Advances in plastic packaging have resulted in complex packages with very high interconnect densities. The requirements for package opening become very stringent when such high densities are incorporated into packages such as micro ball grid arrays (BGAs) and fine pitch BGAs (FPBGAs). Other complex configurations such as multi-die BGAs and chip scale packages pose unique problems. The encapsulant must be removed while preserving the integrity of the die, bond pads, bond wires, and lead frame interconnects.

The EMPF utilizes the JetEtch II decapsulation machine by Nisene Technology Group (Figure 5-1). The JetEtch is very easy to operate using intuitive software that leads the operator step by step through the simple programming sequence. Once set, the software enables an entire etching program to be completed with only two keystrokes. It is fully programmable and capable of storing multiple etch programs for different package types. A high brightness, six-line, alphanumeric display ensures good visibility under all conditions of fume hood illumination.

The etch head assembly can be supplied with a standard fixed etch head or with an optional removable etch head insert (Figure 5-2). Removable inserts offer the ability to select specific etchant dispersion patterns for large or complex packages, such as large quad flat pack (QFP) or extra-long thin-shrink small outline package (TSSOP) devices. Three basic removable inserts are available: the standard slot design, long slot design, and the Quadraport – a multiple-hole design. Additional custom configurations are available to accommodate specific
decapsulation needs.

The sample cover is lightly pressurized with a continuous stream of nitrogen gas to remove water vapor and oxygen from the region of the etch head, eliminating metal corrosion. When the sample cover is first closed, it is purged with nitrogen gas at a high flow rate to ensure complete removal of undesirable gases. The flow then reduces to a low level to maintain a slight positive pressure until the programmed etching and rinse program has finished. At the end of the etching sequence, the entire acid path is gas purged to remove all residual acid. The use of gas is only required during operation – no gas is consumed while in the stand by/idle mode.

The precise and rapid removal of encapsulant material is achieved by maintaining a regular, gentle oscillation of the etchant across the sample surface every two seconds. This VortexEtch produces a high level of decap quality when pure (single) acids are used and is particularly critical when mixed etchants are employed. Unless precautions are taken to ensure thorough and continual mixing, an etchant mix can separate into its constituent parts, resulting in unreproducible decapping. Pulse Etch has the same efficiency for PBGA packages. The JetEtch design is at least 30 times more efficient than less sophisticated acid decapsulators not equipped with VortexEtch and Pulse Etch technology.

For more information or to schedule a demonstration of Nisene’s JetEtch decapsulation machine located at the EMPF, contact Ken Friedman at 610.362.1200, extension 279 or via email at kfriedman@aciusa.org.