Plastic package assembly method for a ferroelectric-based integrated circuit

• US 6,232,153 B1
• Filed: 06/04/1998
• Issued: 05/15/2001
• Est. Priority Date: 06/04/1998
• Status: Expired due to Fees

• Current Assignee: Ramtron International Corporation (Infineon Technologies AG)
• Original Assignee: Ramtron International Corporation (Infineon Technologies AG)
• Inventors: Lau, Vic, Mitra, Sanjay
• Primary Examiner(s): Elms, Richard
• Assistant Examiner(s): Pyonin, Adam
• Application Number:
  US09/090,575
• Time in Patent Office: 1,076 Days
• Field of Search: 438/106, 438/119, 438/112, 438/127, 438/3, 101/487
• US Class Current: 438/127
• CPC Class Codes: H01L 2223/54473 for use after dicing
• CPC Class Codes: H01L 23/544 Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps test patterns for characterising or monitoring manufacturing processes H01L22/00
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A plastic package assembly method suitable for ferroelectric-based integrated circuits includes a strict thermal budget that reduces the time at temperature for four key processing steps: die attach cures, die coat cures, molding cures, and marking cures. The plastic package assembly method uses low temperature mold and die coat materials, as well as low temperature curable inks or laser marking in order to minimize degradation of electrical performance, thus improving yields and reliability. The assembly method uses a snap cure die attach step, a die coat followed by a room temperature cure, and formation of the plastic package with room temperature curable molding compounds not requiring a post mold cure. Front and back marking of the plastic package is accomplished using either an infrared or ultraviolet curable ink followed by minimum cure time at elevated temperature, or by using laser marking.

Claims

1. A plastic package assembly method for significantly improving the yield and reliability of a ferroelectric-based integrated circuit comprising:

attaching the integrated circuit to a lead frame using a snap cure;

coating the integrated circuit;

curing the coated integrated circuit;

encapsulating the lead frame and attached, coated ferroelectric integrated circuit in a plastic package;

marking either or both of a front and back surface of the plastic package; and

curing the marked surface of the plastic package, such that the total time the ferroelectric integrated circuit is exposed to a temperature of above 145°

C. is at most two hours and the short term memory retention is improved by a factor of at least 1.9 when compared with a conventional assembly method involving more than two hours at a temperature above 145°

C.

2. The plastic package assembly method of claim 1 in which the total time the integrated circuit is exposed to a temperature of above 145°

C. is about 1.5 hours.

3. The plastic package assembly method of claim 1 in which the total time the integrated circuit is exposed to a temperature of above 145°

C. is about three minutes.

4. A plastic package assembly method for significantly improving the yield and reliability of a ferroelectric-based integrated circuit comprising:

attaching the integrated circuit to a lead frame using a snap cure;

coating the integrated circuit;

curing the coated integrated circuit;

encapsulating the lead frame and attached, coated ferroelectric integrated circuit in a plastic package;

marking either or both of a front and back surface of the plastic package; and

curing the marked surface of the plastic package, such that the total time the ferroelectric integrated circuit is exposed to a temperature of above 145°

C. is at most two hours and the long term memory retention is improved by a factor of at least 2.8 when compared to a conventional assembly method involving more than two hours at a temperature above 145°

C.

5. The plastic package assembly method of claim 4 in which the total time the integrated circuit is exposed to a temperature of above 145°

C. is at most 1.5 hours.

6. The plastic package assembly method of claim 4 in which the total time the integrated circuit is exposed to a temperature of above 145°

C. is about 3 minutes.

7. A plastic package assembly method for significantly improving the yield and reliability of a ferroelectric-based integrated circuit comprising:

attaching the integrated circuit to a lead frame using a snap cure;

coating the integrated circuit;

curing the coated integrated circuit;

encapsulating the lead frame and attached, coated ferroelectric integrated circuit in a plastic package;

marking either or both of a front and back surface of the plastic package; and

curing the marked surface of the plastic package, such that the total time the ferroelectric integrated circuit is exposed to a temperature of above 145°

C. is at most two hours and the number of failing bits is reduced by a factor of at least 135 for short term memory retention when compared to a conventional assembly method involving more than two hours at a temperature above 145°

C.

8. The plastic package assembly method of claim 7 in which the total time the integrated circuit is exposed to a temperature of above 145°

C. is at most 1.5 hours.

9. The plastic package assembly method of claim 7 in which the total time the integrated circuit is exposed to a temperature of above 145°

C. is about 3 minutes.

10. A plastic package assembly method for significantly improving the yield and reliability of a ferroelectric-based integrated circuit comprising:

attaching the integrated circuit to a lead frame using a snap cure;

coating the integrated circuit;

curing the coated integrated circuit;

encapsulating the lead frame and attached, coated ferroelectric integrated circuit in a plastic package;

marking either or both of a front and back surface of the plastic package; and

curing the marked surface of the plastic package, such that the total time the ferroelectric integrated circuit is exposed to a temperature of above 145°

C. is at most two hours and the number of failing bits is reduced by a factor of at least 113 for long term memory retention when compared to a conventional assembly method involving more than two hours at a temperature above 145°

C.

11. The plastic package assembly method of claim 10 in which the total time the integrated circuit is exposed to a temperature of above 145°

C. is at most 1.5 hours.

12. The plastic package assembly method of claim 10 in which the total time the integrated circuit is exposed to a temperature of above 145°

C. is about 3 minutes.