Energy Biking vs. Energy Biking

– Commercial –

For an influence electronics system that’s to serve an software within the 2 MW vary, the query arose as to which know-how needs to be used and what service life would outcome.

The out there alternate options had been traditional semiconductor modules, constructed utilizing solder-bond know-how, and disc cells with the identical energy score in press pack housings. Examples are displayed in Figures 1 and a pair of.

The anticipated service life is set, amongst different issues, by energy biking (PC). Present adjustments within the semiconductors trigger temperature deviations within the assembly- and connection-technology. Thermal swings within the time vary of some seconds initially trigger microscopically small actions of the bonding wires because of thermal enlargement. In the long run, these result in defects such because the bond connection lifting off or the bond wires breaking on the fastening level.

– Commercial –

Disk cells are constructed with out bonding wires and large-area solder connections are additionally absent on this know-how. The expectation is due to this fact that these elements permit a considerably increased variety of cycles than assemblies with a solder-bond construction.

Nonetheless, the comparability of the corresponding curves in Figures 3 and 4 initially seems to refute this.

Trying on the variety of cycles to be taken from the diagrams for a temperature vary of 80 Ok, it reveals that the disk cell solely survives 30,000 cycles, whereas the solder-bond module survives many occasions that quantity at 200,000 cycles.

Expertise exhibits that this doesn’t occur. There are programs outfitted with disk cell thyristors which were working for many years with out failure.

Why don’t these curves mirror this?

Solely at first look do they not. In case you delve deeper into the topic, additionally, you will discover the boundary situations below which such checks are carried out.

Energy biking for solder-bond modules will be achieved by making use of a pulse of 1.5 seconds period. The small thermal capacities of the bond wires are thus served, and the specified temperature is reached on the precise chip. After the present is switched off, the semiconductor cools down once more to the preliminary worth inside an additional 1.5 seconds. A single cycle due to this fact solely takes three seconds.

The thermal capability of disk cells is given by the stable metallic plates with which they’re contacted. These copper disks, which regularly weigh a number of hundred grams, hardly warmth up in any respect inside seconds.

A typical cycle that heats the semiconductor to the specified temperature requires a switch-on time of three minutes, with cooling taking an additional two minutes. The complete cycle due to this fact takes 5 minutes.

100,000 cycles at 80 Ok swing with the solder-bond method due to this fact lead to an working or check period of 300,000 seconds, which corresponds to 83 hours or simply over three days.

In distinction, 100,000 cycles of 5 minutes every with disk cells symbolize 347 days of operation or testing.

One other element is that the curve for disk cells exhibits “check to go”. It is a routine check that ensures that the elements meet this minimal requirement. It doesn’t point out that an finish of life has been reached and 100% of all disk cells obtain this outcome.

In distinction, the PC curve for solder-bond modules exhibits “check to fail”, which means that this know-how has reached the top of its life at this variety of cycles. On this case, the result’s restricted to 95% of the examined elements in accordance with the usual specs. A 100% curve is normally one magnitude under the curve for the top of life.

The PC curve for disk cells due to this fact makes an especially conservative assertion.

So why don’t producers additionally provide a “check to fail” curve for disk cells?

It’s identified from expertise that disk cells hardly undergo from energy biking and don’t fail within the discipline because of this load. The “check to go” curve is due to this fact actually no less than 2 magnitudes decrease than the “check to fail” curve.

If the cells don’t stand up to 2000 cycles within the check even at temperature swings of 160 Ok however – two magnitudes increased – slightly 200,000 cycles, this ends in a check period of 1 million minutes – or nearly 700 days. Since no less than two or three measuring factors are required for a curve, further checks could be essential at temperature swings of 60 Ok and 100 Ok.

For a 60 Ok swing, the curve already exhibits 100,000 cycles. Only one decade extra would imply a million cycles, 5 million minutes or nearly 10 years within the check.

As well as, no less than 1.5 kW of energy is required for every cell in these checks, which quantities to a check energy of a minimum of 30 kW.

However, checks had been initiated at excessive temperatures so as to attain the precise finish of life, however this highlighted one other problem.

The failure within the check didn’t have an effect on the disc machine – the check gear itself failed because of energy biking lengthy earlier than the units examined confirmed any injury.

What does this imply for the design?

In energy electronics, energy biking is especially thought-about in reference to failures of bond connections. This failure mechanism doesn’t exist in disk cells. As well as, the massive thermal capacities of the disk cell imply that the semiconductor heats up a lot slower, and the double-sided cooling additionally reduces the temperature swing for a similar energy.

Together, the relieving results imply that the traditional “energy biking” failure mechanism has no life-limiting affect on disk units. That is additionally one of many the reason why this design is utilized in railroad functions, marine propulsion programs and electrolysis vegetation, the place an working lifetime of as much as 160,000 working hours in 20 years is anticipated.

Creator: Dr. Martin Schulz, World Principal Software Engineer, Littelfuse

Dr. Martin Schulz joined Littelfuse in February 2021 as World Principal in Software Engineering. He’s chargeable for energy semiconductors for electrical business automobiles, charging infrastructure, power storage programs and industrial drive know-how. He’s an skilled in packaging and interconnect know-how in energy semiconductors in addition to in thermal administration of energy semiconductors. Martin Schulz has greater than 20 years of expertise within the discipline of energy electronics and is a Senior IEEE-Member.