Frame-and-fill processes are used to protect highly complex areas on electronic circuit boards. In the first step, a highly viscous barrier – the so-called frame – is applied. In the next step, this area is quickly filled with lower viscosity filler material – the fill. With this precise process, areas on the circuit board can be protected from mechanical impact factors. The combination of frame-and-fill materials allows the application of minimum barrier and potting heights and cures to a homogeneous coating. Panacol‘s new frame-and-fill adhesives are perfectly matched so that the frame and fill areas can be optimally dispensed wet-on-wet without the still-liquid adhesives leading to undesired flowing on the PCB.
The frame material, Structalit 5704, is a black, thermally curable and single-component epoxy. This frame and glob top compound features excellent bead stability and high glass transition temperature of 150 °C up to 190 °C, depending on the curing parameters and the layer thicknesses. When using Structalit 5704, no bleeding effects occur. Due to the very low ion content of less than 20 ppm, the adhesive is suitable for chip encapsulation on electronic circuit boards.
As a fill material, Panacol has developed a range of adhesives with different rheological properties. The adhesives Structalit 5717 to Structalit 5721 are formulated with optimized flow behavior, so that they can be used on various chip and bonding wire geometries due to the differently adjusted viscosities. Since the fills have the same chemical base as the frame material, the excellent physical and chemical properties of high glass transition range, ion purity, temperature stability and minimal shrinkage behavior are also found in the fills.
Once cured, Structalit 5704 and the matching fill of the Structalit 5717–5721 series form a black, opaque and scratch-resistant coating. These properties together with a temperature resistance of up to 200 °C ensure maximum reliability.