Search results

Currently, the most widely used Printed Circuit Board (PCB) base material is the glass reinforced epoxy known as FR‐4. To improve the electrical or the thermomechanical performance of PCBs, there are two possibilities from a material standpoint: a modification or change of the resin system and a change of the reinforcement. Currently, there are a number of resins used for high performance PCB base materials. These resin systems offer higher Tgs and lower z‐axis‐expansions for improved through hole reliability. Non‐halogenated epoxy resin systems are offered for the production of green PCBs. In addition to new resins, new reinforcements are available for use in PCBs. Which can improve the electrical parameters of the base material and the x and y axis‐ thermal expansion also changes with the use of those reinforcements. This paper compares the thermomechanical and electrical parameters of some new high performance and green base materials with the glass reinforced epoxy materials commonly used in both high layer count boards and microvia applications.

Today a large variety of printed circuit board (PCB) base materials exists on the market and new ones are added frequently. The base material suppliers, having good original equipment manufacturer (OEM) marketing, usually present the materials in an early development stage to the end customers. The customers, on the other hand, expect from their PCB suppliers that the materials are fully characterized and that qualification samples are available immediately. In many cases, the process recommendations given to the PCB manufacturers are very generic (“like FR4”), insufficient, or not practicable (“8 hours baking time”). However, optimized processing ensures the reliability of the finished PCBs, starting from general leadfree compatibility to CAF testing. This demonstrates the importance of thoroughly verified process parameters and of very specific process recommendations to minimize the number of costly and time‐consuming iterations, and to be able to meet the goal of submitting qualification samples and functional PCBs in minimum time. The purpose of this paper is to show the minimum required PCB processing recommendations, and why these have to be fixed by the material supplier before commercialization of a new base material.

The paper examines the base material suppliers' situation, customer expectations and reality and the PCB manufacturers' expectations.

The paper gives the reasons and consequences of early base material marketing.

The paper analyses today's PCB base materials market and shows the reasons and consequences of early base material marketing. Also, the minimum requirements by PCB fabricators concerning processing recommendations are given.

Aims to explain the main requirements for printed circuit boards (PCBs) and to determine the survival rate of boards in lead‐free assembly.

The first two main requirements are the survival of 5‐6 cycles lead free reflow with peak temperatures of up to 260°C and an identical or even better board reliability of such boards compared to todays eutectic soldered ones. In a first series of tests the influence of base materials, reflow temperature gradient and peak temperature on PCB survival rate are investigated. Thermo‐mechanical data of different epoxy‐based materials are compared to survival rate investigations using repeated reflow tests. The impact of PCB manufacturing and design on the lead free performance is discussed. A second series of investigations is air‐to‐air life cycle tests of daisy chain boards out of different epoxy‐based materials with varying preconditioning were done.

The tests showed that dicy cured epoxy base materials are not able to withstand the thermal stress of the mentioned soldering steps. Board design and the heating gradient in reflow also influence the assembly performance. Thermal cycling tests (air‐to‐air), showed clearly the effect of reflow temperature and number of reflow cycles on through‐hole reliability. There was no significant impact of z‐axis‐expansion on the through‐hole failure rate in air‐to‐air cycling.

Provides further information on the lead‐free assembly of PCBs.

There is increasing customer demand for materials with low dissipation factors for reduced loss along the traces and low dielectric constants for higher signal propagation speeds. High performance epoxies such as Nelco's N4000‐13, Isola's FR408 and General Electric's GETEK (similar to Matsushita's MEGTRON) have become essential for boards operating in the higher frequency range. For applications at the highest frequencies material choices are very limited. These materials, tailored for high frequency use, have disadvantages – either with their thermomechanical properties or with their processability. Recently, a number of new “high frequency” or “low loss” materials have been introduced by different suppliers. In an overall relatively small but growing market, these materials have to demonstrate their advantages – from an electrical, thermomechanical, processing, fabrication quality and/or cost standpoint when compared to the established materials. This paper compares the thermomechanical performance and fabrication quality of new “high frequency”/“low loss” base materials.