A Novel Conformal Back-Up Material

Rocky Hilburn and Paul St. John
Laminating Company of America (LCOA)
Lake Forest, CA USA

Interconnects between layers of circuitry in multilayer printed circuit boards are produced by drilling and plating. Drilling quality can have a major impact on the longevity of the plated interconnect. Mechanical drilling is especially challenged when the printed circuit board panel is not perfectly flat.

Many printed circuit boards (PCBs) contain components and features that create topography that is either expensive or impossible to level out during drilling and other manufacturing processes. A novel material and method have been developed, and benefits demonstrated, that is highly conformable providing a means to produce a level drilling surface without altering or negatively impacting the printed circuit board.

In summary, this paper will present a new technology and process in mechanical drill backing material designed to be used in rigid multilayer, rigid-flex and flexible printed circuits. The features and benefits of the technology will be presented as well as examples showing method of use, a comparison to standard drilling methods and the resulting benefits of using this material.

High topography printed circuits require a backing material to minimize drill burring in order to improve yields in downstream processes.

The newly developed conformal back-up material has conformance characteristics and performance properties that demonstrate the ability to minimize drill burring on high topography printed circuits. See Figure 9 and Figure 10 for results of exit burr reduction using the conformal backup.

The materials used will not contaminate the drilled hole and any debris from the drill process is removed using standard cleaning methods already used at the PCB manufacturer.