Comparative study on proper thermocouple attachment for vapour phase soldering profiling

Abstract

Purpose – The paper aims to present a comparative study of various thermocouple (TC) attaching methods for the proper measurement of soldering temperature profiling during vapour phase soldering (VPS). The heat transfer process during VPS is different from common methods, while the required heat for reflow is provided by the condensation. The condensate is a flowing layer on the board, where the dynamic behaviour also affects the local conditions on the surfaces. Temperature measurements based on TCs are also affected this way; it is important to investigate the process for deeper understanding. Design/methodology/approach – Bare printed circuit boards (PCBs) were prepared for standard K-Type TCs attachment with industry standard materials: kapton polyimide tape, aluminium tape, SMD adhesive and high-temperature solder (HTS). Heating experiments were performed in a batch-type VPS oven with Galden LS240 fluid and fixed oven parameters. Findings – According to the specific attachment requirements, HTS and Alu-tape are the suggested methods for better profiling reliability and repeatability. Alu-tape is the preferred all-around method, for fast, exchangeable, cheap, reliable and repeatable profiling in a VPS oven. It was presented that the heating factor (Q?) gives more reliable comparison overview; the time period-based comparisons may be affected by the thermal inertia, while heating factor also includes temperature conditions at the given time points. Originality/value – The paper presents the reliability of the presented methods for VPS and present suggestions for the use of different TC ends and attaching materials during condensation heating of the PCBs. Also a new approach on profiling data evaluation based on the heating factor is presented and suggested for wider use.

Effect of PCB Thickness and Height Position During Heat Level Type Vapour Phase Reflow Soldering

“…The attaching method of the TCs to the surface of the PCB can be varied: it is possible to use different fixing materials such as high-temperature solder (HTS), polyimide tape, Alu-tape or SMD adhesives. According to the previous study [14], the proper method in our investigation is the Alu-tape adhesive fixing, because it has good repeatability and no inconsistent thermal conductivity issues (see Fig. 4).…”

Study of Temperature Measurement Accuracy by Using Different Mounting Adhesives

“…It is observed that the Kapton tape is unable to adhere to the aluminum surface at temperature of 79℃ and above. Tape methods are the least reliable because the adhesive layer of the tapes can suffer from delaminating which can cause instability in measurements [3,4].…”

“…Thermal adhesive/ compounds are used in order to improve contact and have stronger adherence between the thermocouple to the surface being measured, [2]. This method is commonly used by test laboratories [2,3]. In this study, thermal adhesives were used to attach thermocouples on a heated an aluminum block to measure its surface temperature and compare it against the reference (true) value.…”

Investigation of the Mechanical Properties of Mn-Alloyed Tin-Silver-Copper Solder Solidified with Different Cooling Rates

“…The reliability problems are caused by the relatively high silver content, which is regularly hyper-eutectic (>1.35 wt.%) in these alloys [ 6 ]. Even if the reflow profile is precisely monitored [ 7 , 8 ] during the soldering process, and the volume of the solder paste is thoroughly adjusted [ 9 ], electronic assemblies and devices can exist in which reliability criteria cannot be met. For instance, in a harsh operating environment, such as overpressure [ 10 , 11 ], the joints prepared from SAC305 alloy can underperform.…”