Intel researchers are looking for ways to improve the monitoring of humidity in PCB as changes in humidity have important effects on PCB performance and failure mechanisms.
Industry studies have shown that humidity can negatively affect PCB integrity and reliability.The presence of moisture in PCB will change the quality, function, thermal performance and thermal mechanical properties of PCB, thus affecting the overall performance.
Reliability has long been a concern for most engineers studying humidity effects in PCB, which refer to moisture coming from the environment, or air.However, Intel has a different approach.Intel data center, senior director of enterprise systems engineering department engineer Richard Kunze explained that data center's main job is to study the effect of humidity and temperature on the electrical performance, especially for high speed signal of insertion loss, such as the typical computing devices used in the high speed signal, especially high speed signal used in the data center server.
Referring to the deterioration of the performance of high-speed signals, Kunze declared: "humidity in the PCB directly affects various signal propagation characteristics, while we focus on key insertion loss indicators.We acknowledge that moisture is absorbed by the PCB, so the question then becomes how much moisture the PCB will absorb under normal working conditions and how to quantify its impact on high-speed signal performance."
Kunze also said that power dissipation of devices installed on PCB increases PCB temperature, and this temperature rise also leads to increased loss and affects moisture content in PCB.In a forthcoming DesignCon paper, he revealed that Intel would provide a simple examination of both effects under a variety of PCB structures and materials, and try to understand the impact on performance across the entire working state.
Speaking of moisture sensitivity characterization and weight control of moisture content in PCB, Kunze believes that it is difficult to remove moisture in typical PCB with solid copper layers in laminated layers by baking.He added that before PCB assembly, the panels were typically stored in vacuum-sealed bags with desiccant.After assembly, the PCB is exposed to a wide range of temperature and humidity."" one of the issues we wanted to understand was the humidity and temperature state of the PCB when it was operating under normal environmental conditions." "He said.
Kunze explains that many of the humidity studies currently conducted are ipc-certified methods to assess moisture content in PCB, which is to weigh the weight of PCB before and after exposure to moisture.Some people infer humidity in PCB by observing capacitance changes."" our approach is to infer PCB humidity by its effect on insertion loss." "
In fact, Intel introduced at DesignCon three years ago an innovative way to determine insertion loss by performing only two point-of-time measurements at the same end of the traverse.They call it "single-ended time domain reflection to differential insertion loss," or SET2DIL.This interpolation test method developed by Jeff Loyer and Kunze, the head of signal integrity in Intel's enterprise server division, has become an IPC certified test method for determining differential interpolation.
1. The JPG
SET2DIL tests the structure
When asked about ways designers can avoid moisture in PCB, Kunze said it's unclear what role designers can play in limiting moisture diffusion, at least in practical terms.Will, of course, he thought: "moisture suction PCB is hampered by solid copper layer, and to some extent also should pass the dielectric layer of glass fiber, but the PCB designer to components placed some open to achieve the function circuit board, to what extent so design can prevent moisture into the circuit board is not too clear."
But Kunze said that in terms of electrical performance, designers need to carefully consider the effects of humidity and temperature rise to ensure that high-speed signal degradation does not go beyond acceptable limits."We now believe that humidity may not be as bad as you think -- but it's still an important consideration -- after all, humidity has a big impact on PCB performance at high temperatures.
Several tools have been developed to simulate moisture diffusion in structures including PCB.Kunze, who now works at Intel's dupont campus in Washington, d.c., said his future research will use these simulation tools to assess moisture levels in the working PCB.