As a new-type foreign trade service provider driven by dual engines of technology commercialization and foreign trade services, HiSiaddi has established a "1+2+3+4=1" service system and can supply polyimide products from multiple well-known original manufacturers.
As a foreign trader with R&D capabilities, HiSiaddi has repeatedly put forward polyimide product formula optimization schemes and application improvement suggestions through technological transformation cooperation with factories and accurate insight into market needs. Below is a consulting case of polyimide product formula optimization by HiSiaddi.
Please contact HiSiaddi customer service if you need more formula optimization consulting services.
The cooperating buyer is Nexsem Co., Ltd., a listed semiconductor packaging specialized enterprise headquartered in Seoul, South Korea. With over 20 years of experience in high-end Chiplet chip packaging and power semiconductor IGBT wafer passivation, it acts as a secondary core raw material supplier for LG Semiconductor and Hyundai Semiconductor of South Korea. Its products support wafer processes for automotive power chips and computing AI chips, placing it in the mid-to-high-end premium customer tier for global semiconductor PI material procurement. It has long placed fixed orders for semiconductor-specific photosensitive polyimide (PSPI) and low-CTE copper-clad substrate PI from Kaneka Corporation and Ube Industries of Japan, and never purchases low-grade electrical insulation PI or general civil thin films. Procurement standards align with military-grade control specifications adopted by leading Japanese and Korean PI manufacturers.
In H2 2024, impacted by multiple supply chain disruptions including price limits on Japanese and Korean chemical raw materials, extended customized R&D lead times of top PI manufacturers, and refusal to separately develop modified formulas for small batches, the enterprise’s R&D director visited China via the South Korean Industrial Chemical Materials Association for resource matching, establishing formal cooperation with HiSiaddi New Materials Foreign Trade based in Shanghai. The initial demand covered two customized high-end products: photosensitive polyimide resin stock solution for wafer passivation and low-CTE ultra-thin copper-clad PI substrate films, with a total trial order volume of 850 kg. All products must pass four stringent tests at the customer’s domestic laboratory: thermal cycling, etching resistance, ion impurity content, and dielectric performance, meeting the AEC-Q102 automotive electronic certification standard for vehicle chips.
Initially, the customer placed orders following mature parameters from Japanese raw material suppliers based on past procurement experience. However, after the first batch of samples was delivered to South Korea and put into mass production, three linked technical failures emerged covering formula incompatibility, film-forming processes, and post-chip packaging processes, forcing the customer’s mass production line to suspend debugging and facing compensation risks for delayed upstream chip orders. The customer fully entrusted HiSiaddi to form an expert technical team to decompose problems item by item from three dimensions: molecular formula optimization, production process rectification, and end terminal process adaptation, ultimately completing full-chain technical implementation and product finalization.
Initially following general parameter standards of Japanese PI raw materials and specifying the traditional binary copolymer BPDA-PDA base formula, HiSiaddi completed small-scale trial production of samples accordingly. During 260℃ lead-free reflow soldering thermal shock testing at the South Korean customer’s facility, mass failures occurred: First, the linear CTE of PI substrates measured 57.2 ppm/K, far exceeding the mandatory customer requirement of ≤22 ppm/K. Wafer substrates warped under alternating cold and hot conditions, dropping the 12-inch wafer packaging yield from an expected 98% to 61.3%, with massive BGA solder joints suffering cold solder joints and detachment scrappage. Second, semiconductor-grade PI imposes strict control over metal ion content. Residual sodium and potassium ions measured 12.8 ppm in conventional raw materials, exceeding the 1 ppm access threshold. Under high-temperature electrification conditions, internal chip electromigration and leakage easily occur, failing the BT stress aging reliability test at South Korea’s automotive chip laboratory. This constitutes one of the core technical barriers that long enabled Japanese and Korean high-end PI manufacturers to monopolize the semiconductor market.
The customer’s R&D team initially attributed failures to insufficient basic synthesis processes of domestic raw materials and suspected substandard monomer purity in domestic supplies, even proposing to terminate sample cooperation and fully switch back to Japanese original manufacturers.
The customer customized ultra-thin copper-clad PI films with a thickness requirement of 12μm±0.5μm. When HiSiaddi adopted parameter standards for general electrical PI casting production lines for initial mass production, two fatal mass production defects appeared on finished products: First, unilateral film warpage exceeded 0.7 mm per 100 mm after winding and high-temperature imidization curing. After copper cladding and lamination for circuit board production, partial separation and bubbling occurred between copper foil and PI substrates, making it impossible to produce fine circuits with a 0.3 mm pitch. Second, micron-scale pinholes (3–12 μm in diameter) randomly distributed on film surfaces. During wafer passivation coating, etching liquid corroded underlying chip aluminum wiring through pinholes, causing functional chip scrappage, with the scrappage rate exceeding 42% for a single batch of 320 ㎡ films.
Root causes included insufficient molecular chain rigidity of the base formula, accumulating residual internal stress from inconsistent cooling shrinkage rates between surface and bottom layers during curing; additionally, the oven segmented temperature rise curve of domestic production lines followed standards for general materials, with excessively fast temperature increases during high-temperature imidization leading to instantaneous massive solvent volatilization and internal voids plus surface pinholes – a dual mismatch between formula and production processes.
For liquid photosensitive PSPI resin used in wafer passivation, the customer adopted self-developed wafer coating and UV exposure production lines. After initial delivery of HiSiaddi resin for on-machine testing, process failures occurred: under identical exposure power and duration, partial incomplete exposure of PI photoresist left residual PI film lining micropores after development, blocking wafer passivation openings and resulting in open circuits during subsequent electroplating processes. Adjusting exposure parameters led to over-sensitization of non-exposed regions and jagged circuit edges, failing to meet the precision wafer opening tolerance requirement of ±3 μm.
The customer’s original supporting Japanese PSPI adopted fluorine-containing monomer modified formulas with trifluoromethyl groups grafted on molecular side chains to regulate photosensitive group distribution. The initial sample formula omitted fine-tuning of photosensitive monomer proportions, resulting in an excessively wide molecular weight distribution of resin polymerization ranging from 12,000 to 41,000, with uneven distribution of photosensitive groups on molecular chains, directly triggering malfunctions in exposure and development processes. The customer’s packaging production line was forced to suspend small-batch mass production of this chip model, mounting economic losses and risks of order fulfillment delays.
All three challenges are exclusive technical issues of high-end semiconductor PI, distinct from low-grade insulating PI that only needs to meet basic temperature resistance and insulation indicators. They involve interdisciplinary technologies covering molecular synthesis, precision film formation, and semiconductor microfabrication, representing the most common delivery bottlenecks for overseas mid-to-high-end customers switching to domestic PI procurement.
Led by HiSiaddi’s foreign trade team and in collaboration with cooperative polymer laboratories and PI synthesis R&D engineers, online technical seminars were held synchronously with the customer’s South Korean R&D department to dissect shortcomings of the original binary formula, implementing targeted molecular design improvements for the two product lines separately: First, for low-CTE copper-clad PI films: abandoning the single BPDA-PDA binary system, a ternary copolymerization modification scheme combining rigid dianhydride BPDA, semi-alicyclic diamine, and a small proportion of fluorine-containing TFMB monomers was adopted. Introducing rigid cyclic structures into the molecular main chain enhanced chain packing density, while a small volume of fluorine-containing side chains optimized molecular chain free volume. After verification via 17 groups of small-scale trials, the optimal mass ratio of monomers BPDA: semi-alicyclic diamine: TFMB was confirmed as 68:24:8. After modification, the CTE of PI films stabilized between 18.6 ppm/K and 21.3 ppm/K, fully complying with the customer’s mandatory standard of ≤22 ppm/K. Meanwhile, electronic-grade high-purity monomers (monomer purity ≥99.95%) were adopted during polyamic acid (PAA) synthesis, with fully stainless steel sealed reaction kettles and deionized ultrapure water feeding throughout synthesis. Three rounds of precision ion extraction and purification procedures were added post-synthesis, controlling the total Na⁺ and K⁺ ion content of finished products at 0.62 ppm, below the customer’s 1 ppm red line standard and enabling smooth passage of South Korea’s BT aging reliability testing.
Second, for photosensitive PSPI passivation stock solution: the feeding ratio of dianhydride and photosensitive diamine polymerization was adjusted, and polymerization reaction temperature and holding time were precisely regulated to lock the resin weight-average molecular weight within a narrow distribution of 24,000 to 28,000, reducing the proportion of macromolecular and small-molecule impurities. Trace modified fluorine-containing photosensitive additives were incorporated into the resin system to uniformly disperse photosensitive side groups and balance UV exposure sensitivity, resolving incomplete exposure and development residue issues. Five rounds of gradient formula samples were sent to South Korea successively, each accompanied by domestic third-party SGS physical and chemical test reports, cooperating with the customer’s laboratory for itemized thermal shock and photolithography process testing, with the final finalized formula confirmed after 42 days.
After formula finalization, HiSiaddi dispatched process engineers to station at cooperative manufacturing plants and rectify the entire casting and imidization production lines targeting ultra-thin PI film forming defects: First, optimize the casting coating process: lower slurry solid content from 18.5% to 15.8% to enhance slurry fluidity, and install micron-grade precision filters on coating dies to filter trace impurity particles from raw materials in advance, eliminating pinhole generation at the source. Second, redesign a three-stage stepped temperature rise imidization oven curve, abandoning the original rapid temperature rise model: low-temperature section (80–150℃) for slow solvent removal (120 min holding), medium-temperature section (180–280℃) for gradual imidization (90 min holding), high-temperature section (320–350℃) for closed-loop maturation (45 min holding) to slowly release residual internal stress within films. A constant-temperature tension-free annealing procedure above the Tg temperature was added post-film production to further eliminate hidden warpage risks. After optimization, film warpage stabilized at ≤0.12 mm per 100 mm, with the pinhole defect rate falling below 0.3%, reaching mass production pass rate standards equivalent to Japanese and Korean manufacturers.
Synchronously, HiSiaddi technical engineers remotely collaborated with the customer’s South Korean packaging workshop, fine-tuning exposure machine power, developer concentration, and immersion duration based on photosensitive parameters of modified PSPI resin, issuing standardized on-machine process guidance documents. After three rounds of small-batch trial production on-site, the wafer opening yield recovered to 97.9%, completely resolving blockage and jagged circuit defects.
Low-cost industrial-grade dianhydride and diamine raw materials available on the market were completely discarded. All polymer monomers were sourced from high-purity refined raw materials manufactured by leading domestic electronic chemical enterprises, with original factory COA purity reports and metal ion test certificates attached to each batch. Nano-grade high-purity silicon dioxide and boron nitride powder were selected as inorganic modified fillers, pre-treated with silane coupling surface modification to guarantee compatibility between fillers and PI matrices and avoid local performance imbalance caused by filler agglomeration. A dedicated Class 10,000 dust-free production workshop for electronic-grade PI was designated throughout production, isolating dust and metal debris during raw material feeding, synthesis, and film formation to lock mid-to-high-end quality from the supply chain source. Key physical indicators of finished products were benchmarked against Japanese Kaneka original raw materials used by the customer, with performance deviation controlled within 3%.
HiSiaddi unifiedly authorized authoritative domestic third-party testing institutions to conduct full-item physical, chemical, and reliability testing in accordance with South Korean KS electronic material standards, EU REACH, and AEC-Q102 automotive specifications, issuing bilingual Chinese-English SGS test reports and material traceability lists. Full sets of customs declaration documents for chemical imports into South Korea, certificates of origin, and MSDS safety instructions were sorted out. As semiconductor PI belongs to controlled fine chemicals in South Korea, K-REACH pre-registration was completed in advance to avoid customs inspection and detention risks upon arrival. Products were vacuum aluminum foil dust-free sealed and packed, shipped via constant-temperature containers by sea to Incheon Port, South Korea, preventing resin deterioration and film moisture deformation caused by temperature and humidity fluctuations during maritime transport, ensuring goods could directly enter mass production upon port arrival.
1. Stable Mass Production Quality: After rectification and finalization, the full 850 kg batch of formal mass-produced goods was delivered to Nexsem’s South Korean facility. The comprehensive yield of 12-inch power wafers packaged with copper-clad PI films stabilized above 97.5%, and photosensitive PSPI stock solution fully replaced original Japanese imported raw materials. The customer canceled its original annual framework procurement order of 1.6 tons of Japanese PI raw materials. The procurement cost of initial domestic raw materials dropped by 29.4% compared with Japanese original manufacturers, and the delivery cycle was shortened from 65 days for Japanese suppliers to 28 days, greatly optimizing the customer’s supply chain turnover efficiency.
2. Technical Accumulation and Expansion of New Product Development: Relying on ternary copolymerization modification technology accumulated during this project, the customer later added two new customized products for R&D: high-temperature resistant modified PI molding plastics for automotive IGBT modules and low-dielectric PI substrates for high-frequency FCCL, all entrusted to HiSiaddi for R&D and delivery. A yearly framework procurement agreement was signed the following year, with the total annual procurement volume of various high-end PI exceeding 5.2 tons, establishing Nexsem as a benchmark stable mid-to-high-end customer in HiSiaddi’s South Korean semiconductor business segment.
3. Strategic Adjustment of Customer Supply Chain: Based on HiSiaddi’s complete technical problem-solving capabilities demonstrated in this project, Nexsem gradually implemented a dual supply chain strategy for semiconductor PI raw materials and added HiSiaddi Shanghai to its global qualified manufacturer list (QML), breaking its previous sole reliance on Japanese and Korean chemical giants for raw material procurement. The customer simultaneously referred two other listed South Korean automotive semiconductor enterprises to HiSiaddi for PI customization cooperation.
This project focused entirely on high-performance functional polyimide dedicated to automotive chips in the semiconductor industry, with products applied to wafer passivation and core substrates of high-end copper-clad circuit boards. It features high technical thresholds, long certification cycles, and stringent indicator control requirements, with no extensive low-cost bulk production logic adopted by low-grade electrical insulation PI manufacturers. All core project challenges centered on three high-precision fields: molecular formula design, precision film forming processes, and semiconductor micro-process adaptation. Breaking the inherent foreign trade model limited to simple trade docking, HiSiaddi relied on its in-house chemical technical team to deeply participate in customer formula optimization and production delivery, delivering import substitution for overseas mid-to-high-end customers via technical services. This represents the core competitive advantage distinguishing domestic fine chemical foreign trade enterprises from low-volume commodity traders.
Please contact HiSiaddi customer service if you need more formula optimization consulting services.
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info@hisiaddi.com 
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