The science able to observe the inner structure of a material.
Metallographic analysis is needed to understand the chemical, physical, mechanical and technological features of metal materials, to evaluate the influence of working conditions on the behaviour of materials, to check the reaction of a material to specific requests, and to identify possible anomalies and their causes.
Metallography is a science which observes the inner structure of a material by studying the crystal morphology. The details obtained by metallographic analysis allow the condition of the material to be checked.
Main performed tests
Metallographic microsections
The cross-section metallographic analysis is a destructive analysis which allows the correct construction of the printed board to be checked by verifying the copper thickness in the inner layers and on the surface, the correct application of solder mask, the metallisation of the inner holes, and the quality of the circuit boring.
The sample is sectioned and integrated into a specific resin; then, by further mechanical processing and lapping of the surface to be analysed, it is observed through optical microscopy.
Test method: IPC TM 650 2.1.1 (Micro sectioning, Manual method)
Analysis with optical microscope
Optical microscopy is a method of investigation essential for the structure analysis of materials. This technique is effective for the study of anomalies due to thermal treatment, the evaluation of inclusions, the identification of breaks, and the evaluation of soldering and coatings.
Technical regulations: IPC A-600 (Acceptability of Printed Boards), IPC A-610 (Acceptability of Electronic Assemblies), IPC 6012 (Qualification and Performance Specification for Rigid Printed Boards)
SEM (Scanning Electron Microscope) – EDX Spectroscopy
The Scanning Electron Microscope (SEM) is a type of microscope which allows morphological investigation at high magnifications. EDX (Energy Dispersive X-ray) spectrometry is an instrumental analytical method based on the interaction between a primary focused electron beam that strikes the sample and the electrons of the atoms that constitute the sample itself.
The combined use of the two techniques allows morphological (SEM) and compositional (EDX) characterisation, providing an instrument for understanding the composition of a material's structure.
Solderability Test
The solderability test on printed boards is performed on the basis of the IPC J-STD-003 standard, which describes the procedures and methods to define the acceptability criteria for the wettability of the superficial finishing of the sheets. It evaluates the weldability of superficial conductors, fixing points and plated-through holes (PTHs) of printed boards.
The solderability test of components is performed on the basis of the IPC J-STD-002 standard, which sets the testing methods and defines the defects and acceptability criteria for the weldability of terminals and flexible cables — necessary to check that component-terminal (lead) weldability meets the standard's requirements.
Test method: IPC J-STD-002 (Solderability Tests for Component Leads, Terminations, Lugs, Terminals, and Wires), IPC J-STD-003 (Solderability Test for Printed Boards)
Peel Strength Test
The Peel Strength Test is generally used to measure the peel strength of a material, usually of an adhesive. It determines the comparative peeling features or breakout force of adhesive bonds tested on samples of specific sizes and in defined conditions of pre-treatment, temperature and speed of the testing machine.
Test method: IPC TM 650 2.4.8C (Peel Strength of Metallic Clad Laminates)
Solder Float Test
This test is performed on PTHs (Plated-Through-Holes) to determine whether they can support the thermodynamic effects of the extreme heat to which they can be exposed during the assembly, re-working or restoration phases.
Test method: IPC TM-650 2.6.8 (Thermal Stress, Plated-Through Holes)
Dye & Pry Test
The Dye & Pry analysis technique is a destructive test used when it is impossible to solve a problem with optical inspection (for example, in the case of very small defects). It is based on the use of a liquid colourant which soaks into the microfractures existing on the soldering.
When the colourant is dried, the electronic components (BGA, capacitors, resistances, etc.) are removed from the PCB and the solder joints are inspected: the presence of the colourant reveals the problematic areas at the level of the connections of all the interfaces.
Test method: Internal Method
X-Ray (2-D and 3-D defect analysis)
The X-Ray analysis of electronic sheets is a non-destructive technique which allows possible failures and/or defects to be identified and evaluated at the level of opens, voids, solder balls and soldering breakouts. It also allows the correct soldering of components to be checked and possible soldering voids to be identified.
The X-Ray analysis finds factors that could not be noticed with a simple visual inspection. The evaluation can be performed both through 2-D oriented presentations and 3-D volumetric views.
Technical regulations: IPC A-610 (Acceptability of Electronic Assemblies), IPC 7095 (Design and Assembly Process Implementation for BGAs)