Um, no.
Because, physics. Its a combination of the two thermodynamic principles. Thermal mass and radiation. Pretty simple equations. I use Al chill blocks for TIG all the time. No "fins". I guarantee the heat sink in that photo is cold at the edges and 160F in the middle. Useless.
Screw your SSR to a beer can. I really don't care. I'm just pointing out facts, boss.
In the mean time one or two people will just keep whining about "fake chinese SSRs blowing up".
Ok, first my credentials. Before my retirement, I was a Senior Engineer at a major electronics manufacturing firm. My responsibilities were electronic packaging. Thermal management (getting rid of the heat generated by active components) is one of the major functions of, and concerns with, packaging electronics. I have some real expertise here.
Thermal flow systems are often modeled as electrical networks. In a steady state flow situation, the only components in the model that matter are the resistors. A thermal mass is modeled as a capacitor, the higher the thermal mas, the higher the capacitance. A capacitor can collect and store charge in a transient situation, but once it is charged to full capacity, then it cannot absorb any more charge. A thermal mass behaves the same way. It can absorb heat until it's temperature is the same as the source, and at that point it ceases to do anything, except hold the heat it already has. It's the resistors (thermal resistances) in the network that determine how fast the charge (heat) flows from one place to another. The faster the heat flows away from the source, the cooler the source stays. The capacitor (thermal mass) can increase the time it takes to reach equilibrium (and keep the source cooler until equilibrium is reached), but it cannot change the charge (temp) at equilibrium. Thus it is not thermal mass that is important for situations with continuous heat generation, but rather the rate at which heat can be removed once steady state is reached.
Radiation is one way that heat can be removed, and can be the dominating mechanism in some situations. With a finned heat sink, convection is most often the dominant mechanism for heat removal, especially so when a fan is used. Fins are used to improve heat transfer with convection, as they are almost useless for improving radiative heat transfer. (The physics of this is complex, so I won't go into it here.)
In OP's case, in the original configuration, the heat sink remained cool during operation, but after remounting a new SSR on the same heat sink, the heat sink now heats up during operation. This indicates that the problem was with heat flow from the SSR to the heat sink (the thermal interface between SSR and HS was the largest thermal resistance in the system.) I agree that the heat sink will be hotter at the source of the heat and cooler at the periphery, but then this will always be the case, no matter what the geometry of the heat sink.
As far a low quality SSR's, there are published teardowns of Fotek SSR's that found 10A TRIAC's inside a 25A rated SSR. The problem with some SSR's is real.
I see
@passedpawn types faster than I do. The thermal resistances he mentions are derived from the electrical models I discussed, and actual measurements of components under specific operating conditions.
Brew on