Chip impact test

The chip impact test is carried out in a similar way to the Izod test but without a notch. The test specimen is usually 25.4 mm long, 12.7 mm wide, and 1.65 mm thick. The tests are carried out using ASTM D4508 [79]. Because the test involves an un-notched sample, it reflects material toughness rather than the notch sensitivity measured for the Izod and Charpy tests. 

The chip impact test is somewhat similar to the Izod impact test. The specimen can be tested using standard Izod pendulum tester. The chip impact test requires the use of a pendulum hammer type of device and a specimen holding fixture. The test specimens are usually 1 in. long x 1/2 in. wide and 0.065 in. thick. The specimens can be prepared either by injection or compression molding or by simply cutting them from a sheet. 

If the test were used exclusively to study the effect of weathering on a polymer, it would be required that the sample be struck with a pendulum hammer on the weather exposed side. The chip impact test is also useful in measuring the relative toughness of a rather large and a complex-shaped part that is difficult to hold in a conventional hxture. A small chip can be cut from such a part and subjected to the chip impact test. 

Figure 2-43. Diagram illustrating the principle of chip impact test.

The suitability of chip form for sub-flooring and flooring applications was also thought worthy of consideration. In this case resistance to impact is of prime importance, for this reason test specimens, as shown in Figure 5, were prepared and impact tests were carried out. 

The results of the impact tests are shown in Table 4. Chip form of 12mm thickness was seen to have an impact strength exceeding that of 25mm thickness general construction use particle board. 

The crazing effect can be indirectly determined by testing chip impact resistance of specimens which crack either because of weathering or environmental stress cracking. ... 

ASTM D 4508-98. Standard test method for chip impact strength of plastics. 

The pendulum impact test employs a pendulum type of hammer. It is carried out in four ways Izod, Charpy, Chip and Tensile. The apparatus used for the pendulum test consists of a heavy base with a vice for clamping the specimen and a pendulum hammer swinging at a sample. The machine base must be kept on a rigid platform to prevent vibrational energy losses. 

ASTM 4508-06, Standard Test Method for Chip Impact Strength of Plastics,... 

In general, there are four levels of bare die test and burn-in, referred to as four levels of known good die (KGD). In Table 8.10, these test levels are summarized, along with their impact. The lowest KGD level is to just use the same tests normally done at wafer level, referred to as the wafer sort tests. Here the chips are normally subject to a low-speed functional test combined with some parametric measurements (e.g., measurement of transistor curves). With this KGD level, test costs for bare die are limited to wafer test costs only. There is some risk, however, that the chip will not work when tested as part of the MCM. This risk is measured as the test escape rate. With conventional packaging, the chips are tested again, perhaps at full speed, once they are packaged, making the test escape rate zero. 

The ability of a painted plastic part to withstand the impact of foreign objects such as small stones and gravel has been extensively reviewed by Ryntz et al. (11,12). Test methods range from the simple projectile of small stones at cold substrate (e.g., SAE J400) to the more precise impact tests described by Ryntz and others. In a fully painted plastic bumper, chip damage can occur ... 

Mechanical strength of the solder joints was evaluated by applying shear loads on components as fabricated and after thermal cycling (—55°C to 100°C, 66-min cycles) and liquid-to-liquid thermal shock (155-100°C, 15-min dwell). The strength values of the solder remained largely unchanged for the larger chips. However, test results for the 0805 chips indicated that the position of the components on the assembly and their proximity to other components can impact solder joint reliability [99]. 

Crosstalk If two or more channels are multiplexed through a single A/D chip, then a crosstalk test is recommended to see the impact of an overloaded signal on one channel impacts another. 

For hermetically sealed microcircuits several screen tests should be performed before delidding the package. A particle impact noise detection test (FIND [MIL-STD-883 Method 2020 or MEL STD-750D, Method 2052-2]) is recommended. This shake test combines a series of shocks and vibrations and, through an attached transponder, acoustically detects any loose particles (for example, chips of cured adhesive, solder, wire, ceramic, or loose plating) that have detached and can cause shorted or open circuits and damage or breakage of thin wires and connections. 

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