In order to interpret the intervening processes in the energy release during solar flares, an statistical study in 20 events produced in solar active regions, was performed. Their intensities comprises a wide range including from the more intense flares up to microflares. We analyze X2-ray data obtained from the Hard X-Ray Imaging Spectrometer (HXIS) and the Hard X-Ray Burst Mission satellite. We establish correlations among the maximum counting rates in soft and hard X-rays, their slopes, the integrated counting rates over all both HXIS and HXRBS spectral ranges, and the total duration of the events. The results of the correlation coefficients suggest a strong causality between the hard (> 16 keV), and soft X-ray brightening, responsible of the hard X-ray emission during the flare impulsive phase, loose afterwards their energy, producing the soft X-ray emission.