Browse Prior Art Database

Polymeric Barrier to Prevent Wire Contact

IP.com Disclosure Number: IPCOM000173743D
Original Publication Date: 2008-Sep-11
Included in the Prior Art Database: 2008-Sep-11
Document File: 2 page(s) / 84K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The mold flow simulation shows that DR MOS (Metal Oxide Semiconductor) Power QFN (Quad Flat No-Leads) has the tendency of wire contacts after the molding process. The wires number W12 and W13 (see Figure 1) are identified to touch each other and hence this may cause wire short circuits. The mapping shows that 11% of the units in a mold panel have the potential of wire contacts (see Figure 2). The solutions up to now are, firstly, the replacement of the current AW99 33um wires by insulated wires, and secondly, the replacement of the current molding compound with a lower viscosity molding compound in order to reduce wire sweep and wire contact. The viscosity can be reduced by reducing filler content in the molding compound. But there are some disadvantages. In the first solution, the implementation of insulated wire is difficult. Additionally, 33um of Au wires is required to meet DR MOS's electrical requirements, currently only 20um and 25um insulated wire are available in the market. In the second solution, the molding compound formulation of the filler has a lower coefficient of thermal expansion (CTE) in comparison to epoxy. The filler loading has a significant effect to the overall molding compound CTE. The reduction of the filler loading will increase the molding compound CTE; therefore the CTE mismatch for molding compound-die-leadframe will increase. The risk of package crack increases, especially during thermal cycling. Additionally, the increment of molding compound CTE may increase package warpage.

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Polymeric Barrier to Prevent Wire Contact

Idea: Hui Teng Wang, MY-Melaka

The mold flow simulation shows that DR MOS (Metal Oxide Semiconductor) Power QFN (Quad Flat No-Leads) has the tendency of wire contacts after the molding process. The wires number W12 and W13 (see Figure 1) are identified to touch each other and hence this may cause wire short circuits. The mapping shows that 11% of the units in a mold panel have the potential of wire contacts (see Figure 2).

The solutions up to now are, firstly, the replacement of the current AW99 33um wires by insulated wires, and secondly, the replacement of the current molding compound with a lower viscosity molding compound in order to reduce wire sweep and wire contact. The viscosity can be reduced by reducing filler content in the molding compound. But there are some disadvantages. In the first solution, the implementation of insulated wire is difficult. Additionally, 33um of Au wires is required to meet DR MOS's electrical requirements, currently only 20um and 25um insulated wire are available in the market. In the second solution, the molding compound formulation of the filler has a lower coefficient of thermal expansion (CTE) in comparison to epoxy. The filler loading has a significant effect to the overall molding compound CTE. The reduction of the filler loading will increase the molding compound CTE; therefore the CTE mismatch for molding compound-die-leadframe will increase. T...