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April 2015 • SMT Magazine 29 rEliaBiliTy aSSESSMENT OF NO-ClEaN aND WaTEr-SOluBlE SOlDEr paSTES, parT ii continues FeAture with several finishes, on hotplate and reflow oven. The details are described below. Wettability on Copper Coupon using Hotplate and reflow Oven First, a wetting test on 0.4 mm thickness cleaned copper coupons was performed: the pastes were printed on substrates through a 0.250 mm thick stencil with two round open- ings of 5 mm diameter, with a distance between centers of 25 mm. A set of cleaned coupons was placed on a hotplate at 250°C for immediate reflow while the other sets were submitted to preheat before reflow, respectively during two minutes at 160°C and five minutes at 160°C. The profiles recorded on the hotplate are given below (Figure 1). Second, a wetting test on the same copper coupons was done in a reflow oven (BTU VIP70 5 zones) using two profiles: P1 is a gentle profile with a short and linear preheat; P5 is a harsh profile with a long soak at high temperature. A graph of these profiles and their characteristics are given below (Figure 2/ Table 2). Table 2: p1 and p5 characteristics. figure 2: Thermal profiles p1 and p5.

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