METHODS FOR MULTI-STAGE MOLDING OF INTEGRATED CIRCUIT PACKAGE

• US 20100330708A1
• Filed: 09/09/2010
• Published: 12/30/2010
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Taylor, William P., Engel, Raymond W., Sharma, Nirmal
• Granted Patent: US 8,143,169 B2
• Time in Patent Office: Days
• US Class Current: 438/3
• CPC Class Codes: G01D 11/245 Housings for sensors
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: H01L 21/56 Encapsulations, e.g. encapsulation layers, coatings
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• 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 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

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.

Claims

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; and

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.

2. The method according to claim 1, further including selecting a material for the first mold material based at least in part upon similarity of coefficient of expansion with the magnet.

3. The method according to claim 1, wherein the first and second mold material are different.

4. 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.

5. The method according to claim 1, further including selecting the second pressure to eliminate voids in or around a magnet forming a part of a magnetic sensor.

6. The method according to claim 1, wherein the die includes a magnetic field sensor.

7. The method according to claim 6, wherein the magnetic field sensor includes one or more Hall elements.

8. The method according to claim 6, wherein the magnetic field sensor includes a magnetoresistive element.

9. The method according to claim 1, further including attaching a concentrator to the assembly.

10. The method according to claim 1, wherein the wirebond includes a gold wire.

11. The method according to claim 1, further including providing one or more notches in the leadframe to secure the die in position.