PoP designs are particularly popular for processor-and-memory-element combinations. Stacking components not only saves space, but shortens the signal paths, minimizes high-frequency interference and allows the designer to combine processor and memory chips in a highly flexible manner. The most frequent uses of this technique can be found in automotive and telecommunication applications. To be able to handle PoP or CSP stacking, the placement process must meet certain requirements. On the one hand, the programming system has to be able to place two or more components on top of one another in the correct order. Unlike the frequently used level models, Siplace Pro with its precedence model offers significant advantages. Since it specifies the order in which the components will be placed, the upper component can be positioned on the lower component already during the next cycle even if not all lower components have been placed at this time, as is often the case with PCBs consisting of multiple clusters. This improves the machine’s performance considerably, because it optimizes the placement head utilization. On the other hand, PoP placements have to meet the toughest quality requirements. This means that the height of the component stack must be taken into account at all times. Here, too, the Siplace placement principle demonstrates its superiority, because it permanently controls the height of the components and the placement position and is able to make instantaneous changes, for example when the component height changes because of a new batch. To reliably process PoP designs, however, placement machines must not only be able to correctly place the components on top of one another; they also have to be able to wet the contacts of the upper component with flux in order to form a solid connection between the two. The Linear Dipping Module is the ideal way to ensure that this is done correctly even in high-volume production environments. The company’s LDU X for the X-Series allows for the reliable and accurate application of dipping media. The unit uses a rectangular dipping media container with an integrated squeegee, which evenly spreads the medium over the dipping plate when it moves back and forth. The film thickness for small balls can be controlled in the 20 µm to 400 µm range with an accuracy of ±3 µm. After applying the dipping medium, the squeegee returns to its starting position. The dipping plate, which was tilted towards the squeegee, is then raised again so that even the extremely fast and low-traveling 20-nozzle placement head of the X-Series can pass freely. That way, the new dipping unit can be used with all placement heads of the company. The easy integration of the LDU X Dipping Module into the hardware and software of placement machines from the company makes the volume production of PCBs with space-saving PoP designs fast and reliable enough for telecom and automotive applications.
