Package, in particular for MEMS devices and method of making same
A package includes a substrate provided with a passing opening and a MEMS device. The MEMS device includes an active surface wherein a portion of the MEMS device is integrated sensitive to the chemical/physical variations of a fluid. The active surface of the MEMS device faces the substrate and is spaced therefrom, the sensitive portion being aligned to the passing opening. A protective package incorporates the MEMS device and the substrate, leaving at least the sensitive portion of the MEMS device exposed through the passing opening of the substrate.
1. A method for protecting packages comprising a substrate provided with a passing opening, and at least one MEMS device comprising an active surface wherein a portion of said MEMS device is integrated sensitive to chemical/physical variations of a fluid, the method comprising the following steps:
forming on said sensitive portion a protection layer which fills at least partially said passing opening,
forming a protective package, which incorporates said MEMS device and said substrate, leaving said protection layer exposed,
removing said protection layer so that said protective package leaves at least said sensitive portion of said MEMS device exposed, through said passing opening of said substrate.
2. The method according to claim 1 , wherein said protection layer is formed of a paste washable in water.
3. The method according to claim 1 , wherein said protection layer is a viscous paste, with a viscosity comprised between 15.000 and 17.000 cps.
4. The method according to claim 1 , wherein said protection layer is formed at least on said sensitive portion of the MEMS device before it is connected to said substrate.
5. The method according to claim 1 , wherein said protection layer is formed at least on said sensitive portion of said MEMS device by stencil printing.
6. The method according to claim 1 , wherein said protection layer is formed at least on said sensitive portion of the MEMS device after it has been connected to a substrate.
7. The method according to claim 5 , wherein said protection layer is formed on a lower surface of the substrate, then with a spatula it is distributed inside said passing opening.
8. The method according to claim 2 , wherein said protection layer is removed through a washing step first in cold water and then in hot water.
9. The method according to claim 8 , wherein said washing step is carried out with spray jets of cold water at a pressure of about 4 atmospheres and then with spray jets of hot water at about 50° C. at a pressure of about 4 atmospheres.
10. The method according to claim 2 , wherein said protection layer is removed through a washing step in cold water with the help of ultrasounds.
11. A method of protecting packages including a substrate and a die, the die including an active surface including a sensitive portion and the method comprising:
forming a passing opening in the substrate;
forming a protection layer over the sensitive portion of the die;
attaching the die to the substrate;
forming a protective package to house the substrate and the die, the protective package leaving the passing opening exposed; and
removing the protection layer through the passing opening.
12. The method of claim 11 ,
wherein the protection layer forms a projection extending from the active surface of the die;
wherein attaching the die to the substrate includes inserting the projection into the passing opening.
13. The method of claim 11 wherein attaching the die to the substrate is done before forming the protection layer.
14. The method of claim 11 wherein the protection layer comprises a water soluble paste.