Before being designed into a product and added to the Item Master list, a component must be approved by a company's key individuals. The design engineer is usually the person who selects the part for a development effort; he has already determined the part value, the form factor, and the critical electrical performance characteristics.
However, rarely does the design engineer cover all the issues surrounding the part's selection because there are so many other departments affected by a new part introduction. To cover all the bases before component selection for the development project, he or she would be spending an inordinate amount of time on administrative efforts, and the development schedule would extend accordingly.
The schedule consideration is just one reason why another individual -- usually the component engineer -- will dedicate time to qualifying the part, examining not only the form, fit, and function considerations, but also keeping business concerns in mind. Below is a list of questions and issues that are essential to address during a part or a purchased assembly qualification:
- Does the part already exist in the Item Master, either under another class-code, part number, or description?
- If the part is already in the Item Master, is it on the PPL?
- Is this component available only via a single-source?
- Is the part an early engineering sample with datasheets marked as "Preliminary" and not yet in volume production?
- Is there a less expensive alternative that would save the company some money?
- Has the part been previously disqualified from the Item Master for cause?
- Has Purchasing or Materials previously disqualified the supplier from the AML (Approved Manufacturers' List) or AVL (Approved Vendors List)?
- Is the component's form factor optimal for manufacturing and test purposes?
- What are the reliability issues with the part?
- Is there a complete specification document from which to develop the electrical testing qualification process?
- Has purchasing given a preliminary approval based upon early RFQs from suppliers?
- Can the manufacturer's representative or salesperson supply enough samples to allow for a sufficient quantity for board level testing?
- Has the supplier completed a Component Information Request (CIR) form?
- Does the company have the equipment and expertise to test the proposed part in house or does it need to be tested at an outside facility?
- Has the part been reviewed for environmental compliance?
A design engineer may have simply missed seeing the existing part on the Item Master, preferred parts list (PPL), or previous bill-of-materials.
This is the optimal way to develop new designs because the parts on the PPL have already been selected by the component engineer for optimum performance and purchasing criteria.
If so, then the design engineer should immediately be advised to initiate the search for and selection of a replacement part with a second or alternate source -- this is not always possible. In that event, Purchasing should be notified as soon as possible to allow it to check its suppliers for lead-times and costs.
Preliminary datasheets are a heads-up that the specifications for the final datasheet versions may change and therefore may not be 100 percent reliable as a development component. Or perhaps the part may never reach production.
When there are historical disqualification or obsolescence records, they should be reviewed to avoid incorporating disqualified parts on the new development.
The design engineer may not be aware that a manufacturer has been disallowed for business reasons or because it failed a supplier quality audit.
An example might be a part in both a through-hole and a surface mount package. Has the lowest assembly or test cost been taken into consideration? This is a design-for-test (DFT), design-for-assembly (DFA), or a design-for-manufacture (DFM) discipline. Sometimes the assembly or test people should be consulted to help make the decision.
The operating environment may set the criteria for temperature, vibration, and other stress related concerns.
This is the only way to determine if the manufacturer's part performs as stated in the specification and as the design engineer intends. Do not trust datasheets! They are rarely 100 percent accurate.
If purchasing says the part is on allocation or unavailable for any number of reasons, then the design engineer should be notified at once, and the component engineer should suspend the qualification process.
If not, that may be a red flag indicator for non-availability at production quantity requirements.
An example of a CIR form is available for free download and distribution here.
If shock, vibration, temperature, FCC compliance, regulatory, safety, and other environmental considerations are critical qualifiers, then the resources must be allocated prior to part approval.
With Reduction of Hazardous Substances (RoHS) and REACH legislation involving Substances of Very High Concern (SVHC) comes a very stringent qualification process supported by Material Safety Data Sheets (MSDS) and full materials disclosures. Without these records, a product will not be able to ship into the EU or other RoHS and REACH compliant countries around the world. Currently, the enforcement terms and authorities are yet being defined for REACH, but RoHS is in full swing now.
So, now we can add DFC (Design for Compliance) to our list of best-practices. Remember, no component should be added to the Item Master without a full qualification exercise, or you run the risk of having to redesign, rework, or scrap products that cannot perform or compete qualitatively, or may be disallowed for export altogether. Please refer to this link for part qualification procedure.