June 12, 2013
Exclusive - Order of Precedence as Defined in IPC Specifications
All IPC specifications reiterate the order of precedence statement to verify and define the correct specifications which are to be used when building products. The Order of Precedence statement should be specifically identified in the contractual agreement with the customer or anyone sub-contractor who will be building product. Additionally, the contractual agreements, should define the priority order of the documents, or any other specifications or drawings, which must be utilized to build the product.
|Leo Lambert, Vice President/Technical Director, EPTAC Corporation
Whether or not the initiator of the contract is an OEM (original equipment manufacturer), or one who is building the product under their own name, there is a protocol for what specifications should be used to manufacture the product, so the product meets the reliability and quality issues as demanded by its design and its operational cycle. This is all identified within the Order of Precedence sections of the specifications. In this case we are 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 has to 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 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 who are building the product.
One of the typical demands of contractual agreements is to build the product to a certain class requirement as defined by the IPC and the industry, with Class 1 being the lowest class of product and Class 2 and 3 covering almost of all the 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 that the operators be proficient in their job functions that all the chemicals and metals used in the manufacturing process are qualified to meet the requirements of the products. 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 a quality programs in place to make sure 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 the assemblies, there is uncertainty as to whether or not acceptable manufacturing processes and material 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 we need to test and qualify the materials and chemicals to be used in the product?
- Do we want the operators to be proficient in their jobs?
- Is the subcontractor required to have a continuous improvement program in place to collect the productivity improvements?
If the answer to these questions is yes, then you should be specifying that your product is to be built to the requirements of J-STD-001.
Leo Lambert, Vice President/Technical Director