True, but it might also be possible that your soldering iron is too hot, and it is overheating the copper adhesive, weakening it somewhat.
From my experience soldering thousands of PCB ties to rails of different sizes ( Code 40, Code 55 and Code 70 ), what affects the adhesive between copper cladding and whatever the rest of the PCB material is made of, is both heat and the amount of time the heat is applied.
Right off the bat, you might think that a hot iron would be most detrimental and cause the cladding to separate from the rest of the PCB tie, but...in my experience using my 35W iron with a small wedge tip for thousands of PCB/rail solder joints (both making turnouts and laying C40 track) that when the solder won't run between the rail foot and the copper cladding because of oil, or bad flux...THAT is when the adhesive release and burning of the material under the cladding happens. This is always caused by applying heat for several seconds to the joint...like seven to ten seconds.
The same detrimental effect can be made by applying an iron with less wattage for a longer period of time.
So, my experience with soldering PCB ties to NS rails is that you clean the rail foot with Bestine by swiping it with a Bestine dampened paper towel or microfiber cloth when it's still a yard long, buffing the copper oxidation away on the copper cladding on the PCB ties using a pencil eraser...on a pencil, have a clean and tinned iron tip of at least 35W for EVERY JOINT and apply your mashed and split 96/4 Silver/Tin solder fork to the intersection of the PCB cladding and the foot of the rail on the opposite side of the rail as where you are placing your hot iron with its clean and tinned tip....and when you see the solder flow, remove the solder immediately...then remove your iron. Bright solder should be visible on both sides of the joint, meaning it has flowed between the rail foot and the PCB cladding...with a very small solder fillet visible between the vertical edges of the rail foot and the PCB cladding.
This entire heating, applying solder, taking the solder away and then taking the iron away ....should take no longer that 3 seconds.
So, a hot iron is good, because it heats both the copper cladding and the rail foot quickly and thoroughly, but always get it off the joint quickly. There is no need to continue to apply heat after the solder has melted and flowed to both sides of the rail foot.
On PCB ties that I have caused the cladding the separate from the body of the tie...actually "throwbar"...it is very obvious why the cladding separated, because the material under the cladding is blackened and charred. I can't remember ever seeing just the cladding separate from the PCB body without charring.
Of course, the "ideal" solder joint may happen several times during track and turnout construction, but most of the time, there is going to be some smearing of the solder on the tops of the PCB ties. However no "globbies" should be present, but if they are, then learning how to get rid of them using solder wick is something simple to learn, and will easily take care of any solder globs.
Photo (1) - Solder joints on my turnouts I consider to be acceptable:
Cheerio!
Bob Gilmore
