In the maskless lithography technology based on DMD,the optimization of large-area PCB exposure performance is completed through path planning and error correction,which can improve the efficiency and exposure accuracy of PCB production,making it more suitable for industrial mass production,and providing a good technical foundation for maskless lithography in mass manufacturing.