Inkjet printhead assembly

1. A printhead assembly comprising:

a printhead formed from a silicon substrate; and

a support member comprising:

a core element defining a plurality of ink reservoirs, each ink reservoir being in fluid communication with the printhead; and

a multilayer shell formed around at least part of the core element, the multilayer shell having an effective coefficient of thermal expansion which is comparable to that of silicon.

2. A printhead assembly as claimed in claim 1 , wherein the multilayer shell is formed from a plurality of layers of metals, each of the layers having a coefficient of thermal expansion which is different to that of silicon.

3. A printhead assembly as claimed in claim 1 , wherein the printhead comprises a moulding bonded to the core element and a silicon printhead integrated circuit, the moulding defining a plurality of ink passages for passing ink from the ink reservoirs to the printhead integrated circuit.

4. A printhead assembly as claimed in claim 1 , wherein the multilayer shell comprises a triplet of metal layers, one of the layers having a first coefficient of thermal expansion and is located between a pair of layers each having a second coefficient of thermal expansion.

5. A printhead assembly as claimed in claim 4 , wherein the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion.

6. A printhead assembly as claimed in claim 5 , wherein the second coefficient of thermal expansion is about 1.3×10 −6 m/° C.

7. A printhead assembly as claimed in claim 5 , wherein the first coefficient of thermal expansion exceeds 2.5×10 −6 m/° C.