Substrate for liquid ejection head, liquid ejection head, and method for manufacturing substrate for liquid ejection head
Provided is a substrate for a liquid ejection head including: a heating element that generates an energy for ejecting a liquid; an electrode pad portion that has a wiring layer at a lower layer thereof, is electrically connected to the heating element through the wiring layer, and is electrically connected to an external component through a bonding material; and an insulating protection layer. The electrode pad portion further has a lower electrode layer and an upper electrode layer, the insulating protection layer disposed at a first region overlapping the wiring layer in a film thickness direction has a first opening through which the lower and upper electrode layers are connected, and the insulating protection layer disposed at a position including at least a second region overlapping the bonding material in the film thickness direction has a second opening through which the lower and upper electrode layers are connected.
1 . A substrate for a liquid ejection head comprising:
a heating element configured to generate an energy for ejecting a liquid;
an electrode pad portion having a wiring layer at a lower layer thereof, electrically connected to the heating element through the wiring layer, and electrically connected to an external component through a bonding material; and
an insulating protection layer, wherein
the electrode pad portion further has a lower electrode layer and an upper electrode layer,
the insulating protection layer disposed at a first region overlapping the wiring layer in a film thickness direction has a first opening through which the lower electrode layer and the upper electrode layer are connected, and
the insulating protection layer disposed at a position including at least a second region overlapping the bonding material in the film thickness direction has a second opening through which the lower electrode layer and the upper electrode layer are connected.
2 . The substrate for a liquid ejection head according to claim 1 , further comprising an anti-cavitation layer formed so as to cover the heating element, wherein
the lower electrode layer includes a layer made of a same material as at least part of the anti-cavitation layer.
3 . The substrate for a liquid ejection head according to claim 2 , wherein a film thickness of the anti-cavitation layer is 20 nm or more and 300 nm or less.
4 . The substrate for a liquid ejection head according to claim 2 , further comprising a first insulating protection layer electrically insulating the heating element and the anti-cavitation layer from each other, wherein
the insulating protection layer is a second insulating protection layer covering at least part of the anti-cavitation layer.
5 . The substrate for a liquid ejection head according to claim 2 , wherein the number of layers forming the lower electrode layer and the number of layers forming the anti-cavitation layer are the same.
6 . The substrate for a liquid ejection head according to claim 2 , wherein the number of layers forming the lower electrode layer and the number of layers forming the anti-cavitation layer are different.
7 . The substrate for a liquid ejection head according to claim 2 , wherein the anti-cavitation layer is a layer including a laminate of iridium and tantalum.
8 . The substrate for a liquid ejection head according to claim 1 , wherein the wiring layer is connected to the lower electrode layer.
9 . The substrate for a liquid ejection head according to claim 1 , wherein the lower electrode layer in the electrode pad portion contains iridium metal or an iridium alloy.
10 . The substrate for a liquid ejection head according to claim 1 , wherein the upper electrode layer in the electrode pad portion contains gold.
11 . The substrate for a liquid ejection head according to claim 1 , wherein the wiring layer contains aluminum.
12 . The substrate for a liquid ejection head according to claim 1 , wherein no probe mark is formed on the wiring layer.
13 . The substrate for a liquid ejection head according to claim 1 , wherein a plurality of the first openings are provided per the electrode pad portion.
14 . The substrate for a liquid ejection head according to claim 13 , wherein the plurality of first openings are provided in a direction in which a plurality of the heating elements are arrayed.
15 . The substrate for a liquid ejection head according to claim 1 , wherein the second opening is larger in area than the first opening.
16 . The substrate for a liquid ejection head according to claim 1 , wherein a value of sheet resistance of the lower electrode layer is larger than a value of sheet resistance of the upper electrode layer.
17 . The substrate for a liquid ejection head according to claim 1 , wherein the first opening and the second opening are independent of each other.
18 . A liquid ejection head incorporating a substrate, the substrate comprising:
a heating element configured to generate an energy for ejecting a liquid;
an electrode pad portion having a wiring layer at a lower layer thereof, electrically connected to the heating element through the wiring layer, and electrically connected to an external component through a bonding material; and
an insulating protection layer, wherein
the electrode pad portion further has a lower electrode layer and an upper electrode layer,
the insulating protection layer disposed at a first region overlapping the wiring layer in a film thickness direction has a first opening through which the lower electrode layer and the upper electrode layer are connected, and
the insulating protection layer disposed at a position including at least a second region overlapping the bonding material in the film thickness direction has a second opening through which the lower electrode layer and the upper electrode layer are connected.
19 . A manufacturing method of a substrate for a liquid ejection head, the substrate including
a heating element configured to generate an energy for ejecting a liquid,
an electrode pad portion that having a wiring layer at a lower layer thereof, electrically connected to the heating element through the wiring layer, and electrically connected to an external component through a bonding material,
an anti-cavitation layer that is formed so as to cover the heating element, and
an insulating protection layer,
the method comprising:
forming the wiring layer at the lower layer in the electrode pad portion;
forming a lower electrode layer at a region including a first region overlapping the wiring layer in a film thickness direction and a second region overlapping the bonding material in the film thickness direction, the lower electrode layer being made of a same material as at least part of the anti-cavitation layer;
forming the insulating protection layer such that a first opening through which the lower electrode layer and an upper electrode layer are connected is formed at the first region and a second opening through which the lower electrode layer and the upper electrode layer are connected is formed at the second region;
forming the upper electrode layer such that the upper electrode layer covers the first opening and the second opening; and
bonding the bonding material to the upper electrode layer.
20 . The manufacturing method according to claim 19 , wherein
the forming the wiring layer includes forming the heating element, and
the forming the lower electrode layer includes forming the anti-cavitation layer.