TemperatureTEMPERATURE Switching to lead-free solders impacts higher reflow Temp on surface mount components. Numerous lead-free alloys have been proposed as replacements for the conventional Sn/Pb (Tin-Lead), the most common replacement is Sn/Ag/Cu alloys.
The Sn/Ag/Cu alloys have a melting point in the 217°C range vs. 183°C for the conventional 63Sn/37Pb. The 34°C thermal jump raises reflow temp from 225° to 260°C.
Internal Thermal Damage to components may not be detectable by electrical tests. This could increase the chances for infant mortality rate. Acoustic micro-imaging research demonstrated that exposure to high temp can damage plastic encapsulated components in various ways.
The most common damage can be popcorn cracks and molding compound delamination from the lead frame or die paddle. Popcorn cracks are more common in conventional solder processes, due to lower temp. Popcorn cracks may be more likely at Pb-free processes due to higher temp cause lowered adhesion.
Engineers will be required to establish and verify numerous parameters to ensure that product reliability is not compromised.
Properly designed molding compound materials successfully can withstand the higher processing temp without internal damage to the component.
Acoustic micro-imaging is a fast and reliable method for viewing and characterizing internal changes in components.
On a personal basis, thousands of satisfied customers have utilized my VIRTUAL LIBRARY. A library that is current, developed and reliable. THE PAY-OFF CAN BE ENORMOUS!
|
