Package Integrity Testing
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.
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.
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.
- 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
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.
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.
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.
- Continuous monitoring of an established process
- Qualification of a new device or process
- Solder joint inspection and failure analysis