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56 The PCB Magazine • January 2017 critical to the overall reliability of the electronic device in which it is used. Typical properties for the combined deposit are presented in Table 4. Conclusions As technological advances continue in the electronics industry in the manufacturing of substrates for applications in HDI, IC, and LED, new challenges will arise for the design engi- neers. With continued trends toward miniatur- ization, new manufacturing techniques such as stacking of vias, and the use of high power de- vices that generate considerable heat, the need for improved methods of thermal management are required to efficiently conduct heat away from the electronic devices to improve device reliability and life. Copper through-hole plating provides another tool to the engineer for the de- sign of electronic circuitry. Figure 16 illustrates a real-world application of copper through-hole plating to conduct heat away from an LED de- vice allowing it to operate at a lower tempera- ture. In this example, the use of copper through- hole filling reduced the operating temperature of the device from 126°C to 92°C. The copper through-hole plating process provides a versatile two-step process consisting of a periodic pulse reverse step with specialized waveforms that allow the middle of a through- hole to be bridged and sealed, forming two mi- crovias that can subsequently be filled with DC- based via fill chemistries. The design engineer must understand the nuances of the copper through-hole plating process and how the design of the board Figure 15: Effect of hole pitch on dimple size. Figure 17: X-ray imaging of copper through-hole plating. Figure 16: Use of copper through-hole plating to conduct heat (right photograph). Table 4: Typical Properties of Copper Through-Hole Fill Deposit. ELECTROPLATED COPPER FILLING OF THROUGH-HOLES: INFLUENCE ON HOLE GEOMETRY