• WTS Worldwide Mechanical Components BV

Stamping solutions for plastic packages

Worldwide Tooling Service B V offers Stamping solutions for QFN & DFN plastic packages. QFNs (quad flat no-lead) from the semiconductor packaging allows size reduction of up to 62% smaller than TSSOP equivalent packages. While production of lead frames used in QFN packages has been mainly focused on etch processes, in-depth testing at SMS in the Netherlands has proven that stamping is a viable production alternative. The design of the QFN brings with it challenges in stamped lead frame production. Unlike leaded devices such as Tssop"s and Soic"s where the board connection is made via leads that project from the side on the package, the QFN board connection is located on the bottom side of the package. In such a design, flatness and planarity of the leads becomes critical to allow surface mounting of the device and avoid mold flash in assembly. In addition, a mechanical means is required to lock the leads and pad inside the package to prevent delamination. In standard progressive stamp tooling, designed features (such as a lead on a lead frame) are produced in progressive stations. This method of stamping generally creates torque during the blanking operation resulting in a slight twisting of the feature along with generating burr. To prevent this in QFN lead frames SMS developed a one hit cutting system to guarantee a perfectly flat lead free of burr. For lead locking, SMS developed a technique that will allow coining of two edges of the lead frame simultaneously. Coining of the lead edges provides the physical locking mechanism required of QFNs.