PCB Metallographic Mold

A PCB metallographic mold is a specialized fixture used in the preparation of printed circuit board (PCB) samples for microscopic analysis. It plays an important role in metallography, which is the study of the microstructure of metals and materials.

Brief Introduction

When engineers or quality inspectors need to examine the internal structure of a PCB—such as copper layers, vias, plating thickness, or defects—they first cut a small section of the board. This sample is often fragile and uneven, so it must be embedded (mounted) in a mold using resin or epoxy.

The metallographic mold provides:

• A controlled shape and size for the sample
• Protection for delicate PCB features during grinding and polishing
• A stable base for handling under microscopes

advantage of Plastic Molds

• Lightweight and disposable or reusable
• Common in cold mounting
• Low cost

Why It’s Used

After mounting in the mold, the sample undergoes:

1. Grinding – to create a flat surface
2. Polishing – to achieve a mirror-like finish
3. Etching (optional) – to reveal material structures

This preparation allows clear observation of:

• CopMetallographic Mold per trace thickness
• Layer alignment
• Plating quality in vias and holes
• Defects like voids, cracks, or delamination

To make a PCB microsection (cross-section analysis), metallographic molds are only one part of the process. A variety of consumables are required throughout cutting, mounting, grinding, polishing, and etching.

Here’s a clear breakdown:

1. Sectioning (Cutting) Consumables

Used to cut a small piece of the PCB without damaging internal layers:

Diamond cutting wheels / blades – for precise, low-damage cutting
Coolant fluids – prevent overheating and smearing of copper/resin
2. Mounting (Embedding) Materials

Used together with the metallographic mold:

Epoxy resin (cold mounting) – best for PCB microsections due to transparency and low shrinkage
Acrylic resin – faster curing but slightly more shrinkage
Phenolic powder (hot mounting) – for robust samples (less common for PCBs)
Hardener and mixing cups/stirrers
3. Grinding Consumables

Used to flatten the sample and expose the cross-section:

SiC (silicon carbide) abrasive papers
Typical grit sequence: 240 → 400 → 600 → 800 → 1200 → 2000
Grinding lubricants (water or special fluids)
Backing discs or platen liners
4. Polishing Consumables

Critical for achieving a scratch-free, mirror finish:

Polishing cloths/pads (different textures: coarse to fine)
Diamond suspensions/pastes
Common sizes: 6 µm → 3 µm → 1 µm → 0.25 µm
Alumina or silica suspension (final polishing step)
Lubricants for polishing