AN4046 Application note EnFilm™ micro battery EFL700A39 recommendations for manual assembly on PCB Introduction This document provides recommendations to manually mount EnFilmTM micro battery EFL700A39 on printed circuit board (PCB) for prototyping purposes (mount 1 to 6 micro batteries to assemble in one step on PCB). This prototype mounting process is intended for use at room temperature (glue polymerization has to be done at room temperature). STMicroelectronics has developed micro battery packaging with reduced thickness and weight. Micro battery package overview En Fil m EF L7 700 00A µA 39 h/3 V9 Figure 1. ® - anode + cathode March 2012 Doc ID 022792 Rev 1 1/9 www.st.com PCB design recommendations 1 AN4046 PCB design recommendations For optimum electrical performance and highly reliable solder joints, STMicroelectronics recommends the PCB design guidelines listed in Table 1. Note: A too thick gold layer finishing on the PCB pad is not recommended (low joint reliability). 1.1 Micro vias An alternative to routing on the top surface is to route on buried layers. To achieve this, the pads are connected to the lower layers using micro vias. . Table 1. PCB design recommendations PCB pad design Micros vias under pad are not allowed PCB pad size (NSMD design) Same pad size as micro battery (see Figure 2) Solder mask opening (SMD design) Same pad size as micro battery (see Figure 2) PCB pad finishing Cu-Ni (2-6µm max) or Cu OSP (organic substrate protection) Figure 2. Contact dimensions R 0.75 5.46 4.21 0.25 Pink colour: contact pad Pt 5.46 4.21 0.25 25.4 3.45 5.46 R 0.75 3.71 R 0.75 5.46 25.4 Dimensions in mm 2/9 Doc ID 022792 Rev 1 AN4046 2 Conductive glue assembly recommendations Conductive glue assembly recommendations Circuit Works® Conductive epoxy CW 2400. Suppliers: Radio Spares n° 496265 or Farnell n° 604057. 3 Mounting procedure 1. Read conductive epoxy MSDS carefully prior to use. 2. Use surgical gloves and goggles. 3. Clean surface to be contacted with cotton bud soaked with isopropyl alcohol (IPA). Figure 3. Clean contact surface Doc ID 022792 Rev 1 3/9 Mounting procedure 4. Mix equal amounts (1:1) by volume of 2 dots 4 mm diameter only. Mix thoroughly for at least 2 minutes with plastic stick supplied with Conductive epoxy CW 2400. Figure 4. 5. Dot sizing Apply a small quantity, 1mm diameter dot, on each contact of PCB maximum 12 dots. Glue pot life is 10 minutes at 24 °C (75°F). Figure 5. 4/9 AN4046 Application of 1mm dot glue Doc ID 022792 Rev 1 AN4046 Mounting procedure 6. Flip the micro battery. Figure 6. 7. Placement of the micro battery Put a weight of 30 g (for example a nut M16 mm) on the micro battery. Figure 7. Place a weight on the micro battery Room temperature curing can be achieved in 4 hours at or above 24 °C (75°F). Do not use temperature higher than room temperature to accelerate curing. Doc ID 022792 Rev 1 5/9 Underfilling 4 AN4046 Underfilling Underfilling is not needed. 5 Manual rework The conductive glue doesn’t allow micro battery assembly rework. 6/9 Doc ID 022792 Rev 1 AN4046 Gauge for glue dot dimension optimization Appendix A Gauge for glue dot dimension optimization Print paper and laminate it with plastic coating. Figure 8. Gauge for glue dot dimension optimization DOT TEST 4 mm 1 mm Doc ID 022792 Rev 1 7/9 Revision history AN4046 Revision history Table 2. 8/9 Document revision history Date Revision 15-Mar-2012 1 Changes Initial release. Doc ID 022792 Rev 1 AN4046 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. 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