Issue link: https://iconnect007.uberflip.com/i/699765
20 SMT Magazine • July 2016 SIR at bias voltage every 20 minutes for seven days. SIR data were recorded for pattern No. 5, 6, 7 and 8 (Figure 1). The boards were mounted in the temperature/humidity chamber and con- nected to a "Gen3 AutoSIR" instrument for mea- suring the SIR. The chamber was programmed to record SIR readings at 12 V every 20 minutes. No edge card connectors were used. Teflon-in- sulated wires, were soldered with ROL0 solder cored wire. 3. Ionic Contamination Measurements of IPC-B52-Coupons Ten IPC B 52 ionics break away with three populated patterns were measured for each of the two pastes. An Ionograph 500M SMD II was used to measure the ionic contamination of each sub coupon. A 75% isopropanol 25% water extraction solution heated to 45°C was used. A dwell time of 15 minutes in the ionograph was used. This time was a balance between complete removal of ionic contamination, versus CO2 absorption increasing the apparent conductiv- ity of the solution from a source other than the test vehicle. A PCB surface area of 65 cm 2 was used in the calculations. 4. IPC-B-24 Coupon Preparation A. Pre-cleaning Modified IPC-B-24 test coupons, with bare copper FR4 were immersed in a 75% isopropa- nol/25% water solution in an Ionograph 500M SMD II. The solution was heated and circulated. The boards remained in the solution until a so- lution resistivity of >300 ohm-cm was achieved. The boards were then baked at 50°C for one hour. B. Coupon Assembly The solder paste was printed on three test coupons per paste using a 150 µm (6 mil) sten- DIVERGENCE IN TEST RESULTS USING IPC STANDARD SIR AND IONIC CONTAMINATION MEASUREMENTS Figure 3: Applied reflow profile comprising a straight ramp to 243°C under nitrogen (1.1 °C/s, 53 s TAL).