Those who learned about scrum the old fashioned way might call me names for the title of this articles, but since I run into more and more people out there who mingle both terms I think a clarification might be beneficial.
A product backlog is about what you plan to accomplish
“The Product Backlog is an ordered list of everything that might be needed in the product[…]” (Scrumguide 2013)
And it is good practice to keep these things in the bounds of the INVEST properties. This implies that the product-backlog does not prescribe how the requirements are met, but what should be achieved.
A sprint backlog is about what you plan to do
“The Sprint Backlog is the set of Product Backlog items selected for the Sprint, plus a plan for delivering the product Increment and realizing the Sprint Goal. The Sprint Backlog is a forecast by the Development Team about what functionality will be in the next Increment and the work needed to deliver that functionality into a “Done” Increment.“ (ibid, emphasis added)
So yes, sorry mates, if you want to do scrum (and not scrum but) you'll have to do what used to be called ”Sprint planning 2“: Sit down and plan your work.
There are some options to handle things differently – like breaking down the board and “kanbanizing” that part of the workflow – but then these approaches might no longer be exactly what should be called scrum.