This may no be a good reference but here is the story so far. There are a number of possible reasons why chip capacitors have been found to fail during production and in the final products and here are just a few. The design and method of component manufacture can affect the components ability to stand up to modern manufacturing methods. In cases where components are selected at the top of capacitance range for a given package size due to the number of plates, the components can be more sensitive to fracture failures. Often the component manufacture will suggest de-rating parts for a given process. The internal construction and lay up of the internal electrodes may also affect the robustness of the parts. This does vary with different part suppliers and should be evaluated during component assessment. Components, when they are supplied, may be damaged prior to removal from the packaging; this has certainly been seen in the past. Internal cracking may be present and is then exaggerated by the assembly process. Examination of selected components in their packaging can provide examples of defective parts. Machine centring and placement of components on to the board has been a problem area over the years. Again this is exaggerated where the parts are less robust. Recently it has been the use of board support pins supporting the board without any flexture. Poor positioning of pins under components does not allow the board to move when the component is placed. Minor cracking may occur and is then shown up during soldering and test. (For those older engineers who remember a specific type of machine that was called the chip cracker, remember the old America magazine Nut Shell News!!) Wave and reflow soldering temperature settings again have been shown to affect component reliability. Controlling peak temperature and temperature rise during reflow must be monitored. Minimising the temperature of solder baths to between 235/240oC and controlled board pre-heating has mostly eliminated the wave soldering problems in the industry. It is uncommon for the reflow soldering process to cause failures unless parts have already been damaged. Unless the quality of the capacitor is poor with internal voiding or stress cracks the reflow process is less likely to cause problems. In the case of wave or reflow soldering if the board is poorly supported and the board is allowed to sag the board may be warped after soldering. If any subsequent process straightens the board it may cause component cracking. A possible example is in-circuit test where the board is straightened flat during pin contact. Hand soldering and rework has also been shown to damage parts if correct procedures are not followed or poorly trained staff are used. It is common where components come into direct contact with solder bit rather than using the solder to provide effective heat transfer. During any hand soldering operation using soldering irons the solder is used to transfer the heat to the board and component. Today it is more common to use hot air pencils to rework surface mount component minimising physical contact with parts. Board flexture during board handling, break out, in-circuit test or final mounting of the board into the product is more likely to cause failure. This is again true if the component is not correctly specified and tested during initial assessment of the supplier. Most of the cases currently being examined for customers . Existing methods of board break-out needs to be reviewed the board if not supported during separation will flex and cause component damage. Again this is the most common method of failure. The flow solder pallets need to be examined as the boards are not held correctly or supported to minimise warpage. This is causing distortion during the final circuit board during test or breakout. Boards held too firmly in pallets can result in failure, operators tend to peel the board out of a jig if it is a tight fit, crack goes the chip. Bob Willis Electronic Presentation Services 2 Fourth Avenue, Chelmsford, Essex CM1 4HA. England. Tel: (44) 01245 351502 Fax: (44) 01245 496123 Home Page: http://ourworld.compuserve.com/homepages/bwillis Email: [log in to unmask]