What if product name was "MacBook/Dell/Lenovo Laptop cheap case", it contains Macbook at first position, you still want to boost this document?
I think you should try to fix the root cause of your issue instead, the common issue of how to deal with accessories (such as 'case', 'battery', 'lock' etc) scoring better than the products themselves.
The obvious best choice: index a field that says if the doc is an accessory (I gather you don't have that info, otherwise this is the best way), and boost the ones that are not accessories.
If you don't have that info, you can try by penalizing the docs that contain 'typical' accessory words. For this you need to build such a list, but it is not hard. I have used this approach with good result.