Here is a lead test with a long history. (Write or call off-line if you have questions). Number: Date: Revision: Subject: Surface Lead Contaminant Detection Spot Test 1.0 Scope 1.1 This simple and rapid non-destructive colorimetric spot test method is for use in determining if non-ionic lead (primarily lead oxide) contaminant is present on bare printed wiring board and completed assembly surfaces. 1.2 The test will not identify the particular compound of lead present on the surface tested nor separate mixtures of various lead compounds on the surface. After a functional problem is found with boards or assemblies, usually failure at elevated temperature and humidity, this test can be used to confirm or eliminate non-ionic lead contaminant as a root cause. 1.3 The test can detect lead levels easily in the 0.1 microgram range. Lower levels in the presence of interferring metals can be detected by a skilled operator using accurate standards. 2.0 Applicable Documents IPC-TP-135 "Insulation Resistance Degradation by Non-Ionic Surface Contamination-- Its Cause & Cure." Feigl , Fritz, and Suter, Hans A., “Analytical Use of Sodium Rhodiazonate”, Industrial and Engineering Chemistry, Vol. 14, No. 10, 840-2, (1942). 3.0 Test Specimen 3.1 A bare printed wiring board or completed assembly at least 50 mm x 50 mm x thickness. 4.0 Apparatus & Materials 4.1 Sodium rhodizonate 4.2 Tartaric acid 4.3 Sodium bicarbonate 4.4 Cotton tip swabs 4.5 Indicator dropper bottle 4.6 Balance capable of weighing to 0.001 g. 5.0 Procedure 5.1 Preparation 5.1.1 Prepare the stock buffer solution by dissolving 15 grams of tartaric acid and 19 grams of sodium bicarbonate in one liter of distilled water. The pH of the resultant buffer solution should be 2.79. This solution is stable, and can be stored for an extended time in the laboratory. 5.1.2 Prepare the 0.2% sodium rhodizonate indicator solution by dissolving 0.01 g. of sodium rhodizonate in 5 ml. of water. Place the solution in the indicator dropper bottle. [Note: the useful life of the indicator solution is approximately 8 hrs.] 5.2 Test 5.2.1 Using a clean cotton swab, place 2 drops of buffer solution on the cotton swab. 5.2.2 Rub the buffer soaked swab on a dielectric area (non-plated area) of the printed wiring board or assembly surface, being sure not to touch the traces. 5.2.3 Using a second clean cotton swab, place 3 drops of the indicator on the cotton swab. 5.2.4 Rub the indicator soaked swab in the area coated by the buffer swab. 5.3 Evaluation 5.3.1 Any color change from yellow to red on the indicator swab indicates a positive test for lead contaminant. 5.4 Action 5.4.1 The boards or assemblies should also be tested for the presence of organic non-ionic contaminant using the test methods cited in 2.0. 5.4.2 The lead contaminated boards or assemblies can be recovered by applying and curing the lacquer described in 2.0, then washing it off using a suitable cleaning agent. 5.4.3 The organic non-ionic contaminated boards or assemblies can be recovered per methods cited in 2.0 6.0 Notes 6.1 The tartaric acid, sodium bicarbonate and sodium rhodizonate used in this method can be obtained from standard chemical supply houses. Reagent grade chemicals are preferred. 6.2 The literature claims this test can be used to detect the presence of stannous tin (+2 oxidation state) by a color change to violet, however, stannic tin (+3 oxidation state) gives no change. Originally Drafted by: W. G. Kenyon April, 1998 Revised: W. G. Kenyon March, 2005 Bill Kenyon Global Centre Consulting 3336 Birmingham Drive Fort Collins, CO 80526 Tel: 970.207.9586 Cell: 970.980.6373 email: [log in to unmask] --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------