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IPC Specifications and the Order of Precedence
June 19, 2013 |Estimated reading time: 3 minutes
All IPC specifications reiterate the Order of Precedence Statement to verify and define the correct specifications to be used when building products. The Order of Precedence Statement should be specifically identified in the contractual agreement with the customer or any sub-contractor that will build product. Additionally, contractual agreements should define the priority order of the documents, or any other specifications or drawings, to be utilized to build the product.
Whether or not the initiator of the contract is an original equipment manufacturer (OEM), or one who is building the product under their own name, a protocol exists for what specifications should be used to manufacture the product to ensure it meets the reliability and quality issues demanded by its design and operational cycle. This is all identified within the Order of Precedence sections of the specifications. In this case, I am discussing IPC/J-STD-001 – Joint Industry Standard for the Requirements for Soldered Electrical and Electronic Assemblies and IPC-A-610 – Acceptability of Printed Circuit Assemblies.
Care must be exercised to not request only IPC-A-610 in the contractual agreement, as the scope of IPC-A-610 document is to “…present the acceptance requirements for the manufacture of electrical and electronic assemblies,” whereas the J-STD-001 purpose states, “…describes materials, methods, and acceptance criteria for producing soldered electrical and electronic assemblies.” J-STD-001 also states, “… the intent of this document is to rely on process control methodology to ensure consistent quality levels during the manufacture of products.” Hence, the intent of the 610 document is to be used as an inspection document, as opposed to a process specification which provides required information to manufacture the product. The two are different and the results are noticeable. One requests the inspection to review the completed assembly with no regard as to how it was fabricated, whereas the other defines how it is to be fabricated and specifies the qualification of materials and chemicals along with the required skills of the operators building the product.
One of the typical demands of contractual agreements is to build the product to a certain class requirement as defined by IPC and the industry, with Class 1 being the lowest class of product and Class 2 and 3 covering almost all other electronic products manufactured worldwide.
It is strongly recommended that all contracts to subcontractors or internal manufacturing operations within the facility specify the class to which the product is to be built relative to the requirements of J-STD-001. This will mandate the operators be proficient in their job functions and that all chemicals and metals used in the manufacturing process meet product requirements. It will also mandate that the equipment is capable of delivering reliable product in a reliable manner. Secondly, the document also requires the manufacturer to have quality programs in place to ensure there is a continuous improvement program for improving yields and reducing cost.
When the contract only specifies that the IPC-A-610 document is to be used to inspect assemblies, uncertainty exists as to whether or not acceptable manufacturing processes and materials were used to manufacture the product, as IPC-A-610 does not have any requirements for the manufacturing of product. IPC-A-610 is simply used as an inspection tool.
Therefore, the following questions should be asked:
- Do I need to test and qualify the materials and chemicals to be used in the product?
- Do I want operators to be proficient in their jobs?
- Is the subcontractor required to have a continuous improvement program in place to collect productivity improvements?
If the answer to these questions is "yes," you should be specifying that your product be built to the requirements of J-STD-001.As Vice President and Technical Director for EPTAC Corporation, Leo Lambert oversees content of course offerings and provides customers with expert consultation and 40+ years of experience. Lambert has specific expertise in soldering, metallurgy, and cleaning processes. He is co-author of the industry's most popular publications, including the IPC-A-600 Training Program, "The Acceptability of Printed Boards."