What causes tantalum capacitors to fail？

What causes tantalum capacitors to fail

 

Tantalum capacitors are high-performance electrolytic devices. They are more expensive than aluminum electrolytic capacitors but offer the unparalleled advantages, such as compact sizes, durable quality, and stable parameters. They do have some disadvantages, such as relatively low capacitance and low voltage ratings, but those are still sufficient for low voltage and low power applications. Tantalum capacitors generally don’t have the problem of being dry-out or dielectric degradation that often occurs if the capacitors are stored discharged for long time.

 

Known with many advantages, tantalum capacitors have been widely used by many customers. In the applications, we often encounter tantalum capacitor explosion problems, especially in switching power supplies, LED power supplies and other industries. The burning or explosion of tantalum capacitors is the biggest headache for R & D engineers and makes them puzzled sometimes. Because of the danger of the failure mode of tantalum capacitors, many R & D technicians dare not use tantalum capacitors.

 

In fact, if we can fully understand the characteristics of tantalum capacitors, find the reason for the failure of tantalum capacitors (in the form of burnout or explosion). Tantalum capacitors are not so terrible for any applications. After all, the benefits of tantalum capacitors are obvious.

 

The specifications of the tantalum capacitors are required to meet the circuit design requirements. However, we often cannot guarantee that the capacitor specifications and circuit requirements, such as signal characteristics match each other very well. Therefore, sometimes, compromise may be made unintentionally in the completion of design and failures will inevitably occur during use. We now briefly discuss what the main causes of tantalum capacitor failures are.

 

The leakage current of the tantalum capacitor is too large, resulting in insufficient withstand voltage.

 

This problem is generally caused by the fact that the actual rated voltage of the tantalum capacitor is not large enough. When certain field strength is applied to the capacitor for a long time, if the insulation resistance of its dielectric layer is low, the actual leakage current of the product will be large at this time. For products with high current, the actual withstand voltage will drop.

 

Another reason for this problem is that the leakage current standards for tantalum capacitors are too loose resulting in some companies that do not have the capacity to produce high quality tantalum electrolytic capacitors produce low-quality tantalum capacitors. The leakage current is relatively large at normal room temperature. If the product works at a higher temperature, the leakage current will increase exponentially, so the actual withstand voltage at high temperature will drop significantly, a process called thermal derating. When the temperature is high, it will be very easy to break down.

 

To have a small leakage current at high temperatures is one of the most important goals of all capacitor manufacturers, so the decisive impact of this indicator on reliability is self-evident.

 

If the leakage current of the tantalum capacitor you choose to use is too large, we must not use it in the design, if it’s used for any reason, this problem become inevitable. The leakage current is also dependent o the applied voltage. When the applied voltage is lower than the rated voltage, the leakage current drops rapidly. Therefore, the effect of voltage derating is also applicable to the leakage current as shown below

 

Failure caused by production and assembly

 

Many users often only pay attention to the tantalum capacitor selection and design of the product, but ignore the problems that are likely to already occur when installing and assembling chip tantalum capacitors; examples are as follows.

 

Hand soldering is used instead of automatic SMD processing, the product is not preheated, and an electric soldering iron with a temperature higher than 300 degrees is used to heat the capacitor for a long time, resulting in the capacitor performance being degraded due to excessive thermal shock.

 

When soldering in manual mode, does not employ the preheating phase. When soldering the tantalum capacitor, excessively repeated heating was applied to remove cold joints.

 

The temperature of the soldering iron tip is set to 500 degrees or higher. This can solder components quickly, but it is very easy to cause the chip component to fail prematurely.

 

Tantalum capacitors soldering profile

 

 

UF Capacitors offer many types of tantalum capacitors:

 

CA45 chip tantalum capacitors

CA55 polymer tantalum capacitors

CA45U low esr tantalum capacitors

 

 

E PRICE TAG (ESL) application,100UF 6.3V A Case

 

Follow up AVX, we are the second factory who can produce 100uf 6.3V in A case. Standard and common one is B case. A case have technology difficulty, but we managed it years ago.

During the past years, we supply to E price tag customers, we supply them 100uf 6.3V A case and B case both. Huge quantity.

 

 

Common items listed follow:

 

CA45T105K0035000AR000 Cross to AVX  TAJA105K350RNJ

CA45T106K0010000AR000 Cross to AVX  TAJA106K100RNJ

CA45T225K0025000BR000 Cross to AVX  TAJB225K250RNJ

CA45T107K0010000CR000 Cross to AVX  TAJC107K100RNJ

CA45T105K0016000CR000 Cross to AVX  TAJC105K016RNJ

CA45T335K0016000AR000 Cross to AVX  TAJA335K016RNJ

CA45T475K0010000AR000 Cross to AVX  TAJA475K010RNJ

CA45T226K0016000CR000  Cross to  KEMET T491C226K016AT

CA45T476K0035000ER000  Cross to  KEMET T491X476K035AT

CA45T107K0016000CR000  Cross to  KEMET T491C107K016AT.

CA45T106K0016000AR000  Cross to  KEMET T491A106K016AT

CA45T105K000A0035R0000 Cross to  KEMET T491A105K035AT

CA45T476K0010000BR000  Cross to  KEMET T491B476K010AT

CA45T474M000A0035R000  Cross to  KEMET T491A474M035AT

 

TANTALUM CROSS reference.

 

Tantalum Capacitor Cross Reference
Photo	Description	UF Capacitors Series Code	AVX	Kemet	Vishay	Panasonic
	Polymer TantalumCapacitors	CA55 Series	TCJ Series	T1520 Series T1521 Series	T55 Series	TOC Series TPB Series TPF Series TPG Series
	antalum Chip Capacitors. General PurposeA,B,C,D,E Case	CA45 Series	TAJ Series F913 Series TLJ Series	T491 Series T490 Series T1489 Series	293D Series	TE Series ECST Series
	LOW ESR Chip Tantalum Capacitors,A.B,C,D,E Case	CA45U Series	TPS Series F93 Series	T1494 Series T1495 Series	593D Series 594D Series IR3 Series	TEL Series
	Radial Epoxy Dippedantalum Capacitor	CA42 Series	TAP Series	T1350-T7390Series	199D Series 489D Series ETPW Series ETQW Series	ECSF Series