Frantisek Steiner

Influence of reflow soldering profiles on creation of IMC at the interface of SnBi/Cu

The paper describes the effect of the solder profile on the formation of an intermetallic layer in the solder composition of 57.6% Bi-42% Sn-0.4% Ag. Soldered joints were made by soldering of chip resistors of 1206 size with different soldering reflow profiles. Solder pads on the PCB are made of copper therefore they mainly make Cu6Sn5 IMC. This layer has an effect on the mechanical strength of the soldered joint. Samples are measured by using the shear strength test. The thickness of the IMC layer is measured by Confocal Laser Scanning Microscope. IMC layer thickness grows with greater delivered energy into the joint during soldering.

Optimization of solder paste quantity considering the properties of solder joints

Purpose The purpose of this paper is to find an optimum between the quantity of solder paste and the desired properties of the soldered joint. A reduction of solder paste quantity is recognized as an opportunity to save money. On the other hand, the quantity of solder paste significantly influences the final properties of the soldered joint. The purpose is also to design recommendations for manufacturers of electronic assemblies. Design/methodology/approach The processing of the paper was initiated by a literature review. The expert analysis was the next step. The result of analysis was a fishbone diagram. Subsequently, the experiment was designed. Seven types and three volume of solder pastes and two aperture shapes of the stencil were used. The measured parameters were mechanical strength, electrical resistance, voids area and intermetallic compound (IMC) thicknesses. The results of the experiment were evaluated and recommendations for practice were defined. Findings The carried out research has confirmed the influence of solder paste quantity on the shear strength, electrical resistance, voids area and IMC thickness of solder joint. The article presents the results achieved for solders Sn42Bi58, Sn42Bi57.6Ag0.4, SnAg3.0Cu0.5, SnCu0.7Ag1.0NiGe, SnAg3.5Bi0.5In8.0 and Sn62.5Pb36.5Ag1.0. Reduction of solder paste quantity down to 74 per cent (i.e. one quarter of quantity) decreases mechanical shear strength less than 10 per cent. Recommendations relating to the optimal reduction of solder paste quantity have been designed for each solder paste. Originality/value Contribution of the paper is impact assessment of solder paste quantity on the properties of the soldered joint. It was carried out a large number of experiments and measurements which verify this effect. Such a comprehensive overview of the results is not yet available in the literature. Recommendations for manufacturers of electronic assemblies are also the benefit of article.

Influence of intermetallic compounds growth on properties of lead-free solder joints

This article deals with the growth of intermetallic compounds (IMCs) in solder joints and influence of these IMCs on properties of soldered joints. The test specimens of printed circuit boards (PCBs) with different surface finishes were made for this experiment. Tin_G (galvanic tin), Tin_C (immersion tin), Cu (pure copper), OSP (organic solderability preservative) and ENIG (electroless nickel immersion gold) surface finishes were chosen. The soldered joints were created on the test specimens by reflow soldering process concretely vapour-phase soldering. The surface mount solder joints of LCCC resistor of size 1206 were studied. Two lead-free solder paste and one tin-lead solder paste were chosen for research of IMCs and their influence on properties of soldered joints. The test specimens were exposed to elevated aging for research of IMCs growth in solder joint. The specimens were thermal stressed in hot air oven at the temperature of 150°C for a periods of 0, 1, 2, 4, 8, and 16 days. The shear test was used for research of IMCs growth influence on strength of soldered joints. The results of analysis of IMCs in solder joints using confocal and metallographic microscopes and the results of shear strength measurement will be presented in this article.

Surface roughness influence on solderability

The article deals with results of solderability testing of printed circuit boards. The wetting balance test was used for solderability testing. This test makes wetting force measurement possible as a function of time. Measured values are recorded automatically. Surface roughness is one of parameters, which influence surface wetting. The article will present the results and comparison of tested printed circuit boards with different surface roughness. This comparison will be made for several surface finish types. Test specimens of printed circuit boards with surface finishes SnG (galvanic tin), SnC (immersion tin), Cu (pure copper), OSP (organic solderability preservative) and ENIG (electroless nickel immersion gold) were tested. The test specimens were purposely roughened by different abrasive paper before solderability testing. Roughness created on surface finishes were oriented vertically and horizontally.

Solderability of lead-free surface finished PCB

This paper deals with results of solderability testing. The wetting balance test is used for the evaluation of wetting performance. Dissolving and removing of oxides and contaminations from the surface of a metal or alloy are the primary purposes of flux. Activated metal surface is easily wetted by the molten solder. However flux is corrosive. Other way of cleaning is the special cleaning liquid, e.g. Decotron F10. The paper presents the comparison of printed circuit board solderability test results measured before and after cleaning. This comparison will be made for several surface finish types. Coupons of printed circuit boards with surface finishes galvanic tin, immersion tin, pure copper, OSP (organic solderability preservative) and ENIG (electro less nickel immersion gold) were tested. The environment of storage can affect the solderability of surface. That is why the solderability was measured before and after ageing also.

A comparison of the shear strength of conductive adhesives and soldering alloys

This paper describes the influence of the cure schedule on the shear strength of the joint glued by EPO-TEK® H20S and 8331S. This work also describes the influence of solder alloy types on the shear strength of the solder joint. Joints were made by soldering and gluing of chip resistors 1206, 0805 and 0603 with different temperature profiles on rigid and flexible substrates. For soldering profiles were calculated heating factors. These profiles have an effect on the mechanical strength of the joint. Samples are measured after curing/soldering process by using shear strength test.

Solderability of the Lead Free Surface Finishes

Paper deals with results of solderability testing. The importance of solderability testing grows up with implementing of lead free technology. Different properties of lead free solders, which replace SnPb solders, are first reason. Lead is also contained in surface finishes on component leads or printed circuit boards. Therefore the lead displacement in electronics assembly needs changes in surface finishes too. Lead has to be removed from surface layers of both component leads and printed circuit boards (PCB). In practice there are several types of lead free surface finishes. New surface finishes are second reason for solderability testing. This paper presents the comparison of individual lead-free possibilities. The solderability of several surface finish types was tested. Experiment was composed of resistor (1206) lead testing and of PCB coupon testing. The environment can affect the solderability of surface. That is why the solderability was measured before and after ageing. The results after aging were also presented

Risk Management Methodology Covering the Entire Product Lifecycle

This paper deals with a new risk management methodology covering the entire product lifecycle. Since, no complex and lucid methodology involving all product lifecycle phases has ever occurred. Currently, not all phases are covered or different risk management methods are used for single phases. The proposed methodology copes with two types of risks which may occur during the life-cycle. Predictive risk are the first type and incident investigation the second. At the beginning of an each phase, all possible risks entering the process are considered. These risks are taken into consideration during the entire cycle. Nevertheless, some risk may stay undiscovered and impact. Then incident investigation starts in order to identify risks. The identified risks are treated and considered. Generally, it can be said the methodology makes a closed and never-ending circle of risk management. It is a part of universal process improvement.

The area of spread solderability test use for roughness influence assessment

The article deals with the influence of surface roughness on solderability. The area of spread test was used as a method for solderability measurement. For this measurement, test samples made from substrates for printed circuit boards, small solder balls, and two soldering technologies – vapor-phase and reflow soldering - were used. These technologies have been used because of similarity with the industrial process of soldering. The subjects of examination and comparison were wetting angle and expanse of melted solder on the surface. The paper presents results and conclusions from solderability testing of printed circuit boards with various surface roughnesses. Other conclusion is comparison of several types of fluxes and their impact on solder wetting on roughened surface.

Double-sided preheating influence on solderability

Paper deals with results of solderability testing of Printed Circuit Boards (PCBs). For measurement was used one of the solderability evaluation methods known as the wetting balance test. The wetting balance test measures the wetting forces imposed by the molten solder on the test surface as it is dipped into and held in the solder bath as a function of time. Paper will present the comparison of results of printed circuit board solderability test with preheating in agreement with IPC/EIA J-STD-003A, with IEC 60068-2-54 and with hot air double-sided preheating. This comparison will be also made for several lead-free surface finish types. It was tested printed circuit board coupons with surface finishing of galvanic tin, immersion tin, ENIG (electroless nickel immersion gold), OSP (organic solderability preservative) and pure copper.