Workmanship_Summary

Workmanship is the skill in an occupation or trade [1]. Workmanship is the quality and accuracy of a pre-described or intended output that is constructed particularly by a human with or without the use of aides such as machinery. High quality workmanship is not necessarily attributed to the talent of an individual but can be acquired through training, experience and control mechanisms.
NASA defines Workmanship as a shorthand term for quality rules applied to the assembly of electronic boards and electrical cable harnesses [10].

The researhc of Dr. Swartwout [12] shows that two-thirds of CubeSat mission failures are failures in functional integration. These results [12], shows that there is room for improvement in terms of Workmanship and Quality Control areas applied to CubeSat spacecraft development. Figure 1 shows the statistics for success/failure CubeSat missions from 2000 to 2012.

Establishment of Workmanship Training can be conducted using the following four step approach:
 

  • Training on all applicable procedures, standards, and best practices
  • Instruct rhe student to make he/she become familiar with SMT concepts and processes
  • Provide hands-on practice
  • Provide follow-up inspection of resulting product or service as a feedback mechanism

Quality control mechanisms should be put in place to ensure adequate levels of workmanship. Proper documentation management and adherence to configuration management processes and procedures are also critical in maintaining a high level of workmanship.

 

NASA defines the following Workmanship Requirements Categories [10].

  • Design Requirements: Controls materials and configurations (e.g. dimensions, placement, interface materials) selected to provide operational performance.
    • Workmanship Examples: Solder material, flux material, staking of wire runs to enable performance in shock/vibration environment.
  • Processing Requirements: Controls the manufacturing methods or techniques.
    • Workmanship Examples: Use of certain type of container to mix polymers to avoid contaminating the polymer, periodic alloy check of solder pot to ensure material purity, control of environmental conditions such as humidity.
  • Defect Criteria (aka accept/reject criteria, quality criteria): Physical attributes that are evidence of a defect or known to be indicative of the presence of a defect that will result in premature failure.
    • Workmanship Examples: solder joint appearance, presence of extraneous material, nicks and scrapes in conductors, missing material, delaminated material.
  • Training and Certification of Operators, Inspectors, and Instructors

 

Workmanship Standards:

  • Are directed at those responsible for fabricating, assembling or inspecting.
  • Provide processing instructions (and some design rules).
  • Provide screening criteria for known defects for standard technologies, configurations, and materials.
  • Remove units with defects from mission subsystems at a low level of assembly when it is less expensive to repair or replace. Require seeking prior approval for the use of non-standard technologies, configurations, and materials. Require justification of non-standard technologies, configurations, and materials with qualification data.
  • Require definitino of relevant inspection criteria for non-standard technologies, configurations, and materials.

 

Workmanship Standards Program Authority

In the case of NASA, there is no third party certification for compliance to workmanship Standards. NASA uses NSC audits, Project quality engineering oversight, and DCMA to verify supplier capability and ongoing compliance. In the case of COTS suppliers may offer compliance with VCS (e.g. IPC Standards) however the supplier’s interpretation of the requirements may not be NASA’s (e.g. use of IPC-STD-001 Class 3, or IPC-A-610, instead of J-STD-001ES or NASA-STD-8739.2). DoD contracts are not required to specify Workmanship requirements. DoD do not use supplier assessments or quality oversight that include Workmanship (except Army AMCOM). Suppliers offer what they use to military customers using their own interpretation of and adherence to the requirements. Use of military subsystems or COTS subsystems may not meet NASA Workmanship requirements [10].

 

For NASA, all Programs and Projects must baseline these requirements and must flow them to all prime contractors and subcontractors [10]:

  • NASA-STD-8739.1 Polymeric Applications.
  • NASA-STD-8739.2 Surface Mount Technology.
  • NASA-STD-8739.3 Soldered Electrical Connections.
  • NASA-STD-8739.4 Crimp, Cable and Harnesses process for seeking relief.
  • NASA-STD-8739.5 Fiber Optic Terminations.
  • NASA HQ OSMA.
  • NASA-STD-8739.X Workmanship Implementation Requirements.
  • ANSI/ESD S20.20 Electrostatic Discharge Control.
  • IPC J-STD-001ES Space Applications Electronic Hardware Addendum to J-STD- 001D Requirements for Soldered Electrical and Electronic Assemblie.