Lead Free Dynamic Repair Simulator      

The software on this website was developed by the CALCE Electronic Products and Systems Consortium at the University of Maryland, College Park (Project Numbers: C09-11 and C10-11). The Lead Free Dynamic Simulator (LFDS) is designed to demonstrate to program managers the life cycle cost and availability impacts of reliability changes and various repair scenarios for mixtures of legacy and new systems.


With the onset of lead-free technology integration in electronics, concern has arisen amongst engineers regarding the system- and enterprise- level impact of legacy tin-lead assemblies that have been repaired with lead-free solder, i.e., the reliability of repaired systems could decrease. Enterprise-level impact, refers to the ability to determine and quantify the adverse effects of lead-free performance on support logistics (repair flow: repair time, repair cost, backlog) over the life cycle of equipment, as compared to tin-lead. In general, a model is required in order to quantify performance expectations and provide risk mitigation if and when needed.

Program level management hears from engineers that the “sky is falling” every day due to some previously unforeseen technical issue, but is rarely moved to action without a quantitative demonstration of the system- or enterprise-level risks posed by the issue. Unfortunately, engineers don’t have the tools to articulate these risks/impacts in the terms that management understands, i.e., cost and availability. The target of this project is to provide the necessary support to engineers to articulate to program management the cost and availability impacts of fielding (and repairing) systems that contain lead-free electronics.

The Lead-Free Dynamic Simulator (LFDS)

The Lead-Free Dynamic Simulator (LFDS) models the flow of electronic assemblies to and through a repair process. The model includes the effects of repair prioritization, multiple possible failure mechanisms, no-fault-founds, and un-repairable units. Outputs include life cycle cost, module-level availability, repair time, and number of failures.  The model was developed to quantify the impacts of the conversion from tin-lead solder to lead-free solder, however, it can be used for modeling any type of electronic system repair process.

The LFDS tool implements the simulation process shown in Figure 1.  This process starts on the earliest LRU introduction date for introducing all LRUs into the field. Upon fielding an LRU, the simulation samples multiple reliability distributions (representing different failure mechanisms), which are the future failure dates for the LRU.  The soonest failure date causes the LRU to enter the repair process.  The length of the repair process, is determined by the individual process times and the capacity of the repair queues.  Upon completing the repair process, the LRU returns to the field and the corresponding post-repair reliability distribution is sampled and considered along with the other previously sampled dates (from the other failure mechanisms that did not cause the just fixed failure) to determine the next failure date.  If the LRU should fail again, it will enter the repair process for a 2nd or nth time.  This process will continue until the end of support date for the last LRU is reached.  This process, although described in terms of a single LRU, happens concurrently for the whole population of LRUs.


Figure 1. Visual overview of the simulated repair process.

Download LFDS (CALCE login and password is required)

The Lead Free Dynamic Simulator and associated documentation can be downloaded from the following links.  You will be queried for a CALCE login and password when downloading the materials below.  If you do not have a login and password please contact sandborn@calce.umd.edu; at this time, appropriate logins and passwords are available only for CALCE members and other organizations associated with the development of the Part Total Ownership Cost Model.

   Release Date    Model Version    Documentation    Release Notes
September 1, 2010   LFDS - Version 2.1   Version 2.0 documentation is applicable

LFDS Version 2.1 Changes and Bug Fixes

Bug fixed version of initial software release

March 8, 2010

  LFDS - Version 2.0

User's Manual 2.0

Initial software release

Important Note: The model has been developed and tested in the Java Runtime Environment (JRE 6.0 Update 14).

For questions or problems contact: sandborn@umd.edu

CALCE Electronic Systems Cost Modeling Laboratory, University of Maryland, College Park

Home Page: http://www.enme.umd.edu/ESCML

Last Updated: September 1, 2010