Why More Manufacturers Are Choosing the NOVICK AF Series EDM for ASP‑23 Powder Metallurgy High‑Speed Steel Encapsulation Mold Cavity Machining

In the semiconductor encapsulation field, the material selection for IC encapsulation molds and lead frame molds directly determines mold life and encapsulation quality. In recent years, ASP‑23 powder metallurgy high‑speed steel has been increasingly widely used in this scenario due to its excellent overall performance. However, ASP‑23 has high hardness after heat treatment, making traditional cutting very difficult – cavity finishing can only rely on die‑sinking EDM. So what kind of EDM machine is capable of ASP‑23 encapsulation mold cavity machining? And what level can the NOVICK AF Series EDM achieve?

What Is ASP‑23? Why Is It Used in Chip Encapsulation Molds?

ASP‑23 is a powder metallurgy high‑speed steel from ASSAB (Sweden), belonging to the chromium‑molybdenum‑tungsten‑vanadium alloy system. Unlike traditional ingot‑cast high‑speed steel, it is manufactured using powder metallurgy – molten steel is atomized into fine powder and then hot isostatically pressed, resulting in extremely uniform carbide distribution with no segregation.

Typical chemical composition of ASP‑23 includes: carbon 1.28%, chromium 4.2%, tungsten 6.4%, molybdenum 5.0%, vanadium 3.1%. Delivery hardness is approximately 260HB, and hardness after heat treatment can reach HRC64‑66.

ASP‑23 is chosen as an encapsulation mold material primarily for several reasons: uniform carbide distribution ensures uniform erosion during EDM without localized over‑erosion; good dimensional stability during heat treatment means controllable deformation after hardening; high hardness combined with toughness withstands repeated loads during encapsulation; and it is suitable for PVD coating, with uniform carbide distribution improving coating adhesion. Because of these characteristics, ASP‑23 is widely used in semiconductor IC molds, precision high‑speed stamping dies, and similar applications.

In Encapsulation Mold Manufacturing, What Step Does the EDM Machine Handle?

In the actual manufacturing process of chip encapsulation molds, after ASP‑23 material reaches standard hardness through heat treatment, die‑sinking EDM is used for cavity finishing. This step directly determines the dimensional accuracy and surface quality of the mold cavity – whether cavity dimensions are accurate and whether the surface is smooth depends on the EDM machine‘s precision and discharge control capability.

When selecting an EDM machine for ASP‑23 encapsulation molds, mold shops typically focus on three core indicators: positioning accuracy determines whether cavity dimensions are accurate; repeat positioning accuracy determines consistency in multi‑cavity machining (especially important for multi‑cavity encapsulation molds); surface roughness determines whether the cavity requires hand polishing.

The NOVICK AF Series precision CNC Die‑sinker EDM Machines have the following measured data in these three dimensions: the AF50 model achieves bidirectional positioning accuracy of 0.008mm on the X/Y axes and 0.006mm on the Z‑axis, with unidirectional repeat positioning accuracy of 0.004mm. Optimal surface roughness reaches Ra ≤ 0.1μm, entering the realm of mirror finishing. What do these three data points mean? Positioning accuracy ensures accurate cavity dimensions, repeat positioning accuracy ensures batch machining consistency, and mirror‑grade surface roughness means the machined mold cavity requires virtually no hand polishing.

Four Core Capabilities of the AF Series EDM in ASP‑23 Mold Cavity Machining

Not limited by material hardness. ASP‑23 reaches HRC64‑66 after heat treatment – traditional tools simply cannot cut it. The AF Series uses EDM discharge machining, removing material through discharge without relying on tool cutting. Material hardness does not affect machining feasibility. This solves the fundamental problem of “the material is too hard to machine.“

Capable of machining complex micro‑cavity structures. Encapsulation mold cavities often have complex geometries and micro‑features that traditional cutting tools cannot reach. The AF Series can “copy“ complex cavity structures through formed electrodes. In general mold applications such as narrow slot machining, the AF Series achieves stable machining with a minimum corner radius of 0.03mm and machining depth of 30mm, meeting the micro‑structure machining requirements of encapsulation molds.

Ensuring multi‑cavity machining consistency. IC encapsulation molds typically have multiple cavities – dozens or even hundreds of cavities on a single mold, with each cavity‘s dimensions, position, and surface quality needing to be highly consistent. The AF Series is equipped with an intelligent discharge control system that precisely detects and controls each discharge pulse. The AC servo full closed‑loop motion control system performs real‑time detection, feedback, and correction of each motion axis position. Through its high‑rigidity Ram‑type structure, precision linear guides, and ball screws, the AF Series maintains stable accuracy over long‑term use. These technologies work together to ensure dimensional consistency across hundreds of cavities.

Achieving mirror‑grade surface quality. After EDM, ASP‑23 surfaces form a “white layer“ (recast layer and re‑hardened untempered layer), both of which are relatively brittle. The AF Series supports a “fine discharge“ mode – low current, high frequency – which can control surface roughness to Ra ≤ 0.1μm. Many customers report that when machining materials such as S136 mirror steel, a mirror finish is achieved directly with virtually no subsequent polishing required.

Precautions for ASP‑23 EDM

After EDM of ASP‑23, it is recommended to grind or polish to remove the surface white layer, then temper again at around 535°C. Alternatively, low‑temperature tempering at 300‑400°C can eliminate approximately 70% of machining stress, avoiding micro‑cracks in subsequent use. The all‑digital pulse power supply of the AF Series monitors every discharge pulse in real time and automatically adjusts the discharge gap, preventing surface damage from abnormal discharges and providing a high‑quality machined surface for subsequent processing.

Summary

ASP‑23 powder metallurgy high‑speed steel, with its uniform carbide distribution, excellent heat treatment dimensional stability, and high hardness, is increasingly used in semiconductor encapsulation applications such as IC encapsulation molds and lead frame molds. The high hardness of ASP‑23 after heat treatment makes die‑sinking EDM a key process for cavity finishing.

The NOVICK AF Series precision CNC Die‑sinker EDM Machines have measured data supporting three core dimensions: positioning accuracy (X/Y axis 0.008mm), repeat positioning accuracy (0.004mm), and surface roughness (Ra ≤ 0.1μm, mirror grade) – meeting the comprehensive requirements of ASP‑23 encapsulation molds for cavity accuracy, multi‑cavity consistency, and surface quality.

About NOVICK

Beijing Novick Digital Equipment Co., Ltd., founded in 2002, specializes in the R&D, manufacturing, and sales of mid‑to‑high‑end CNC EDM machines. It is a national “Little Giant“ enterprise recognized for using specialized and sophisticated technologies to create novel and unique products. Its product portfolio covers Die‑sinker EDM Machines (AF Series), Brass Wire Cut EDM Machines (AW Series, AG Series), Molybdenum Wire Cut EDM Machines (MWE Series, AR Series), and Laser Tool Cutting Machines (CL Series), meeting the diverse machining needs of customers in semiconductor encapsulation molds, precision molds, tooling, and precision manufacturing.