Measuring Multiple Lamination Reliability for Low-loss Materials


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Taiwan Union Technology Corporation (TUC) provides copper-clad laminates and dielectric resin composites used to manufacture printed circuit boards. The enthalpy of these resin composites meets and exceeds customers’ objectives and shows the deterioration of the resin’s physical properties as a result of multiple lamination cycles (up to 10X). This article describes how TUC evaluates the possible change in resin structure due to multi-thermal laminations.

Polymer Degradation Based on Stress-Strain Curve
The curve describes the method of measuring polymer degradation using tan δ (tan delta)—ratio of G'' to G'. With regard to material compounds of synthetic macromolecules, the degradation is evaluated by measuring the resin composite interfaces and adhesion, and how they collectively play a role in determining the properties of the polymers during processing. The strength of polymer-polymer interface between polymers depends on the structure that develops during its formation.

The accumulating cycles on these resin composites can be analyzed by applying the principles of the stress-strain curve, a graphical representation of the relationship between stress (derived from measuring the load applied on the sample), and strain (derived from measuring the deformation of the sample).

The stress-strain curve provides design engineers with a long list of important parameters needed for application design. It is obtained by gradually applying load to the sample and measuring the deformation. These curves reveal many properties of a material, such as the Young’s modulus, the yield strength, and the ultimate tensile strength. Laboratory instruments are used to assess these responses, otherwise known as viscoelastic properties, under conditions of low mechanical force. Controlled heating and cooling are incorporated to study temperature effects on polymer stiffness and resiliency.

Method of Assessment 
In this evaluation, we used dynamic mechanical analysis (DMA) to study and characterize storage modulus (E'), loss modulus (E''), and loss factor tan (delta) as a function of temperature. This is all captured by applying the glass transition temperature of resin composites. 

From the elastic and storage modulus, we can calculate tan delta—ratio of G'' to G'—showing the relative degree of damping of the material. This is an indicator of the material’s efficiency in preventing energy loss from molecular rearrangements and internal friction. Tangent of delta, or tan delta, quantifies the way in which a material absorbs and disperses energy. It expresses the out-of-phase time relationship between an impact force and the resultant force transmitted to the supporting body, whereas loss modulus and storage modulus are attributes to the given tan delta.

To read this entire article, which appeared in the March 2022 issue of PCB007 Magazine, click here.

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