If enough employees join the same union at a company, they can vote to install a union board to negotiate a CBA on their behalf.
This isn't correct, this sounds like they are thinking of the US's National Labor Relations Act. In Sweden, the coercive option that a union has to implement a collective agreement ("kollektivavtal"), is only to organize a strike against the employer until a collective agreement is signed.
This is why Tesla employees in Sweden have been in a strike for over a year, and why many unions in Europe are engaging in solidarity blockades against Tesla. As Tesla has refused to sign a collective agreement with its employees, something that would be illegal under the US's NLRA. Obviously, strikes are very costly for a company, as they must both preserve the positions of those striking, but also buy in labor from non-unionized employees to replace the shortfall. But it's obviously a worthwhile cost for some people's political goals, as the Tesla strike nears its second year.
There is also a large loophole in Swedish labor law, where a company can simply sign a collective agreement with another union than the union that the employees are members of. All employees are then banned from going on strike, as they technically have a collective agreement. This is a loophole that Klarna exploited in order to prevent their tech workers from unionizing. I believe that the courts have not yet ruled on whether this is legal or not.