News Releases

The Showa Denko Group Develops New Grade of Solder Resist
—Insulating ink with high tolerance to bending improves LCDs’ performance—

Showa Denko K.K.
January 8, 2016

Showa Denko K.K. (SDK) (TOKYO: 4004) and its subsidiary Nippon Polytech Corporation have jointly developed a new grade product of solder resist to be used for manufacturing of Chip on Film* (COF) circuits. Compared with our conventional grade product “NPRTM-3400,” the new grade product has 2.5 times of tolerance to bending, and protects finer patterns, while maintaining excellent levels of withstanding voltage, thermal resistance and moisture resistance.

Solder resists are insulating inks applicable to circuit boards and films, and protect electric circuits from extraneous materials and moisture. LCDs with frameless structure are increasing their share among flat screen TVs, PCs and smartphones, because the progress in definition of images increases the demand for larger displays with more flexible designs including less oppressive one. Our conventional solder resist “NPRTM-3400” has already secured 50% share of the global market for solder resists applied to COF circuits in LCDs, due to its reliable electric properties including applicability to fine circuit patterns with pitch of 20 to 30µm, and competent tolerance to bending.

Recently, LCDs are getting larger and required to raise picture quality. On the other hand, wearable devices are getting smaller and required to have flexibility. Thus the contents of needs for LCD’s are more and more diversified, and circuit boards and films for these LCDs are required to have less thickness and finer pitches. The new grade product of solder resist we developed this time has so much improved tenacity and flexibility that it can protect circuits with wiring pitch of 20µm or less, and maintains its insulating property even after repeated bending.

The Showa Denko Group aims to make the most of its knowledge and know-how about designing and synthesizing resins including solder resists we cultivated over many years, and contribute to further improvement of properties and performance of electronic devices through fulfillment of the needs of our customers in electronics.

The Showa Denko Group will exhibit the solder resist we announced this time at the “45th INTERNEPCON JAPAN,” a world’s leading surface mount technology (SMT) exhibition gathering equipment, solutions and services for electronics manufacturing, to be held from January 13 to 15, 2016 at Tokyo Big Sight (SDK’s booth: E43-46, East Hall 5).

  • *Chip on Film (COF): A type of integrated circuit product that has semiconductor chips and circuits directly mounted on polyimide resin films )

[Outline of Nippon Polytech Corporation]

Head office  :370-1 Nibukata-machi, Hachioji City, Tokyo 193-0822 Japan
Establishment  :July 1989 
Scope of business  :Development, manufacturing and sale of resist ink for flexible electronic circuit boards and films 
Capital stock  :10 million yen
Shareholder  :Showa Denko K.K. (100%)

[Results of tests]

1)Evaluation of electricity insulation property through high temperature and high humidity bias test (HHBT)
Conditions: Temperature: 85℃ Humidity: 85%
Continuously load 60V of direct current on electronic circuit board equipped with 16µm pitch circuit coated with each sample of solder resist. Measure changes in insulation resistances of each sample. (We prepared and tested three samples for each of SDK Group’s product and other manufacturer’s product.)

Evaluation of electricity insulation property

2)Evaluation of fatigue durability and tenacity through twist test
Connect glass panel and glass-epoxy based circuit board equipped with 25µm pitch circuit coated with each sample of solder resist. Swing it right and left at 60 cycles per second, for the amplitude of 1mm, and measure how many cycles it will take to see circuit disconnection.

Cycles of bending

3)Evaluation of thermal resistance and moisture resistance through pressure cooker test (PCT)
Conditions: Temperature: 121℃, Pressure inside the cooker: Twice atmospheric pressure
Expose each sample of solder resist to the conditions above for 168 hours.

SDK Thermal resistance and moisture resistance that last longer than ever

Thermal resistance and moisture resistance that last longer than eve



◆  Customer contact: Sales Department, Nippon Polytech Corporation (Phone: 81-42-652-0126)
◆  Media contact: Public Relations Office, Showa Denko K.K. (Phone: 81-3-5470-3235)

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