Experiment § Variables affecting chain length
1. Light source wavelength: If the correct light source wavelength is not given, the reflected cross-linking structure characteristics may be poor.
2. Selection of initiator: The selection of initiator must be able to match the light source so that it can be optimized. The absorption wavelengths of the two should be matched to achieve the best cross-linked polymer.
3. Whether the light energy is sufficient: It depends on the formula. If the light energy of the high functional group is insufficient, the properties of the colloid are good. If the formula is low and has low cross-linking, it may be necessary to give enough energy to have a higher reaction rate.
4. Whether the amount of the initiator is too much or not enough: Generally speaking, the greater the concentration of the photoinitiator, the smaller the light penetration thickness. The smaller the photoinitiator concentration, the greater the light penetration thickness. For a thick coating, a lower concentration of photoinitiators should be added if the underlying layer has enough light to polymerize.
5. The structure and ratio of formulation oligomer and monomer: The secret of UV glue formulation lies in how to formulate a set of optimal formulation ratios for oligomer, monomer, and starter. If you have all the keys, it is not difficult to develop high-quality glue.
6. Coating thickness and oxygen influence: Oxygen molecules in the air have a hindering effect on the polymerization reaction that cannot be ignored (please refer to the previous bi-weekly report data). This hindering effect is most pronounced at the position (usually the surface) where the resin is in contact with the air. The slightest case is that the reaction rate of the resin surface is slightly lower and the scratch resistance is poor. Seriously, the surface will feel oily and sticky to the touch. When the coating film is very thin, there are even cases where it cannot be cured at all.
─Author: Ms. Miao-Ling, Lin R&D Engineer, Everwide Chemical
Product introduction § Packaging application materials for COB industry
COB-Chip on Board, the chip is directly planted on the circuit board, is a way of integrated circuit packaging. The COB method is to directly stick the bare chip on the circuit board or substrate, and combine three basic processes: (1) chip attach. (2) Wire connection. (3) Using packaging technology, the packaging and testing steps in the IC manufacturing process are effectively transferred to the circuit board assembly stage. At present, the IC semiconductor chip packaging process mostly uses transfer molding compounds. As a packaging material, a specific mold is used to preheat the glue material and inject it into the mold containing the IC chip lead frame to achieve the purpose of packaging. However, with the development trend of thinning, high pin count, and modularization of semiconductor chips, especially in recent years, in addition to the original Hybrid component packaging applications, the development of COB, TAB, PBGA, and Flip Chip packaging technologies have gradually adopted the liquid state, the liquid encapsulant is injected into the semiconductor chip through the dispenser to achieve the protection function. 1. Glob Top: ①Low temperature curing, 80℃/30min or 120℃/10min. ②Good formability. ③Good adhesion to FR4, FR5, BT, FPC, and can reach the breaking strength of the substrate. ④High surface flatness. ⑤ Pass the reliability test, cold and heat cycle, cold and heat shock, high temperature and high humidity, high-temperature cooking, etc. Recommended products: JB397, JB408. 2. Dam & Fill: ①Low temperature curing, 120℃/45min. ②Dam glue has good compatibility with Fill glue. ③Good adhesion to FR4, FR5, BT, FPC, and can reach the breaking strength of the substrate. ④Good workability. ⑤ Pass the reliability test, cold and heat cycle, cold and heat shock, high temperature and high humidity, high-temperature cooking, etc. Recommended products: JB206, JB207. 3. Encapsulate by Printing: ①Low temperature curing, 130℃/45min. ②Good printability. ③Good adhesion to FR4, FR5, BT, FPC, and can reach the breaking strength of the substrate. ④ Good formability. ⑤ Pass the reliability test, cold and heat cycle, cold and heat shock, high temperature and high humidity, high-temperature cooking, etc. Recommended products: FE128, JB430.
For related product information, please visit the official website of Everwide Chemical: http://www.everwide.com.tw/manuals/dm/cob.pdf
Knowledge § What should be paid attention to in the packaging of UV glue?
1. Store in a place away from sunlight. 2. Store in a cool and ventilated place. 3. Do not arbitrarily change the resin packaging. 4. Select the appropriate resin container when sub-packaging. (For example PE, PP plastic drums, stainless steel drums, resin-coated carbon steel drums, or glassware.) 5. Avoid contact with metals such as copper, iron, etc., which will cause polymerization. 6. Do not vacuum the resin. 7. Do not fill the resin package with nitrogen or non-oxygen gas. 8. Do not fill the container with resin. Space must be reserved in the vessel to provide the oxygen necessary to inhibit the reaction.
Living § Overtime
The position of the pilot has the concept of "flying hours". Those who fly for more than a few hours can serve as the main pilot, and those who have less than a few hours can only serve as the co-pilot. In other words, pilots distinguish the qualifications of pilots and co-pilots by the number of hours they actually operate, not simply by age and seniority. The aviation industry looks at the qualifications of pilots with the concept of "flying hours". I guess it is because flying attaches great importance to the experience accumulated during the operation process. This kind of experience cannot be obtained by taking classes, reciting knowledge, or taking exams. Yes! When we encounter various conditions such as wind and rain, turbulence, take-off, and landing, etc. during the flight, and our attitudes and emotions in the face of these conditions, how can we replace personal experience with abstract teaching? The same is true for R&D work, which is not just for those who are familiar with the theory. There are many variables in the success or failure of development work, such as the mastery of materials, the use of instruments, the cooperation of customers, time constraints, the efforts of R&D personnel, etc. There are many situations to be considered. Since the variables are many and complex, the most efficient approach is to accumulate cases. Only through a lot of experiments can we train solid R&D engineers. Then again, how long does it take to complete a large number of experiments? It may take three or five years to slowly build up meaningful R&D capabilities. If I can face it positively, other people work eight hours a day, and if I spend an extra two or three hours on it, I may have basic research and development capabilities in about two years. For individuals, the rapid accumulation of skills is the greatest guarantee of a career. Because there are unpredictable circumstances, not everyone can spend three or five years smoothly. When some factors (such as family, economy, accidents, etc.) occur, we will lose the opportunity to accumulate professional skills. From these perspectives, I encourage everyone to work overtime as an opportunity to gain experience and improve their strengths.
─Author: Dr. Ming-Xu Li, Everwide Chemical
