Application Note AN2222 Flex-Pod Soldering Guide Abstract This Application Note provides instructions on soldering PSoC Flex-Pods. Author: Matt Basinger Associated Project: No Associated Part Family: CY8C21x34, CY8C29x66 Suggested Shop Supplies o Solder o Flat/Wide Tip Solder Iron o Flux (Water-Wash) o Water o Brush to Remove Flux (Optional) o Dental Pick (Optional) o Masking Tape (Optional) o Light Source o Microscope or Magnifying Lens (Optional) Y Z Suggested Vendor and Part Number o AIM LF218 o METCAL STTC-036 Replacement Tip Cartridge o Kester 2331-Zx X Picture 2. Flex-Pod Picture 1. Flex-Pod Head Tips o Avoid shining a lamp directly down from on the top of the Flex-Pod, as there may be a glare that makes it hard to see the pad s line up through the flex material of the Flex-Pod. o Use of a microscope or magnifying lens can be helpful in lining up the pads of the Flex- Pod. Quick Steps 1. Pre-tin the top of the vias (if not pre-tinned already). 2. Apply flux to the PCB (under Flex-Pod) to make the flex material more transparent. a. Line up the Flex-Pod with the PCB footprint. 3. Solder the Flex-Pod to the PCB by touching the vias and pads. 4. Verify that the Flex-Pod is securely soldered to the PCB using a dental pick. 5. Water wash the PCB to remove flux
Detailed Steps 1. Pre-tin the top of the vias (to determine if already pre-tinned see pictures 5 and 6): a. Position the Flex-Pod so that the tail is toward you and that the pad side (or bottom) is in contact with the PCB. b. Put a drop of flux on the top of the head of the Flex-Pod. c. Add solder to each of the vias on top (being careful not to make any solder bridges). Vias Pads Top is labeled TOP Picture 3. Top of Flex-Pod Head - Vias Picture 4. Bottom of Flex-Pod Head - Pads Picture 5. Un-Pre-Tinned Vias Picture 6. Pre-Tinned Vias Window Picture 7. MLF Flex-Pod (Does not Require Pre-Tinning)
2. Line up the Flex-Pod with the PCB footprint: a. Put a drop of flux on the PCB footprint (Picture 8 shows how it is difficult to line up the pads without the flux). b. For non-mlf Flex-Pods, position the Flex-Pod so that the top of the head of the Flex-Pod is at the bottom of the PCB footprint so that the vias of the Flex-Pod are parallel to the pads on the PCB. (For MLF Flex-Pods, use the window to line up the pads as shown in Picture 11.) c. Slowly slide the Flex-Pod up along the length of the PCB footprint to align the pads. As you move the Flex-Pod you will be able to see the pads on the Flex- Pods through the flex material. Notice the blinds effect as the pads align (Picture 10), then un-align. (Picture 9 shows how you can clearly see PCB pads in between the Flex-Pod pads.) d. When you reach full alignment you can either tightly hold the Flex-Pod in place or attach a piece of tape to one corner of the Flex-Pod to secure it to the PCB. Picture 8. Pads Un-Aligned (Without Flux - Hard to Align) Picture 9. Pads Un-Aligned (with Flux) Picture 10. Pads Aligned (with Flux) Picture 11. MLF Pads Aligned (with Flux)
3. Solder the Flex-Pod to the PCB: a. Put a drop of flux on the top of the Flex-Pod. (For MLFs, apply flux in window as shown in Picture 7.) b. Position the tip of the soldering iron so that it is horizontal (parallel to the y plane of the Flex-Pod) the tip should be parallel to the pads. c. Touch the tip of the soldering iron to the pad and via on top of the Flex-Pod for approximately one second. The tip of the iron should touch the pad evenly so that the length of the tip is evenly distributed along the pad. d. Remove the iron from the pad by rolling it away from the via. This means that the end of the tip of the iron that is closest to the via should be removed first then the end of the tip of the iron that is away from the via should be removed. e. Complete this process for each pad (if using tape to secure the Flex-Pod, remove it after the opposite side has been soldered down). * MLF Flex-Pods do not have vias so instead apply the tip of the soldering iron directly to the pads. Remove the via side of the tip first, then role off the other side of tip. Picture 12. Removing the Soldering Iron Tip Via Side First 4. Verify that the Flex-Pod is securely soldered to the PCB: a. Gently slide a dental pick or similar tool under the edge of the Flex-Pod near the soldered down pads, gently prying the Flex-Pod to test for a secure soldering job. b. If you can gently lift the Flex-Pod off of the PCB so that the pads are exposed, than the Flex-Pod is not soldered down correctly or securely. c. A microscope can also be used to verify connections for MLF Flex-Pods. 5. Water wash PCB to remove flux: a. If using a water flux, rinse the PCB with water. b. Use a brush or Q-tip to remove flux. c. Rinse the PCB with water again as needed. d. Dry the PCB.
Tips o Once you have completed the entire soldering process, add a crease to the Flex-Pod tail approximately one-half inch away from the head of the Flex-Pod. You can do this by bending the flex material around another PCB (or as in Picture 13 a posted-note book is used). This crease will act as a stress relief to the Flex-Pod/PCB connection and transfer a great deal of the stress from the z plane to the x-y plane. o Once the Flex-Pod is soldered to the target PCB, consider rolling up the tail with a rubber band to avoid catching the tail on equipment in the lab. Picture 13. Bend the Flex-Pod Tail Picture 14. Crease Can Provide Stress Relief in Z Direction
Theory of Operation Heat is conducted down to the pad on the bottom of the PCB through the via connected to each pad. Adding solder to the vias increases the thermal mass and allows more heat to be conducted to the bottom. By pressing down onto the via and the pad, the Flex-Pod pad is pressed onto the top of the PCB pad by the pressure from the iron. Heat is transferred to the pad through the via, which melts the solder on the pads, creating a solder connection. Soldering Iron Flex-Pod Pad Pressure Via Heat Pad PCB Cypress MicroSystems, Inc. 2700 162 nd Street SW, Building D Lynnwood, WA 98037 Phone: 800.669.0557 Fax: 425.787.4641 http://www.cypress.com/ / http://www.cypress.com/support/mysupport.cfm Copyright 2004 Cypress MicroSystems, Inc. All rights reserved. PSoC, Programmable System-on-Chip, and PSoC Designer are trademarks of Cypress MicroSystems, Inc. All other trademarks or registered trademarks referenced herein are the property of their respective owners. The information contained herein is subject to change without notice. Made in the U.S.A.