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1、c EIA ENGINEERING BULLETIN X-Ray Fluorescence for Measuring Plating Thickness CB13 September 1990 ELECTRONIC INDUSTRIES ASSOCIATION ENGINEERING DEPARTMENT i Copyright Electronic Components, Assemblies Le., measure the same product at various count times and evaluate the results for precision. Many o
2、f the units available today are equipped with software programs that will predict the percent uncertainty of a measurement at various count times. 7. DENSITY A s with a l l mass-per-unit-area techniques, the x-ray measurement is based on a conversion of mass to thickness. Therefore, the density of t
3、he plate must be considered. For many electro-deposited coatings, such as nickel, the density is fairly straightforward and the value employed is consistent throughout the industry. Gold, however, is a different story with many densities reported. MZtary specifications for hard gold specify, by grad
4、e and type, acceptable purity and hardness - but not density. Densities ranging from l 5 . 3 to 1 9 . 3 G/CC have been reported for gold, with hard gold electrodeposits at the lower end of the scale. The densiy of the plate will vary with bath chemistry and current density. When performing thickness
5、 measurements and comparisons an agreed upon density should be established based on the plating conditions. 8. DRIFT Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2
6、007 20:10:42 MDTNo reproduction or networking permitted without license from IHS -,-,- E I A CBL3 90 3234600 0000157 O M t CB13 Page 4 The x-ray tube and detector are subject to some degree of drift over time. This drift must be corrected for at some frequency. The correction procedure is handled di
7、fferently by each unit manufacturer but the general principle involves the realigning of specific spectral peaks and count rates in comparison to initial calibration conditions. The frequency at which this correction will need to be performed should be established by each user based on accuracy and
8、repeatability requirements. 9. SAMPLE CONDITION The geometrical configuration and condition o f the sample should be considered before taking measurements. If the sample has surface damage or poor adhesion, the measurements will not be accurate. I f the sample is significantly curved, the unit may n
9、eed to be calibrated with standards of the same geometrical configuration. 10, LOCATION AND POSITIONING Most connector products today are selectively plated. Therefore, the thickness measurement must not only show that the thickness is correct but that the coating is in the proper location for produ
10、ct functionality. Many x-ray units do not have an easy, accurate means of determining location. The user should consider, if location accuracy is a concern, retrofitting these units with electronic, digital x-y stages. 11. GENERAL USE PRECAUTIONS A s with any instrumentation there are always a numbe
11、r of general rules or precautions which must be followed in order to obtain optimum results. Listed below are some general use guidelines to incorporate into any x-ray fluorescence testing techniques. 11.1 As mentioned earlier, the collimator is the mechanism by which the x-ray beam is aimed onto th
12、e correct measurement area, Therefore, the alignment of this collimator to the microscope is critical and should be verified at a frequency that the user feels is adequate to ensure proper alignment. 11.2 Along with the collimator alignment, another factor to consider is the size of the collimator i
13、n relation to the size of the measurement area. The area that the x-ray beam is striking must be totally covered by the sample being measured. The user should also be aware of the fact that the x-ray beam will spread from the time it exits the collimator until it strikes the part. 11.3 The orientati
14、on of the sample in relation to the detector is also important. The general rule is that nothing should be between the measurement area and the detector that would block the path of the x- rays. (ex, detector shadowing). 11.4 Samples must be flat on the staging area and must be in clear focus. Indiv
15、idual eyesight may affect the focal length significantly enough to give inaccurate readings on some instruments. Each user should test their eyesight (Le., focusing ability) on a known sample or thickness standard. Copyright Electronic Components, Assemblies & Materials Association Provided by IHS u
16、nder license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:10:42 MDTNo reproduction or networking permitted without license from IHS -,-,- I E I A CB13 90 m 3234600 0000158 2 I n I CBl.3 page5 e, a O v) Copyright Electronic Components, Assemblies & Mater
17、ials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:10:42 MDTNo reproduction or networking permitted without license from IHS -,-,- E I A CBL3 90 = 3234600 OOOOL59 4 CB13 Page 6 11.5 Cylindrical parts should be po
18、sitioned with their length perpendicular to the detector. 11.6 Sampling frequency should be considered if using x-ray fluorescence as a process control. Frequency should be adequate enough to detect shifts in the process. SPC programs tied into x-ray fluorescence measurements are very effective for
19、this purpose. 12. REFERENCES 1 . “The Key to Plating Process Control“, P. L. Hoffman, DuPont Electronics Division of E. I. DuPont Company, Emigsville, Pennsylvania. Fluorodemm Users Manual, VEECO/UPA Technology, Inc., Syosset, New York. ASTM A754-79, Standard Test Method for Coating Thickness by X-ray fluorescence. 2. 3. i -&? Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:10:42 MDTNo reproduction or networking permitted without license from IHS -,-,-