What is Mil-Std-2000 For Making Soldered Electrical And Electronic Connections
Solderability of printed wiring has been a consistent concern of the electronic industry in recent years. Modern electronics equipment assembly is increasingly becoming a solder application process. When this process is flawed by solderability problems of component leads, circuit boards, or machine processes, solder joint repair is a significant part of the assembly operation cost. Until about six years ago, European industry was pursuing improved solder platings, while the United States seemed to be more interested in using aggressive fluxes to solve the problem during mass soldering. As limits were approached in flux activity, without really resolving repair action issues, some consultants and individuals began suggesting a look at basic solderability criteria of the components and circuit boards.
And recently, the United States Department of Defense has come out with its own series of soldering standards, MILSTD-2000. For more information on MIL-STD-2000 write to Commanding Officer, Naval Air Engineering Center, Code 5321, Lakehurst, NJ 08733-5100.
MIL-STD-2000 is a reformatting of the DOD-STD-2000 series of soldering standards. MIL-STD-2000 requires 100% inspection, except in cases where statistical sampling is done as part of a statistical process control program. All inspections must be documented internally and sent back to the government. The documentation includes individual article, summary, and rework reports. All rework must be documented.
What follows is an example of how one aerospace contractor is using MIL-STD-2000 to improve the quality of its printed wiring assemblies. MIL-STD-2000 requires that 100% inspection be done on all soldered connections and assemblies. Any defects found must be documented and recorded for future reference. The manufacturer must calculate defect rates for the printed wiring assemblies and keep a daily rate of defects. This requires individual records for each printed wiring assembly, as well as a summary of daily production.
The manufacturer divided the defects into three types: printed wiring board, component and part, and solder joint. Then the manufacturer divided the defective parts into two groups: rework and repair. From the different types of categories and two groups, the manufacturer had 77 total defects.