The J-STD-001, (Joint Industry Standard),”Requirements for Soldered Electrical and Electronic Assemblies” was first published in January 1992 as a “parallel document” to complement and subsequently replace the existing MIL-STD-2000, High Reliability Soldering Requirements. The prime difference between the two standards is that the J-STD-001 is a commercial or industrial “guide-line”, applicable to assemblies separated into “product classes” that are based on their end use environment, and to a lesser degree, the assembly costs. Unlike the J-STD-001, the MIL-STD-2000A and related standards such as WS-6536, referred to as the Navy Weapons Specification, and the MIL-S-45743 Army Soldering Specification, has only one product class. The goal of MIL Standards is to establish procedures and requirements in attaining the highest possible quality and reliability levels, for uninterrupted operation in the harshest of end use environments.
Both the MIL standards and IPC J-STD were intended to serve the same purpose of providing definition and requirements in achieving a measure of quality and reliability in assemblies subjected to real field conditions. The MIL-STDs for the most part served their purpose, and were processed through revisions from their inception, following an approximate five year cycle where revisions were introduced to reflect changes and advances in electrical and electronics technology. The J-STD-001, for its part, seemed to adopt the same length revision cycle. However, over a period of time, the J-STD-001 as a specification, separated itself from the MIL Standards and pursued an alternate system of classification from the “High Reliability Procedures”. From 1992 to 2005, the J-STD-001 advanced to the “D Revision with the Class 3, “High Performance Products” requirements that were driven by the “quality agenda” of the Class 2 “Dedicated Service Electronics Products”. A prime example of this condition is exemplified by the inclusion of numerous “process indicators” – a condition defined as not requiring disposition, while referencing the inadequacies of a process that is not producing products to the requirements intended to meet specifications applicable to Class 3.
Some areas of immediate concern and examples of conditions which retreat from known “High Reliability Procedures” are as follows:
- The allowance of a solder fillet in the bend radius – specifically, of an axial leaded component negating the designed and specified stress relief to both the soldered connection, and the lead to body seal, yielded by proper lead bend radius formation.
- The loss of a clear definition of a proper solder fillet - by allowing solder peaks, voids, blow holes, pin holes as process indicators, and not requiring surface wetting of primary side land patterns for through hole technology. Additionally, by allowing wetting angles exceeding 90 degrees, and solder fillets in such quantities on small surface mount components, renders proper wetting difficult to determine. Proper wetting is the most important attribute of an acceptable and reliable solder connection.
- The allowance for any form of substrate delamination in Class 3 Products. This is done specifically, by prohibiting the presence of measles bridging more than 50% spacing between non-common circuits in J-STD-001, and by allowing all forms of measles in the inspection specification for laminate and fabricated printed circuit boards. The underlying assumption states that measles formed in the Printed Wiring Assembly process are a separation of materials but not a form of delamination.
- The introduction of new solder alloys into high reliability assemblies - this introduces the prospect of insufficient data available to assess any long term reliability behavior of the soldered connections, as opposed to the known reliability of the time tested tin-lead alloys. Lead-Free alloys can be very brittle and predominately rich in tin, which tend to prorogate the uncontrolled formation of “tin wiskers”, the long time nemesis of the electronics assembly industry.
- The loss of requirements in material identification - materials such as conformal coating, solder alloys, components, and substrate, underlie the importance of tracking reliability and origin of materials in the manufacture of high reliability assemblies.
While there are many other examples and issues affecting the quality of High Reliability Assemblies, those listed above exemplify the typical causes that create the greatest impact on the Hi-Rel electronics industry. The EMPF has recognized the need to provide training which will differentiate between standard commercial electronics assemblies, and ones specifying higher reliability. The EMPF now provides a high reliability addendum to their IPC - J-STD 001 training which will meet the additional requirements to qualify as high end electronic soldered assembly.
For more information on the benefits and of customized training, or to inquire about any of the EMPF course offerings, please contact the Training Center Registrar at (610) 362-1289, or call our Helpline.