Solder paste for IMS boards

Hi,
Using IMS (aluminium) PCB’s is new to me and we found that if our cooling fails at any point, some SMD components will basically desolder themselves and fall off. Do you have a recommendation for a higher temperature solder paste that can solve this problem?

J

Hello Jensa,
Thank you for your inquiry. The information provided is not searchable parameters. Your link to Euro has a contact tab and would be the best source for information also they have PCB assembly guidelines to offer.

The linked resource indicates use of a lead-free solder process having a melting point in 220°C territory. While there are higher-temperature solder materials available, the PCB material and the components on it have temperature limitations, both in regard to normal operating conditions and during assembly.

The typical solution to this issue is to build in over-temperature shut down protections, since components that are getting hot enough to de-solder themselves generally get damaged or degraded in the process. When a cooling failure occurs, the cooled devices will increase in temperature until a new thermal equilibrium is reached, power is disconnected, or something breaks. Failure is failure whether the parts fall off the board or the magic smoke comes out.

Obviously, but the whole intent of this board is to be a LED lighting board that connects straight to 24V/GND. It’s just high power LEDs in series and a matching high power resistor on a board.

I could obviously make this much more complicated, but the whole idea is to not introduce anything that uses lots of power with PWM that can produce ripple on the PSU. I just want something that pulls a steady current and a side-effect of that is that it gets hot. I’ll just heatsink the board to the physical machine then.

The added complexity of switch mode regulation over one single resistor is certainly real, but the benefits in terms of reduced power consumption, ease of thermal management usually also cost are substantial. Ripple in load current drawn is also a real thing, but it can be dealt with and in many instances is not as major an issue as some might expect.

If you’re just looking at in-case-of-fan-failure sort of situations, a bimetallic thermostat might be a suitable protection mechanism with a similar benefit of simplicity.

1 Like