This part is a kind of semiconductor called BCR20KM.
Function of this product has TRIAC.
Manufacturers : Mitsubishi Electric Semiconductor
Image and pinout :
Some of the text within the PDF file :
Refer to the page 6 as to the product guaranteed maximum junction temperature 150°C BCR20KM MITSUBISHI SEMICONDUCTOR 〈TRIAC〉 BCR20KM MEDIUM POWER USE INSULATED TYPE, PLANAR PASSIVATION TYPE OUTLINE DRAWING 10 ± 0.3 Dimensions in mm 2.8 ± 0.2 6.5 ± 0.3 15 ± 0.3 3 ± 0.3 φ 3.2 ± 0.2 14 ± 0.5 3.6 ± 0.3 2.54 ± 0.25 1.1 ± 0.2 1.1 ± 0.2 E 0.75 ± 0.15 0.75 ± 0.15 2.54 ± 0.25 2.6 ± 0.2 4.5 ± 0.2 q IT (RMS) 20A q VDRM . 600V q IFGT !, IRGT ! , IRGT # 20mA q Viso . 2000V q UL Recognized: Yellow Card No.E80276(N) File No. E80271 ➀➁➂ [ ... ]