If you are talking about on a backsplash, this is usually okay. Just sand the formica to remove any shiny or slick areas. The sanding will also help the mastic adhere to the wall much better so your tiles will not come loose.
-Tiling over laminate is not the best solution. Even the boring but dependable pre-laminated slabs from Home Depot or Lowe's are often better. In fact, if you happen to have wrapped edge laminate (see below), this may be the very deal-breaker that causes you to purchase new counters over the tiling method. But tile does allow for maximum creativity, plus you can carry and easily transport tile in all vehicles (unlike those 73 1/2" by 25 5/8" laminate slabs).
Improve Your Base and Laminate To Make Them Structurally Sound
Base: Counter laminate often rests on a base of particle board (medium-density fiber board or MDF) which falls apart over time, especially in contact with water. If you have hollow spots, that means the base is bad. Any installed tile will look fine for awhile, but will eventually crack. Fill these areas with wood putty.
Laminate: While the point of installing tile over laminate is to cover up bad laminate, there is a limit as to how bad that laminate can be. If the laminate is de-laminating in areas, the tile will not hold. Use contact cement to reapply the laminate. It does not have to look beautiful; it just has to be firmly stuck to the MDF.
Install Only On Square-Edged, Not Wrapped, Laminate
Wrapped edge laminate is great stuff. It looks great, and it better resists chipping than square edge laminate.
Unfortunately, you cannot tile over wrapped edge laminate. You will need squared, vertical edges in order to accept the tile.
By carefully cutting with a circular saw, you can strip away the rolled section.
Roughen Surface of Laminate For Better Adhesion
Give the laminate surface a pass with an orbital sander outfitted with 60 grit paper. The aim is not to sand deeply but to give the surface a light sanding that covers it in a field of fine scratches.
Thoroughly Clean the Laminate
Sanding is easy; cleaning is hard. Use TSP, rather than cleaning solutions which leave residue.
Remember, thinset mortar is for applying tile to porous backer board. Tile mastic is what you'll want. It has the "grab" that you need for these non-porous surfaces.
A New Substrate Is Still Not a Bad Idea
While it does seem to run contrary to the spirit of tiling right over laminate, it never hurts to put down a cement backer board such as Durock. You don't need to worry about beauty: screw the backer board straight onto the laminate, run strips on the counter edges, and tape up the seams with fiberglass mesh tape. Now you have a fail-proof surface on which to install your tile (and no sanding of the laminate is required!).
If you are talking about on a backsplash, this is usually okay. Just sand the formica to remove any shiny or slick areas. The sanding will also help the mastic adhere to the wall much better so your tiles will not come loose.
Yes you can. Whether on wall or countertop use tile mastic instead of thinset. As Michele states lightly sand to remove any gloss.
The following information on tiling over formica (aka laminate) came from https://www.thespruce.com/can-i-tile-laminate-counters-182206
-Tiling over laminate is not the best solution. Even the boring but dependable pre-laminated slabs from Home Depot or Lowe's are often better. In fact, if you happen to have wrapped edge laminate (see below), this may be the very deal-breaker that causes you to purchase new counters over the tiling method. But tile does allow for maximum creativity, plus you can carry and easily transport tile in all vehicles (unlike those 73 1/2" by 25 5/8" laminate slabs).
Improve Your Base and Laminate To Make Them Structurally Sound
Install Only On Square-Edged, Not Wrapped, Laminate
Wrapped edge laminate is great stuff. It looks great, and it better resists chipping than square edge laminate.
Unfortunately, you cannot tile over wrapped edge laminate. You will need squared, vertical edges in order to accept the tile.
By carefully cutting with a circular saw, you can strip away the rolled section.
Roughen Surface of Laminate For Better Adhesion
Give the laminate surface a pass with an orbital sander outfitted with 60 grit paper. The aim is not to sand deeply but to give the surface a light sanding that covers it in a field of fine scratches.
Thoroughly Clean the Laminate
Sanding is easy; cleaning is hard. Use TSP, rather than cleaning solutions which leave residue.
Tack cloth is another great way to pull up dust.
Use The Right Adhesive
Remember, thinset mortar is for applying tile to porous backer board. Tile mastic is what you'll want. It has the "grab" that you need for these non-porous surfaces.
A New Substrate Is Still Not a Bad Idea
While it does seem to run contrary to the spirit of tiling right over laminate, it never hurts to put down a cement backer board such as Durock. You don't need to worry about beauty: screw the backer board straight onto the laminate, run strips on the counter edges, and tape up the seams with fiberglass mesh tape. Now you have a fail-proof surface on which to install your tile (and no sanding of the laminate is required!).
Yes it gives you a good base to follow, as long as it is level..go for it