|Ask the Experts|
September 30, 2020
Seeking IPC and J-STD Definitions
What is the definition of a body seal on a component? What is the definition of a lead seal? These terms are used in both IPC and J-STD, but I cannot find a good definition of what they are. Can you explain?
|Expert Panel Responses|
A Body seal is a lidded device and the seal can be of many forms. Welds, Epoxies and other forms of lid/body seals can be used. A Lead seal can be a solder seal or a glass seal (common examples) at the leads exit point of the package body.
All above mentioned seals are typically related to hermetically "sealed" devices.
Circuit Technology Center, Inc.
Let's begin with the definition from Merriam-Webster Dictionary
Seal noun (2)
Definition of seal (Entry 3 of 5)
b: to close or make secure against access, leakage, or passage by a fastening or coating
The intent of a seal on a component body or lead is to prevent the entry of moisture or contaminants within the confines of the body of the particular component. Hence any hermetically sealed component is fabricated to prevent any moisture from entering or permeating into the component either through the body of the components or through seepage from any protruding termination or lead .
Axial leaded Glass diodes are an example where the lead exits the glass body, the seal is between the glass and the component lead to prevent penetration of moisture or contaminants. The same applies to leaded ceramic components.
IPC-T-50M, Terms and Definitions for Interconnecting and Packaging Electronic Circuits, is the IPC dictionary for all the terms used within the IPC documents and specifications. The word "seal" is used throughout this document and I would highly recommend to acquiring a copy of the document
Vice President, Technical Director
This terms are used on J-STD standards and refers to components hermetically sealed with plastic, glass, ceramic, metal etc. and have terminals that comes up of this kind of component bodies or packages.
Both terms refers to the manufacturing encapsuling process of the component and typically is mentioned on the standard in several ways like "Lead to body seal shall not be damage".
That means that any damage on the area of union or between the component body and the lead or terminal outgoing from the component body or package is not allowed.
Body seal is common used to refers component packages like SOD, SOT, SOIC, QFP, QFN, PLCC etc.
Lead seal is common used on ceramic or crystal components or PTH components with meniscus.
Engineering Director / Master IPC Trainer (MIT)
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