Base member or light-emitting device

1 . A base member comprising:

a lower portion having an upper surface; and

a lateral portion surrounding the upper surface of the lower portion in a top view, the lateral portion including

a plurality of inner lateral surfaces including a first lateral surface, a second lateral surface not adjacent to the first lateral surface and facing the first lateral surface, a third lateral surface adjacent to the first lateral surface, and a fourth surface adjacent to the first lateral surface and facing the third lateral surface, the inner lateral surfaces defining a rectangular shape in the top view with the first lateral surface and the second lateral surface being a pair of short sides and the third lateral surface and the fourth lateral surface being a pair of long sides,

a first step portion arranged inward of the first lateral surface along an entirety of the first lateral surface in the top view, the first step portion having a first upper surface provided with a wiring pattern,

a second step portion arranged inward of the second lateral surface along an entirety of the second lateral surface in the top view, the second step portion having a second upper surface provided with a wiring pattern, and

a third step portion arranged inward of the third lateral surface along only a portion of the third lateral surface in the top view, the third step portion having a third upper surface provided with a wiring pattern, wherein

the second step portion and the third step portion are spaced apart from each other in the top view,

the first step portion and the third step portion are spaced apart from each other in the top view, and

a length of the third step portion along the third lateral surface is smaller than a length of the second step portion along the second lateral surface in the top view.

2 . The base member according to claim 1 , wherein

the third step portion has the length of 10% or more and 75% or less of a length of the third lateral surface in a direction parallel to the upper surface of the lower portion.

3 . The base member according to claim 1 , wherein

in the top view, the length of the third step portion along the third lateral surface is 10% or more and 75% or less of the length of the second step portion along the second lateral surface.

4 . The base member according to claim 1 , wherein

in a direction parallel to the upper surface of the lower portion, a length of the second lateral surface is 20% or more and 90% or less of a length of the third lateral surface.

5 . A light-emitting device comprising:

a plurality of semiconductor laser elements including a first semiconductor laser element, and a second semiconductor laser element having a length in a first direction smaller than a length of the first semiconductor laser element in the first direction;

a base member including a lower portion having an upper surface on which the plurality of semiconductor laser elements are disposed along a second direction perpendicular to the first direction, and a lateral portion surrounding the upper surface of the lower portion in a top view, the lateral portion including

a plurality of inner lateral surfaces including a first lateral surface, a second lateral surface not adjacent to the first lateral surface and facing the first lateral surface, a third lateral surface adjacent to the first lateral surface, and a fourth lateral surface adjacent to the first lateral surface and facing the third lateral surface, the third lateral surface extending along the second direction, the inner lateral surfaces defining a rectangular shape in the top view with the first lateral surface and the second lateral surface being a pair of short sides and the third lateral surface and the fourth lateral surface being a pair of long sides,

a first step portion arranged inward of the first lateral surface along a portion of or an entirety of the first lateral surface in the top view, the first step portion having a first upper surface provided with a first wiring pattern,

a second step portion arranged inward of the second lateral surface along a portion of or an entirety of the second lateral surface in the top view, the second step portion having a second upper surface provided with a second wiring pattern, and

a third step portion arranged inward of the third lateral surface along only a portion of the third lateral surface in the top view, the third step portion having a third upper surface provided with a third wiring pattern,

the second step portion and the third step portion being spaced apart from each other in the top view,

the first step portion and the third step portion being spaced apart from each other in the top view, and

a length of the third step portion along the third lateral surface being smaller than a length of the second step portion along the second lateral surface in the top view; and

a plurality of wirings electrically connecting the semiconductor laser elements to the base member, the wirings including a first wiring bonded to the first wiring pattern, a second wiring bonded to the second wiring pattern, and a third wiring bonded to the third wiring pattern, wherein

each of the semiconductor laser elements having a rectangular shape with a length along the first direction being longer than a width along the second direction, and

each of the semiconductor laser elements is configured to emit light in the first direction.

6 . The light-emitting device according to claim 5 , wherein

the third step portion is located closer to the second semiconductor laser element than to the first semiconductor laser element.

7 . The light-emitting device according to claim 5 , wherein

the first semiconductor laser element is disposed such that there is no virtual straight line perpendicular to the third lateral surface and passing through both of the third step portion and the first semiconductor laser element in the top view, and

the second semiconductor laser element is disposed such that there is a virtual straight line perpendicular to the third lateral surface and passing through both of the third step portion and the second semiconductor laser element in the top view.

8 . The light-emitting device according to claim 5 , wherein

in the top view, a shortest distance between the first second semiconductor laser element and a virtual straight line, which is parallel to the third lateral surface and which passes through a point on the third step portion farthest from the third lateral surface in a direction perpendicular to the third lateral surface, is 50 μm or greater and less than 400 μm.

9 . The light-emitting device according to claim 5 , wherein

in the top view, a shortest distance between the third lateral surface and the first semiconductor laser element in a direction perpendicular to the third lateral surface is 50 μm or greater.

10 . The light-emitting device according to claim 5 , wherein

in the top view, a shortest distance between the first semiconductor laser element and a virtual straight line, which is parallel to the third lateral surface and which passes through a point on the third step portion farthest from the third lateral surface in a direction perpendicular to the third lateral surface, is shorter than a shortest distance between the second semiconductor laser element and the virtual straight line.

11 . The light-emitting device according to claim 5 , further comprising:

a first submount on which the first semiconductor laser element is disposed, the first submount being disposed on the upper surface of the lower portion; and

a second submount on which the second semiconductor laser element is disposed, the second submount being disposed on the upper surface of the lower portion and having a length in the first direction smaller than a length of the first submount in the first direction, wherein

the first submount is disposed at a position in which a virtual straight line, which is parallel to the third lateral surface and which passes through a point on the third step portion farthest from the third lateral surface in a direction perpendicular to the third lateral surface, passes through the first submount in the top view.

12 . The light-emitting device according to claim 5 , further comprising:

a wiring substrate including a first wiring pattern and having a bonding surface, the first wiring pattern of the wiring substrate having a first bonding region, a second bonding region, and a conductive region, the bonding surface, the first bonding region, the second bonding region, and the conductive region being located on an upper surface of the wiring substrate; and

a first connector bonded to the second bonding region of the first wiring pattern of the wiring substrate, wherein

the base member is bonded to the bonding surface and electrically connected to the first bonding region of the first wiring pattern of the wiring substrate, and

the conductive region is located between the first bonding region and the second bonding region in the top view.

13 . The light-emitting device according to claim 5 , further comprising:

a wiring substrate including a plurality of wiring patterns including the first wiring pattern of the wiring substrate and a second wiring pattern and having a bonding surface, each of the plurality of wiring patterns having a first bonding region and a second bonding region, the bonding surface, the first bonding region, and the second bonding region being located on an upper surface of the wiring substrate;

a first connector bonded to the second bonding region of the first wiring pattern of the wiring substrate; and

a second connector bonded to the second bonding region of the second wiring pattern of the wiring substrate, wherein

the base member is bonded to the bonding surface and electrically connected to the first bonding region of the first wiring pattern of the wiring substrate and the first bonding region of the second wiring pattern of the wiring substrate,

the base member is disposed between the first connector and the second connector in the top view, and

the first light-emitting element and the second semiconductor laser element are disposed in a direction in which the first connector, the base member, and the second connector are aligned in the top view.