Film-assist molded gel-fill cavity package with overflow reservoir
A semiconductor device package having a cavity formed using film-assisted molding techniques is provided. Through the use of such techniques the cavity can be formed in specific locations in the molded package, such as on top of a device die mounted on the package substrate or a lead frame. In order to overcome cavity wall angular limitations introduced by conformability issues associated with film-assisted molding, a gel reservoir feature is formed so that gel used to protect components in the cavity does not come in contact with a lid covering the cavity or the junction between the lid and the package attachment region. The gel reservoir is used in conjunction with a formed level setting feature that controls the height of gel in the cavity. Benefits include decreased volume of the cavity, thereby decreasing an amount of gel-fill needed and thus reducing production cost of the package.
1. A method comprising:
providing a second semiconductor device embodied within a packaged semiconductor device assembly, wherein the second semiconductor device comprises a first and second major surface;
forming an encapsulated region over the second major surface of the second semiconductor device using an encapsulant;
forming a cavity region in the encapsulant over a first portion of the second major surface of the second semiconductor device using a film-assisted molding technique, wherein
a mold used for the film-assisted molding technique defines a gel stop feature along a wall of the cavity region,
the gel stop feature comprises a gel level set feature and a gel overflow reservoir feature, wherein the gel stop feature is configured to permit silicone gel rising to a level above the gel level set feature to flow over the gel level set feature into the gel overflow reservoir feature;
the first portion of the second major surface of the second semiconductor device is exposed in the cavity region; and
affixing a first semiconductor device on at least a portion of the first portion of the second major surface of the second semiconductor device, wherein the first semiconductor device is located entirely within the cavity region.
2. The method of claim 1 further comprising: providing a lead frame comprising a plurality of leads and a flag portion of the lead frame;
affixing the second semiconductor device to the flag portion of the lead frame, wherein
the first major surface is affixed to the flag portion of the lead frame and electrically coupling the second semiconductor device to one or more of the plurality of leads, wherein said forming the encapsulated region comprises encapsulating the lead frame, electrical contacts of the second semiconductor device coupled to the lead frame, and a portion of the second semiconductor device excluding the first portion of the surface.
3. The method of claim 2 wherein the second semiconductor device is a control die, the first semiconductor device is a pressure sensor, and the control die is configured to process signals from the pressure sensor.
4. The method of claim 1 further comprising: placing a silicone gel in the cavity region and over and surrounding the first semiconductor device, and placing a pressure permeable cap over the cavity region on a lid attach shoulder formed in the cavity by the mold, wherein a bottom portion of the lid attach shoulder is above a maximum silicone gel depth permitted by the gel stop feature, and the pressure permeable cap is not in contact with the silicone gel.
5. The method of claim 4 further comprising: curing the silicone gel subsequent to said placing the silicone gel in the cavity region.