It is most commonly obtained with a spike suit, but can also be obtained by interrupting a Crystal Flash, as well as other methods.
Samus will lose a flash suit when shinecharging, using X-ray, or Crystal Flashing,
and she will use the flash suit when performing any inputs that would normally use a shinespark when having a shinecharge, such as standing jump, or aiming up or diagonally up after jumping.
See also: Tech Page