RBO, Resin Bleed Out or Epoxy Bleed Out, is a surface wetting phenomenon whereby fractions of the organic resin system migrate along the substrate surface. RBO can cause substrate contamination which leads to wire bond non-stick on pad or weak wire bond.  It can also reduce the adhesion of mold compound to substrate which may lead to delamination.

RBO is related to both the adhesive and the substrate.  Water beads up on lotus leaves because water cannot wet the surface of lotus leaves, but water can wet glass surface and peanut oil can wet the surface of lotus leaves.  Hence, RBO can be controlled either by changing the die attach adhesive or the substrate.

RBO is an important parameter during material qualification as device manufacturers aim to find a compatible combination of die attach adhesive and substrate. For RBO problems suddenly appear during mass production, people tend to take two containment actions. One is to ask the die attach adhesive supplier to audit the problematic batches, both raw materials and manufacturing processes, to see if these adhesive batches were contaminated by some low surface tension materials such as silicones. Even at ppm level, silicones can change adhesive surface tension and cause RBO. The another is to ask the substrate supplier to audit their manufacturing processes, particularly the final cleaning and drying processes.  Even minor changes in these processes can drastically affect the substate surface and cause RBO.

Over the past 14 years,  Yongoo has evaluated numerous adhesive-substrate combinations and accumulated significant amount of knowledge on how to control RBO. To further ensure product quality, Yongoo does not allow any silicone materials entering its clean room manufacturing.  We are happy to be our customers’ partner to solve their RBO problems.

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