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70 SMT Magazine • April 2015 pair of calibrated calipers. A five-minute reflow profile with a peak profile temperature of 230°C was applied at the reference site location. Four Omega type K thermocouples were at- tached to heat-sensitive compo- nents in the vicinity of the ref- erence IC site. The thermocou- ples were connected to a MOLE scan thermal profile scanning system and profiles were devel- oped for each of the five trials per part. The first shield tested was a stainless steel 304 formed rectangular open box shields of sizes 38 x 38 mm (polyimide tape coated) and 26 x 26 mm. The second, product number 1650 Venture Tape, was a cop- per based shielding tape. Next, a ceramic fiber heat shield was used. Polyimide tape was used to hold one 38 x 38 mm and one 38 x 76 piece a ceramic material in place. Polyimide tape of one-inch in width and 3 mils in thickness was then used by itself as a shield. A control condition with no shielding followed. Each material includ- ing the control was heated five times for a total of 25 heating cycles. A sample profile is found in Figure 3. The board was first placed on a board holder as part of a hot air system used for the tri- als. The wires were placed on a speaker, connector, battery, and the IC reference site location (Figure 4). The ceramic fiber heat shield was then held in place on the board using a polyimide tape in order to protect the connector, battery, and speaker (Figure 5). Copper tape was then applied. Next, polyimide tape alone was applied liberally and used as the only shielding material for one of the trials. Stainless steel 304 open-ended "boxes" were used to shield com- ponents. A gel type heat shield made of clay and water was easiest to work into the board spaces. After heating, the gel left a whitish gray figure 4: locations on pcb where temperature measurements were taken. figure 5: ceramic non-woven fiber heat shields affixed to different board locations. FeAture pOlyiMiDE TapE iS NOT THE ONly aNSWEr DuriNG rEWOrK continues