Methods for multi-stage molding of integrated circuit package
Methods for providing an integrated circuit using a multi-stage molding process to protect wirebonds. In one embodiment, a method includes attaching a die to a leadframe having a lead finger, attaching a wirebond between the die and the leadfinger, applying a first mold material over at least a portion of the wirebond and the die and the leadfinger to form an assembly, waiting for the first mold material to at least partially cure, and applying a second mold material over the assembly.
1. A method, comprising:
attaching at least one die to a leadframe having lead fingers;
attaching wirebonds to make connections between the at least one die and the leadfingers;
injecting a first mold material at a first pressure for preventing wire sway of the wirebonds, encapsulating the wirebonds, and covering at least a portion of the at least one die and the leadfingers to form an assembly, wherein the first mold material is only on a die-side of the leadframe and overmolds all wirebonds connected to the at least one die;
waiting for the first mold material to at least partially cure;
securing a magnet to the assembly;
injecting a second mold material at a second pressure greater than the first pressure for overmolding the at least one die, the first mold material, and the magnet; and
selecting a material for the first mold material based at least in part upon similarity of coefficient of expansion with the magnet.
2. The method according to claim 1 , wherein the first and second mold material are different.
3. The method according to claim 1 , further including selecting a material for the first and/or second mold material based at least in part upon filler size.
4. The method according to claim 1 , further including attaching a concentrator to the assembly.
5. The method according to claim 1 , wherein the wirebond includes a gold wire.
6. The method according to claim 1 , further including providing one or more notches in the leadframe to secure the die in position.
7. A method, comprising:
attaching at least one die to a leadframe having lead fingers;
attaching wirebonds to make connections between the at least one die and the leadfingers;
injecting a first mold material at a first pressure for preventing wire sway of the wirebonds, encapsulating the wirebonds, and covering at least a portion of the at least one die and the leadfingers to form an assembly, wherein the first mold material is only on a die-side of the leadframe and overmolds all wirebonds connected to the at least one die;
waiting for the first mold material to at least partially cure;
securing a magnet to the assembly;
injecting a second mold material at a second pressure greater than the first pressure for overmolding the at least one die, the first mold material, and the magnet; and
selecting the second pressure to eliminate voids in or around a magnet forming a part of a magnetic sensor.
8. A method, comprising:
attaching at least one die to a leadframe having lead fingers;
attaching wirebonds to make connections between the at least one die and the leadfingers;
injecting a first mold material at a first pressure for preventing wire sway of the wirebonds, encapsulating the wirebonds, and covering at least a portion of the at least one die and the leadfingers to form an assembly, wherein the first mold material is only on a die-side of the leadframe and overmolds all wirebonds connected to the at least one die;
waiting for the first mold material to at least partially cure;
securing a magnet to the assembly;
injecting a second mold material at a second pressure greater than the first pressure for overmolding the at least one die, the first mold material, and the magnet,
wherein the die includes a magnetic field sensor.
9. The method according to claim 8 , wherein the magnetic field sensor includes one or more Hall elements.
10. The method according to claim 8 , wherein the magnetic field sensor includes a magnetoresistive element.