Tie bar removal for semiconductor device packaging

Patent metadata

Field	Value
Publication number	US-11222790-B2
Application number	US-202016862027-A
Country	US
Kind code	B2
Filing date	Apr 29, 2020
Priority date	Dec 26, 2019
Publication date	Jan 11, 2022
Grant date	Jan 11, 2022

Abstract

A method of tie bar removal is provided. The method includes forming a leadframe including a tie bar and a flag. The tie bar extends from a side rail of the leadframe and has a distal portion at an angle different from a plane of the flag. A semiconductor die is attached to the flag of the leadframe. A molding compound encapsulates the semiconductor die, a portion of the leadframe, and the distal portion of the tie bar. The tie bar is separated from the molding compound with an angled cavity remaining in the molding compound.

First claim

What is claimed is:

1. A method comprising:
forming a leadframe including a tie bar and a flag, the tie bar extending from a side rail and having a distal portion at an angle different from a plane of the flag;
attaching a semiconductor die to the flag of the leadframe;
encapsulating with a molding compound the semiconductor die, a portion of the leadframe, and the distal portion of the tie bar; and
separating the tie bar from the molding compound, an angled cavity remaining in the molding compound.

2. The method of claim 1 , wherein the distal portion is formed at an angle in a range of 15 to 75 degrees relative to the plane of the flag.

3. The method of claim 1 , further comprising applying a low adhesion material to the distal portion of the tie bar.

4. The method of claim 3 , wherein applying the low adhesion material to the distal portion of the tie bar comprises plating the distal portion of the tie bar with a silver, gold, palladium, or nickel material.

5. The method of claim 1 , wherein a tip of the distal portion of the tie bar comprises a tetrahedron or pyramid structure.

6. The method of claim 1 , wherein separating the tie bar from the molding compound occurs during a singulation operation.

7. The method of claim 1 , wherein forming the leadframe occurs during a leadframe stamping process.

8. The method of claim 1 , wherein separating the tie bar from the molding compound increases a creepage distance between an end conductive lead of a first plurality of leadframe leads and an end conductive lead of a second plurality of leadframe leads.

9. A method comprising:
providing a leadframe including a plurality of conductive leads, a tie bar, and a flag, the tie bar extending from a side rail of the leadframe;
bending to form a distal portion of the tie bar at an angle different from a plane of the flag;
attaching a semiconductor die to the flag of the leadframe;
encapsulating with a molding compound the semiconductor die, a portion of the leadframe, and the distal portion of the tie bar; and
separating the tie bar from the molding compound, an angled cavity remaining in the molding compound.

10. The method of claim 9 , wherein the distal portion is formed at an angle in a range of 15 to 75 degrees relative to the plane of the flag.

11. The method of claim 9 , further comprising applying a low adhesion material to the distal portion of the tie bar.

12. The method of claim 11 , wherein applying the low adhesion material to the distal portion of the tie bar comprises coating the distal portion of the tie bar with material including silver, gold, or nickel.

13. The method of claim 9 , wherein a tip of the distal portion of the tie bar comprises a semi-spherical or semi-cylindrical structure.

14. The method of claim 9 , wherein separating the tie bar from the molding compound occurs during a singulation operation.

15. The method of claim 9 , wherein bending the distal portion of the tie bar at the angle different from the plane of the flag occurs during a leadframe stamping process.

16. The method of claim 9 , wherein separating the tie bar from the molding compound increases a creepage distance between two conductive leads of the plurality of conductive leads.

Assignees

• Nxp Usa Inc

Inventors

• Gan Richard Te
• Tank Rushik Prabhudas
• Gong Zhiwei
• Carpenter Burton Jesse
• Liu Jinmei

Classifications

• H10W74/129

  forming a chip-scale package [CSP] · CPC title

• H10W74/016

  using moulds · CPC title

• H10W70/424

  Cross-sectional shapes (H10W70/481 takes precedence) · CPC title

• H10W70/411

  Chip-supporting parts, e.g. die pads · CPC title

• H10W70/041

  Connecting or disconnecting interconnections to or from leadframes, e.g. connecting bond wires or bumps · CPC title