USER MANUAL
SOLDERABILITY TESTER
METRONELEC
V2.0
–
10/2021
6 Avenue Eiffel - 78420 Carrières-sur-Seine
Tél : 01 30 15 20 00
Web :
http://www.metronelec.com| Mail : [email protected]
Page
6
sur
83
INTRODUCTION
Physical approach
When a solid is partially immersed into a molten alloy bath, it is subject to a set of forces
due to the buoyancy and to the surface tensions which are particularly high at the alloy - flux
interface.
The measurement of the force resultant is representative of the meniscus and, consequently,
of the
wetting angle
and function of the
solderability quality
.
We distinguish the three following phases:
•
The solid phase (component or coupon),
•
The liquid phase (molten alloy),
•
The vapor phase (atmospheric air in most cases).
Surface tensions
The molecular interactions of these three phases taken in pairs are surface tensions called:
•
SL solid-liquid phases,
•
SV solid-vapour phases,
•
LV liquid-vapour phases.
Θ the wetting angle is the angle defined by the angle between
SL and LV
Laplace & Young’s equations
The balance of those three forces is attained when the liquid which wets the solid forms a
stable meniscus represented by the Young’s relation:
SV
+
SL
+
LV
= 0
The angle 8 formed by the surface of the solid, gaseous (vapour) and the liquid at their
extreme point of contact is the wetting angle.
Vapor (V)
Solid (S)
Liquid
(L)