Encapsulation

Transfer and compression molding · epoxy mold compound · lids, TIM and hermetic seals

Molding is the last physical step in making a chip, and the materials and presses for it come mostly from Japan. Towa ranks itself first in molding equipment and leads compression molding, the method HBM stacks and fan-out panels need; Sumitomo Bakelite and Resonac lead mold compound, with Changzhou Huawei Electronics the one large Chinese maker.

Who makes the parts of a molded package. Epoxy mold compound: Sumitomo Bakelite, Resonac and Nagase ChemteX in Japan, and Changzhou Huawei Electronics, China's largest. Molding presses: Towa, which ranks itself first in molding equipment, then Apic Yamada and ASMPT. Underfill between die and substrate: Namics, Henkel and Resonac. HBM stacks are filled with molded underfill and compression molded. WHO MAKES EACH PART OF A MOLDED PACKAGE LOGIC DIE Mold compound SUMITOMO BAKELITE, RESONAC, NAGASE CHINA: CHANGZHOU HUAWEI ELECTRONICS Molding press TOWA, APIC YAMADA, ASMPT HBM molded underfill NAMICS FOR SK HYNIX MR-MUF Underfill NAMICS, HENKEL, RESONAC Substrate IBIDEN, UNIMICRON, NAN YA SIX OF THE NINE MATERIAL AND PRESS MAKERS ARE JAPANESE JAPAN 6 DE CN SG MAKERS NAMED ABOVE, EXCLUDING SUBSTRATES, BY HEADQUARTERS: GERMANY, CHINA, SINGAPORE.
Molding press leader
Towa
Towa sales, FY to Mar 2026
¥54.4B
Largest Chinese EMC maker
Huawei Electronics
SK hynix HBM fill
MR-MUF
Cure temperature
150-175 °C
Hub
Process

The sealing flow

Mold, Cure, Mark, Cut

Encapsulation seals the bonded die inside molded epoxy, under a metal lid or in a hermetic can.

By encapsulation the die has been diced, attached and wired or bumped, and it is still fragile and moisture-sensitive. Sealing gives it a rigid body: molded epoxy for almost every chip, a metal lid for high-power processors, or a hermetic ceramic or metal can for space and defense parts.

The molded-package flow
StepWhat happensMain yield risk
Plasma cleanPlasma cleans the substrate and wires so the compound sticksResidue causes delamination and moisture paths
Mold, lid or sealTransfer or compression molding, lid attach, glob-top or hermetic seal, by package typeWire sweep, voids, flash at mold parting lines, uneven lid bondline
Post-mold cureBatch ovens at 150 to 175 °C finish cross-linking for one to several hoursUnder-cure makes moisture-sensitive packages
Deflash and plateMold flash removed from leads and package facesDamaged leads; residue that will not solder
MarkLaser mark with part number, date code and lotIllegible mark or surface damage
SingulateSaw or punch the molded strip into packagesEdge chipping, cracked compound

The molding press cycles in minutes; the cure ovens take hours. Lines are sized around oven capacity so the press never waits.

Methods

Transfer Molding for Volume, Compression for Thin and Stacked

Three ways to seal a package. Transfer molding forces melted compound through runners into cavities around dies on a strip. Compression molding lays compound granules over dies on a carrier and presses them, with no flow across the wires. Lid attach bonds a copper lid over a flip-chip die with thermal interface material under the lid. Transfer molding COMPOUND FLOWS THROUGH RUNNERS UPPER MOLD CHASE RUNNER QFN, QFP, BGA: MOST UNITS Compression molding COMPOUND PRESSED IN PLACE PRESS FAN-OUT, HBM, LARGE THIN MODULES Lid attach COPPER LID OVER A FLIP-CHIP DIE COPPER LID; TIM BELOW IT CPUs, GPUs, AI ACCELERATORS COMPOUND IN GRAY, DIES IN BLUE, WIRES IN RED, LID AND TIM IN COPPER. NOT TO SCALE.
Encapsulation methods
MethodHow it worksTypical packages
Transfer moldingMelted compound forced through runners into a multi-cavity mold around a strip of diesQFN, QFP, SOP, BGA; most units by count
Compression moldingCompound granules or sheet laid over dies on a carrier and pressed in place; nothing flows across the wiresFan-out wafer and panel packages, HBM, SiP, large thin modules
Glob-top and dam-and-fillEpoxy dispensed over the die and cured with no mold toolSensors, MEMS, prototypes, low volume
Lid attachCopper or nickel-plated lid bonded over a flip-chip die, with thermal interface material under it; not airtightCPUs, GPUs, AI accelerators, RF modules
Hermetic sealCeramic or Kovar package closed by solder, seam weld or glass frit; filled with dry nitrogen or heliumSpace, defense, high-reliability sensors, some optoelectronics

Transfer molding wins on cost and cycle time. Compression molding is gaining because thin, wide packages crack and warp under flowing compound, and because a fan-out panel or HBM stack has no wires to sweep but many dies to keep flat.

Mold compound

Mold Compound Is a Japanese Industry

Epoxy mold compound (EMC) is a family of silica-filled epoxy resins with flame retardants, ion scavengers and stress modifiers, formulated per package. Automotive grades survive -40 to 150 °C cycling; memory grades use low-alpha silica to keep radiation from flipping bits; thin-package grades are tuned for low warpage.

Mold compound makers
MakerBasePosition
Sumitomo BakeliteJapanBroadest EMC range; qualified at most OSATs and IDMs
Resonac (formerly Hitachi Chemical)JapanEMC plus underfill and other packaging materials
Nagase ChemteXJapanEMC including liquid and compression grades for advanced packaging
KyoceraJapanEMC alongside ceramic packages
Shin-Etsu ChemicalJapanLiquid encapsulants and compression-mold materials
Changzhou Huawei ElectronicsChinaChina's largest EMC maker and third in the world by volume in 2023; acquired by Jiangsu Huahai Chengke
KCCKoreaEMC for Korean memory and logic lines

EMC is a Japanese industry for the same reason wire is: formulation know-how, filler supply and decades of customer qualifications built around Japan's chip industry in the 1980s and 1990s. A qualified EMC grade in an automotive or memory program can take quarters to years to replace. China's domestic suppliers cover under 30% of its own packaging-material needs, which is why the Huahai Chengke purchase drew attention.

Molding presses

Towa Leads the Presses

Towa of Kyoto ranks itself first in semiconductor molding equipment and calls its compression molding unrivaled since the 2009 launch, citing patents and process difficulty. It reported record orders for compression equipment and molds in its year to March 2026, on net sales of ¥54.4 billion, driven by memory and advanced-package investment, and introduced a lower-cost compression system, INOMOS, in May 2026.

Molding and sealing equipment makers
MakerBasePosition
TowaKyoto, JapanTransfer and compression presses; the compression standard for fan-out and HBM
Apic YamadaJapanTransfer and compression presses, trim and form
ASMPTSingaporeMolding systems within a full back-end line
BoschmanNetherlandsCompression molding and sinter presses for power modules
Palomar TechnologiesCarlsbad, CALid attach and seam sealing for hermetic and optical packages

HBM and AI modules

HBM Stacks Are Filled and Molded as One Unit

HBM and AI modules put molding on the critical path. An HBM stack of 12 to 16 dies is filled and sealed as one unit, and the fill must reach gaps of a few tens of micrometers between every die without voids.

  • SK hynix MR-MUF: the whole stack is reflowed at once, then a molded underfill fills the gaps and forms the outer body in one step. The material comes from Namics under an exclusive agreement that is reported to be nearing its end. SK hynix plans to stay with MR-MUF through 12- and 16-high HBM4E.
  • Samsung and Micron TC-NCF: a non-conductive film between dies does the underfill job during bonding; the stack is then molded.
  • Fan-out and CoWoS modules: compression molding over a whole reconstituted wafer or panel, where warpage control decides yield.

Bonding detail for the stack is on Flip-Chip Bonding; panel-level molding is on Fan-Out WLP.

Lids and thermal

On AI Chips the Lid Is Part of the Cooler

High-power processors are lidded, not molded, because the lid is the first stage of the heat path. A GPU or AI accelerator lid is nickel-plated copper, bonded around the substrate edge with sealant, with a thermal interface material (TIM) between die and lid. Above roughly 1,000 W per package the TIM and lid become the limit, and cold plates sit directly on the lid.

Lid and thermal materials
MaterialWhat it doesMain suppliers
TIM1 (die to lid)Indium solder, metal-filled polymer or graphite pads that carry heat from die to lidIndium Corporation, Dow, Henkel, Honeywell, Shin-Etsu
Lid and stiffenerNickel-plated copper lid and frame that spread heat and hold the substrate flatShinko, Jentech, Lotes and in-house designs
SealantAdhesive that bonds the lid to the substrate edgeHenkel, Dow, Shin-Etsu

The cooling beyond the lid is covered at Module Integration and, for racks, on DatacentersX.

Hermetic sealing

Space and Defense Still Need Hermetic Cans

Hermetic packages keep moisture out completely, which molding cannot. They are slow and costly, and they remain required for space, defense and some optical and sensor parts. The cavity is back-filled with dry nitrogen or helium, then closed by solder sealing a Kovar frame, by laser or resistance seam welding, or by fusing glass frit on ceramic. Growing low-Earth-orbit constellations add demand for rad-hard and rad-tolerant parts in these packages; see Rad-Hard and Rad-Tolerant Chips.

Reliability

Moisture Is the Main Enemy

  • Moisture sensitivity (JEDEC MSL): MSL 1 parts can sit in open air indefinitely; MSL 3 parts must be baked and dry-packed. Moisture trapped in compound turns to steam in board reflow and splits the package, a failure called popcorning.
  • Stress tests: temperature cycling, HAST (highly accelerated stress test) and biased temperature-humidity tests.
  • Inspection: scanning acoustic microscopy finds voids and delamination inside a molded body without opening it.

Record

Page Record

This page also carries the material from Encapsulation and Thermal Management in Packaging.

Covers
Encapsulation flow, methods, mold compound makers, molding equipment, HBM fill and molding, lids and thermal materials, hermetic sealing and reliability tests
Sources
Towa FY2025 results presentation (May 2026) and earnings coverage, BigGo Finance (May 2026); TrendForce (Changzhou Huawei Electronics acquisition, December 2024; SK hynix MR-MUF and Namics, January 2026)
Last verified
October 2026