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KOA Corporation > Technology > Fundamental Technology

Fundamental Technology


Welded section of leaded
resistor’s lead wire and cap

We are employing technologies such as resistance welding and cold pressure welding for joining similar and dissimilar metals to make a variety of products.
There are joining technologies to weld the cap and the lead wire of leaded resistors and to weld printed terminations formed on the ceramic substrate and the lead wire.
And we also possess electrode formation technologies suited to wire-bonding and die-bonding.

Electrical discharge observed in sputtering
Functional Film Formation

Functional films including resistive film, sensor film, electrode and protective films are formed with film-forming methodologies such as screen printing, sputtering, CVD, non-electrolytic & electrolytic plating combined with our proprietary material blending ratios.
We are capable of forming nickel-chrome ultra-high-precision film and platinum film which is used in high-precision temperature sensors.

Product design

Thermal Design

When an electrical current flows, resistors generate heat.
For the use in high-temperature environment and when applying high power, the construction of the component has to be designed in consideration of heat resistance and heat dissipation properties, which we do by employing materials with high heat-resistance characteristics and establishing heat dissipation paths.
Also, we conduct simulations to analyze the heat generation under transient phenomena such as inrush current to design product construction in consideration of dynamic characteristics.

What is terminal part temperature regulation?
Microstructural design

In addition to designing microscopic patterns with photolithography technology, we also use high-precision screen printing to create fine patterns.
Additionally, we possess technologies for designing and fabricating multilayered structure of fine-line patterns within an LTCC substrate.
These technologies are also utilized in the manufacturing of 0201mm-size micro miniature chip resistors.


Package Design

For the purpose of properly protecting functional layers electrically, mechanically and environmentally, just like IC package, it is possible to encapsulate multiple elements in a package with the use of thermoset resin or thermoplastic resins.
Packaged products featuring metal terminals have the advantage of exhibiting high reliability characteristics under temperature cycle tests.

High-density Mounting

With the use of an LTCC substrate as an interposer or a package, elements developed by customers can be embedded within the substrate.
For the high-density placement of electronic components, we use highly integrated mounting package using glass-epoxy substrates, alumina substrates and LTCC substrates. As terminals, SOP, BGA and LGA are available. We also have the capability to downsize multi-chip modules (MCM).


Accelerated Tests

We are determining the life prediction of our products with the use of constant-temperature bath, constant-temperature constant-humidity bath, pressure cooker, thermal shock device, etc.
Also we possess the technology to predict with accelerated tests the changes in product characteristics under exposure to severe temperature and humidity conditions.
In addition, we possess unique knowhow for accelerated tests to evaluate anti-sulfur characteristics.

Observation of a cross section of
the interface between nickel
and copper layers after being cut
and processed with FIB
(Upper layer is copper.)
Chemical・Physical Analysis

To ensure compliance to the RoHS regulations, despite being an electronic components manufacturer, we have a testing and calibration laboratory accredited with ISO/IEC17025, which enable us to internally analyze RoHS 6 substances and issue certifications.
We possess a wide range of physical analysis devices such as FIB-SEM(*1), X-ray CT(*2) and ICP-AES(*3) to allow us to analyze characteristics of products and materials and conduct failure analysis.

*1 : This is a device to cut out a microscopic area then observe and analyze it.
*2 : This is a device to three-dimensionally observe the inside of a test specimen with an X-ray.
*3 : This is a device to measure infinitesimal amounts of element content inside of a test specimen.


Multi-cavity Structure/Dimensional Precision

Excellent shrinkage control in sintering process makes the creation of high-precision multistage cavities possible to realize sensor package and interposer.
To achieve even greater dimensional precision, polishing of the top and end surfaces are the options we can offer.


Thermal fluid produced by
multiple leaded resistors
Heat Conduction/Fluid

With electronic component mounting shifting from through-hole to surface mount, in relation to heat dissipation, the transmission of heat from the component to circuit board is more dominant than from the component to ambient air.
Accordingly, thermal design to electronic components on the PCB is critical. KOA is verifying the temperature rise by performing simulations on thermal conduction and thermal fluid.

Stress distribution in a chip resistor
mounted on a circuit board

To meet long-term reliability requirements in temperature cycle tests, structural design for electronic component in consideration of that differences thermal expansion ratio of materials that comprise an electronic component is necessary.
Also termination design that takes into account electronic components and printed circuit board having different thermal expansion coefficients is necessary.
KOA is designing its products by performing simulations to alleviate the stress generated in electronic components.


1005mm chip resistor and thermocouple
Temperature Measurement

For temperature measurement, there are contact methods like thermocouple and non-contact methods like thermography to discern in-plate temperature distribution. To correctly measure the temperature of a small area, optimization of wire diameter of thermocouple and lens resolution of thermography is necessary. KOA has accumulated a variety of know-how for temperature measurement.

Resistance Measurement

For measuring resistance values, 2-terminal and 4-terminal methods are well-known. But for the measurement of ultra-low-value, ultra-high-value and miniature resistors, insulation properties of terminal cable, the layout of measuring terminals, and measuring environment (e.g. humidity and noise) greatly influence the results.
We have the capability to establish a system of precisely measuring resistance values suited to each product.


Green sheet, which is the base material
for LTCC substrate
Materials Formulation

We are capable of designing materials that enable resistors to deliver prescribed ohmic values, temperature coefficient of resistance, and durability and environmental characteristics.
Our proprietary materials technologies allow our LTCC substrates to achieve high dimensional precision.

Material development

Resistive materials developed in-house realize current-sense resistors with low temperature coefficient of resistance and temperature sensors and resistors with superior anti-surge properties.
Our materials developed in-house make possible varistors high in Maximum energy and low in leakage current.