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Assembly and PCB Layout Guidelines for QFN Packages Introduction

Hàng kép hoặc dòng đa QFN gói là một quy mô Chip gần, đóng gói gói nhựa với một chất nền leadframe đồng. Chết tiếp xúc gắn mái chèo ở phía dưới có hiệu quả tiến hành nhiệt PCB và cung cấp một nền tảng ổn định thông qua các trái phiếu xuống hoặc bằng cách kết nối điện thông qua chết dẫn đính kèm tài liệu. | Wefel POWER MATTERS Application Note AC322 Assembly and PCB Layout Guidelines for QFN Packages Introduction The dual-row or multi-row QFN package is a near Chip Scale plastic-encapsulated package with a copper leadframe substrate. The exposed die attach paddle on the bottom efficiently conducts heat to the PCB and provides a stable ground through down bonds or by electrical connections through conductive die attach material. The design of dual-row and multi-row QFN packages allows for flexibility and enhances electrical performance to very high-speed operating frequencies. The dual-row or multi-row QFN package utilizes an interstitial lead design that results in a staggered lead arrangement. The inner row is offset 0.5 mm which results in a compact design that maximizes die size while not exceeding the surface mount technology SMT capability of a typical 0.5 mm pitch SMT process. Actel offers QFN packages in three configurations QN180 QN132 and QN108. The package footprint and outlines are covered under JEDEC MO-247 Plastic Quad No-lead Staggered Multi-Row Packages with Optional Thermal Enhancements and JEDEC Design Guide 4.19 Quad No-lead Staggered Multi-Row Packages. QFN Package Overview Figure 1 and Figure 2 show that the package height is minimized by having both the die and wirebond pad on the same plane. Figure 3 on page 2 illustrates the detail construction of the land pad. When mounted the leads are directly attached to the board without the space-consuming standoff inherent in a leaded package such as a Plastic Quad PQ or Thin Quad TQ . In addition the QFN package has excellent thermal dissipation with the die attach paddle attaching directly to the PCB. The QFN package also reduces electrical parasitics due to its efficient and compact design. Bottom View Die Attach Epoxy Die Attach Pad Terminals Mold Compound Figure 1 Bottom View and Cross Section of Dual-Row QFN Bottom View Die Attach Epoxy Die Attach Pad Terminals Mold Compound Figure 2 Bottom View and