我做过的几个项目ESD解决问题的方法

Case 1 S888 S888 ESD problem improvement For S888 V00 there are some ESD problems as follow 1 The mobile will lose communication and search network again when discharging to arrow key and data key at air 6KV in communication state 2 The mobile will lose communication and search network again when discharging to side key and camera decoration ring at air 5KV in communication state with mobile downwards 3 The mobile will power off or lost network when releasing static from the headset speaker at air 5KV in mobile with headset state 4 The PA will destroy when discharging to the camera decoration ring at air 5KV For these problems the solutions are as follow Problem 1 improvement Make the metal dome and MMI GND well connected with two points and keep the resistance between metal dome and the GND under 2 ohm After improvement it is OK for ESD at air 10KV on the arrow key and data key Problem 2 improvement 1 Scratch the NBSCAN test point which is just under the metal dome 2 Add a 10nf capacitor on the NBSCAN test point 3 Change the former sparse metal dome with dense metal dome After improvement it is OK for ESD at air 10KV on the position of side key and camera decoration ring Problem 3 improvement 1 Add TVS ESDAVLC6V1 1M2 on the HSGND it is OK for ESD at air 10KV 2 Add 10nf capacitor on the HSGND it is OK for ESD at air 10KV After improvement it is OK for ESD at air 10KV when releasing static from the headset speaker Problem 4 improvement Use isolated tape to cover the antenna which is near the gap of the camera decoration ring After improvement it is OK for ESD at air 10KV when discharging to the camera decoration ring 1 1 KEY PAD PROBLEM Description When discharging to arrow key and data key at air 6KV in communication state the mobile will lose communication and search network again Problem analysis At first the metal dome is connected with the GND by one point and the resistance between the metal dome and the GND is bigger than 2 ohm when discharging to arrow key and data key at air 7KV in communication status the mobile will lose network and search network again Improvement When keep the resistance between metal dome and the GND under 2 ohm it will not lose network again at air 10KV so it is advised to keep the metal dome connected with the GND by two point and keep the resistance between them under 2 ohm After improvement it is OK for ESD at air 10KV on the arrow key and data key 1 2 SIDE KEY AND CAMERA DECORATION RING PROBLEM Description When discharging to side key and camera decoration ring at air 5KV in communication state with mobile downwards the mobile will lose communication and search network again Problem analysis As the NBSCAN test point is just under the metal dome and very sensitive to ESD when mobile downwards the NBSCAN test point is easily affected by coupling electric field formed between workbench and the MMI When discharging to side key and camera decoration ring Only one point for metal dome to connect with GND the resistance between metal dome and GND is bigger than 2 ohm Use two points to make metal dome connect with the GND well and keep the resistance between them under 2 ohm at air 5KV in communication state with mobile downwards the mobile will lose communication and search network again Improvement 1 Scratch the NBSCAN test point which is just under the metal dome it is OK for ESD at air 10KV on the position of side key and camera decoration ring 2 Add a 10nf capacitor on the NBSCAN test point it is OK for ESD at air 10KV on the position of side key and camera decoration ring 3 Change the former sparse metal dome with dense metal dome it is OK for ESD at air 10KV on the position of side key and camera decoration ring 1 3 RELEASING STATIC PROBLEM Description The NBSCAN test point is very sensitive to ESD Sparse metal dome Dense metal dome Change the former sparse metal dome with dense metal dome The mobile will power off or lost network when releasing static from the headset speaker at air 5KV in mobile with headset state Problem analysis As the C501 10nf capacitor on the HSGND is not mounted when releasing static from the headset speaker the mobile will power off or lost network Improvement 1 Add TVS ESDAVLC6V1 1M2 on the HSGND it is OK for ESD at air 10KV 2 Add 10nf capacitor on the HSGND it is OK for ESD at air 10KV After improvement it is OK for ESD at air 10KV when releasing static from the headset speaker 1 4 PA DESTROY PROBLEM Description The PA will destroy when discharging to the camera decoration ring at air 5KV Problem analysis As antenna is very near from the camera decoration ring when discharging to the gap of the ring ESD will easily release to the antenna and destroy the PA Improvement When use isolated tape to cover the antenna it will prevent ESD directly release to the antenna and then it can protect the PA from being damaged by ESD As NM C501 when releasing static from the headset speaker the mobile will power off or lost network Antenna is very near from the camera decoration ring and can be easily discharged by ESD directly After improvement it is OK for ESD at air 10KV when discharging to the camera decoration ring Case 2 DX2007B1 ESD problem improvement During qualification there are some ESD problems 1 There will be power off when discharging to I O connector at contact 3 5KV 2 There will be power off when discharging to T flash connector at air 7KV 3 There will be communication lost and can t read SIM card when discharging to keypad T flash connector and gap at air 7KV For these problems the solutions are as follow Problem 1 improvement Increase the GND area of the battery s cathode by scraping the green painting near the cathode to expose more GND and linking the cathode with the exposed GND by solder After improvement it is OK for ESD at contact 6KV on the I O connector Problem 2 improvement Link the metal panel of the back cover with the SIM card shielding cover by conductive fabric After improvement it is OK for ESD at air 10KV on the position of T flash connector Problem 3 improvement Link the metal panel of the back cover with the SIM card shielding cover by conductive fabric After improvement it is OK for ESD at air 10KV on the position of keypad T flash connector and gap After modifications above the mobile can pass air 10KV and contact 6KV 1 5 I O CONNECTOR PROBLEM Description When discharging to I O connector at contact 3 5KV the mobile will power off Use isolated tape to cover the antenna which is near from the ring Problem analysis The line which used to link the GND of the battery s cathode with the GND of the main board is too thin when discharging to the I O connector the GND of the battery s cathode will be easily affected by the high electrostatic voltage the power supply will easily become unstable Improvement In order to improve ESD performance it needs to make the link line between the GND of the battery s cathode with the GND of the main board wider which is helpful to keep the power supply stable When scraping the green painting near the cathode to expose more GND and linking the cathode with the exposed GND by solder it can make mobile pass contact 6KV on the position of I O connector 1 6 T FLASH CONNECTOR PROBLEM Description When discharge to T flash connector at air 7KV there will be power off The link line between the GND of the battery s cathode with the GND of the main board is too thin The link line between the GND of the battery s cathode with the GND of the main board is too thin Scrape the green painting near the cathode to expose more GND Link the cathode with the exposed GND by solder Problem analysis There is a piece of metal panel of the back cover above the T flash connector the metal panel is isolated and neither connected with the GND nor contacted with the SIM card shielding cover When discharging to T flash connector there will be electromagnetic coupling between the metal panel and the SIM card shielding cover which will affect the signal of the T flash connector and make the mobile power off Improvement The metal panel of the back cover is isolated and is not connected with the GND The metal panel of the back cover is not contacted with the SIM card shielding cover In order to improve ESD performance of the T flash connector the metal panel of the back cover should connect with the GND For the metal panel of the back cover is not contacted with the SIM card shielding cover it can stick conductive fabric on the both sides of the SIM card shielding cover to contact the metal panel After improvement it is OK for ESD at air 10KV on the position of T flash connector Case 3 AX2007B2 V01 ESD Problem Improvement For AX2007B2 V01 there are some ESD problems as follow 1 There will be missing line on the LCD screen and can t restore when discharging to LCD window at air 7KV 2 The mobile will lose network and search network again when discharging to data key at air 7KV 3 The keypad will not response even reset again when discharging to data key at air air 7KV For these problems the solutions are as follow Problem 1 improvement Use conductive fabric and foam to make the metal sheet of the front cover and the metal shelves well connected and keep the resistance between metal sheet and the GND under 2 ohm After improvement it is OK for ESD at air 10KV on the LCD window Problem 2 improvement 1 Use insulative tape to cover the two screws which are just below the data key and very close to the antenna 2 Use new metal dome which could cover these two screws After improvement it is OK for ESD at air 10KV on the position of data key Problem 3 improvement Stick conductive fabric on the both sides of the SIM card shielding cover Use insulative tape to cover the six inductors which are under the data key and exposed outsides of the metal dome and used to link keypad signal and CPU After improvement it is OK for ESD at air 10KV on the position of data key Note Synthesis problem 2 and problem 3 sticking insulative tape maybe will not be good for mass production it is better to use new metal dome which could both cover the two screws and the six inductors instead of the former metal dome 1 7 LCD PROBLEM Description When discharging to LCD window at air 7KV there will be missing line on the LCD screen and can t restore even restart Problem analysis Below the front cover and upon the LCD screen there is a piece of metal sheet which is not connected with the GND when discharging to LCD window gap at air 8KV the ESD will discharge to the metal sheet and damage the LCD screen Improvement Later we keep the metal cover connected with the GND by conductive fabric and foam but if the resistance between the metal sheet and the GND is bigger than 2 ohm when discharging to LCD window gap at air 8KV ESD still will damage the LCD screen When keep the resistance between metal sheet and the GND under 2 ohm it will not damage LCD screen again at air 10KV so it is advised to keep the metal sheet connected with the GND well and keep the resistance between them under 2 ohm The metal sheet is not connected with the GND Use conductive fabric and foam to make metal sheet connect with the GND After improvement it is OK for ESD at air 10KV on the LCD window 1 8 DATA KEY PROBLEM Description When discharging to data key at air 7KV in idle with headset status the mobile will lose network and search network again Problem analysis For the antenna is near the gap of the data key and the antenna is fixed by two screws which are very close to antenna while these screws are just under the data key without connected with the GND when discharging to data key at air 8KV the ESD will discharge to the antenna through screws and the mobile will lose network Improvement Use insulative tape to cover the two screws it will prevent ESD discharging to these screws directly and the mobile will not lose network and be OK at air 10KV 1 9 KEYPAD LOSE FUNCTION PROBLEM These two screws are very close to antenna and just under the data key without connected with the GND Use insulative tape to cover the two screws Description The keypad will not response even restart when discharging to data key at air air 7KV Problem analysis For the six inductors which used to link keypad signal and CPU is under the data key and exposed outsides of the metal dome and then ESD will enter CPU through them when discharging to data key It will damage CPU and make keypad lose function Improvement When use insulative tape to cover these six inductors it will prevent ESD discharging to these inductors directly and the keypad will be OK at air 10KV so it is advised to use insulative tape to cover these six inductances After improvement it is OK for ESD at air 10KV on the position of keypad Note Synthesis problem 2 2 and problem 2 3 sticking insulative tape maybe will not be good for mass production it is better to use new metal dome which could both cover the two screws and the six inductors instead of the former metal dome Case 4 MX2006B2 V01 ESD Problem Improvement These six inductors are exposed outsides of the metal dome and just under the data key which will be discharged by ESD Use insulative tape to cover these six inductors After modification V00 there are still some ESD problems 1 There will be power off when discharging to navigation key and numeric key at air 6KV 2 There will be power off when discharging to I O connector at contact 3KV For these problems the solutions are as follow Problem 1 1 Increase the GND area of the battery s cathode by scraping the green painting near the cathode to expose more GND and linking the cathode with the exposed GND by solder 2 Change the navigation key of water galvanization with vacuum galvanization 3 Change the metal dome with two points to connect the shielding cover with four points to connect the shielding cover After improvement it is OK for ESD at air 10KV on the position of navigation and numeric key Problem 2 Add a conductor of 1000nH on the battery s anode After improvement it is OK for ESD at contact 6KV on the position of I O connector 1 10 KEYPAD PROBLEM Description When discharging to navigation key and numeric key at air 6 KV the mobile will power off Problem analysis The line which used to link the V00 battery s cathode GND with the main board GND is wide For V00 mobile s navigation key is made of vacuum galvanization material which is un conductive when the metal dome below navigation keypad is well connected to the main board GND by shielding cover the V00 mobile is OK for ESD at air 10KV But the V01 mobile s navigation key is made of water galvanization material which is conductive and the navigation key could not be connected with GND in mechanical design so it is easy to produce electromagnetic affect between navigation key and metal dome when discharging to navigation key When discharging to navigation key at air 6KV the V01 mobile will be power off On the V01 PCB the line which used to link the battery s cathode GND with the main board GND is too thin when electrostatic discharging to the GND the battery s cathode GND will be affected by the high electrostatic voltage the power supply is easily becoming unstable When discharging to numeric key at air 6KV the V01 mobile will be power off Compare with V01 on the V00 PCB the line which used to link the battery s cathode GND with the main board GND is wider than V01 the V00 mobile battery s cathode GND is difficult to be affected by the high electrostatic voltage it is OK for ESD at air 10KV when discharging to numeric key Improvement 1 Increase the GND area of the battery s cathode by scraping the green painting near the cathode to expose more GND and linking the cathode with the exposed GND by solder 2 Change the navigation key of water galvanization with vacuum galvanization The line which used to link the V01 battery s cathode GND with the main board GND is thin 3 Change the metal dome with two points to connect the shielding cover with four points to connect the shielding cover After improvement it is OK for ESD at air 10KV on the position of navigation and numeric key 1 11 I O CONNECTOR PROBLEM Description When discharging to I O connector at contact 3KV the mobile will power off Problem analysis For V00 PCB layout mistake the polarity of the battery is opposite and the battery had to be soldered with the battery connector by a wire based on V00 PCB it is OK for ESD when discharging to I O connector at contact 6KV but on V01 PCB it is NOK at contact 4KV As battery is soldered with connector by a wire the wire act as a inductor which is useful to prevent ESD enter battery s cathode GND the mobile is difficult to be affected by the high electrostatic voltage Improvement Add a conductor of 1000nH on the battery s anode After improvement it is OK for ESD at contact 6KV on the position of I O connector Case 5 AX2007B1 V01 ESD Problem Improvement For AX2007B1 V01 there are some ESD problems as follow 1 The mobile will lose network and search network again when discharging to arrow key at air 7KV and contact 3KV 2 The mobile will lose network and search network again when discharging to data key at air 7KV 3 The keypad will not response even reset again when discharging to data key at air air 9KV 4 There will be blue screen when discharging to mobile when mobile is downwards at air 2KV For these problems the solutions are as follow Problem 1 improvement Make the metal dome and GND well connected and keep the resistance between metal dome and the GND under 2 ohm by changing the former bad conductive fabric with good conductibility and quality conductive fabric After improvement it is OK for ESD at air 10KV and contact 6KV on the arrow key Problem 2 improvement 1 Use insulative tape to cover the two screws which is just below the data key and very close to the antenna 2 Use new metal dome which could cover these three screws After improvement it is OK for ESD at air 10KV on the position of data key Problem 3 improvement 1 Use insulative tape to c