Preserving solderability and inhibiting whisker growth in tin surfaces of electronic components
A technology of electronic components and tin whiskers, applied in the performance field of electronic components, can solve problems such as short circuit of electrical contacts
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example 1
[0035] Five samples were obtained by electroplating a suitable nickel first metal layer onto a C19400 copper alloy substrate using a Sulfamex MLS electrodeposition system available from Enthone Corporation (West Haven, CT, USA). For this purpose, prepare an electrolyzer in deionized water comprising the following components:
[0036] Ni(NH 2 SO 3 ) 2 319-383g / L
[0037] NiCl 2 *6H 2 O 5-15g / L
[0038] h 3 BO 3 20-40g / L
[0039] CH 3 (CH 2 ) 11 OSO 3 Na 0.2-0.4g / L
[0040] The pH of the electrolyzer is maintained between approximately 2.0-2.5. The electrolyte is maintained between approximately 55°C-65°C. Keep the current density at about 20A / ft 2 -300A / ft 2 The time in between is long enough to attach a nickel alloy first metal layer approximately 2 microns thick.
[0041] A layer of sulfonium tin alloy was then electroplated on each of the five samples using the STANNOSTAR electroplating system available from Ent...
example 2
[0047] Five samples prepared according to Example 1 were subjected to 1000 thermal shock cycles from about -55°C to about 85°C. 7-11 are photomicrographs of samples after thermal shock testing. Figures 7a and 7b show 1000X and 500X photomicrographs, respectively, of numerous large-sized tin whiskers growing in a sample with a 10 micron thick tin alloy layer. Figures 8a and 8b show 1000X and 500X photomicrographs, respectively, of a small number of prominently sized tin whiskers growing in a sample with a 3 micron thick tin alloy layer. Figures 9a and 9b show 1000X and 500X photomicrographs, respectively, of few tin whiskers of negligible size grown in a sample with a 2 micron thick tin alloy layer. Figures 10a and 10b show 1000X and 500X photomicrographs, respectively, of almost no tin whiskers growing in a sample with a 1 micron thick tin alloy layer. Similarly, Figures 11a and lib show 1000X and 500X photomicrographs, respectively, of no tin whisker growth in a sample with...
example 3
[0049] FIG. 12 shows a graph comparing the whisker index (WI) of five samples prepared according to Example 1 after being subjected to the thermal shock test of Example 2. FIG. The WI of a tin alloy layer is defined as a function of the number, length, diameter, and "weight factor" of whiskers in a given area of the sample. The weighting factor is used to differentiate between short and long whiskers. Here, 500X photomicrographs were used to determine WI for each of five samples: 7b, 8b, 9b, 10b, and lib. As shown in Figure 12, WI increased significantly from a value close to 0 for the 2 micron sample, to a value close to 825 for the 3 micron sample, and to even larger values for tin-based layers greater than about 3 micron thick.
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