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56 The PCB Magazine • November 2015 Solutions for Today's and Tomorrow's requirements Heavy Copper T² Heavy Copper T² is based on convention- al heavy copper technology. In conventional heavy copper technology, the PCB design is characterized mainly by etched areas that must be filled with large resin volumes released by the prepregs used during the lamination pro- cess. Due to the large amount of resin used, multiple prepregs must be used, leading to large insulation thickness between the outer layer and the inner heavy copper layer. This means that the microvia technologies such as laser-drilled blind holes could not be used with heavy copper technology due to the large insu - lation thickness. Furthermore, the insulation thickness increases the thermal resistance of the printed circuit board and decreases its re- liability as interconnections of thicker circuits are subject to more stress during cyclic thermal loads. Heavy Copper T² technology overcomes these disadvantages by filling the etched areas of heavy copper circuits in a special manufactur- ing step. Therefore, thin prepregs can be used in the subsequent lamination process. This results in the following advantages: • Lower overall thickness of the printed circuit board • Lower clearances between the copper layers • Increased reliability in cyclic thermal loads • Increased thermal conductivity in the Z-axis (through plane) of the design The Power Combi Board The Power Combi Board uses a combined in- ner layer with heavy copper areas used for high- current conduction. However, the same level also has copper layers with a standard thickness of 18 or 35 µm that help to ease the routing for the use of complex components. With this technology, the power and logic parts of an application can be implemented with just one circuit board, whereas previously, two circuit boards were necessary, which had to be connected with a plug connector. The new solution helps increasing the reli- ability and making optimal use of the required installation space. The Inlay Board Printed circuit boards with pressed-in cop- per coins are well-known in the area of thermal management. The main disadvantage of this technology is the challenging thickness adjust- ment of the copper coins to the circuit board. While the coins have very low tolerances, mul- tilayer circuit boards have a thickness tolerance of up to 10% due to the manufacturing process- es. Therefore, flush fitting of the circuit board ArTiCle Figure 5: heavy copper t² cross-section. Figure 6: cross-section of the Power combi Board. ConDUCTInG Very HIGH CUrrenTS THroUGH PCB SUBSTrATeS AT HIGH AMBIenT TeMPerATUreS