![]() The solder paste containing 2%Ag significantly reduces the migration of silver from the AgPt pad into the solder paste. Merit pressure sensors should be soldered with “no-clean” type solder paste which contains 62%Sn36%Pb2%Ag and has a melting point of 179 ☌. Temperatures should not go beyond 225 ☌ for 30 seconds if Pb-containing solder is employed. Soldering Pressure Sensors with Pb-Containing Solder Pre-heating can be used to decrease the amount of heat caused on the surrounding components during hand soldering, as is done with reflow soldering. Use of solder stations of at least 80 watts of power is highly recommended. It may need an increased tip temperature to 360-390 ☌ and/or a longer period. When using a soldering iron, it should be remembered that Pb-free soldering needs a rapid heat transfer to attain a successful solder joint. The heat transfer to the solder joint is critical and should never be tried with a soldering iron. An excess amount of energy is required for Pb-free soldering when compared to Pb-containing solder alloys. Hand Soldering - Merit Sensor does not recommend hand soldering. Nitrogen may be used if the solder joints do not have adequate wetting. Use of nitrogen - It may be essential to work in nitrogen if air leads to unsatisfactory solder joints due to increased temperature and oxidation of Pb-free solder however, the majority of Pb-free solder pastes can be used in air. Pb-free Classification reflow profile according to IPC/JEDEC J-STD-020. Time within 5 ☌ of actual peak temperature (tp)įigure 2. Pb-free classification reflow profile according to IPC/JEDEC J-STD-020C Profile Feature The recommended profile according to IPC/JEDEC J-STD-020C is shown in Table 2 and Figure 2. The best temperature profile is defined by the board and the solder paste used. For identifying the best temperature profile, each process must be assessed. The pressure sensors offered by Merit Sensor can be soldered with profiles that are based on the standard IPC/JEDEC J-STD-020C (January 2004). Due to this fact, Merit Sensor does not recommend IR Reflow systems for Pb-free soldering, and instead suggests using forced convection reflow systems to ensure a successful Pb-free reflow soldering. The temperature differences on the board should be reduced because the process time for Pb-free solder is less than Pb-containing solder. Examples of a Pb-containing solder joint (left) and a typical finished surface of a Pb-free solder joint (right).Ī reflow soldering profile for Pb-free soldering demands a higher melting point when compared to Pb-containing solders. Compared to the Pb-containing solder joints, the Pb-free solder joints are often smaller but this would have no effect on the reliability as these are simply cosmetic characteristics.įigure 1. This roughness is attributed to the increased volume contraction of the Pb-free alloys. This is because the surface of the solder joint will become rough when Pb-free alloys begin to cool. Additionally, when compared to a Pb-containing solder joint, a Pb-free solder joint will have a dull or matte finish. The surface of Pb-free solder alloys can appear significantly different when compared to Pb-containing solder (See Figure 1). Pb-free solder alloys of the SnAgCu family Metal Table 1 shows the Pb-free solder alloys in the SnAgCu family. Merit Sensor suggests using solder alloys with SnAgCu that have a melting point of 217-221 ☌. Soldering with Pb-Free SolderĪs the pressure sensors from Merit Sensor are fabricated on ceramic, a Pb-free solder should be chosen that is well-suited with the solder pads. In order to meet the RoHS directive, products must be soldered with Pb-free solder. The aim of this article is to guide customers on how to solder Merit Sensor parts using either Pb-free solder or Pb-containing solder. Merit Sensor parts can be soldered using either Pb-containing or Pb-free solder process. The lead-free solder pads are plated with AgPt to assure an excellent solder joint for most PCB connections. Merit Sensor provides pressure sensors that are fixed on ceramic substrates and are RoHS compliant. The RoHS Directive has banned the European sale of new electrical and electronic equipment containing more than the specified levels of cadmium, hexavalent chromium, lead, mercury, polybrominated biphenyl (PBB), and polybrominated diphenyl ether (PBDE) flame retardants. All profiles must be assessed and tested for best performance.ĭue to concerns over the safety of lead and new regulations prohibiting its use, such as the Restriction on Hazardous Substances (RoHS) Directive in Europe, an increasing number of companies have stopped using conventional tin-lead (Sn/Pb) solder in the manufacture of circuit boards. The objective of this article is to explain the best techniques for soldering sensors manufactured by Merit Sensor using automated equipment.
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