电容crack原因

Appendix 1 CRACKING CAUSE CLASSIFIED BY CRACKING MODE Mechanical stress PHOTO 1 PHOTO.2 PHOTO.3 PHOTO.4 PHOTO.5 PHOTO.6 Thermal stress PHOTO.7 PHOTO.8 PHOTO.9 Appendix-2 MODE AND CAUSE OF CRACK BY MECHANICAL AND THERMAL STRESS Item Cracking mode Typical cause Excessive fillet height solder crack Excess solder at one or both side is the cause of crack by solder shrinkage. Cracking could be beneath the termination. Chip placer impact stress pick-up nozzle crack centering jaws(length) centering jaws(width) shell shaped crack chipping The bottom dead center adjusting error is the cause of cracking at the mid-point of the chip. Excess impact stress of centering jaws or sharp worn tweezer jaws of placer are the cause of chipping or cracking as figures. PC Board bending stress crack crack Mechanical stress by PC Board bending causes cracks as figures. Thermal shock by soldering iron soldering crack Iron Sudden heating of the chip by soldering iron could result in distortion due to great temperature differential, causing cracked chips. Appendix-3 MONOLITHIC CERAMIC CAPACITOR / CRACKING BY THE BENDING OF BOARD ITS MECHANISM AND FACTORS OF OCCURRENCE, AND COUNTERMEASURE Analysis of the stress applied by board-bending using definite element method. When pressure is applied to the board, (1) stretch of board ③ ③ (2) bend of board (3) stretch of solder we can see them. Stretch of the board-surface causes the stretch of solder, then solder gives a tensile stress to terminal electrodes. On the other hand, pressure is applied to joining point between ceramic and terminal electrodes. ④ Stress is the cause of ceramic cracking. Mode of cracking is shown below. solder-terminal joining point T board ceramic-terminal joing point The mode of cracking changes in the direction B from A by the thickness of capacitor and the amount of solder Crack mode A : (1)Thick capacitor (2)Small amount of solder Crack mode B : (1)Thin capacitor (2)Excessive amount of solder B A terminal electrode inner electrodes ② ② ④ ④ ① ① Appendix-4 MONOLITHIC CHIP CAPACITOR CRACKING BY P. C. BOARD BENDING Factor Point Board splitting We propose to avoid hand-splitting. Chip layout on a board A chip capacitor is liable to be warped. A>C>B≒D Amount of solder Too much amount of solder produces the P.C.Board deflection of a chip capacitor. Pressure by the other components inserting, adhesives applying and probe of in-circuit. nozzle Support pins should be placed at suitable positions under P.C.Board. chip The board is liable to warp, The dead point should be set suitably. if the dead point of the nozzle is set too low. solder A B C D slit Appendix-5 Factor Cause Notes and improvement ideas Installing another parts (A) When you put connectors and so on by the hand. PCB bending which is caused by embeding the connector to the substrate. (B)When you insert or pull out the socket. PCB bending which is caused by inserting or pulling out socket when the substrate itself is a connector. (C)When you tighten the machine screw. PCB bending which is caused by tightening the machine screw when you install the shield plate to the substrate and install the substrate to the chassis. Set the suitable clearance to the hole for setting. Set the work not to bend the substrate. Set the work setting that the substrate does not bend. Use the suitable and torque screwdriver which does not tighten screws too much. screwdriver socket parts put by hand Appendix-6 Factor Cause Notes and improvement ideas Inspecting the substrate (A)When you apply the contact pins for inspection. (B)PCB bending which is caused by the substrate holding device. PCB bending which is caused by wears and projections of the substrate holding device. Confirm the positions of backup pins and state of terminal such as wears, difference of length. Loosen the push pressure of the contact pins. Remove the projections, repair the wear parts. Loosen the holding pressure. contact pin substrate holding device substrate contact pin backup pin Appendix1 MES crack reference material-2