Method for packaging microsensors

A method of packaging a sensor unit having an active face which includes a sensor element on the active face of said sensor, said method comprising the steps of:

• providing a substrate having a rear surface, a front surface, and electrical connection means on said rear surface;
• forming a cavity in said substrate, said a cavity being formed as an aperture extending completely through said substrate;
• locating said sensor unit over said substrate, with said active face facing in the direction of said rear surface of said substrate, and said sensor element over said cavity;
• electrically connecting said sensor unit to said electrical connection means;
• securing said sensor unit to said substrate;
• dispensing an underfill material at an interface between said sensor unit and said substrate;
• due to capillary force on said underfill material, drawing said underfill material between said interface such that said underfill material fills at least a portion of said interface between said sensor unit and said substrate without covering said sensor element;
• and
• forming a seal at said interface between said sensor unit and said substrate, said seal completely circumscribing said sensor element and isolating said sensor element and said cavity from said rear surface of said substrate;
• and
• forming a cover over said electronic connection means of said sensor unit, said cover extending from said sensor element at one end and terminating at another end within said underfill material such that said electrical connection means of said sensor unit is isolated from a sensed environment.

A method of packaging a sensor unit having an active face which includes a sensor element on the active face of said sensor unit, said method comprising the steps of:

• providing a substrate having a rear surface, a front surface, and electrical connection means on said rear surface;
• forming a cavity in said substrate, said a cavity being formed as an aperture extending completely through said substrate;
• locating said sensor unit over said substrate, with said active face facing in the direction of said rear surface of said substrate, and said sensor element over said cavity;
• electrically connecting said sensor unit to said electrical connection means;
• securing said sensor unit to said substrate;
• dispensing an underfill material at an interface between said sensor unit and said substrate;
• due to capillary force on said underfill material, drawing said underfill material between said interface such that said underfill material fills at least a portion of said interface between said sensor unit and said substrate without covering said sensor element;
• and
• forming a seal at said interface between said sensor unit and said substrate, said seal completely circumscribing said sensor element and isolating said sensor element and said cavity from said rear surface of said substrate;
• and
• depositing a protective layer over said electrical connection means of said sensor unit, said protective layer extending from said sensor element at one end and terminating at another end within said underfill material such that said electrical connection means of said sensor unit is isolated from a sensed environment.

A method of packaging a sensor unit having an active face which includes a sensor element on said active face of said sensor unit, said method comprising the steps of:

• providing a substrate having a rear surface, a front surface, and electrical connection means on said rear surface;
• forming a cavity in said substrate, said electrical connection means having at least one end terminating on said portion at least partially defining said cavity;
• locating said sensor unit over said cavity with said active face facing in a direction away from said rear surface of said substrate;
• securing said sensor unit to said substrate;
• electrically connecting said sensor unit to said electrical connection means;
• placing a cap on said rear surface of said substrate and over said sensor unit to completely enclose said sensor unit therein, said cap and said portion of said substrate defining said cavity;
• securing said cap to said substrate through non-conductive connecting bumps formed on at least one of said cap and said substrate;
• and
• dispensing an underfill material at an interface between said cap and said substrate;
• due to the existing capillary force on said underfill material and said interface between said sensor unit and said substrate, drawing said underfill material between said interface whereby said underfill material fills said interface between said sensor unit and said substrate without covering said sensor element, and
• forming a seal at said interface between said sensor unit and said substrate, said seal completely circumscribing said sensor element and isolating said sensor element and said cavity from said rear surface of said substrate.