Protection of tombstone problems for small chip devices

Small chip components (Such as 0402 or 0603 Chip Device) may have "tombstone" problems during the solder paste reflow process. Tombstoning is a phenomenon where the chip component is raised and detached from the printed circuit board at one end while remaining bonded to the circuit board at the opposite end. In this case the chip component takes a vertical orientation. The tombstone effect is caused by a difference in the length of time at which the solder paste is melted at opposite ends of the component during heating in a reflow furnace. When the melting of solder paste adhering to the first electrode at one end of the chip component occurs earlier than that solder adhering to the second electrode located at the opposite end, the earlier melted solder paste acts to pull down the first electrode by the surface tension force of the molten solder, thus creating tombstone problems in the PCB sub-assembly process. In this case the tombstone problem may be dramatically reduced by adjusting the area between the liquidus and solidus temperatures. Use of a two (2) peak melting point alloy has proven very effective for tombstone problems by keeping a good equality balance with power of moment at both sides of the chip device electrode.