Locking of mold compound to conductive substrate panels

• US 6,808,961 B1
• Filed: 04/14/2003
• Issued: 10/26/2004
• Est. Priority Date: 11/28/2000
• Status: Expired due to Term

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Yeen, Chan Peng, Bayan, Jaime, Nadarajah, Santhiran, Wan, Sharon Ko Mei, Lek, Hu Ah, Spalding, Peter Howard, Hong, Harry Kam Cheng
• Primary Examiner(s): Picardat, Kevin M.
• Application Number:
  US10/414,131
• Time in Patent Office: 561 Days
• Field of Search: 438/112, 438/113, 438/121, 438/122, 438/123, 438/124, 438/125, 438/126, 438/127
• US Class Current: 438/112
• CPC Class Codes: H01L 23/13 characterised by the shape
• CPC Class Codes: H01L 23/3121 a substrate forming part of the encapsulation
• 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 2924/14 Integrated circuits
• CPC Class Codes: H01L 2924/181 Encapsulation

Abstract

A panel assembly of packaged integrated circuit devices comprising a conductive substrate panel having an array of device areas and a plurality of locking passageways. The locking passageways are positioned about an inactive buffer area which surrounds the periphery of the array of device areas. The locking passageways extend from a topside of the panel toward a bottom side of the panel. The panel assembly also includes a molded cap that is molded over the topside of the panel to encapsulate the array of device areas and the inactive buffer area. The molded cap includes conforming locking stem portions that extend into each of the locking passageways in a manner locking the molded cap to the substrate panel such that during singulation of the device areas, the molded cap will not separate from the substrate panel at the inactive buffer area. In another aspect of the invention, a method for producing the panel assembly having the locking passageways is described. The method involves providing a conductive substrate panel having the locking passageways and applying molding material to the topside of the substrate panel such that the solidified molding material forms stems that conform to the passageways.

Claims

1. A method for manufacturing a panel assembly in which a mold cap is locked onto a conductive substrate panel, the method comprising:

providing the conductive substrate panel that has an array of device areas and an inactive buffer area that surrounds the array, a plurality of locking passageways that are positioned within the inactive buffer area, the locking passageways extending from a topside of the panel toward a bottom side thereof; and

applying molding material onto the topside of the panel to form a molded cap that encapsulates the array of device areas and the inactive buffer area, the molded cap further having conforming locking stem portions that extend into each of the locking passageways such that contact between each of the locking stems and locking passageways locks the molded cap to the substrate panel, wherein a portion the molded cap will not separate from the substrate panel at the inactive buffer area when the device areas are singulated.

2. The method as recited in claim 1, further comprising:

cutting through the conductive substrate panel and the molded cap by cutting along a path that runs between the array of device areas and the plurality of locking passageways wherein at least a portion of the inactive buffer area is separated from the array of device areas and wherein the contact between each of the locking stems and the locking passageways prevents a portion of the molded cap from separating from the inactive buffer area.

3. The method as recited in claim 1, further comprising:

cutting through the conductive substrate panel and the molded cap by cutting along a path that runs across the array of device areas and the inactive buffer area.

4. The method as recited in claim 3, further comprising:

cutting through the conductive substrate panel and the molded cap by cutting along a path that runs between the array of device areas and the plurality of locking passageways wherein the contact between each of the locking stems and the locking passageways keeps a portion of the molded cap attached to the inactive buffer area.

5. The method as recited in claim 2, further comprising:

cutting through the conductive substrate panel and the molded cap simultaneously.

6. The method as recited in claim 1, wherein each of the locking stems have substantially the same shape and size as the locking passageway into which each of the locking stems extend.

7. The method as recited in claim 1 further comprising:

forming the locking passageways using a chemical etching process.

8. The method as recited in claim 7, wherein the chemical etching operation further comprises:

partially etching a back side opening on the topside of the conductive substrate panel; and

partially etching a bottom side opening on the bottom side of the conductive substrate panel such that the partial etching on the bottom side and the topside of the conductive substrate panel results in locking passageways that extends from the bottom side to the topside.

9. The method as recited in claim 8, wherein the chemical etching operation results in the bottom side opening having a cross-sectional dimension larger than that of the topside opening.

10. The method as recited in claim 1, further comprising

attaching an adhesive tape to the surface of the molded cap so to secure the panel assembly during a singulation process.

11. The method as recited in claim 1, wherein the conforming locking stem portions are integrally formed with the molded cap.

12. A method for manufacturing a panel assembly in which a mold cap is locked onto a conductive substrate panel, the method comprising:

providing the conductive substrate panel which has an array of device areas and an inactive buffer area that surrounds the array;

defining a plurality of locking passageways positioned within the inactive buffer area, the locking passageways extending from a topside of the panel toward a bottom side thereof; and

injecting liquid molding material onto the topside of the panel so that the molding material encapsulates the array of device areas and the inactive buffer area, and so that the molding material flows into and fills the locking passageways; and

curing the liquid molding material to form a solid molded cap with integrally formed locking stems wherein the molded cap is bonded to and encapsulates the array of device areas and the inactive buffer area, and the locking stems extend into each of the locking passageways such that the contact between each of the locking stems and the locking passageways lock at least a portion of the molded cap to the substrate panel.

13. A method as recited in claim 12 further comprising:

separating the portion of the leadframe containing the array of device areas from the portion containing the inactive buffer area, wherein the contact between each of the locking stems and the locking passageways keeps a portion of the molded cap attached to the inactive buffer area.

14. A method as recited in claim 13 wherein the operation of separation is performed by passing a saw blade through the conductive substrate panel and the molded cap along a path that runs between the array of device areas and the plurality of locking passageways.

15. The method as recited in claim 12, further comprising:

cutting through the conductive substrate panel and the molded cap by cutting along a path that runs across the array of device areas and the inactive buffer area.

16. The method as recited in claim 15, further comprising:

cutting through the conductive substrate panel and the molded cap simultaneously.

17. The method as recited in claim 12, wherein each of the locking stems have substantially the same shape and size as the locking passageway into which each of the locking stems extend.

18. A method as recited in claim 12, wherein defining at least some of the plurality of locking passageway includes:

forming a lock section having a transverse cross-sectional width that is larger than a transverse cross-sectional width at a topside entrance into a respective locking passageway such that a corresponding lock section of the corresponding stem has a larger transverse cross-sectional width than a corresponding section of the stem at the topside entrance into the passageway.

19. A method as recited in claim 12, wherein defining the plurality of locking passageway includes:

forming each locking passageway to have a bottom side entrance that has a cross-sectional width that is larger than that of a topside entrance, the corresponding stem having a cross-sectional width at the bottom side entrance that is larger than a cross-sectional width at the topside entrance.

20. A method as recited in claim 12, wherein defining the plurality of locking passageway includes:

defining at least one of the locking passageways with a transverse cross-sectional area substantially having the shape of an elongated oval, a circle, a square or an “

L”

.

21. A method as recited in claim 12, wherein defining the plurality of locking passageway includes:

grouping at least two of the locking passageways together such that the at least two locking passageways are positioned proximate to each other.

22. A method as recited in claim 12, wherein defining the plurality of locking passageway includes:

forming each locking passageway to have its smallest width located at some point in between the topside entrance and the bottom side entrance.

23. A method as recited in claim 22, wherein forming each locking passageway includes:

defining the topside entrance and the bottom side entrance of each locking passageway with widths larger than the smallest width dimension such that each locking passageway and locking stem have an hourglass shape.

24. A method as recited in claim 12, wherein the method further comprises:

providing the device areas with a semiconductor die, a plurality of electrical contacts positioned adjacent to the semiconductor die, and a plurality of interconnecting wires that connect the semiconductor die to each of the electrical contacts.