Vishay Stacked Capacitors with Increased Capacitance

Challenge

The existing design offered an available height that could be used for the restricted space if an appropriate solution could be found. In addition to the specific length and width of the capacitor and the footprint of the recommended solder pad dimensions, there were also "keep out" areas on the PCB that couldn't be used in order to prevent mechanical and electrical interference.

Solution

To address this problem, Vishay's engineers developed a stacked capacitor assembly solution that vertically mounted multiple T54 series polymer tantalum capacitors using a flexible mechanical termination design. Structurally, the metal termination constructed for the stack also provided robust shock and vibration performance while addressing heatsink considerations.

When considering utilizing the board area, numerous measurements are involved, including the dimensions of the capacitor itself, the PCB recommended pad dimensions required for assembly, and the manufacturer's recommended "keep out" area.

Since this double-stack (two-capacitor) solution was developed, Vishay has expanded this range to offer combinations of three, four, and six T54 series devices that feature much higher overall capacitance values.

Benefit

The stacking of T54 polymer capacitors allowed the engineers to significantly increase the capacitance density for the given PCB area. This custom solution took advantage of the height available by minimizing part placement on the linear plane and provided 35.6% space savings. Utilizing this mechanical design provides additional electrical performance enhancements, and mounting multiple capacitor devices in parallel reduces the overall capacitor ESR performance value. Additionally, the nominal capacitance and tolerances applied during the testing of individual parts mean the assembled unit can be rated with a slightly higher combined total capacitance.

Other mechanical advantages of the stacked capacitor terminations include better heatsinking and more robust shock and vibration performance.