1、c EIA ENGINEERING BULLETIN X-Ray Fluorescence for Measuring Plating Thickness CB13 September 1990 ELECTRONIC INDUSTRIES ASSOCIATION ENGINEERING DEPARTMENT i EIA CE13 90 3234b00 0000153 3 I NOTXCE i ELA Engineering Standards and Publications are designed to serve the public interest through eliminati
2、ng misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and Publications shall not in any
3、respect preclude any member or nonmember of EIA from manufacturing or selling products not conforming to such Standards and Publications, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than EIA members, whether the standard is to be used either
4、 domestically or internationally. c Recommended Standards and Publications are adopted by EIA without regard to whether their adoption may involve patents on articles, materials, or processes. By such action, EU does not assume any liability to any patent owner, nor does it assume any obligation wha
5、tever to parties adopting the Recommended Standard or Publication. Technical Bulletins are distinguished from EIA Recommended Standards or Interim Standards, in that they contain a compilation of engineering data or information useful to the technical community, and represent approaches to good engi
6、neering practices that are suggested by the formulating committee. This Bulletin is not intended to preclude or discourage other approaches that similarly represent good engineering practice, or that may be acceptable to, or have been accepted by, appropriate bodies. Parties who wish to bring other
7、approaches to the attention of the formulating committee to be considered for inclusion in future revisions of this Bulletin are encouraged to do so. It is the intention of the formulating committee to revise and update practice, or government regulations, or for other appropriate reasons. this Bull
8、etin from time to time as may be occasioned by changes in technology, industry Published by ELIECIRONIC INDUSTRIES ASSOCIATION Engineering Department 2001 Pennsylvania Ave., N.W. Washington, D.C. 20006 PRICE Please refer to the current Catalog of ELA Le., measure the same product at various count ti
9、mes and evaluate the results for precision. Many of the units available today are equipped with software programs that will predict the percent uncertainty of a measurement at various count times. 7. DENSITY As with all mass-per-unit-area techniques, the x-ray measurement is based on a conversion of
10、 mass to thickness. Therefore, the density of the 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. MZtar
11、y specifications for hard gold specify, by grade and type, acceptable purity and hardness - but not density. Densities ranging from l5.3 to 19.3 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 c
12、urrent density. When performing thickness measurements and comparisons an agreed upon density should be established based on the plating conditions. 8. DRIFT EIA 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 co
13、rrected for at some frequency. The correction procedure is handled differently 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 b
14、e performed should be established by each user based on accuracy and repeatability requirements. 9. SAMPLE CONDITION The geometrical configuration and condition of the sample should be considered before taking measurements. If the sample has surface damage or poor adhesion, the measurements will not
15、 be accurate. If the sample is significantly curved, the unit may need 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
16、is correct but that the coating is in the proper location for product 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 US
17、E PRECAUTIONS As with any instrumentation there are always a number 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 co
18、llimator is the mechanism by which the x-ray beam is aimed onto the 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 ali
19、gnment, another factor to consider is the size of the collimator in 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
20、exits the collimator until it strikes the part. 11.3 The orientation 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
21、must be flat on the staging area and must be in clear focus. Individual 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. I EIA CB13 90 m 323
22、4600 0000158 2 I n I CBl.3 page5 e, a O v) EIA CBL3 90 = 3234600 OOOOL59 4 CB13 Page 6 11.5 Cylindrical parts should be positioned 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 adequ
23、ate enough to detect shifts in the process. SPC programs tied into x-ray fluorescence measurements are very effective for 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 -&?
