Electronics Forum | Wed Sep 12 03:43:48 EDT 2018 | vlad_saviuk
Hello, have some problem and interesting, does any body faced with same issue. On most of our products we have NTC thermistor(like on the photo), and during assembly process and handling great amount of components cracked on PCBA so we need to replac
Electronics Forum | Tue Jul 01 07:08:33 EDT 2003 | iman
suggest you check the preheat conditioning in the wavesolder process is sufficient, as this is the main culprit for micro-crack CAPs ?
Industry News | 2018-04-22 19:12:45.0
SMTA Europe announces Session 7 Technical Program on High Temperature PCB Materials and Fabrication at the “Electronics in Harsh Environments Conference” to be held in Amsterdam, Netherlands, on April 25th, 2018.
Industry News | 2016-10-09 20:43:23.0
The SMTA Capital Chapter is pleased to announce its final meeting of 2016 will be on November 10th, from 5:00 pm to 7:00 pm at Zentech, 6980 Tudsbury Road, Baltimore, Maryland 21244. The focus of this chapter meeting will be “AXI and MXI; How They Complement Each Other” presented by John Travis, Nordson Dage.
Technical Library | 2015-12-23 16:57:27.0
The onset of copper barrel cracks is typically induced by the presence of manufacturing defects. In the absence of discernible manufacturing defects, the causes of copper barrel cracks in printed circuit board (PCB) plated through holes is not well understood. Accordingly, there is a need to determine what affects the onset of barrel cracks and then control those causes to mitigate their initiation.The objective of this research is to conduct a design of experiment (DOE) to determine if there is a relationship between PCB fabrication processes and the prevalence of fine barrel cracks. The test vehicle used will be a 16-layer epoxy-based PCB that has two different sized plated through holes as well as buried vias.
Technical Library | 2021-07-20 20:02:29.0
During the manufacturing of printed circuit boards (PCBs) for a Flight Project, it was found that a European manufacturer was building its boards to a European standard that had no requirement for copper wrap on the vias. The amount of copper wrap that was measured on coupons from the panel containing the boards of interest was less than the amount specified in IPC-6012 Rev B, Class 3. To help determine the reliability and usability of the boards, three sets of tests and a simulation were run. The test results, along with results of simulation and destructive physical analysis, are presented in this paper. The first experiment involved subjecting coupons from the panels supplied by the European manufacturer to thermal cycling. After 17 000 cycles, the test was stopped with no failures. A second set of accelerated tests involved comparing the thermal fatigue life of test samples made from FR4 and polyimide with varying amounts of copper wrap. Again, the testing did not reveal any failures. The third test involved using interconnect stress test coupons with through-hole vias and blind vias that were subjected to elevated temperatures to accelerate fatigue failures. While there were failures, as expected, the failures were at barrel cracks. In addition to the experiments, this paper also discusses the results of finite-element analysis using simulation software that was used to model plated-through holes under thermal stress using a steady-state analysis, also showing the main failure mode was barrel cracking. The tests show that although copper wrap was sought as a better alternative to butt joints between barrel plating and copper foil layers, manufacturability remains challenging and attempts to meet the requirements often result in features that reduce the reliability of the boards. Experimental and simulation work discussed in this paper indicate that the standard requirements for copper wrap are not contributing to the overall board reliability, although it should be added that a design with a butt joint is going to be a higher risk than a reduced copper wrap design. The study further shows that procurement requirements for wrap plating thickness from Class 3 to Class 2 would pose little risk to reliability (minimum 5 μm/0.197 mil for all via types).Experimental results corroborated by modeling indicate that the stress maxima are internal to the barrels rather than at the wrap location. In fact, the existence of Cu wrap was determined to have no appreciable effect on reliability.
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