Even with a 2000 watt 1/2in router a 38mm worktop requires 5 or 6 passes at increasing depths to get a good quality cut. A 1/4 router will require a lot more passes.
Remember that the router cutter must always enter the laminate at the front of the worktop (the post formed edge) to avoid chip out. The rule of thumb for routing is that the material is on the left, the cutter to the right of it, and you push the router away from your body.
This also means that if you are cutting a right hand end you work with the top of the worktop material uppermost.
When cutting a left hand end, on the other hand, you need to flip the worktop over (so the underside is uppermost) then end to end (so that what will become the left hand end is now to the right, face down with the post formed laminated edge at the front, facing you) before making the cut.
If using a 1/2in (12.7mm) diameter router cutter limit the width of the cut to about 3mm to avoid overloading the cutter. It may be better to cut the worktop slightly oversize (4 to 6mm over length) with a circular saw and a fine tooth blade, or even just a fine tooth handsaw before using the router - the circular saw needs to cut from the front to the rear with the worktop flipped over so the saw is running on the underside with the cut starting into the post formed edge. Hand saws are different. The hand saw is used from the rear to the front of the worktop, top surface uppermost, taking care to follow the edge round at the end of the cut (and making sure you support the offcut piece in all instances). This is to avoid chip out.