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Ductility Test and Interpretation for Printed Circuit Products

IP.com Disclosure Number: IPCOM000080931D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Joshi, KC: AUTHOR [+2]

Abstract

Product performance predictability, especially with copper plating, has been difficult because the printed-circuit industry does not have suitable tests to measure and interpret the mechanical properties required to withstand manufacturing and service stresses, as for example, solder shock, mechanical and thermal stresses.

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Ductility Test and Interpretation for Printed Circuit Products

Product performance predictability, especially with copper plating, has been difficult because the printed-circuit industry does not have suitable tests to measure and interpret the mechanical properties required to withstand manufacturing and service stresses, as for example, solder shock, mechanical and thermal stresses.

This is accomplished in a process as follows:
1. The sample design incorporates a singular fracture plane

where a known amount of plastic strain is concentrated. The

higher the concentration, the closer the simulation of the

plated through-hole failure can be. A technique of

indentation can be best

utilized to determine the strain concentration. The sample

is indented (Vickers or Knoop hardness indentor) before

pulling and the interspacings are measured. After pulling the

sample to initiation of fracture, the spacings are remeasured

and the increase in the spacings reflect the local plastic

elongation. Several samples have been studied with various

types of notches. It is clear that the geometry can be

further optimized to improve

the strain concentration in the failure region.
2. A test is run at the strain rate corresponding to the

expansion rate of the printed-circuit

board during solder shock. This has been

established to be the equivalent of approximately 0.5 inches

per minute cross-head speed on the Instron machine. The

test is run at a temperature corresponding to the solder shock

shock temperature. A simple

means has been developed of simulating the

test temperature during Instron test as follows: A thin

solder foil is attached to the notch area, as shown in Fig.

1. The sample is gripped in the Instron and is then heated

from the back side with hot air or flame. As soon as the

solder melts the sample is pulled and tensile data recorded.

Since the solder shock temperature is approximatel...