Die attach film die pad isolation for semiconductor devices
In a described example, an apparatus includes: a semiconductor die having a device side surface and an opposing backside surface, the backside surface mounted to a die pad of a lead frame using a die attach film; bond pads overlying the device side surface of the semiconductor die; bond wires electrically coupling the bond pads to leads of the lead frame spaced from the die pad; and mold compound covering the semiconductor die, the bond wires, and portions of the lead frame, where portions of the leads are exposed from the mold compound to form terminals of the packaged semiconductor device. The die attach film has a partially cut die attach film layer with a cut side edge normal to the backside surface, and the die attach film has an uncut die attach film layer with a torn side edge normal to the backside surface.
1 . A method for packaging electronic devices, comprising:
forming semiconductor devices on a device side surface of a semiconductor wafer, the semiconductor devices spaced for one another by scribe lanes on the semiconductor wafer;
mounting the semiconductor wafer on a die attach film over a dicing tape, the die attach film contacting a backside surface of the semiconductor wafer that is opposite the device side surface;
cutting through at least a portion of the semiconductor wafer in the scribe lanes;
partially cutting through the die attach film along the scribe lanes, forming a cut die attach film layer lying over an uncut die attach film layer; and
separating the semiconductor devices from one another, the semiconductor devices including a corresponding portion of the die attach film on the backside surfaces, the corresponding portion of the die attach film having the cut die attach film layer with cut side edges, and the uncut die attach film layer with torn side edges.
2 . The method of claim 1 , wherein cutting through at least a portion of the semiconductor wafer in the scribe lanes further comprises:
cutting at least a portion of the semiconductor wafer with a first blade having a first width; and
cutting the remaining portion of the semiconductor wafer and a portion of the die attach film with a second blade having a second width that is less than the first thickness to form the cut die attach film layer and an uncut die attach film layer along the scribe lanes.
3 . The method of claim 2 , wherein cutting at least a portion of the semiconductor wafer further comprises cutting an entire thickness of the semiconductor wafer with the first blade, without cutting the die attach film with the first blade.
4 . The method of claim 2 , wherein stretching the dicing tape further comprises:
cooling the dicing tape, the semiconductor wafer and the die attach film to a temperature less than 0 degrees C.; and
pulling the dicing tape to expand the dicing tape, the uncut die attach film layer tearing along the scribe lanes to allow the semiconductor devices and corresponding portions of the die attach film attached to the semiconductor devices to separate from one another.
5 . The method of claim 4 , wherein pulling the dicing tape to expand the dicing tape cause the uncut die attach film layer to form a torn side edge in the uncut die attach film layer underlying the cut side edge of the partially cut die attach film layer.
6 . The method of claim 4 , and further comprising:
mounting the semiconductor devices with the die attach film on a package substrate using the die attach film to adhere the semiconductor devices to the package substrate, the package substrate carrying an array of semiconductor devices, the semiconductor devices spaced from one another on the package substrate by saw streets;
electrically coupling bond pads on the semiconductor devices to leads on the package substrate;
covering the semiconductor devices and portions of the package substrate with mold compound; and
sawing through the mold compound and the package substrate along the saw streets to separate the packaged semiconductor devices one from another.
7 . The method of claim 2 , wherein cutting comprises sawing using a rotating mechanical blade.
8 . The method of claim 2 , wherein cutting at least a portion of the semiconductor wafer forms a cut side edge on semiconductor dies formed in the semiconductor wafer, and partially cutting the die attach film forms a cut side edge on the partially cut die attach film layer.
9 . A method for packaging a semiconductor device, comprising:
mounting a backside surface of a semiconductor wafer to a die attach film layer on a dicing tape, the semiconductor wafer having semiconductor dies formed on a device side surface opposite the backside surface;
cutting the semiconductor wafer along scribe lanes on a device side surface of a semiconductor wafer, the scribe lanes separating individual semiconductor dies formed in the semiconductor wafer one from another;
partially cutting the die attach film layer along the scribe lanes forming a cut die attach film layer overlying an uncut die attach film layer;
cooling the die attach film layer, the semiconductor wafer, and the dicing tape to a temperature of between −40 degrees C. and 0 degrees C.;
stretching the dicing tape causing the uncut die attach film layer to tear along the scribe lanes between the semiconductor dies, allowing a gap to form between the semiconductor dies and a corresponding portion of the die attach film attached to the semiconductor dies to singulate the semiconductor dies and the corresponding portion of die attach film one from another;
using the die attach film, mounting the semiconductor dies to die pads of a conductive lead frame;
electrically coupling bond pads of the semiconductor dies to conductive leads on the lead frames using bond wires or ribbon bonds;
covering the semiconductor dies, the bond wires or ribbon bonds, and a portion of the conductive lead frame with mold compound, the leads of the conductive lead frame partially exposed from the mold compound to form terminals; and
sawing the mold compound and the lead frame apart in saw streets between the semiconductor dies to form the packaged semiconductor devices.
10 . The method of claim 9 , wherein cutting the semiconductor wafer and partially cutting the die attach film further comprises cutting through the semiconductor wafer using a single saw blade to form a single cut that extends through the semiconductor wafer and into the die attach film layer to form the cut die attach film layer and the uncut die attach film layer.
11 . The method of claim 9 , wherein cutting the semiconductor wafer and partially cutting the die attach film further comprises:
in a first sawing operation, cutting at least a portion of the semiconductor wafer along the scribe lanes using a first blade having a first width; and
in a second sawing operation, cutting through any remaining portion of the semiconductor wafer along the scribe lanes using a second blade having a second width that is less than the first width and cutting into the die attach film layer underlying the backside surface of the semiconductor wafer to form the cut die attach film layer and the uncut die attach film layer.
12 . The method of claim 11 , wherein in the first sawing operation, the first blade cuts through the semiconductor wafer but does not cut the die attach film layer, and the second blade partially cuts the die attach film layer to form the cut die attach film layer and the uncut die attach film layer.
13 . The method of claim 9 , wherein cooling further comprises cooling the semiconductor wafer, the die attach film and the dicing tape to a temperature of about −15 degrees C.
14 . A method for packaging electronic devices, comprising:
forming semiconductor devices on a device side surface of a semiconductor wafer, the semiconductor devices spaced for one another by scribe lanes on the semiconductor wafer;
mounting the semiconductor wafer on a die attach film over a dicing tape, the die attach film contacting a backside surface of the semiconductor wafer that is opposite the device side surface;
cutting through at least a portion of the semiconductor wafer;
partially cutting through the die attach film forming a cut die attach film layer lying over an uncut die attach film layer; and
separating the semiconductor devices from one another, and after separation, the semiconductor devices including a corresponding portion the die attach film having the cut die attach film layer with a first side edge, and a corresponding portion of the uncut die attach film layer with a second side edge, the first side edge different from the second side edge in surface roughness.
15 . The method of claim 14 , wherein the first side edge is a cut side as a result of a mechanical saw.
16 . The method of claim 14 , wherein the second side edge is a torn side as a result of stretching to separate the semiconductor devices from one another.