Issue link: https://iconnect007.uberflip.com/i/1323994
JANUARY 2021 I SMT007 MAGAZINE 47 Case Study In order to exactly measure the results of the TAP process, we undertook the following case study. Objectives were as follows: 1. Achieve LED placement accuracy within +/-25-micron accuracy post reflow. 2. Measure baseline accuracy. 3. Document the full process for a repeatable solution. Goal: Achieve LED placement accuracy within +/-25-micron accuracy post reflow. Process: • Use of two drill holes on each circuit for alignment reference • Placement accuracy measured from a reference hole on each circuit • Pick and place of typical SMT devices for LEDs to mimic process The following materials were used for the test (Tables 1 and 2): Process Steps Step 1: Solder paste printing • Print solder paste • Speed: 25 mm/sec • Pressure: 4.0 kg Step 2: Adhesive dispense • Dispense low temperature cure adhesive Step 3: Automated optical inspection • Inspect solder paste volume Step 4: Pick & place • LED placement with TAP process • Place force 150 grams Step 5: Reflow oven • Ramp rate: 1.4°C/sec • TAL: 50 sec • Peak: 237°C Figure 3: Image of LED accuracy materials. Table 1: List of LED accuracy materials. Table 2: Process information for LED accuracy test.