Surface Insulation Resistance (SIR) Testing

Surface Insulation Resistance (SIR) is defined as the resistance, across the surface of the base material, between adjacent conductors of a Printed Circuit Board (PCB). On a typical PCB surface there are primarily four paths for current leakage between adjacent conductors; 1) through the air, 2) through surface contamination, 3) along the surface, and 4) through the substrate.

The Surface Insulation Resistance test method is used to quantify the deleterious effects of fabrication, process or handling residues on Surface Insulation Resistance (SIR) in the presence of moisture. The electrodes are parallel traces (printed comb patterns) on a standardized printed board or assembly. Samples shall be conditioned, and measurements taken at a specified interval under elevated temperature & humidity. Electrodes are electrically biased during conditioning to facilitate electrochemical reactions.

IPC-TM 650 Test Method 2.6.3.5 - Bare Board Cleanliness by Surface Insulation Resistance

This IPC-TM-650, Test Method 2.6.3.5 is used to characterize the cleanliness of printed wiring board fabrication processes by determining the degradation of electrical insulation resistance under conditions of high temperature and humidity. This test method examines the cleanliness of a test substrate prior to solder mask application, after solder mask application, and after any final metallization and/or surface finish operation (e.g., HASL or OSP), and may be used to demonstrate the cleanliness of internal layers of a multilayer board prior to lamination.

IPC-TM 650 Test Method 2.6.3.6 - Surface Insulation Resistance - Fluxes - Telecommunications

This IPC-TM-650, Test Method 2.6.3.6 is used to characterize the effects of flux residues on electrical performance by determining the degradation of electrical insulation resistance under conditions of high temperature and humidity. This method, in conjunction with the supporting documentation in IPC-J-STD-004, is intended to be equivalent to Telcordia Technologies GR-78-CORE, Section 13.1, (Corrosiveness of Soldering Fluxes) and is used primarily by telecommunications companies to qualify the candidate flux or solder paste.

IPC-TM 650 Test Method 2.6.3.6 - Surface Insulation Resistance - Fluxes - Telecommunications

This IPC-TM-650, Test Method 2.6.3.6 is used to quantify the deleterious effects of fabrication, process or handling residues on Surface Insulation Resistance (SIR) in the presence of moisture. The electrodes are long parallel traces (printed interdigitated comb patterns) on a standardized printed board or assembly. Samples shall be conditioned and measurements taken at a high humidity. Electrodes are electrically biased during conditioning to facilitate electrochemical reactions.

Specifically, this method is designed to:

Simultaneously assess a) leakage current caused by ionized water films and b) electrochemical degradation of test vehicle, (corrosion, dendritic growth)

Provide metric(s) that can appropriately be used for binary classification (e.g., go/no go, pass/fail)

Compare, rank or characterize materials and processes.

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Referenced Document and Specifications

IPC-TM 650 Test Method 2.6.3.5 Bare Board Cleanliness by Surface Insulation Resistance
IPC-TM 650 Test Method 2.6.3.6 Surface Insulation Resistance – Fluxes – Telecommunications
IPC-TM 650 Test Method 2.6.3.7 Surface Insulation Resistance – Fluxes – Telecommunications
IPC-A-24-G-KIT1 Surface Insulation Resistance – Gerber Kit
J-STD-004 Requirements for Soldering Fluxes
IPC-A-600 Acceptability of Printed Boards
IPC-9201 Surface Insulation Resistance Handbook
IEC-61189-5 Test methods for electrical materials, interconnection structures and assemblies – Test methods for printed board assemblies
IPC/EIA J-STD 001 Requirements for Soldered Electrical and Electronic Assemblies
IPC-SM 840 Qualification and Performance Specification of Permanent Solder Mask
BELLCORE TR-NWT-000078
GR-78-CORE Physical Design and Manufacture of Telecommunications Product – Telcordia Technologies (Formerly Bellcore)
ASTM D-257 Standard Test Methods for DC Resistance or Conductance of Insulating Materials