LCD Monitor Reliability Issues.ppt

1、Copyright 2004 reliability solutions all rights reserved,LCD Monitor Reliability Testing,Focusing on Key Areas which affect Reliability,Copyright 2004 reliability solutions all rights reserved,LCD Monitor Reliability Testing,Key commodities which cause repetitive problems for all LCD Monitor Supplie

2、rs Inverter Under-rated Fuse Fails, Solder problems LCD Weak Tab bonds / ITO corrosion LCD Gap Mura defects Motherboard Mcu Firmware Upgrades Motherboard problems causing Distorted Display Poor Cable connection between LCD / Mother Bd Power Board voltage overload Power Adapter issues with Voltage Sp

3、ikes leading to Display Flashing / Intermittent Display Loss NFF problems which lead to eventual failure Power Adapter Failures BackLight performance degradation,Copyright 2004 reliability solutions all rights reserved,LCD MONITOR Q Under-rated fuses being overstressed , causing long life problems a

4、nd high return rates (often epidemic) Solution expensive with upgrade costs of around $5 per board Rogue signals leading to FOS noise, often needs cap add to take signal to ground Requires inverter test at 10-15% above normal voltage input with repeated power switching and long periods of power on T

5、hermal Shock Testing is fast and effective in finding weak solder joints and poorly soldered SMT components Use extreme temp points of +60 and 20 deg C 30 mins in each environment, move immediately after 30 mins into cold or hot environment Cycle minimum of 4 times providing 4 hr thermal shock condi

6、tions Run Elevated temp test at minimum 50deg C with same inverters built into test monitors, run normal ORT test profile,Copyright 2004 reliability solutions all rights reserved,LCD Monitor Reliability Testing,LCD Reliability Often Tab defects can be excessive due to poor boding process Poor bondin

7、g evident if Tab Peel Test is performed on sample LCD panels Poor control of production environment can result in moisture / chemicals trapped between Tab chip carrier and Glass panel Will result in accelerated ITO corrosion and loss of signal leading to dead line on screen which cannot be repaired

8、Accelerated testing in humid conditions very effective in accelerating failure mechanism, LCD supplier must be able to show Env test data to prove LCD panel robustness,Copyright 2004 reliability solutions all rights reserved,LCD Monitor Reliability Testing,CORROSION CAUSED BY INTIAL CONTAMINATION. C

9、REATING CONDUCTIVITY (SHORT CIRCUIT BETWEEN ITO LINES),ITO LINES,Copyright 2004 reliability solutions all rights reserved,LCD Monitor Reliability Testing,ITO CORROSION,ITO LINES,Copyright 2004 reliability solutions all rights reserved,LCD Monitor Reliability Testing,NFF PROBLEMS Often difficult to r

10、e-create the problem If NFF 20-25%, assume inherent problem exists Inherent design problem or graphics card / monitor interface problem Power adapter component tolerance ? LCD monitor extended B/I is effective in finding true defects which are waiting to happen Often means NFF returns from customer

11、need b/i at 40 deg for up to 16-24 hrs for hard fail to occur Focus on NFF returns at early stage in new monitor lifetime will bring significant benefits Repetitive Stress Testing Successful at bringing NFF problems to Hard defect,Copyright 2004 reliability solutions all rights reserved,LCD Monitor

12、Reliability Testing,Power Adapter Failures Often caused by change of source / components used creating problem with Voltage Spikes above Monitor Design spec Recent Catastrophic Problem for Taiwan Supplier caused by missing capacitor on Input Voltage lines between earth and ground New Supplier not fu

13、lly verified, Adapter samples should have been stripped down and compared in detail to original source Testing of Adapter should Include ; Output Voltages of +ve and Gnd lines should be smooth with variable load applied under differing temp conditions (0 deg C to +50), check for and measure spikes C

14、heck output from transformer to check AC to DC conversion with constant DC, checking secondary output pins (normally 2 pins), change AC from outer tolerance levels to within tolerance (Input Voltage and Frequency) Ensure Power Consumption of adapter under varying loads is within spec. If input load

15、is varied and power consumption is excessive, adapter will wear-out early . If 20W required by monitor, but on occasion pulls 30 or 40W (say inverter fails) , adapter should shut down to prevent LCD damage,Copyright 2004 reliability solutions all rights reserved,LCD Monitor Reliability Testing,B/L p

16、erformance degradation (18” Monitor Example),Copyright 2004 reliability solutions all rights reserved,LCD Monitor Reliability Testing,B/L performance degradation Often higher spec monitors run 24hrs / day, 7 days per week in Banking / Stock Exchange applications 36 mth warranty still provided to the

17、 corporate accounts Annual power on usage will average 8500 hrs Monitors will require to have brightness of 150 cd / m2 to be acceptable to customer Must specify B/L spec with LCD Supplier as minimal brightness of 150 cd/m2 after B/L ON-Time of 12,000 hrs,Copyright 2004 reliability solutions all rights reserved,LCD Monitor Reliability Testing,Summary Range of Commodity Tests need to