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Unmasking a Counterfeit BGA
Tuesday, December 14, 2010 | Tom Adams, Consultant, Sonoscan, Inc.

Editor's Note: This article was originally published in the October issue of SMT Magazine.

The BGA component (Figure 1) that is the subject of this article was purchased from an open-market supplier by SMT Corporation, an independent stocking distributor in Sandy Hook, Connecticut, as a pre-purchase lot/date code sample of a much larger lot quantity being considered. As part of SMT's robust counterfeit mitigation process, technicians perform this pre-screening whenever possible to determine authenticity and overall quality of a lot sampling before the full order quantity is placed. If this component had passed the initial pre-screening process, and if a full quantity order had been purchased, all testing processes would have been repeated, even though the initial lot samples had already been inspected.

Figure 1: The sample BGA that turned out to be counterfeit. Note the lot/date code information at the bottom.

Anyone walking through SMT's facility might easily conclude that the company really consists of a series of well-equipped component inspection lab areas surrounding large, spotless, humidity controlled warehouses. In fact, the company is an independent stocking distributor that has been forced by the increasing amount of counterfeit electronic components being dumped into the open market to invest heavily in the latest test and inspection technologies to protect customers.

Although there are several main types of counterfeit components, by far the most abundant are components that have been stripped off used PCBs (E-scrap), refurbished, resurfaced and re-marked to reflect a newer single lot/date code. They are then misrepresented and resold as original factory-new product. Another common source for counterfeits is component product that has been scrapped by the component manufacturer and that has somehow made it into the hands of the counterfeiter. These counterfeits may harbor internal surprises, such as missing or broken die and bond wires.

Counterfeiters are working harder to copy the new, original appearance of the component manufacturers' surface finishes and part markings. In recent years, these efforts have become much more sophisticated and difficult to spot without expensive test equipment and proper training.

SMT's main market focus is supplying electronic components to the hi-reliability industry needs of defense and aerospace, medical, energy, telecom and other critical technology applications. It has in stock over 120,000 line items of obsolete, hard-to-find and DMS-type component products. SMT also serves as an authentication and quality lab for OEMs, CMs and other open-market suppliers.

The various SMT laboratories use these methods to identify counterfeit components:

  • Visual inspection: Light and hi-res microscopy;
  • Data-sheet comparison, including mechanical measurements;
  • Real-time X-ray;
  • X-ray fluorescence (XRF);
  • Energy dispersive spectroscopy (EDX);
  • Scanning electron microscopy (SEM);
  • Scanning acoustic microscopy (SAM);
  • Automated solderability testing;
  • Automated BGA co-planarity measurement;
  • Resistance to solvents (RTS), including heated solvent testing;
  • Acid-etch and mechanical decapsulation for die verification; and
  • Electrical testing.

The Sonoscan C-SAM® acoustic microscope system is a recent addition, useful because ultrasound is reflected from internal interfaces between materials—a capability that lets it image telltale internal signs of counterfeiting. In its work with counterfeit plastic parts, Sonoscan has imaged such items as misplaced die (in a made-from-scratch counterfeit) and die face delaminations (in a "recycled" component that is near the end of its useful life). In one part, it was the precise location of wire bonds on a plastic-encapsulated die that revealed the counterfeit. For decades Sonoscan's work has focused on finding internal defects, characterizing materials and the like, but, in recent years, the menu has expanded to include the identification of counterfeits.

The first step in the SMT inspection of a component is visual inspection, chiefly performed with visual inspection and light microscopy. Visual inspection sounds simple enough, but technicians have learned so many of the "red flags" that counterfeit parts exhibit that the check-off list for light-microscopy visual inspection contains 23 distinct areas of scrutiny.

The first look at the BGA in Figure 1 raised a few questions. Although the genuine National Semiconductor part had been fabricated as a plastic package with a nickel top, the top surface of the sample component had a color and texture that closely resembled silver/gray paint. (Counterfeiters often resurface or "blacktop" a component with a paint-like substance before re-marking it.)

Visual inspection of the edges of the BGA raised suspicions even higher. When a used component is spray-painted by the counterfeiter, some of the paint typically winds up on the upper areas of the sides of the component.

Figure 2: Very strong evidence that the top surface has been spray-painted. Excess paint can clearly be seen extending part of the way down the side of the component.

At this point there was essentially no possibility that this BGA was a genuine new component. But it was worthwhile to continue the inspection process to find out more about the counterfeit process used on the component and to try to determine what its original identity had been.

Figure 3: DynaSolve safely removed the paint applied by the counterfeiter.

The next step was to immerse part of the component in a heated solvent called DynaSolv™ (Figure 3). DynaSolve has the ability to remove overlying paint or urethane coatings to expose the sanded surfaces below.

Figure 4: This SEM image clearly shows sanding marks on the plated nickel top of the BGA.

A scanning electron microscope image made after the heated DynaSolve™ treatment and showing, at high magnification, the nickel surface of the component and the adjacent bubbled-up edge of the remaining paint.

The multiple scratch marks on the surface of the nickel are a clear indication that the original component part markings were hand-sanded off before the counterfeiter resurfaced the part with paint and then remarked it with an ink-marking process.

There is now no question about the history of this BGA. It was undoubtedly shipped from the U.S., or another country, to China, packed in one of many containers that deliver used PCBs (E-scrap) every day. The board, along with hundreds or even thousands of other identical boards, then traveled to a town such as Shantou, where workers toiling for low wages in primitive conditions try to turn scrap electronic components into cosmetically-acceptable fakes that can be passed off as new, originally-manufactured parts.

The process of removing used components from scrap PCBs typically entails a worker holding a board over an open flame or other heat source until the solder re-flows. At this point, the board is slammed down on a hard flat surface causing the components to drop off. Other workers gather up the components and take them to the next process—washing to remove the soot residue from the heating step. Incredibly, most components are washed by dunking them into nearby rivers and streams or spreading them on sidewalks in the rain. Later they are sorted, often by young children and elder women. Sorting is carried out according to the specific package type of a component and the number of leads. What this means is that all ICs having the same x-y dimensions and having, for example, 16 leads go in the same pile. After washing, the components are taken into multi-story buildings that double as homes, where the sanding and remarking process take place prior to resale. (In a 2008 trip to China, Tom Sharpe, Vice President of SMT Corporation, photo-documented these crude processes first-hand while touring the counterfeiting districts of Shantou.)

There are undoubtedly vast differences in the die revisions, year of original manufacturer, performance capabilities and overall functional lifespan of these parts, but after their cosmetic rebirth they will all carry the same lot/dc labeling and will be represented and sold as though they were a new, unused homogenous lot.

Figure 5: An optical close-up view of the BGA after heated DynaSolve™ treatment. Most of the paint has been removed, and the shiny, sanded surface of the nickel plated top is visible.

The original labeling on this component, it turns out, was applied by laser etching. In the upper part of Figure 5, a small part of the counterfeit ink-printed logo is visible to the right, and to its left an etched portion of the original logo is still faintly visible in the nickel. The purpose of sanding was clearly to grind off enough nickel plate to remove the traces of the original laser etch part marking. It is possible that the worker doing the sanding was told to remove the etching, but not to go much deeper because he would then create a component that was suspiciously thin (SMT mechanically measures component critical body dimensions with digital calipers as part of their counterfeit mitigation process), although the paint that will be applied after sanding will increase the thickness. As it turned out, the worker did not go quite deep enough and, by doing so, left behind additional evidence for investigators. The optical image in Figure 5 shows some of the laser-etched logo in the nickel, but the copyright and lot/dc that are normally seen at the bottom of the part in Figure 1 are no longer visible to the naked eye.

This is where acoustic microscopy came in handy. An acoustic microscope pulses VHF or UHF ultrasound into a part from a raster-scanning transducer. The distance to internal features in the part is short and the speed of ultrasound is high, with the result that return signals (echoes) can be received from thousands of x-y locations per second. The return signals can be processed in various ways, but most often the amplitude of the signal determines the color of the pixel in the acoustic image.

An acoustic image can also be confined vertically to a desired depth within the component. In general component inspection work, for example, this might be the die face depth, the die attach depth or the lead frame depth—all of which include material interfaces. It even images, from the back side of advanced flip chips, cracks in the exceedingly thin low-k dielectric layers. If required, the return echoes can provide images of up to 100 different depths from the same scan.

At any point in the scanned depth, there are three possibilities: 1) ultrasound encounters no material interface and sends back no echo; the pixel is black; 2) ultrasound encounters a bonded interface between two materials; the pixel is some shade of gray; 3) ultrasound encounters the interface between a solid and a gap such as a crack; the pixel is bright white.

In the case of this BGA a single, somewhat unusual depth was selected, ranging from the top surface of the nickel to a fraction of a millimeter below the top surface.

Figure 6: Acoustic microscopy of the sanded surface and immediate subsurface shows that the lot/date code information ink-printed on the BGA (Figure 1) was a fake.

As it turned out, sanding removed visual evidence of the original markings, but not acoustic evidence. Most likely the original manufacturers' laser etch process changed the acoustic properties of the nickel beneath the laser cut itself, with the result that ultrasound encountered two slightly different materials: unaltered nickel and altered nickel. The bottom image in Figure 6 shows an acoustic image containing the originally marked copyright and manufacturing on the top line, followed on the bottom line by manufacturing codes denoting country of assembly, lot/dot code, wafer lot and die-revision among other things. The top image in Figure 6 shows the similar paint re-marking code that was selected by the counterfeiter for this particular lot from Figure 1. Rectangles show the critical difference between the two. The genuine lot/dot code and wafer lot revision was "302AF;" the counterfeited version has been changed to "251AH." (For reference, "302" is the year/week code of manufacturer—2003, second week of the year, while the "AF" stands for the wafer lot the die contained inside was taken from. The "A2" at the end is the die revision.)

This was a somewhat unusual application of acoustic imaging, which more often looks deeper into components to analyze internal features. But acoustic microscopes can use ultrasound in other ways; for example, to characterize a mold compound by measuring its acoustic impedance, or to nondestructively cross-section a component. Dr. Lawrence Kessler, President of Sonoscan, notes that the company's SonoLabs have already compiled a list of internal acoustically visible features that are specific to counterfeits. The list is somewhat parallel to, and about the same size as, SMT's list of 23 items for visual inspection. For the inspection of this BGA, acoustic imaging uncovered the original specific identity that the counterfeiters had worked so hard to conceal.

Sonoscan is a registered trademark of Sonoscan, Inc. DynaSolve™ is a trademark of Ellsworth Adhesives.