"Electronic packaging companies can use the warpage information to make changes in their PCB design early in the design phase," Ume says. "They may choose to make some design or process adjustments and send the board to us again to be retested. That way, there's no mass production of a product that has a problem."
A patent is pending on Ume's process, which is commercially known as TherMoiré(TM).
The TherMoiré(TM) technique can be used to simulate the three major kinds of soldering processes -- infrared reflow, convective reflow and wave. The automated oven system measures warpage in real time. It can reproduce any given soldering temperature history used in producing a board, while measuring PCB warpage at any specified interval or temperature. As a result, the system can pinpoint which processes or designs may cause the most warping.
Companies can use the results to make design or process changes before production, such as changing soldering temperature profiles, reducing or extending processing times, relocating key components, and changing types of materials used in the construction of the PCB.
In addition to measuring thermally induced warpage, the technique can be used to validate manufacturers' numerical warpage predictions using the finite element technique.
"Most of the companies that manufacture PCBs have experts who can predict when a board will warp using finite element analysis," Ume says. "They can use the techniques we've developed here to check their results. We can also do numerical predictions for them."
If a certain amount of warpage is allowable, the new techniques allow manufacturers to measure initial warpage, rather than assuming that the board is flat before transistors and other items are added to it. Manufacturers can then determine how much additional warpage is added with further processing or addition of components.
Ume's techniques also allow warpage measurement of the different materials that are sandwiched together to make a wiring board -- FR-4 laminates, fiber (prepreg), several varieties of copper foil and newly developed materials.
"These are unique measurement techniques, and the electronic packaging industry is very excited about them," Ume says. "These systems and prediction capabilities will help PCB designers and process engineers to understand how a PCB will warp when it goes through different manufacturing cycles -- even before it is built.
"Savings in scrap PCBs, rework, down time and loss in market share can run into the millions of dollars," Ume says.
Going Commercial
The sponsors of Ume's work asked him to turn his findings into a commercial venture. With help from Georgia Tech's Advanced Technology Development Center, the Electronic Packaging Services Ltd., Co. licensed the technology and began offering help to the electronics industry in August 1994.
Georgia Tech is a partner in the company.
"Industrial sponsors were a driving force behind getting this technology to the marketplace," says business development manager Patrick Hassell. "Current trends in the industry, with respect to outsourcing and dowsizing of internal R&D efforts, make EPS a valuable contract services provider of fast, reliable analysis." |
