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EPTE Newsletter: Flexible Metal Laminates Made With Chemical Processes

DKN Research is fielding many inquiries about a semi-additive process for the fine-line generation on thin, flexible substrates, including transparent heat-resistant plastic films. Most inquiries are from chip-on-film (COF) manufacturers with reel-to-reel (RTR) processes. They are extremely interested because the new chemical process can be a practical solution for the next generation of high-density substrates with microvia holes.

A few COF substrate manufacturers have been successful in generating traces smaller than 20 microns using a semi-additive process with via holes smaller than 20 microns in prototype production. However, there are a few hurdles to overcome before actual volume production is realized. The most critical issue is creating reliable bond strength between plastic films and metallic seed layers without glue.

The new chemicals developed for this improved semi-additive process have made progress with the bond strength for the thin seed layer on substrate films. However, circuit manufacturers need to manage many critical areas to have stable bond strength, including molecular structures of the base films, surface conditions of the substrates, surface cleaning, supplemental surface activation, hole quality during laser processing, plating bath conditioning, post baking, and more.

Surprisingly, it is our experience that surface conditions from substrates sometimes fluctuate significantly. Unfortunately, film manufacturers often choose to ignore the surface qualities of the films; they think nothing can change since the plastic films are produced using the same compounds and process conditions. The surface qualities on the plastic films will change drastically when stored, transported, or due to other circumstances. Most film manufacturers are not capable of managing surface quality.

Circuit manufacturers have two choices to use the semi-additive process for high-density flexible circuits with microvia holes. The first is to develop the entire process on their own; however, it is very difficult to create base films. They must purchase films from outside vendors before moving forward and processing on their own.

Manufacturers have to establish electroless plating to form thin seed layers on base films—a monumental task that requires a huge investment and team of engineers. Since this takes lots of time and money, the second choice for manufacturers is to use the semi-additive process for high-density flexible circuits with microvia holes to purchase metallized laminates from outside vendors. This will eliminate the complicated electroless metallization process and huge investment. Manufacturers can focus on circuit building without the need for a special process other than a standard circuit manufacturing processes.

There are a limited number of capable laminate suppliers in the industry, among them DKN Research. Their manufacturing capacity is limited, but the processes are very flexible when selecting base films and conductors. Traditional polyimide films are certainly available as well as transparent polyimide films with shiny surfaces. Special films, such as PEEK, COP, PEN, LCP, PVDF, and PET are also available.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  Headlines

1. Tohoku University (Japan) 7/13
Developed a new heat-resistant molybdenum alloy as the basic material of pressing dies. It keeps the mechanical strength up to 1600°C.
 
2. Panasonic (Major electronics company in Japan) 7/17
Agreed to do a new project with Sekisui Resin, major plastic device supplier, to develop unit-heat wave systems.
 
3. Taiyo Yuden (Major component manufacturer in Japan) 7/17
Rolled out a new metallic-base chip-type power inductor series—MCOIL (2.0 x 1.6 x 1.00 mm).
 
4. Miyazaki University (Japan) 7/19
Successful field test of a hydrogen generation plant utilizing solar power. The test recorded the highest conversion rate of 18.8%.
 
5. Toshiba (Major electric & electronics company in Japan) 7/20
Co-developed the world’s largest capacity flash memory—BiCS FLASH (2.66 TB)—with Western Digital, using a 96-layer process.
 
6. Ricoh (Major electronics company in Japan) 7/23
Co-developed a new stereo camera module that detects surface conditions of streets for auto-drive systems with auto-module manufacturer Denso.
 
7. USHIO (Major lighting equipment manufacturer in Japan) 7/23
Commercialized a new UV-LED dryer module—Unijet A1220—as the dryer of offset printing lines.
 
8. Oki Electric (Major electronics company in Japan) 7/23
Commercialized a new optical fiber sensor system—WX-1033A/BJ—that detects temperature and distortion by remote control.
 
9. AGC (Major glass material supplier in Japan) 7/26
Agreed to acquire the electronic material division of Park Electrochemical for 16 billion yen.
 
10. Murata (Major electronic module manufacturer in Japan) 7/31
Developed a new detection system for road surface conditions. Several different types of sensors detect street defects.

Dominique Numakura is the managing director of DKN Research LLC. To read past columns or contact him, click here. Contact haverhill@dknreseach.com for further information and news.