Low battery? Localized screening tests help pinpoint the cause of battery leakage failures.We were recently presented with the following problem: A company's batteries on its new product were draining while sitting in the storage box. As it turned out, dirty 0805 chip capacitors on the battery circuit were causing the three-volt battery to drain in less than two weeks. A high humidity screening test was developed to separate the good units from the bad until a root cause and corrective action A corrective action is a change implemented to address a weakness identified in a management system. Normally corrective actions are instigated in response to a customer complaint, abnormal levels if internal nonconformity, nonconformities identified during an internal audit or plan could be developed. The assemblies were failing approximately 3 to 5% of the screening tests. We originally thought that the capacitors were cracked; however, multiple cross sectioning tests proved this idea wrong. Standard cleanliness Cleanliness See also Orderliness. Cleverness (See CUNNING.) Berchta unkempt herself, demands cleanliness from others, especially children. [Ger. Folklore: Leach, 137] cat continually “washes” itself. testing showed that the assemblies from the no-clean process were in fact clean. The total board extraction showed an acceptable level of residues, indicating that cleanliness was not a problem (Table 1). Since we knew there was no problem with the capacitors, we believed that cleanliness in the critical area of the board was the problem. Further testing with a localized extraction system in the area of the capacitor capacitor or condenser, device for the storage of electric charge. Simple capacitors consist of two plates made of an electrically conducting material (e.g., a metal) and separated by a nonconducting material or dielectric (e.g. on the failing units allowed us to better understand the pockets of contamination. Our testing revealed a high level of sulfate sulfate, chemical compound containing the sulfate (SO4) radical. Sulfates are salts or esters of sulfuric acid, H2SO4, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a radical (e.g., ammonium or ethyl). residue on the capacitors of the failed assemblies (Table 2). The sulfate was not present in high quantities on the units that passed the screening test. Additional areas on both groups were also tested, and all areas showed similar acceptable results. The localized extraction allowed us to see the pockets of chloride chloride (klōr`īd, klôr`–), chemical compound containing chlorine. Most chlorides are salts that are formed either by direct union of chlorine with a metal or by reaction of hydrochloric acid (a water solution of hydrogen chloride) , sulfate and weak organic acid (WOA WOA Wacken Open Air (music festival) WOA Work of Art WOA Western Orthopaedic Association WOA Web Offset Association (Nashville, TN) WOA World Airways, Inc (ICAO code) ) residues that were located on the specific area of the board.
Ion Chromatography
(All values are [mu]glin.sub.2) Cl Br SO4 WOA
Boards That Passed
Assembly #1 - Total board extraction 0.99 0.68 0.00 7.95
Assembly #2 - Total board extraction 0.70 0.72 0.00 15.78
Assembly #3 - Total board extraction 0.51 0.47 0.00 9.48
Assembly #4 - Total board extraction 0.68 0.58 0.00 7.93
Assembly #5 - Total board extraction 0.55 0.59 0.00 16.69
Failed Boards
Assembly #6 - Total board extraction 0.93 0.32 0.00 14.93
Assembly #7 - Total board extraction 1.05 0.57 0.00 14.41
Assembly #8 - Total board extraction 0.83 0.33 0.00 11.92
Assembly #9 - Total board extraction 1.18 0.46 0.00 8.38
Assembly #10 - Total board extraction 0.99 0.68 0.00 11.05
Table 1: Total board extraction results of the high humidity screening
test.
Ion Chromatography
(All values are [mu]glin.sub.2) Cl Br SO4 WOA
Boards That Passed
Assembly #1 - Localized extraction 1.11 0.57 0.13 11.62
Assembly #2 - Localized extraction 2.25 0.54 0.24 9.36
Assembly #3 - Localized extraction 1.54 0.60 0.16 10.92
Assembly #4 - Localized extraction 1.06 0.58 0.17 10.36
Assembly #5 - Localized extraction 2.04 0.48 0.21 11.52
Failed Boards
Assembly #1 - Localized extraction 2.36 0.43 20.36 12.57
Assembly #2 - Localized extraction 2.15 0.53 28.26 10.14
Assembly #3 - Localized extraction 2.28 0.54 24.12 10.95
Assembly #4 - Localized extraction 2.06 0.34 29.36 11.41
Assembly #5 - Localized extraction 2.03 0.55 27.15 10.65
Table 2: Localized extraction results of the high humidity screening
test.
Conclusion When examining the cause of the residues on the capacitors, we found that the post-plating rinses after the barrel plating process using methane methane (mĕth`ān), CH4, colorless, odorless, gaseous saturated hydrocarbon; the simplest alkane. It is less dense than air, melts at −184°C;, and boils at −161.4°C;. sulfonic acid sulfonic acid (səlfŏn`ĭk), organic compound containing the functional group RSO2OH, which consists of a sulfur atom, S, bonded to a carbon atom that may be part of a large aliphatic or aromatic hydrocarbon, R, (MSA (Metropolitan Service Area) An urban area with at least 50,000 people plus surrounding counties. There are 306 MSAs and 428 RSAs (rural service areas) in the U.S. MSAs and RSAs are used to allocate cellular licenses. ) as the primary plating chemistry were not neutralized neu·tral·ize tr.v. neu·tral·ized, neu·tral·iz·ing, neu·tral·iz·es 1. To make neutral. 2. To counterbalance or counteract the effect of; render ineffective. 3. or uniformly rinsed. The residues allowed a percentage of dirty capacitors into the total population. Localized pockets of contamination were not identified when analyzing the whole board using standard extraction techniques. The localized conductive conductive having the quality of readily conducting electric current. conductive flooring flooring or floor covering made specially conductive to electrical current, usually by the inclusion of copper wiring that is earthed plating residue (sulfate) left on the capacitor surface created an invisible conductive pathway, causing the failure of the battery circuit while sitting in the box on the shelf waiting for shipment. Terry Munson is with Foresite Inc., Kokomo, IN; (765) 457-8095; email: ResiduGuru@aol. com; Web page:ww. residues.com |
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