Handbook and Guide to Supplement J-STD-001
|Publication Date:||1 February 2012|
The Standard sets forth practices and requirements for the assembly, soldering processes, soldered connections, cleaning, coating/encapsulatio
The Standard describes materials, methods, and verification criteria that, when applied as recommended or required, will produce quality soldered electrical and electronic assemblies. The intent of the Standard is to implement control over processes rather than depending on end-item inspection to determine product quality. The Standard does not exclude any acceptable process used to make the electrical connections, as long as the methods used will produce completed solder joints conforming to the acceptability requirements of the Standard.
The user (the individual, organization, company, or agency responsible for the procurement of electrical/electroni
CLASS 1 GENERAL ELECTRONIC PRODUCTS
INCLUDES PRODUCTS SUITABLE FOR APPLICATIONS WHERE THE MAJOR REQUIREMENT IS FUNCTION OF THE COMPLETED ASSEMBLY.
CLASS 2 DEDICATED SERVICE ELECTRONIC PRODUCTS
INCLUDES PRODUCTS WHERE CONTINUED PERFORMANCE AND EXTENDED LIFE IS REQUIRED, AND FOR WHICH UNITERRUPTED SERVICE IS DESIRED BUT NOT CRITICAL.TYPICALLY THE END-USE ENVIRONMENT WOULD NOT CAUSE FAILURES.
CLASS 3 HIGH PERFORMANCE ELECTRONIC PRODUCTS
INCLUDES PRODUCTS WHERE CONTINUED HIGH PERFORMANCE OR PERFORMANCE-ON-DEMAN
NOTE: See 1.4, which discusses the implementation of the requirements for each class.
Measurement Units and Applications
Table 1-1 is a list of common Metric (SI) prefixes. Many engineering drawings or other process documents are not provided in SI units. For those instances where dimensions, temperatures, or other process parameters are provided in English units, conversion formulae are provided in Table 1-2. Non-critical features should be rounded to the first decimal place using standard rounding techniques (use the hundredths value - zero to four rounds down, five to nine rounds up). Critical features should be converted to the appropriate accuracy as required by engineering documentation.
Verification of Dimensions
The dimensions provided in the Standard are targets for a manufacturer to use in establishing a process control system. It is not the intent of the Standard to require actual measurements for determining compliance to each of the various part mounting, solder fillet dimensions, or other requirements listed. They are provided as reference measurements to be used by the manufacturer in order to resolve internal process problems.
The manufacturer should evaluate assemblies that are not clearly rejectable, using 1.4.1 and 1.4.2 for guidance. Reworking a product simply because it does not exhibit the preferred conditions described in the Standard will not necessarily result in a more reliable product and may actually induce premature failure. Excessive or unnecessary rework can damage parts, the printed wiring substrate, or internal connections of PTHs and vias, not to mention the impact on schedules and profitability. Because of this, the recommended practice is: If the inspector feels the need to evaluate the suspected anomaly from several angles for more than a few seconds, or increase magnification above that listed in Table 12-1 of J-STD-001B, the suspected anomaly should be accepted. After a defect has been identified, magnification may be increased to determine its features.
Definition of Requirements
The figures and tables in the Standard are used to clarify the written requirements. Any condition that appears in a figure or table, but is not described in the text of the Standard, must not be used for the acceptance or rejection of the product. The only exception to this is when tables or figures provide information not included in a written paragraph. In those cases, the information in the table or figure takes precedence over the text of the Standard.
Process Control Requirements
The philosophy of process control is to establish and control each process involved in the manufacture of a product with an ultimate goal of exacting a 100% acceptable product yield. The process is monitored and adjustments are made to ensure that the process remains in control and that a minimum of defective products is produced. Process parameters and product output are monitored to provide feedback of performance and assist in identifying the necessary corrective action.
Effective corrective action systems usually begin with documenting the discrepancy and identifying the discrepant hardware. The discrepancy is then evaluated against the process and end product requirements to determine if the product is useable, requires rework, or cannot be used. If the fault is attributable to the manufacturer's internal processes, corrective action to eliminate the cause is usually prescribed. Where faults are attributable to external causes, such as purchased parts or assemblies, the supplier is usually asked to provide root cause analysis and corrective action. All actions in the corrective action system should be recorded for reference. Trends and overall activity levels are typically monitored to allow management of the procurement and assembly processes.
Continuous improvement means constantly looking for ways to improve the yield of a process and reduce production costs and cycle time. Practically speaking, there is a point where the cost of improving the process exceeds the gains of the improvement. Care must be taken to recognize that gains may occur outside of the traditional manufacturing cost environment, such as product life, costs, and customer satisfaction.
Section 12, as well as 12.0 of Revision B and 11.3 of Revision C, provides in-depth details on applying process controls.