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|How to Deal with Resonances in Wirebonding|
|Keywords: Wirebonding, quality problem, resonance|
|A recurrent but intractable problem in wirebonding is often referred to as 'resonance'. What is meant by this are bonding surfaces which are not sufficiently rigid during the wirebonding and therefore counteract the wire movement, reducing or canceling the friction required for bond formation in an inconsistent manner. This sometimes leads to extremely serious quality problems. It is important to realize, however, that such resonance phenomena at the are sometimes true resonances (characterized by an eigen frequency typical for a given part) and sometimes just a passive (following) vibration with no characteristic frequency dependence. They differ in that a change of US frequency will remove the true resonance while the passive resonance is independent of the US frequency and can only be cured by a stiffer setup. Therefore it is recommended to have a choice of US frequencies in the bonding equipment, especially when both cases of resonance can occur in the same part. Modern bonding equipment usually has digital US generators with switchable frequencies so that only the transducer itself needs to be changed physically. We discuss the causes and effects of the two phenomena and how to deal with them.|
|Dr Josef Sedlmair,
F&K Delvotec Bondtechnik GmbH