Gaskets
Monolithic Gaskets
The cornerstone of successful acid decapsulation is the correct selection of gaskets that both locate the region of a package to be decapsulated with respect to the etch head (the location gasket) and the correct selection of a gasket that defines the size of the aperture to be subjected to acid exposure (the definition gasket).
Irrespective of the package of interest the “stack up” of definition gasket and location gasket remains the same. The definition gasket is positioned onto the etch head and the location gasket is then placed on the definition gasket. Both gaskets are contained within the location ring that ensures the concentricity relative to the etch head itself.
As the function of the location gasket is simply to position the package relative to the definition gasket aperture all NTG definition gaskets are manufactured from a proprietary 0.8 mm thick Fluoro Elastomer material blend.
The definition gasket defines the area of a package that will be exposed to acid and these definition gaskets are always manufactured from a proprietary blend of Fluoro Elastomer material that is 1.6 mm in thickness.
Combination Gasket Sets
Gaskets are made of rubber and by their very nature are not rigid. Thus some lateral movement is possible when they are placed into a ceramic location ring on the etch head assembly.
For many packages this is not a problem, but for some packages e.g. FBGAs and die-down BGAs it is necessary to construct a sealing surface around features that are present on the same side of the package as the die surface to be exposed. In this case a glued gasket set is frequently employed. Similarly with many chip scale packets the ratio of die size to package is such that any misalignment in the gasket set that may occur with compression of the safety cover ram nose is unacceptable. In the past, to negate this problem a glued gasket set was employed.
Monolithic Gasket Design Concept
To alleviate all concerns with possible misalignment of a location gasket relative to a definition gasket Nisene Technology Group introduced our complete range of Monolithic Gaskets.
With the introduction of these gaskets there is no longer any requirement for a separate location gasket and definition gasket. However Nisene Technology Group shall continue to offer standard definition and location gaskets for our customers that do not require high accuracy X, Y location of a part. Laser cutting of these gaskets provides high precision and alignment in all but the most stringent applications. But for high precision package application e.g. CSPs and certain die-down and multi-die packages, Nisene Technology Group provides monolithic gasket designs that incorporate both the location and the definition gasket into a single fabricated piece of Fluoro Elastomer material containing rubber blend.
Please contact Nisene Technology Group, your local representative, or your local distributor for more details.
