A photosensitive assembly, comprising: a circuit board having a rectangular-shaped rigid board region and comprising a flexible board extension portion extending from the rigid board region, wherein the rigid board region has a lamination side and a non-lamination side, the lamination side being one side of the rigid board region to which the flexible board extension portion is connected and the non-lamination side being the other side(s) to which no flexible board extension portion is connected, and wherein the rigid board region has a lamination region on the lamination side, and the flexible board extension portion extends out from the lamination side; a photosensitive element mounted in the rigid board portion of the circuit board; and a molded portion formed on the rigid board region, surrounding the photosensitive element, and extending towards the photosensitive element and coming into contact with the photosensitive element, wherein the molded portion has an inner side surface, an outer side surface and a top surface, the molded portion does not cover the lamination region of the rigid board region, and the top surface has a flat portion, wherein the top surface of a part of the molded portion on the lamination side has a descending portion, and the descending portion is located between the flat portion and the outer side surface of the molded portion on the lamination side, and the descending portion is lower than the flat portion, wherein the descending portion, in a first section therethrough, has a contour of a first arc shape, the first section being in a plane perpendicular to an outer lateral edge of the rigid board region on the lamination side, and the outer side surface of a part of the molded portion on the non-lamination side is perpendicular to the flat portion, and wherein the molded portion comprises a connecting portion connecting the inner side surface and the flat portion on the lamination side, and the connecting portion, in a second section therethrough, has a contour of a second arc shape, the second section being in a plane perpendicular to the flat portion adjacent to the connecting portion and the inner side surface, and a radius of curvature of the first arc shape is greater than a radius of curvature of the second arc shape. a circuit board having a rectangular-shaped rigid board region and comprising a flexible board extension portion extending from the rigid board region, wherein the rigid board region has a lamination side and a non-lamination side, the lamination side being one side of the rigid board region to which the flexible board extension portion is connected and the non-lamination side being the other side(s) to which no flexible board extension portion is connected, and wherein the rigid board region has a lamination region on the lamination side, and the flexible board extension portion extends out from the lamination side; a photosensitive element mounted in the rigid board portion of the circuit board; and a molded portion formed on the rigid board region, surrounding the photosensitive element, and extending towards the photosensitive element and coming into contact with the photosensitive element, wherein the molded portion has an inner side surface, an outer side surface and a top surface, the molded portion does not cover the lamination region of the rigid board region, and the top surface has a flat portion, wherein the top surface of a part of the molded portion on the lamination side has a descending portion, and the descending portion is located between the flat portion and the outer side surface of the molded portion on the lamination side, and the descending portion is lower than the flat portion, wherein the descending portion, in a first section therethrough, has a contour of a first arc shape, the first section being in a plane perpendicular to an outer lateral edge of the rigid board region on the lamination side, and the outer side surface of a part of the molded portion on the non-lamination side is perpendicular to the flat portion, and wherein the molded portion comprises a connecting portion connecting the inner side surface and the flat portion on the lamination side, and the connecting portion, in a second section therethrough, has a contour of a second arc shape, the second section being in a plane perpendicular to the flat portion adjacent to the connecting portion and the inner side surface, and a radius of curvature of the first arc shape is greater than a radius of curvature of the second arc shape.