1. The experimental data demonstrates that the soldering strength of OSP surface treatment is superior to that of ENIG surface treatment PCBs. However, it has also been confirmed that the solder strength of OSP deteriorates over time. Consequently, the longer a product is on the market, the higher its defect rate is likely to be.
2. The experimental data demonstrates that the soldering strength of OSP surface treatment is superior to that of ENIG surface treatment PCBs. However, it has also been confirmed that the solder strength of OSP deteriorates over time. Consequently, the longer a product is on the market, the higher its defect rate is likely to be.
3. Those of you who have spent considerable time in the SMT and PCBA circuit board assembly industry may have encountered experts or seasoned professionals sharing insights, stating, “The soldering strength of OSP surface treatment circuit boards is greater than that of ENIG surface treatment.” A more technical expression would be, “The solder joint strength of copper-based circuit boards exceeds that of nickel-based ones.” Yet, few seem able to provide data that quantifies “How much stronger the soldering strength of OSP is compared to ENIG?
1. Are you familiar with what an ENIG (Electroless Nickel Immersion Gold) surface treatment circuit board is? What does ENIG surface treatment entail? What are its advantages and disadvantages?
2. Do you know about OSP (Organic Solderability Preservative) surface treatment for circuit boards? What does OSP surface treatment involve? What are its pros and cons?
3. After searching extensively online, I found that the English report titled “Strength of Lead-free BGA Spheres in High Speed Loading” published by “Niho Superior, Japan” is relatively straightforward and easy to understand. This article will primarily use this report as a basis to delve into the capabilities of OSP and ENIG soldering in terms of stress resistance.
4. Given the popularity of portable devices, users often drop them accidentally. Consequently, this report examines different shear test speeds to assess the reliability of BGA solder balls on OSP and ENIG surface treatments, calculating the fracture energy as a standard for evaluating solder strength.
5. The test samples and conditions of this report are outlined below. Interested readers can search for the original report online for further details:
▪ BGA ball diameter: 0.5 +/- 0.01 mm
▪ Laminate: FR4
▪ Thickness: 1.6 mm
▪ Using Solder Mask Defined Pad: 0.42 +/- 0.02 mm
▪ Resist Thickness: 30-40 µm
▪ Circuit board surface treatment (Finish): OSP, ENIG (0.3 µm Ni/0.03 µm Au)
▪ Ball solder alloy: Sn-3.0Ag-0.5Cu, Sn-0.7Cu-0.05Ni-0.006Ge, 63Sn-37Pb
▪ Shear speeds: 10, 100, 1000, 2000, and 4000 mm/sec
6. This report employs two test methods: thrust (Shear-test) and pull-test (Pull-test), but here we focus solely on the thrust test. The thrust represents the lateral shear force acting on the solder ball.
7. It’s important to note that this report uses the “Fracture Energy” of the solder ball to evaluate its welding strength. When maximum shear force occurs, the solder ball might not completely detach, resulting in only partial cracking. Therefore, using only the maximum shear force without considering the solder strength could yield misleading results. The area under the shear force versus distance curve should be calculated, as it accurately reflects the welding strength.
8. Average fracture energy as a function of shear speed shows that:
▪ As shear speed increases, the fracture energy of solder balls—whether attached to OSP or ENIG surfaces—drops rapidly. This indicates that the speed of a PCB’s fall critically impacts the solder strength of electronic components, with heavier parts suffering greater damage due to F=ma; higher fall heights exacerbate this issue.
9. For SAC305 solder, the shear rupture strength on the OSP-treated PCB surpasses that on the ENIG-treated board, particularly at a shear speed of 100 mm/sec, where the difference is most pronounced. However, as shear speeds exceed 1000 mm/sec, the performance gap narrows, suggesting minimal differences in bare metal drop tests, while OSP clearly outperforms ENIG in tumble tests.
10. Additionally, the report investigates experiments and comparisons involving As reflow, Double reflow, and a 200-hour test (Reflow + 200 hr @ 150°C) at 150°C post-reflow. The main goal is to understand the effect of IMC (Intermetallic Compounds) on the solder strength of BGA solder balls under varying time and temperature conditions.
