METHOD FOR NON-DESTRUCTIVE DIAGNOSTICS OF DEFECTS OF A PLATED HOLE OF A PRINTED-CIRCUIT BOARD Russian patent published in 2021 - IPC G01N33/202 G01N25/72 H05K13/08 H05K3/42 

FIELD: non-destructive quality control.

SUBSTANCE: invention relates to a means of non-destructive quality control of plated through holes (PTH) of printed circuit boards (PCB). The effect is achieved by the fact that in the method of non-destructive diagnostics of defects of the PTH PCB, the upper edge of the metallization during the t_heat is heated by a laser beam of a given power, focused along its boundaries, where t_heat ≈ 3(8r)²/a_{t, r} is the hole radius, a_t is the thermal diffusivity of the PCB material. At the end of heating, the temperature of the upper Т_U and lower Т_L edges of the hole metallization is measured using an IR camera in a non-contact way, and the defects of the PTH are judged by the difference of these temperatures δT = Т_U - Т_L and by the ratio of their increments: ΔТ_U/Т_L, where ΔТ_U = Т_U - Т₀, ΔТ_L = Т_L - Т₀, Т₀ is the initial temperature. In this case, when δT exceeds the threshold value δT_thr, a conclusion is made about the defectiveness of the hole metallization, and if q = [(ΔТ_U/ΔТ_L)-1]^-1 exceeds the threshold value q_thr, a conclusion is made about the defectiveness of the adhesion of the metallization with the PCB dielectric, where the values of δT_thr and q_thr are determined from the results of sample measurements on a representative sample of the PTH of a given standard size.

EFFECT: increase in the reliability of detecting defects and ensuring the possibility of their identification.

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