The present invention relates to a desoldering material for simultaneously desoldering each solder joint between an electronic component and a surface, and more particularly to the removal of a component which is both solder bonded and adhesively bonded to a surface
Solder mounted electronic components or devices such as integrated circuit chips are typically positioned in close proximity to other components on a surface, such as the top of a high density substrate or a printed circuit board. When an electronic component fails, it is usually more economical to replace merely the bad device than to replace the entire substrate. But this removal and replacement operation needs to be done without damaging other components on the substrate.
There are numerous conventional methods for surface repair where the solder is heated and the device removed from the molten solder. For instance, heating by directing a hot gas is described in U.S. Pat. No. 4,813,589 to Palmer et al. where a tube allows hot air to be directed from an external heat source to an integrated circuit chip on a circuit board to be removed without permitting heat to flow to adjacent components. The chip is protected from heat by placing a vacuum suction cup on top of the chip. Heating by means of heated blades is described in U.S. Pat. No. 4,614,858 to Vial where a desoldering tool contains heater bars shaped to contact the solder terminations to be desoldered as well as grasp the component to be removed. These conventional techniques have the drawbacks of leaving the reworked site on the substrate with uneven amounts of solder, leaving varying amounts of brittle intermetallic compounds and oxides that can lead to poor soldering joints for replacement devices, and other reliability problems Further, the adverse effect of uneven solder thickness and intermetallic compounds becomes acute when the device lead center lines are less than 0.020 inches, since at these dimensions the total volume of solder is small and the effect of solder thickness variations and intermetallic particles is great. Additionally, with conventional repair techniques, broken leads not attached to electronic components will often remain on the substrate after the electronic components are desoldered and removed. It may then be necessary to remove the broken leads manually with tweezers and a soldering iron. This manual removal is time consuming and can also result in damage to the substrate or nearby components.
There exists a need for removing a solder mounted electronic component and any broken leads from a multi-component module in a single step while leaving a minimal amount of solder and intermetallic particles on the module surface, particularly for components which are also adhesively bonded to a module and have outer lead bonds with center lines spaced less than 0.020 inches.