Thermal print head and method for manufacturing thermal print head

1 . A thermal print head comprising:

a substrate;

an insulating layer;

a wiring layer;

a resistor layer; and

a protective layer, wherein

the substrate has a first surface and a second surface opposite to the first surface,

a raised portion protruding toward a side opposite to the second surface and extending along a first direction in a plan view is formed on the first surface,

the insulating layer is disposed on the first surface,

the wiring layer is disposed on the insulating layer with the resistor layer interposed therebetween,

the wiring layer has a bonding pad,

a constituent material of the wiring layer is aluminum or an aluminum alloy,

the protective layer is disposed on the insulating layer to cover the wiring layer,

an opening that exposes the bonding pad is formed in the protective layer,

a width of the opening in the first direction is greater than a width of the bonding pad in the first direction,

the bonding pad has an upper surface and a bottom surface opposite to the upper surface,

a width of the bottom surface in a second direction is 1.1 times or more as great as a width of the upper surface in the second direction, and

the second direction is orthogonal to the first direction in a plan view,

in a cross-sectional view orthogonal to a second direction, the bonding pad has an upper surface, a bottom surface opposite to the upper surface, and a side surface continuous to the upper surface and the bottom surface,

aluminum chloride is not detected at the side surface of the bonding pad when analyzed using energy dispersive X-ray spectroscopy, and

the second direction is orthogonal to the first direction in a plan view.

2 . The thermal print head according to claim 1 , wherein the width of the opening in the first direction is equal to or greater than 100 μm.

3 . A method for manufacturing a thermal print head, the method comprising:

preparing a substrate having a first surface and a second surface opposite to the first surface;

forming, on the first surface, a raised portion protruding toward a side opposite to the second surface and extending along a first direction in a plan view;

forming an insulating layer on the first surface;

forming a wiring layer on the insulating layer with a resistor layer interposed therebetween; and

forming a protective layer on the insulating layer to cover the wiring layer, wherein

a constituent material of the wiring layer is aluminum or an aluminum alloy,

the wiring layer has a bonding pad,

an opening that exposes the bonding pad is formed in the protective layer,

a width of the opening in the first direction is greater than a width of the bonding pad in the first direction,

the bonding pad has an upper surface and a bottom surface opposite to the upper surface,

a width of the bottom surface in a second direction is 1.1 times or more as great as a width of the upper surface in the second direction, and

the second direction is orthogonal to the first direction in a plan view,

in a cross-sectional view orthogonal to a second direction, the bonding pad has an upper surface, a bottom surface opposite to the upper surface, and a side surface continuous to the upper surface and the bottom surface,

aluminum chloride is not detected at the side surface of the bonding pad when analyzed using energy dispersive X-ray spectroscopy, and

the second direction is orthogonal to the first direction in a plan view, and

the forming of the wiring layer includes:

depositing the constituent material of the wiring layer, and

patterning the deposited constituent material of the wiring layer by wet etching using a resist pattern as a mask.

4 . The method for manufacturing a thermal print head according to claim 3 , further comprising:

performing wire bonding on the bonding pad by using a capillary,

wherein the width of the opening in the first direction is greater than a diameter of the capillary.