Semiconductor device with webbing between leads
View Patent ↗A quad flat package integrated circuit (IC) device has alternating inner and outer leads that protrude from a package body. The inner leads are j-shaped leads and the outer leads are gull-wing shaped leads. The package body is formed such that it includes plastic lead webbings between adjacent leads, which help prevent metal particles from getting lodged between the leads and causing electrical shorts. The webbings are made of the same molding compound as the package body and are formed together with the package body.
1. A packaged integrated circuit (IC) device, comprising:
a lead frame having a plurality of leads, including first and second leads;
a case encapsulating a first portion of the lead frame, wherein:
each of the first and second leads has (i) an encapsulated portion covered by the case and (ii) an exposed portion that protrudes from the case;
the exposed portion of each of the first and second leads has an exposed flat segment proximal to the case;
the first lead is adjacent to the second lead; and
the exposed flat segment of the first lead is parallel to the exposed flat segment of the second lead; and
a first lead webbing located between the exposed flat segment of the first lead and the exposed flat segment of the second lead,
wherein a thickness of the first lead webbing is within 20% of a thickness of the first lead.
2. The device of claim 1 , wherein the device further comprises:
a semiconductor die attached to the lead frame and electrically coupled to the plurality of leads.
3. The device of claim 1 , wherein:
the first lead is one of a plurality of inner leads;
the second lead is one of a plurality of outer leads;
each of the inner leads is bent into a j-shaped lead; and
each of the outer leads is bent into a gull-wing-shaped lead.
4. The device of claim 3 , wherein each of the inner and outer leads has a pair of exposed perpendicular burrs corresponding to a dam bar that has been cut.
5. The device of claim 3 , wherein:
the device has four sides in a plan view;
each side of the device has one fourth of the inner leads; and
each side of the device has one fourth of the outer leads.
6. The device of claim 3 , wherein:
the device has sides crenellated with alternating recesses and tabs;
each of the inner leads emerges from the case in a corresponding recess; and
each of the outer leads emerges from the case at a corresponding tab.
7. The device of claim 6 , wherein each of the tabs and recesses is tapered.
8. The device of claim 7 , wherein the taper is linear.
9. The device of claim 7 , wherein the taper is non-linear.
10. The device of claim 6 , wherein, for each recess, the device has a corresponding channel in the bottom of the case to provide space for the corresponding inner lead.
11. The device of claim 6 , wherein:
the first lead webbing extends from the first lead to a first side of the corresponding recess;
the exposed flat segment of the first lead extends to a top elbow of the first lead; and
the first lead webbing extends from the back of the corresponding recess to a point not beyond the top elbow of the first lead.
12. The device of claim 6 , wherein:
the tabs are saw-tooth shaped; and
the first lead webbing is substantially triangular.
13. A method for packaging an integrated circuit (IC) device comprising a lead frame having a plurality of leads, the plurality of leads including adjacent first and second leads, the method comprising:
(a) attaching a semiconductor die to the lead frame;
(b) electrically connecting the die to the lead frame with bond wires, thereby forming an assembly of the lead frame, die, and bond wires;
(c) encapsulating the assembly, wherein the encapsulating comprises:
placing the assembly inside a cavity of a mold form;
injecting uncured molding compound into the cavity, wherein:
the lead frame comprises a first dam bar perpendicularly attached to the first and second leads;
the molding compound extends out to the first dam bar to form a preliminary first lead webbing; and
each of the first and second leads has:
(i) an encapsulated portion covered by the molding compound; and
(ii) an exposed portion that protrudes from the molding compound;
curing the molding compound; and
removing the encapsulated assembly from the mold form;
(d) cutting the first dam bar between the first and second leads;
(e) trimming the IC device; and
(f) forming the IC device, wherein:
the exposed portion of the first and second leads has an exposed flat segment proximal to the case;
the exposed flat segment of the first lead is parallel to the exposed flat segment of the second lead;
the first lead webbing is formed from the preliminary first lead webbing; and
the first lead webbing is located between the exposed flat segment of the first lead and the exposed flat segment of the second lead.
14. The method of claim 13 , wherein the first lead webbing is reduced in size in at least one of the trimming and forming steps.
15. The method of claim 13 , wherein, in the forming step:
the first lead is an inner lead bent into a j-shaped lead; and
the second lead is an outer lead bent into a gull-wing-shaped lead.
16. The method of claim 13 , wherein:
after the first dam bar is cut, burrs corresponding to the first dam bar remain on the first and second leads; and
the burrs remain on the first and second leads after the forming step.
17. The method of claim 13 , wherein:
after the first dam bar is cut, burrs corresponding to the first dam bar remain on the first and second leads; and
the burrs on the first and second leads are removed in the trimming step.
18. The method of claim 13 , wherein, in the forming step:
the first lead is bent down at a top elbow;
distal portions of the preliminary first lead webbing beyond the top elbow of the first lead break off to leave behind the first lead webbing.