This article looks at Kimball's techniques for seamlessly integrating into the original equipment manufacturer (OEM) or third-party design firm's product development efforts.
Consideration must be given to product functionality and to any qualification testing and design for manufacturability.
Efficient electronics manufacturing processes begin with the design process. Consideration must given not only to product functionality, but to any qualification testing and design for manufacturing (DFM) as the consequences of not doing so may add time and cost to the development cycle or production.
Industrial products have unique challenges including long lifecycles, the need to operate in hostile environments, and limits on redesign options over time. In these applications, a disconnect between design and manufacturing will not only slow down product development cycles, but may also create added costs due to unnecessary field failures and end customer dissatisfaction.
Kimball Electronics Group’s Industrial Solutions engineering team has routinely encountered these challenges. This article looks at the Company’s techniques for seamlessly integrating into the original equipment manufacturer (OEM) or third-party design firm’s product development efforts. It will also discuss the role of qualification testing and use of its Reliability Test Lab in validating design assumptions and in identifying root causes of field failures.
ADVERTISEMENT
Robust Design & Qualification Process
Industrial products must often function in harsh operating environments which may include rain, snow, extreme temperatures, vibration, and/or frequent power cycling. Additionally, some products have life expectancy requirements of 25-years minimum. This drives design requirements which may include special product enclosures, potting, or other coating applications.
Integrating manufacturer input and observations from Highly-Accelerated Stress Screening (HASS) or Highly-Accelerated Life Testing (HALT ), and other validation testing into the design cycle can identify potential weak links in the design prior to launching the product. When done correctly, this will help avoid costly design and early life failures when the product is first launched.
However, in a world of shorter design cycles, reduced engineering resources and a focus on continuously cutting cost, not all companies utilize a robust design process where manufacturing input and validation testing help identify design flaws early in the process.
This can be seen in unexpected field failures, end customer dissatisfaction, a need for either a significant redesign, or modifications to units in the field. These field failures may be caused by material issues, manufacturing issues or design issues. A few of the most common drivers of field failures are discussed below.
In the case of apparent material issues, the cause may be related to a supplier or may be in the design itself. For example, if a field effect transistor (FET) experiences voltage or current spikes, it can fail in a shorted condition and is typically seen as an electrical overstress event (EOS).
In these types of situations, Kimball looks at the supply base for any trends or special causes and failure analysis of the component itself provided by suppliers and also evaluates the design and manufacturing process to see if either may be contributing to the problem.
Manufacturing issues typically arise when DFM guidelines are ignored in the design process. For example, when MELF resistors, which are supplied as a cylindrical package, are placed on a square flat pad, solder issues can result. There must be an adequate solder fillet around the MELF to ensure a good interconnect to the pad.
In some cases, the MELF may require hand touch-up if there is not an adequate solder fillet. This secondary operation requirement creates variability and the potential for defects due to missed touch-ups, re-heating the solder joint, and unnecessary handling of the assembly. When there is an inadequate solder fillet, the MELF may pass testing but may create an intermittent contact situation in the field.
Optimum solutions in avoiding this problem can include changing the stencil layout, changing the board layout, using a more robust inspection process such as AOI, or redesigning to a square package component.
Through-hole devices are also potential areas for manufacturing issues. When the right lead-to-hole ratio is not used on a through-hole device, such as a connector, there generally will not be an adequate amount of solder in the connection. It can be difficult to achieve 75 percent or 100 percent barrel fill through the manufacturing process. While this becomes a manufacturing issue, the root cause is an inadequate design.
Lead-to-hole ratio issues are often driven by conversion from a leaded to a lead-free solder chemistry. These two different types of solder chemistries require different ratios to be manufactured properly and may be different than what is recommended by the component manufacturer.
Connectors also drive some significant failure issues and resolving these issues can be difficult because the connection system typically is customized for the application. Connectors are one area of strong focus in design because of their sensitivity to processing temperatures.
Another challenge is that connectors may be specified as lead-free processing safe but really can’t withstand the temperatures of lead-free reflow. In the case of failure to meet specifications, the supplier is contacted and informed that the component as designed doesn’t meet specifications, and a joint solution is developed. However, many of these issues can be avoided in the design phase by having the manufacturer review both the design and specified components.
Lead-free processes also drive higher processing temperatures and may bring out material incompatibility issues. For instance, lead-free BGAs may create both long- and short-term issues if placed on a leaded board. If reflowed in a leaded process, ball collapse isn’t achieved because processing isn’t done at high enough temperatures.
If higher temperatures are used, the flux is burned off and an oxidation layer that is more resistive is formed, which doesn’t create the required mechanical connection and would only provide for a marginal electrical connection at best.
Additionally, if the higher temperatures are used in order to obtain proper ball collapse, other issues may arise if there are other components on the assembly that are not intended or designed for the higher processing temperatures. This drives higher production fallout and reliability issues.
Integrating Manufacturing Expertise & Reliability Testing
Outsourced product development, qualification testing and/or manufacturing offer one way for OEMs to control cost, compensate for a reduction in internal resources and take time out of product development, provided the respective partners and team work well together. This example looks at best practices in integration between a third-party product development firm and Kimball.
According to Derek Hampson, vice president of BIT 7, Inc. (www.bit7.com), a product development firm near Chicago, IL, strong teaming between third-party designers and the end manufacturer can save both time and money. Product development should not be viewed as a segregated process. Tooling, design, and procurement are all critical elements, and there should be clear definition of which team members are taking the lead in each area.
A typical design cycle normally includes:
- Top level product design.
- Concept development.
- Concept validation (breadboard).
- Alpha phase prototypes.
- Beta phase prototypes.
- Production.
The third party design firm becomes involved in the process after the OEM’s marketing team has the product specification defined. They do a top level design with an architectural overview of hardware, software, mechanical design and industrial design. This is reviewed by the OEM. Then the firm begins mechanical, electrical, software and enclosure design. The OEM’s engineering team or manufacturing partner typically takes the lead for the alpha and beta prototype stages.
Early manufacturing involvement in product development may start at the top level design phase. This is particularly important when exotic materials or packaging requiring specialized production processing are involved. More generic parts are specified at the concept development stage. Determining who takes the lead in this effort often depends on the strengths of the partners.
While a strong design partner may make recommendations based on the form, fit and function requirements of the design, the manufacturer looks at issues such as component commonality and availability, supplier quality and price, availability of second sources and potential processing issues.
In the case of a multinational EMS provider such as Kimball, procurement issues associated with the region in which the product will be produced may also be considered. The design firm and Kimball typically team on bill of materials (BOM) and approved vendor list (AVL) development.
DFM and design for testability DFT) are also best done at the concept development stage. Typically the test strategy is also in development at this point. Some companies may see these stages as a single phase vs. two distinct points in the process.
Robust validation testing evaluates product ruggedization against environmental conditions and generally includes some kind of humidity and thermal cycling. When quick testing such as HALT covering thermal extremes, fast thermal cycling, vibration and combined environmental testing is done in the late concept validation or early alpha phase, weak links in the design or materials choices usually become apparent.
This allows modifications to be made in the alpha phase that increase the reliability of the overall product and this early focus minimizes the time and cost associated with design modifications later in the process, as well as eliminates the customer dissatisfaction that can occur when the design robustness is “tested” in the field instead of being verified during the design cycle.
Once the recommended changes are made from HALT, the testing should be repeated to verify the reliability improvement. Additional testing would also be appropriate as HALT does not typically address environmental conditions such as humidity or chemical exposure. Typically durable electronic products in the field require some type of environmental protection such as an enclosure or design element that otherwise mitigates the effect of nature.
This last stage of testing should include any enclosures, coatings or sealing process specified to protect the product. Thermal cycling, humidity testing, air-to-water thermal shock or other seal testing may be included. Normally at this stage the base circuitry is at least 90 percent firm and the printed circuit board (PCB) layout is at least 75 percent firm.
Design reviews between project phases are critical to ensuring the recommendations of all team members are addressed. BIT 7 uses checklists, and invites both the OEM and the manufacturing partner in their development efforts to ensure a consistent process. Prototyping may be done by the design firm or the designated manufacturer, depending on the capabilities and location of the designated manufacturer.
Ideally, having prototypes built at the volume manufacturer provides a good check and balance, but full service design firms such as BIT 7 also maintain limited component procurement and prototyping capabilities to provide support when prototyping at the end manufacturer isn’t feasible. In Kimball’s efforts to insure a robust manufacturing process, a PFMEA (Process Failure Modes and Effects Analysis) is typically completed to identify and mitigate any risks associated with the manufacturing process.
Keeping Product Development On Track
Another area that can drive inefficient product development efforts is lack of clear understanding of expectations and capabilities within the team. Key questions to ask when selecting good design and manufacturing partners include:
- Do the firms have expertise in ruggedized product applications?
- Are the product qualification test requirements clearly understood by the design firm?
- Is there sufficient capacity and expertise to complete the product development in the preferred timeframe?
- Who owns the intellectual property (IP) rights of the product or any of its custom components?
- Who will own the tooling?
- Are all the needed support partners identified?
- Are there agreements in place that govern an efficient disengagement should one of the parties fail to perform?
- Are risks and liabilities clearly identified?
The end result of focused evaluation of potential design and manufacturing suppliers, followed by early involvement of all partners, drives a robust product development process. Tapping the expertise of each of those partners can save time and cost over the entire product lifecycle.
For more information visit www.kimball.com