Methodology Drawbacks

Every test method, however, has its limitations, which may be exacerbated by recent industry trends toward component miniaturization, increased board densities, greater use of area-array devices and larger board sizes. For example, miniaturization coupled with greater component density has made it increasingly difficult to probe PCBA's reliably and repeatability using ICT technology. This is because increased component density and board size call for larger and more complex fixturing, which can raise fixturing costs and program development time substantially. Lastly, as assembly complexity increases, fault isolation becomes more difficult because of issues associated with parallel circuitry and obscure short circuits (e.g., high-resistance shorts). Similarly, while FT can determine whether a board actually works, the technique does not isolate the source of the problem easily, especially as product complexity grows.

Generally, the task of recovering failed products becomes nearly impossible — notwithstanding having the most highly trained rework personnel on hand — if defects are not diagnosed in a timely and accurate manner. This problem is even more acute for electronics manufacturing services (EMS) providers who historically have not had the benefit of the same degree of product knowledge and support that OEMs usually enjoy. The result has been to impede their ability to perform rework and repair effectively and efficiently as reflected by prolonged times at those tasks plus large scrap piles and return inventories.

IR imaging, as an alternative technology, can equip manufacturers with new capabilities for effectively combating these problems. It offers a methodology to detect many assembly and faulty component defects that may be missed by other tests. Figure 1 summarizes the capabilities of the various test methodologies to detect different types of defects.