LED pn junction is the main material, and brake fluid (Thyristor) is commonly used in electronic power control element when its thickness uneven situation when there will be staggered to produce pn level, then there will be a voltage difference big difference, which is the "brake fluid effect", and if the voltage difference is too large to display quality of this product is not very good, so it can also be used to measure the quality of the LED.

However, the general effect will not be used to judge the quality of brake fluid LED's, LED's VFD usually test to determine. VFD less than 0.1V for qualified contractors.