Experiments done in Tin Whiskers Growth

Table 1: Details on the number of test samples and terminations required for comparison of screening inspection data.

Figure 1. A schematic drawing depicting a leadless component and the top and 3 sides of the terminations that should be inspected.

Figure 2. View onto a contact.

The beads were inspected before the tests using a binocular microscope at 72.5x magnification in order to determine if whiskers were present at the beginning of this study.

Detailed inspections were performed on the leads of all the samples from the three lots after each test condition using a scanning electron microscope.

Moreover, and as recommended by the JEDEC standard, a preconditioning heating treatment was applied to all parts prior to the start of the test programme.

Figure 3. Temperature profile applied for preconditioning the three lots of 39 SMD beads.

During the screening performed at Alter Technology, each lot of surface mount device beads (39 per part type) was divided into three groups of 13 beads:

The first group of 13 parts was submitted to Temperature Cycling (1000 cycles per run).

The second group of 13 parts was submitted to Ambient Temperature/Humidity Storage(1000 hours per run).

The last group of 13 parts was submitted to High Temperature/Humidity Storage(1000 hours per run).

Each test was repeated four times (or runs) in order to exceed the minimum duration recommended by JEDEC.

Figure 4. Temperature shock test cabinet and humidity chamber.

A summary of the conditions used for testing and a schematic of the test flow is shown in Table 2 and Figure 5 respectively.

Table 2: Tests and conditions applied for accelerating the growth of Stanium whiskers.

Figure 5. Schematic of acceptance test flow carried in Alter Technology on each lot x (x = 1, 2 and 3) of 39 SMD beads. The tests are applicable for two leaded Class 2 components using Copper (Cu) lead frame with Ni underlay mitigation technology and Stanium (Sn) 100% finish.