Beyond the Board: Empowering the Next Generation of Tech Innovators in Electronics
The Government Circuit: Trump’s Trade War Disrupts the Electronics Ecosystem
Defense Speak Interpreted: Update on the Continuing Resolution and Budget Process for Defense
X-Ray Inspection of Lead and Lead-Free Solder Joints
July 31, 2017 | Glen Thomas, Ph.D., and Bill Cardoso, Ph.D., Creative Electron Inc.Estimated reading time: 13 minutes
where Emax is the maximum energy in the spectrum, which is 150keV for the X-ray machine used in this paper.
TIN-LEAD SOLDER VS. LEAD-FREE SOLDERS
There are a number of lead-free solder compounds in the market today. For examples in this analysis we used some of the solder compounds discussed in [5]. In particular, we compare eutectic tin-lead solder (63Sn/37Pb), tin-bismuth (42Sn/58Bi), and a variety of predominantly tin based solders, including tin-silver (98Sn/2Ag), tin-antimony (95Sn/5Sb), tin-indium-silver (77.2Sn/10In/2.8Ag), and tin-silver-copper (96.3Sn/3.2Ag/0.5Cu).
Solder compounds can be classified according to those he deems most likely lead-free alternatives, all of which have at least 95% Sn content[5]. In our analysis, we consider three of these (98Sn/2Ag, 95Sn/5Sb, and 96.3Sn/3.2Ag/0.5Cu). The others are provided for comparison purposes. Equation 4 must be discretized for evaluation. Using a Creative Electron’s proprietary emulation and simulation software, we computed the energy spectra and attenuation coefficients for 16 bands of 10keV width spanning 10keV to 160keV. Equation 4 in discrete form then becomes:
Using this data and accounting for filtration due to the X-ray source anode materials, we obtain values for all p(Ei ). The results are summarized in Figure 5. In Figure 6 we provide the stopping power (i.e., 1-I/I0) for five lead-free solder compounds and eutectic tin-lead solder at thicknesses of 2 mil, 5 mil, 10 mil, and 20 mil. The stopping power indicates the relative amount of X-rays that are attenuated in the material. For example, a stopping power of 0.75 means that three-quarters of the incident radiation is attenuated. Higher numbers consequently imply higher attenuation.
Figure 5: Energy spectrum of a TruView FUSION with a 150kV microfocus X-ray source.
Figure 6: Attenuation of lead-free solders and eutectic tin-lead solder. Note that the amount of attenuation at different material thicknesses is similar.
X-RAY IMAGE ANALYSIS
To validate the analysis presented in the previous session our Advanced Technology Group inspected a wide range of samples with both lead and lead-free solder composites. We compared eutectic tin-lead (63Sn/37Pb) and tin-bismuth (42Sn/58Bi) solders for their imaging profile using a TruView FUSION running at a maximum of 150kV. As expected, the X-ray images obtained from the samples using both types of solder did not present a notable difference. Please note that it is not the focus of this paper to compare the overall performance between lead and lead-free solders. Instead, the objective of this analysis is to validate that the X-ray machine settings work for both lead and lead-free solders.
Figure 7: Gullwing solder joints using both lead and leadfree solder paste. Note that the lead-free solder is slightly lighter (less dense) than the lead solder joint.
Page 3 of 5
Share on:
Suggested Items
Koh Young Installs 24,000th Inspection System at Top 20 EMS
05/14/2025 | Koh YoungKoh Young, the global leader in True 3D measurement-based inspection and metrology solutions, proudly announces the installation of its 24,000th inspection system at a Top 20 Global EMS in Thailand.
Indium’s Karthik Vijay to Present on Dual Alloy Solder Paste Systems at SMTA’s Electronics in Harsh Environments Conference
05/06/2025 | Indium CorporationIndium Corporation Technical Manager, Europe, Africa, and the Middle East Karthik Vijay will deliver a technical presentation on dual alloy solder paste systems at SMTA’s Electronics in Harsh Environments Conference, May 20-22 in Amsterdam, Netherlands.
SolderKing Achieves the Prestigious King’s Award for Enterprise in International Trade
05/06/2025 | SolderKingSolderKing Assembly Materials Ltd, a leading British manufacturer of high-performance soldering materials and consumables, has been honoured with a King’s Award for Enterprise, one of the UK’s most respected business honours.
Knocking Down the Bone Pile: Gold Mitigation for Class 2 Electronics
05/07/2025 | Nash Bell -- Column: Knocking Down the Bone PileIn electronic assemblies, the integrity of connections between components is paramount for ensuring reliability and performance. Gold embrittlement and dissolution are two critical phenomena that can compromise this integrity. Gold embrittlement occurs when gold diffuses into solder joints or alloys, resulting in mechanical brittleness and an increased susceptibility to cracking. Conversely, gold dissolution involves the melting away of gold into solder or metal matrices, potentially altering the electrical and mechanical properties of the joint.
'Chill Out' with TopLine’s President Martin Hart to Discuss Cold Electronics at SPWG 2025
05/02/2025 | TopLineBraided Solder Columns can withstand the rigors of deep space cold and cryogenic environments, and represent a robust new solution to challenges facing next generation large packages in electronics assembly.