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RoHS Auditing Inspection

Overview

In an attempt to minimize the ecological impact of the increasing amounts of “e-waste” generated as electronic devices reach the end of their lifespan, the European Union passed the Restriction on Harmful Substances (RoHS) directive. This directive is an edict prohibiting the use of a handful of different materials in any electronic devices manufactured after a certain date (with some exceptions allowed for some applications like medical devices). As a manufacturer, ensuring that your supply chain is RoHS compliant is vital; not only would accidental inclusion of non-RoHS parts bring the final product out of compliance, but may have adverse reliability effects as well.

Fundamentals

The primary tools for RoHS auditing are chemical analysis methods. Some of the restricted materials – lead, mercury, cadmium, and chromium – are elemental in nature, and can easily be identified with elemental analysis tools like energy dispersive spectroscopy (EDS) or x-ray fluorescence (XRF). Depending on the size and shape of the device to be analyzed, this analysis can even be performed in-situ, with no destructive sample preparation necessary.

The other substances restricted by RoHS are molecular in nature, and require more sophisticated techniques for identification. Polybrominated biphenyls and polybrominated diphenyl ethers (PBBs and PBDEs, respectively) are both proscribed from use by the RoHS directive due to their relatively severe ecological and medical impact; however, they cannot be reliably identified with elemental analysis techniques, since there are relatively innocuous compounds containing bromine that are not banned from use. Instead, a technique that analyzes the molecule as a whole, like Fourier transform infrared spectroscopy (FTIR) must be used, often requiring destructive preparation of the sample.

 

Sample Types

Active or passive components, printed circuit boards or printed circuit assemblies, are all candidates for RoHS auditing. Even simple electronics building blocks like connectors, thermoplastics, or other raw materials should be checked to ensure compliance to RoHS restrictions.

Applications

  • Screening samples purchased from a third-party vendor
  • Certifying new assemblies

Inspection Services

Maintaining a quality product involves countless levels of inspection and process screening. Materials coming from new suppliers must be qualified to ensure that it meets stringent specifications; product from established suppliers must be periodically checked as a safeguard against slipping standards. In other cases, compliance to an external standard or edict, like a MIL-STD or RoHS restriction, must be verified routinely as a process indicator. To help our customers to provide only the highest quality of products, IAL offers a wide range of inspection services for semiconductor devices, printed circuit assemblies, and practically any other electronic assemblies. Our in-depth inspections are based around industry accepted practices and standards combined with extensive experience with product reliability and potential sources of defects, providing the most complete data possible about your product and its construction.

Our inspection services run the gamut of microelectronics, including analysis of semiconductor die for wafer lot acceptance, examination of packaged ICs for authenticity or packaging anomalies, all the way up to printed circuit board and system level inspections. Thanks to our comprehensive suite analytical tools and microscopy lab, IAL can efficiently and effectively screen your devices regardless of their size or complexity.

PCB Failure Analysis

Overview

The modern printed circuit board (PCB) is comprised of hundreds of individual components, multiple layers of copper conductors and fire retardant insulators, and countless vias, plated thru holes, and connectors. Despite industry’s best efforts, 100% yield and perpetual reliability from PCB manufacturing have yet to be realized; manufacturing defects, early life failures, and improper use are still inescapable facts of life. PCB failure analysis aims to identify and study these defects and damaged devices, so that manufacturing processes can be improved and product lifespan can be extended.

Fundamentals

Just as with a failure analysis investigation of an integrated circuit, PCB failure analysis can be broken down into four main phases. After a failing PCB has been received, it is first non-destructively tested, going through an in-depth optical and x-ray inspection to document any immediately obvious anomalies that might have caused the failure. Next, the analyst verifies the fault on the board, recreating the circumstances under which the device was reported to fail to confirm that the system is still malfunctioning. With a confirmed failure, the next step is fault isolation - an analyst might use thermal imaging or time domain reflectometry to identify a potential problem on the board, or may simply use hand probes to trace signals along a board looking for anomalous connections. The goal of fault isolation is to identify a target for destructive analysis and documentation; an analyst might use methodical probing to isolate an open circuit to a single via, for example, which can then be cross-sectioned to reveal improper etchback or mechanical stresses.

 

Sample Types

Whether your failing product is a freshly produced PCB or a fully populated printed circuit assembly (PCA / PCBA), IAL has the capabilities to chase down even the most subtle of failures. With our wide range of capabilities, we can isolate and document defects in the PCB itself, in the components on the board, or even environmental factors that caused the failure (e.g. contamination).

Applications

  • Examining solder or plating failures
  • Characterizing the effects of mechanical stresses on a product
  • Identifying root cause of board conflagration
  • Inspecting devices after initial qualification and reliability testing

Limitations

Since the modern circuit board is so complex, an analyst will often not be able to completely trace a signal based on visual cues alone; buried traces and blind vias obscure the signal path from the naked eye. Should you have access to Gerber files or other drawings showing the layout of the board, providing them can greatly simplify the failure analysis process.

Package Integrity Testing

Overview

One common investigation during a failure analysis project or reliability study is a package integrity evaluation - looking for delamination, popcorn cracking, or other anomalies that may reduce or even end the lifespan of a part. These sorts of anomalies can cause mechanical stresses on bond wires, provide a point of ingress for corrosive chemicals or other contaminants, or make the device unsuitable for use in its intended environment. With the huge variety of package types on the market, understanding which tests to apply can be difficult; fortunately, IAL has extensive experience with a wide range of tools and techniques to facilitate your package integrity analysis needs.

Fundamentals

Most package integrity analysis begins with an optical inspection to identify any gross anomalies (obvious cracks or voids, for example). Optical inspections take very little time, and can be done with no impact to the device under test; no reconditioning or special care is needed to use the sample in production if an optical inspection is the only test a device is subjected to. While this inspection is a good first step, the absence of visible defects does not necessarily imply good package integrity, as other anomalies may be lurking beneath the device’s surface.

 

Generally speaking, the majority of microelectronics are encapsulated using an epoxy mold compound that is formed over the semiconductor die and related interconnects (e.g. the leadframe of an SOIC, or the circuit board substrate of a BGA). The most common way of determining integrity of these types of packages is acoustic microscopy, a technique that uses focused ultrasonic waves to non-destructively probe a package for delamination or cracking. These defects commonly result from mechanical stresses, and as such are often screened for during reliability testing (such as Moisture Sensitivity Level qualification).

In other cases, it may be necessary to perform more destructive analysis in order to get a greater depth of detail in determining package integrity. Dye penetrant is one such destructive test; plastic encapsulated or hermetically sealed samples are immersed in a vat of dye, then subjected to vacuum and pressure to force the dye into any cracks or voids. The device is then fractured, and any dye incursion is documented. Cross-sectional analysis also provides excellent information, allowing cracks, delamination, or other anomalies to be directly viewed under a microscope.

Sample Types

Though there are a multitude of package integrity tests, not all tests are applicable to each type of sample; as an example, acoustic microscopy does not generally make sense to analyze hermetically sealed packages, as the thick ceramic layers and air gaps in the package do not allow good propagation of the ultrasonic waves. For more information about which tests may be applicable to your products, please feel free to consult with one of IAL’s engineers, who are glad to help determine an optimal course of analysis.

Applications

  • Moisture Sensitivity Level (MSL) qualification and screening
  • Finding voids or poor adhesion in die attach material
  • Inspecting the underfill and solder connections of a flip-chip BGA
  • Identifying leaks in a hermetically sealed package

PCB Inspection Services

Overview

An in-depth inspection of a printed circuit board (PCB) or printed circuit board assembly (PCA/PCBA) is a quick, cost effective way to ensure the delivery of exceptional quality products. Whether qualifying your own product or screening a subcontractor’s deliverables, a detailed inspection can provide invaluable information about potential process weaknesses that might result in reduced lifespan or reliability.

Fundamentals

For quality screening or product qualification, IAL can perform PCB or PCA inspection to the standards set forth in IPC-A-600 and IPC-A-610. This inspection is designed to encompass many of the typical pitfalls of PCB manufacturing; from plating thickness to via registration, solder mask coverage to resin fill, an IPC inspection is a comprehensive examination of many of the key characteristics of an assembly. Many of the features called out by the IPC specs can be inspected non-destructively, and therefore are appropriate as a final inspection or quality screen of a product before shipping; for more in-depth examination, destructive analysis is usually necessary.

PCB/PCA Construction Analysis (sometimes also referred to as Destructive Physical Analysis, or DPA) adds cross-sectional analysis and device delayering to the standard IPC inspection. This deeper dive may target suspected defects buried within the board, like improper via etchback or cracked thru-hole plating, or may simply be part of a more stringent quality control program. In other cases, this type of analysis may be performed in support of a competitive analysis, to look for potential intellectual property infringement or to better understand where a competitor has positioned themselves in the market.

Another, more specialized subset of PCB Inspection is dye penetrant testing (also colloquially referred to as Dye and Pry). Dye penetrant is primarily used in support of failure analysis to look for solder failures. By immersing a PCA in a vat of dye and subjecting it to vacuum and pressure, dye is forced into all available spaces on the PCA - including any cracked or non-wetted solder joints. Suspect devices are then pried from the board, and any failing solder joints can be identified by the presence of the brightly colored dye.

 

Sample Types

Both unpopulated PCBs and fully populated PCAs can be inspected per IPC-A-600 or IPC-A-610 (respectively). Dye penetrant testing is appropriate for BGAs, LGAs, and QFNs that have not been coated with a conformal coating.

Applications

  • Continuous monitoring of an established process
  • Qualification of a new device or process
  • Solder joint inspection and failure analysis