The perfect cleaning of laser-activated LDS MIDs is crucial for product quality. Ablation residues after laser structuring could cause problems during further processing, especially around fine tracks. The surfaces can be cleaned using methods involving ultrasound baths, compressed air or high pressure water.
 
An excellent cleaning method is CO₂ snow-jet cleaning, as perfected by Esslingen-based acp – advanced clean production. The acp technology loosens dirt with liquid carbon dioxide combined with a unique nozzle system. When the liquid CO₂ expands as it leaves an innovative nozzle system, it forms a mixture of CO₂ gas and CO₂ snow transported and accelerated by the enclosing compressed air-jet envelope to reach supersonic speeds. This jet hits the surface being cleaned. The sudden cooling creates thermal stress which makes the contamination so brittle that it is easily removed.

The combined thermal chemical and mechanical cleaning effects reliably removes solid residues and contaminating films. The jet itself vaporizes completely without any residues. Developed at the Fraunhofer IPA in Stuttgart/Germany, this technique is currently the most efficient CO₂ snow-jet cleaning method, and is ideal for dry and gentle cleaning processes, especially for surfaces with fine structures. Another advantage of the technique is its ability to be integrated within existing production lines.

In addition to the outstanding cleaning effect, another advantage for LDS MIDs is the extra planarization of the roughened LDS structures. The flattening effect of CO₂ snow-jet cleaning for LCP in particular was very impressively demonstrated by an AiF-funded project “Investigations to improve LDS-MID contacting through planarization” conducted at HSG-IMAT in Stuttgart (photos).