Pressure sensor and method of assembling same

• US 8,378,435 B2
• Filed: 12/06/2010
• Issued: 02/19/2013
• Est. Priority Date: 12/06/2010
• Status: Expired due to Fees

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Lo, Wai Yew, Tan, Lan Chu
• Primary Examiner(s): Blum, David S
• Application Number:
  US12/960,571
• Publication Number:
  US 20120139063A1
• Time in Patent Office: 806 Days
• Field of Search: 257/415, 257/E21.04, 257/E21.499, 257/E29.324, 438/51
• US Class Current: 257/415
• CPC Class Codes: G01L 19/0069 from the sensor to its support
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: H01L 2224/16245 the item being metallic
• CPC Class Codes: H01L 2224/32145 the bodies being stacked
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/81 using a bump connector
• CPC Class Codes: H01L 2224/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 24/73 Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• CPC Class Codes: H01L 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01L 2924/181 Encapsulation

Abstract

A method of packaging a pressure sensing die includes providing a lead frame with lead fingers and attaching the pressure sensing die to the lead fingers such that bond pads of the die are electrically coupled to the lead fingers and a void is formed between the die and the lead fingers. A gel material is dispensed via an underside of the lead frame into the void such that the gel material substantially fills the void. The gel material is then cured and the die and the lead frame are encapsulated with a mold compound. The finished package does not include a metal lid.

Claims

1. A pressure sensor package, comprising:

a lead frame having a centrally located void;

a pressure sensing die electrically coupled to the lead frame, wherein the void is located between the lead frame and the pressure sensing die; and

an internal fill material disposed within the void between the lead frame and the pressure sensing die.

2. The pressure sensor package of claim 1, further comprising an encapsulation material at least partially surrounding the pressure sensing die and the lead frame.

3. The pressure sensor package of claim 2, wherein the encapsulation material comprises an epoxy molding compound.

4. The pressure sensor package of claim 1, wherein the pressure sensor package comprises a flat no-leads type package.

5. The pressure sensor package of claim 1, wherein the internal fill material comprises a silicon-based gel.

6. The pressure sensor package of claim 1, wherein the pressure sensing die comprises a piezo resistive transducer (PRT) die.

7. The pressure sensor package of claim 6, further comprising a second die disposed on a top surface of the PRT die and electrically coupled to the lead frame.

8. The pressure sensor package of claim 7, wherein the second die is coupled to the lead frame via bond wires.

9. The pressure sensor package of claim 1, wherein the pressure sensing die is coupled to the lead frame via a plurality of electrically conductive bumps.

10. The pressure sensor package of claim 1, wherein the lead frames include respective pluralities of lead fingers that provide for the electrical connection between the lead frames and the dies, wherein respective ones of the lead fingers are disposed adjacent to at least two opposing sides of the pressure sensing dies.

11. The pressure sensor package of claim 10, wherein the respective pluralities of lead fingers are disposed adjacent to each of four sides of the pressure sensing dies.

12. A pressure sensor package, comprising:

a lead frame;

at least one die electrically coupled to the lead frame, wherein a void is located between the lead frame and the at least one die;

a gel material disposed within the void between the lead frame and the at least one die; and

an encapsulation material substantially surrounding the at least one die and the lead frame.

13. The pressure sensor package of claim 12, wherein the at least one die comprises one of two stacked dies and two side-by-side dies, wherein the dies include a piezo resistive transducer die and an application-specific integrated circuit die.

14. The pressure sensor package of claim 12, wherein the pressure sensor package comprises one of a dual flat no-leads package and a quad flat no-leads package.

15. A method of assembling a pressure sensor package, comprising:

providing a lead frame having a plurality of lead fingers disposed in at least two opposing rows;

attaching a pressure sensing die to a first surface of the lead frame, wherein a void is formed between the die and the rows of lead fingers of the lead frame;

electrically coupling bond pads of the pressure sensing die to respective ones of the plurality of lead fingers of the lead frame;

dispensing a gel material into the void such that the gel material substantially fills the void and covers an active surface of the pressure sensing die;

encapsulating the pressure sensing die and the lead frame with a mold compound, wherein the mold compound covers the pressure sensing die, electrical connections between the pressure sensing die and the lead frame, and the lead frame except that a second surface of the lead fingers of the lead frame is exposed to allow external electrical connection to the pressure sensing die.

16. The method of packaging a pressure sensing die of claim 15, wherein the pressure sensing die is attached and electrically coupled to the lead fingers via a plurality of conductive bumps and the electrically coupling step comprises performing a reflow operation.

17. The method of assembling a pressure sensor package of claim 16, further comprising inverting the lead frame and the pressure sensing die then injecting the gel material through the lead frame and into the void, and curing the gel material.

18. The method of assembling a pressure sensor package of claim 17, further comprising covering a second surface of the lead frame with a tape, opposite the lead frame first surface, before the encapsulation step, and removing the tape after the encapsulation step, wherein after the tape is removed, at least a portion of the second surface of the lead frame is exposed.

19. The method of packaging a pressure sensing die of claim 17, further comprising covering a surface of the lead frame opposite the pressure sensing die before attaching of the pressure sensing die to the lead frame, and removing the covering before dispensing the gel material.

20. The method of packaging a pressure sensing die of claim 15, wherein the lead frame has a tape on a second surface thereof prior to attaching the pressure sensing die to the lead frame first surface and said tape is removed after the reflow operation is performed.