Depaneling: a study in yield and productivity: saw systems can provide a low stress and fast alternative to hand breaking methods.

Depaneling is an overlooked step in surface-mount production and involves the separation of a single piece from its carrier frame (the scrap) and its sibling printed circuit boards (PCBs). Ironically, when considering the overall value-add equation of assembly, and the cumulative impact of each additive process, little attention is given to depaneling, which is one of the most critical steps in the assembly process.

Literally, millions of dollars in capital equipment are allocated to placement systems, reflow and inspection to maintain a high degree of process control. Then, in many cases, boards are simply snapped apart in an uncontrolled fashion. In reflow, thermal ramp rates are managed and thermal soak periods controlled; in placement, loads are monitored to ensure joint and component integrity. However, the loads a panel is subject to after assembly technology has been deployed--giving parts 100% of their value--are invariably ignored or given minimal consideration.

Various manual tools are available to assist the process and limit the exposure of the product to strain. But, none of these alternatives has any level of control other than the individual who is operating the tool.

The one factor that has consistently driven higher levels of sophistication in the depaneling process has been component density. As a board shrinks in size and its component count stays static or increases, it becomes more susceptible to joint failure when a bending load is applied. This issue was particularly evident in the telecom industry, as the reduced size of the device (handset) and increased functionality became enormous drivers to sales volumes. Automated depaneling machines became a necessity to yield and cost control.

The bottom line drivers for automated and repeatable process-driven machines are twofold. First, the total cost of the circuit is often lost when failures occur due to a poorly controlled depaneling process. Reworking a delaminated product is simply not feasible. Second, and more insidious, are field failures. A fractured joint or a delaminated board may not show itself during test but will fail as a result of thermal cycling (use) and environmental exposure. The tangible costs such as warranties and intangible costs such as customer loyalty involved at this stage are difficult to quantify. However, many studies have shown that intangible costs often outweigh tangible costs by a significant margin.