Ultrasonics
for the future

Remove the solder

Die Casting Dies
Recent studies from 2006 and continuing into 2008 by various labs and organizations have found that one of the many causes of soldering is due to the impingement of aluminum to the die steel which effectively weakens the steel.  This along with temperature, wettability, and metal velocity are other contributing factors.  To make a bad situation even worse, aluminum (Al) and iron (Fe) have a natural chemical affinity to one another because of their make up and electron imbalance.  When contacting each other, they want to form intermetallic compounds.
 

Stage Description Cause I Erosion of grain boundaries Weak regions - cavitation II Pitting of die surface Loose grain - cavitation III Formation of iron-aluminum compounds Chemical - electron imbalance IV Formation of pyramid shapes Rapid diffusion of iron V Adherence of Aluminum Cracks in surface at pyramids VI Erosion pits Cavitation loss of yield strength

 
courtesy - Worcester Polytechnic Institute - Diran Apelian

Loss of the tool's protective surface or lubrication barrier between the die and cast molten metal allows the creation of intermetallic compounds that cause a chemical adhesion or soldering of the metal to the die's surface. This is most prevalent when an aluminum component is present in the cast metal alloy which can also include some zinc alloys. The aluminum alloy and tool steel iron content have a natural affinity for each other... The compressive stress topography increases the effective yield strength of the die steel and because of the topography compression, the tool is able to retain more lubricant than a polished or flat surface (see below figures).  This maintains the needed barrier to prevent the covalent electron bonding from occurring between the aluminum and iron. 

The uniform topography of the MetaLL ifeÒ appearance also affords more surface area for the lube to adhere to than a flat one and creates greater heat dissipation at the die's surface without causing excessive lube build-up on the tool. This increased heat dissipation allows the tool to run cooler thus extending the tool's life while increasing lube retention ability.  If no topography change is required or if certain die locations receive inadequate lubrication, then our - TherMaLLifeÒ - (low temperature nitro-carburizing) process offers another choice for correcting solder problems.
 

Since a coating is only as durable as the substrate, MetaLL ifeÒ  or TherMaLLifeÒ before  coating is a must.   PVD (low temperature) coatings are extremely thin and hard.  They have a columnar matrix structure.  For this reason it is important to have an established supportive base prior to their application.  It is critical, therefore, to properly prepare the substrate by putting it in compression and/or diffusion prior to application of the coating.  MetaLL ifeÒ is the best method for increasing the effective yield strength.  TherMaLLifeÒ is effective at providing the barrier to stopping intermetallic action.