Technical Library | 2024-09-02 18:48:58.0
The conversion to higher temperature "Lead Free" assembly reflow conditions has created an increased awareness that entrapped or absorbed moisture is a frequent root cause of thermally induced delamination at assembly reflow. There are two connected failure modes from entrapped moisture; incomplete resin cross-linking resulting in premature resin decomposition and also severe Z axis expansion from "explosive vaporization of the entrapped moisture at elevated temperatures at assembly reflow". Ultimately, both result in delamination failure. Other papers have shown the negative effects of entrapped moisture before lamination including delamination, red color, reduced thermal reliability and increased high speed signal loss. In this paper, various materials were tested for moisture sensitivity during lamination. Tests were performed at varying lamination conditions including a pre-vacuum step and "kiss" step. Pressure and cure temperature parameters were evaluated for minimizing or eliminating the effect of trapped moisture. Also included are the results of inner layer moisture removal baking conditions and their effect on peel strength and thermal reliability.
Technical Library | 2015-01-26 15:30:00.0
In 2005 Raytheon Technical Services Company, now Raytheon Information, Intelligence and Services (Raytheon IIS), approached Ensil regarding the repair of their manufactured Radar Control Terminal (RCT) units. The RCT TRS P/N 13563090-2, a key component in the AN/MPQ-64 Sentinel System, consisted of outdated parts which caused minor to major unit failures. Ensil repaired the RCT's at every turn, correcting any component with the parts still in circulation (mother boards, displays, power supplies) to provide the client with the best available technology. These repairs were completed to military standards and kept the RCT effective, allowing for the Sentinel radar to remain operational. However, the supply of outdated parts was eventually no longer available. Ensil offered the best possible solution, utilizing the skills of their knowledgeable engineering staff, they would reverse engineer a new computer to replace the obsolete RCT while maintaining the same form, fit and function.
Technical Library | 2021-11-26 14:34:07.0
The use of desiccant bags filled with Silica Sand and or Clay beads used in conjunction with a Moisture Barrier Bag to control moisture for storage of printed circuit boards has long been an accepted practice and standard from both JEDEC and IPC organizations. Additionally, the use heated ovens for baking off moisture using the evaporation process has also been a long#2;standing practice from these organizations. This paper on alternative drying methods will be accompanied by completed independent, unbiased tests conducted by Vinny Nguyen, an engineering student (now graduated) from San Jose State University. The accompanied paper will examine the performance levels of different technologies of desiccant bags to control moisture in enclosed spaces. The tests and equipment set were reviewed by an engineer and consultant to the Lockheed Martin Aerospace Division and the IPC - TM-650 2.6.28 test method was review by engineer from pSemi. The tests were designed to mimic performance tests outlined in Mil Spec 3464, which both IPC and JEDEC have adopted for their respective standards. The test examined variables including absorption capacity rates, weight gain and release of moisture back into the enclosed area. The presentation will also address and highlight: • Similarities of PCBs and Heavy Equipment as it applies to Inspections, Causes of Failure, Types of Corrosion and Moisture Collection Points. • Performance Attributes of Different Desiccant Technologies as it applies to shape, texture, change outs, labeling and regeneration. • Venn Diagram of Electromechanical Failure with the circles 1. Current 2. Contamination 3. Humidity Presentation Available
Technical Library | 2020-10-27 02:07:31.0
For companies that choose to take the Pb-free exemption under the European Union's RoHS Directive and continue to manufacture tin-lead (Sn-Pb) electronic products, there is a growing concern about the lack of Sn-Pb ball grid array (BGA) components. Many companies are compelled to use the Pb-free Sn-Ag-Cu (SAC) BGA components in a Sn-Pb process, for which the assembly process and solder joint reliability have not yet been fully characterized. A careful experimental investigation was undertaken to evaluate the reliability of solder joints of SAC BGA components formed using Sn-Pb solder paste. This evaluation specifically looked at the impact of package size, solder ball volume, printed circuit board (PCB) surface finish, time above liquidus and peak temperature on reliability. Four different BGA package sizes (ranging from 8 to 45 mm2) were selected with ball-to-ball pitch size ranging from 0.5mm to 1.27mm. Two different PCB finishes were used: electroless nickel immersion gold (ENIG) and organic solderability preservative (OSP) on copper. Four different profiles were developed with the maximum peak temperatures of 210oC and 215oC and time above liquidus ranging from 60 to 120 seconds using Sn-Pb paste. One profile was generated for a lead-free control. A total of 60 boards were assembled. Some of the boards were subjected to an as assembled analysis while others were subjected to an accelerated thermal cycling (ATC) test in the temperature range of -40oC to 125oC for a maximum of 3500 cycles in accordance with IPC 9701A standard. Weibull plots were created and failure analysis performed. Analysis of as-assembled solder joints revealed that for a time above liquidus of 120 seconds and below, the degree of mixing between the BGA SAC ball alloy and the Sn-Pb solder paste was less than 100 percent for packages with a ball pitch of 0.8mm or greater. Depending on package size, the peak reflow temperature was observed to have a significant impact on the solder joint microstructural homogeneity. The influence of reflow process parameters on solder joint reliability was clearly manifested in the Weibull plots. This paper provides a discussion of the impact of various profiles' characteristics on the extent of mixing between SAC and Sn-Pb solder alloys and the associated thermal cyclic fatigue performance.
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