A low, heavy backspin serve is difficult to attack, especially if you serve it short or to the opponent's weaker side. For that reason it is often the serve of choice for many attacking players who are looking for a passive return to attack. However, there are several problems you face with this serve. If you serve with heavy backspin, it's easy for an opponent to dig into it and push it back low and heavy - your own backspin rebounds off their open racket with backspin. If you serve it long, it's easy to loop with heavy topspin, converting your own backspin into topspin. If you serve it short, it's easy to push back short and low, making it difficult to attack. How do you overcome these problems?
The answer is to develop other serves as variations, such as a good sidepin or topspin serve - and you should develop these. However, there's an easier way that most top players use, and that's to mix in no-spin serves.
A key to getting heavy spin on the serve is to contact the ball near the racket tip, which is the fastest moving part of the racket when you snap your wrist into a serve for heavy spin. Suppose you use the same motion, but contact the ball near the handle, where the racket is moving much more slowly. You get an almost spinless ball. If you really exaggerate the spin motion but serve with no spin, it's a "heavy no-spin serve."
Now it's more difficult for an opponent to push it back heavy as they can't use your spin against you, plus they are probably expecting backspin, and so their push pops up. If the serve goes long and they attack it, they'll likely misread it as backspin, and go off the end. If they try to push it back short, it'll likely pop up as well as go long.
It's extremely important to serve no-spin very low to the net. There's no spin to directly mess up an opponent, and if it goes high, it's easy to attack. If you serve it low, it's surprisingly difficult to flip aggressively - if an opponent does attack it easily, you are probably not serving low to the net.
At the higher levels, no-spin serves are the most common serve in doubles, often with backspin serves mixed in as the main variation. Since your opponent knows which court you are serving to in doubles, he is camped out ready to make a return from his stronger side. At these higher levels, deep serves are looped, short sidespin and topspin serves are flipped aggressively, and short backspin serves are dropped short and low. Since the opponent can use your own spin against you, the no-spin serve is often more effective than the spinny one. A short no-spin serve may not force as many outright mistakes, but there's no one easy way to return it effectively.
So develop a no-spin serve as a variation to your spin serves, and learn to really load up the ball with so much no-spin that no opponent can possibly overcome that dizzying lack of spin you throw at them.