Abstract: In a method of attaching an electronic component to a printed circuit board by a plurality of screws that are inserted into corresponding through holes cut in the board from a surface of the board and then screwed into corresponding screw holes formed in the component mounted on an opposite surface, the component is screwed onto the board using one of the screws and the component and the screw are soldered onto the board with lead-free solder. After they have been cooled down, the component is screwed onto the board using remaining screws. With this, the strength of the connection between the component and board is improved and also the occurrence of warp of the board and component can be prevented.

Abstract: In a method of attaching an electronic component to a printed circuit board by a plurality of screws that are inserted into corresponding through holes cut in the board from a surface of the board and then screwed into corresponding screw holes formed in the component mounted on an opposite surface, the component is screwed onto the board using one of the screws and the component and the screw are soldered onto the board with lead-free solder. After they have been cooled down, the component is screwed onto the board using remaining screws. With this, the strength of the connection between the component and board is improved and also the occurrence of warp of the board and component can be prevented.

Abstract: An ignition timing control system for an internal combustion engine that estimates the octane number of the fuel being used based on the state of engine combustion knocking and controls the ignition timing to a value not exceeding the knocking limit. The basic ignition timing is set along the knocking limit of fuel having least octane number and the maximum advance amount is set between the knocking limit and the second knocking limit of fuel having maximum octane number. Octane number is estimated from the occurrence of knocking. On the other hand, upper limit of the estimated octane number is set based on the MBT of the engine such that the estimated octane number is limited with the upper limit. Advance rate is determined based on the estimated octane number and is multiplied to the maximum advance amount to determine an ignition timing correction amount. The ignition timing is finally determined from the basic ignition timing and the ignition timing correction amount.

Abstract: An exhaust gas recirculation control system for an internal combustion engine includes an exhaust gas recirculation passage extending between the intake system of the engine and the exhaust system thereof, and an exhaust gas recirculation control valve for controlling the flow rate of exhaust gases to be recirculated through the exhaust gas recirculation passage. The system further includes an ECU which calculates a desired air-fuel ratio of a mixture supplied to the engine, based on engine operating conditions detected by engine operating parameter sensors, and also a desired valve opening of the exhaust gas recirculation control valve, based on engine operating conditions detected by the operating parameter sensors and the calculated desired air-fuel ratio.