This is the first of a series of perspectives on common, but avoidable, problems that I have encountered in the development and qualification of components for use in high reliability opto-electronic applications. Some of these problems may appear intuitive, and therefore absurd, to engineers with specific academic or established telecom OEM backgrounds, where projects run for many years and are supported by significant past experience and/or applied research. However, the proliferation of start-ups, radical shortening of development cycles, general dilution of knowledgeable engineers (both in vendors’ product development and customers’ reliability assessment groups), constant cost reduction pressure from customers, and outsourcing/offshore production have all colluded to promote quick, ill-informed design and process decisions. One of the key value propositions of DfR Solutions is to provide guidance during the design and development phases, in order to avoid expensive and reputation-damaging mistakes in the future.
The use of epoxy is common in the opto-electronic components industry for many reasons, the most important being limiting attachment-induced residual stresses and their impact on optical alignment. There is a wide array of epoxy chemistries to choose from, including filler-reinforced adhesives that exhibit much better mechanical, thermal, and/or electrical properties, as well as a similarly broad group of epoxy manufacturers in terms of size, maturity, and markets served.
Unfortunately, many ‘telecom’ adhesives were developed and optimized for other markets and uses; in some cases, they are acceptable for network applications with sufficient process development, but more often than not may introduce new failure modes (debonding, creep, residual moisture, optical surface contamination, etc.) that take substantial engineering resources and time to solve. A common misconception is that epoxies allow greater process flexibility (lower process temperatures, easier rework, less intensive capital equipment costs, etc.) than solder or welding solutions, when in fact they require something close to religion in terms of consistency of manufacturing practices and controls. The following are common mistakes in epoxy selection and process development:
- Epoxies are often not optimized for the materials being bonded or the required properties (low stress attachment; long term stability; outgassing; thermal performance; etc.)
-Manufacturers’ data sheets are often misleading
- Elevated temperature curing is immediately and often incorrectly associated with increased component stress
- Surface preparation is critical to adhesive strength and is often overlooked
- Lot-to-lot variability in adhesive chemistry requires strict quality assurance procedures
- Epoxies are often used past their effective working times and expiration dates
DfR Solutions can provide guidance with respect to adhesive selection, cure process development, storage & usage guidelines, process monitoring tests, and additional characterization methods to enable reliable long-term performance of your components.
The constant demand for smaller, faster, more reliable electronic components continues to drive innovation in component packaging. Component engineers are relentless in their quest for new and better ways to improve BGAs and packaging silicon. Recent advancements include going coreless and multi-chip modules, but silicon technology advances dictate continued improvement in packaging.
Conformal coatings and potting materials are an important part of printed circuit board (PCB) technology, but they also cause many issues in the electronics industry, including: Coefficient of Thermal Expansion (CTE), Delamination, cracking and de-wetting, Pinholes/bubbles and orange peel issues, Glass Transition Temperature (Tg), and PCB warpage. Watch our webinar Coatings and Pottings — A Critical Update for a deep dive into the issues of these materials and how to address them, including a look at the effects of improper curing and potential methods for correcting these situations. Plus, hear about advances in superhydrophobic materials technology.