Process for manufacturing a monolithic printhead with truncated cone shape nozzles

1. Process for manufacturing a thermal ink jet printhead comprising a tank suitable for containing ink, comprising steps of:

providing a wafer comprising a plurality of dice, each of which includes a substrate and a plurality of resistors, said dice having an upper face and a lower face;

making elementary blind holes through said upper face, in correspondence with each of said resistors;

etching a first part of a groove in said substrate on said lower face of each of said dice, said groove being intended for conveying said ink of said tank;

applying a first layer of positive photoresist on said upper face of each of said dice, and obtaining a plurality of cavities on said first layer of positive photoresist, each of said cavities being in correspondence with each of said resistors and having a shape that covers the corresponding resistor and at least one of said elementary holes;

depositing a plurality of sacrificial layers inside each of said cavities;

applying a second layer of positive photoresist on said upper face of each of said dice and on said sacrificial layers;

producing from said second layer of positive photoresist a plurality of casts, each of said casts being adherent to each of said sacrificial layers and having an outer face;

applying a structural layer on said upper face of each of said dice, on said sacrificial layers and on said casts, said structural layer having an outer surface co-planar with said outer face of said casts;

etching a second part of said groove in said substrate on said lower face of each of said dice, until said elementary holes are reached and rendered through-holes;

removing said positive photoresist from said elementary holes—separating said dice;

removing said casts; and

removing said sacrificial layers.

2. Process according to claim 1 , wherein said steps of depositing a plurality of sacrificial layers ( 31 ) on each of said dice ( 61 ); and of etching a second part of said groove ( 45 ) are carried out by means of electrochemical processes.

3. Process according to claim 2 , wherein said steps of depositing a plurality of sacrificial layers on each of said dice; and of etching a second part of said groove use as the electrode a conducting layer, which forms a single network connected on the inside of each of said dice.

4. Process according to claim 3 , wherein said conducting layer forms a single network connected between at least two different ones of said dice.

5. Process according to claim 4 , wherein said conducting layer forms a single network connected between all of said dice belonging to said wafer ( 60 ).

6. Process according to claim 1 , wherein said sacrificial layers are made of metal.

7. Process according to claim 1 , wherein said step of applying a second layer of positive photoresist is conducted using a first PDMS mould.

8. Process according to claim 7 , wherein said step of applying a second layer of positive photoresist is carried out by capillarity.

9. Process according to claim 1 , wherein said step of applying a structural layer is conducted using a second PDMS mould.

10. Process according to claim 9 , wherein said step of applying a structural layer is carried out by capillarity.

11. Process according to claim 1 , wherein said step of applying a second layer of positive photoresist and said step of applying a structural layer are conducted using a single PDMS mould.

12. Process for manufacturing a thermal ink jet printhead ( 40 ) comprising a tank suitable for containing ink ( 142 ), comprising the steps of:

providing a wafer comprising a plurality of dice, each of which includes a substrate and a plurality of resistors, said dice ( 61 ) having an upper face and a lower face;

making elementary blind holes through said upper face, in correspondence with each of said resistors;

etching a first part of a groove in said substrate on said lower face of each of said dice ( 61 ), said groove ( 45 ) being intended for conveying said ink ( 142 ) of said tank ( 103 );

applying a first layer of positive photoresist on said upper face of each of said dice, and obtaining a plurality of cavities on said first layer of positive photoresist, each of said cavities being in correspondence with each of said resistors and having a shape that covers the corresponding resistor and at least one of said elementary holes;

depositing a plurality of sacrificial layers inside each of said cavities;

applying a second layer of positive photoresist on said upper face of each of said dice and on said sacrificial layers;

producing from said second layer of positive photoresist a plurality of casts, each of said casts being adherent to each of said sacrificial layers ( 31 ) and having an outer face;

applying a structural layer on said upper face of each of said dice, on said sacrificial layers and on said casts, said structural layer having an outer surface co-planar with said outer face of said casts;

removing said casts;

etching a second part of said groove in said substrate on said lower face of each of said dice, until said elementary holes are reached and rendered through-holes;

removing said positive photoresist from said elementary holes;

removing said sacrificial layers; and

separating said dice.

13. Process according to claim 12 , wherein said steps of ( 206 ) depositing a plurality of sacrificial layers ( 31 ) on each of said dice ( 61 );

etching a second part of said groove; and

removing said plurality of sacrificial layers are carried out by means of electrochemical processes.

14. Process according to claim 13 , wherein said steps of ( 206 ) depositing a plurality of sacrificial layers ( 31 ) on each of said dice ( 61 );

etching a second part of said groove; and

removing said plurality of sacrificial layers use as the electrode a conducting layer, which forms a single network connected on the inside of each of said dice.

15. Process according to claim 14 , wherein said conducting layer forms a single network connected between at least two different ones of said dice.

16. Process according to claim 15 , wherein said conducting layer forms a single network connected between all of said dice belonging to said wafer ( 60 ).

17. Process according to claim 12 , wherein said sacrificial layers are made of metal.

18. Process according to claim 12 , wherein said step of applying a second layer of positive photoresist is conducted using a first PDMS mould.

19. Process according to claim 18 , wherein said step of applying a second layer of positive photoresist is carried out by capillarity.

20. Process according to claim 12 , wherein said step of applying a structural layer is carried out using a second PDMS mould.

21. Process according to claim 20 , wherein said step of applying a structural layer is carried out by capillarity.

22. Process according to claim 12 , wherein said step of applying a second layer of positive photoresist and said step of applying a structural layer are carried out by means of a single PDMS mould.