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This paper aims to analyze the effect of surface roughness and hardness of leadframe on the bondability of gold (Au) wedge bond using in situ inspection of laser interferometer and its relationship with the deformation and wire pull strength.

The in situ inspection of ultrasonic vibration waveform through the changes of vertical axis (y-axis) amplitude of wire bonder capillary was carried out using laser interferometer to analyze the formation of Au wedge bond. The relationship between the changes of ultrasonic waveform of capillary with the deformation and the pull strength was analyzed to evaluate the bondability of Au wedge bonds.

It was observed that the changes in vertical axis amplitude of ultrasonic vibration waveform of wire bonder capillary can be used to describe the process of bonding formation. The loss of ultrasonic energy was exhibited in ultrasonic vibration waveform of wire bonding on leadframe that has higher value of roughness (leadframe A) as compared to that of leadframe that has lower value of roughness (leadframe B). The lower pull strength obtained by Au wedge bond further confirms the reduction of bond formation because of the higher deformation on leadframe A as compared to that of leadframe B.

The relationship between in situ measurement using laser interferometer with the bondability or deformation and wire pull strength of Au wedge bonds on different surface roughness and hardness of leadframes is still lacking. These findings provide a valuable data in analyzing the bonding mechanisms that can be identified based on the in situ measurement of ultrasonic vibration and the bondability of Au wedge bonds.

The purpose of this paper was to attempt to confirm the root cause of unstable stitch pull strength in PQFN package and propose some permanent solutions for it.

A screen experiment was designed to find the key process out of the manufacturing flow; a non‐destructive detaching method and cross section polishing were used to inspect the bond integrity; Auger analysis assisted with argon ion sputter was tried to confirm the contamination; finally the manufacturing processes were redesigned to prevent the contamination.

Some first aids of process optimization got little improvement; the screen experiment of processes found solder die bonding was the one resulted into a poor bond integrity which was demonstrated by non‐destructive detaching method and cross section inspection; Auger analysis assisted with argon ion sputter detected that there was a tin layer thicker than 20 nm coated on the bonding surface and the wire bondability of gold wire on this tin coating was poor; the lead frame was redesigned to prevent the wetting and flowing of tin and got a perfect performance.

Because of the limitation of time and resources, the proposed solutions for this issue could be studied more deeply.

This paper set up an example how to find out the root cause from the complex manufacturing process flow and put forward a quick solution accordingly for the issue.

A study was undertaken to evaluate the thermosonic gold‐wire bonding capability to Ti‐Pd‐Cu‐Ni‐Au thin film metallisation on newly developed polymer hybrid integrated circuits (POLYHICs). (The POLYHIC technology incorporates alternating layers of polymer and metal added to conventional Hybrid Integrated Circuits which provide for increased interconnection density.) Destructive wire‐pull strengths were measured as a function of varying wire‐bonding machine operating parameters of wedge bond force, wedge bond time, temperature, and ultrasonic energy. All data were evaluated and compared with wire bonding under similar conditions to thin film circuits on Al2O3 ceramic. The results for wedge‐bond associated failures indicated that machine operating parameters of wedge bond force, time and ultrasonic energy similarly affected the average wire‐pull strength for both the ceramic and POLYHIC circuits. Pull strengths for equivalent metallisation schemes and bonding parameters were generally slightly higher and more tightly distributed for bonds made to metal films on ceramic. A strong correlation was found to exist between wire‐pull strengths and surface topography (as measured by a profilometer technique) of the thin film metallisation for the POLYHICs which had both smooth and rough metallisation surfaces for metal films on top of the polymer. The results indicated that rough metallisation bonded more easily and yielded much higher wire‐pull strengths. Also, rougher films were shown to effectively increase the parameter‐operating windows for producing reliable wire bonds. A semi‐quantitative analysis was developed to help explain this correlation. Surface topography effects were also found to be a key factor when evaluating wire bondability as a function of substrate bonding temperature. Wedge‐bond strength was essentially independent of temperature for bonds made to rougher metallisation while a strong temperature dependency was found when wire bonds were made to smoother films.

The bonding of surface mounted components to printed wiring boards (PWBs) is critical to the high yield assembly of components to the PWB. This process is one of the last steps performed in a complicated manufacturing and assembly sequence. Poor bondability at this late stage of assembly produces costly scrap. Aggressive wet‐chemical processes may succeed in cleaning the residues from the metal bonding lands, but in the process the polymeric materials that surround the land areas may be mechanically or visually damaged. Even when processing is carefully controlled during the final formation of land areas in the conformal coating, a thin residue, often invisible to the eye, can partially or fully cover the bonding land area. The residue may be extremely thin, but it inhibits bonding and is very resistant to conventional wet‐chemical cleaning methods. Plasma chemical etching is the one chemical process which can remove the residue from the metal lands and restore bondability without damaging other surfaces of the ready‐to‐assemble PWB. This paper reports examples of plasma removed residues from PWB surface mount bonding lands. The land areas are defined in photodefinable conformal coatings by conventional photolithographic techniques and have a non‐visible surface residue which inhibits the subsequent plating or soldering of the copper land. Auger analyses of the copper land surfaces prior to plasma processing show significant carbon peaks indicative of a polymeric residue. Auger analyses of the copper land surfaces following plasma processing show that the strong carbon peaks are gone.

An overview has been presented on the topic of alternative surface finishes for package I/Os and circuit board features. Aspects of processability and solder joint reliability were described for the following coatings: baseline hot‐dipped, plated, and plated‐and‐fused 100Sn and Sn‐Pb coatings; Ni/Au; Pd, Ni/Pd, and Ni/Pd/Au finishes; and the recently marketed immersion Ag coatings. The Ni/Au coatings appear to provide the all‐around best options in terms of solderability protection and wire bondability. Nickel/Pd finishes offer a slightly reduced level of performance in these areas which is most likely due to variable Pd surface conditions. It is necessary to minimize dissolved Au or Pd contents in the solder material to prevent solder joint embrittlement. Ancillary aspects that include thickness measurement techniques; the importance of finish compatibility with conformal coatings and conductive adhesives; and the need for alternative finishes for the processing of non‐Pb bearing solders are discussed.

This paper reports the results of development work conducted on nitrogen‐based atmospheres in order to improve the firing of copper thick film systems through continuous furnaces. The proposed solution is particularly suitable for industrial production conditions since it allows variations of the material quantity processed per unit time, resulting not only in an improvement in quality but also in productivity. Such improvements have been achieved by using a new gas distribution system which provides both zone control and regulation of oxygen additions in the nitrogen furnace atmosphere. An efficient set‐up of this system has become possible thanks to precise control of the oxygen profile in relation to the temperature cycle, taking into account various inks' characterisation, and owing to an extensive study of the effects of oxygen additions on copper thick film properties. The solution was tested in a muffle‐lined belt furnace with several commercial dielectric and copper inks, and for increasing oxygen additions into the furnace preheat zone. Different sample patterns were designed to test both monolayer and multilayer systems. The test programme includes measurements of resistivity, bondability, solderability, dielectric breakdown voltage and adhesion of copper films on alumina and on dielectric layers before and after ageing. Ink characterisation by thermogravimetry and by several gas analyses has confirmed that the organic vehicle removal mechanism under nitrogen atmospheres doped with oxygen is a burnout. Indeed, significant oxygen consumption occurs within the temperature range of the removal, as a function of the amount of ink processed. Oxygen additions in the furnace burnout zone greatly improve both the dielectric breakdown voltage and the adhesion of copper on alumina and on dielectric (especially after ageing), while sheet resistivity, wire bondability and soft solderability are not altered below a defined O2 level. It is therefore possible to determine an optimum oxygen addition range for which the thick films fired under such conditions will have the best characteristics. This optimum oxygen window is achieved thanks to a new regulation system which operates whenever variations occur in the quantity of paste processed.

The purpose of this study is to address two kinds of printed circuit board (PCB) failures with electrolytic Ni/Au as the surface finish. One was the weak bondability of gold wires to Ni/Au pads and the other was “dull gold” and weak solder wettability, which both caused great loss for the PCB manufacturer.

The failure samples were studied and analyzed in terms of macro- and micro-morphology of the surface finish, its element composition and thickness by various characterization techniques, such as three-dimensional stereo microscope, scanning electron microscope, energy dispersive spectroscopy and X-ray fluorescence spectrum.

Then the causes of the two failures were both found to be the inadequate thickness of gold deposit and other surface finish defects, but these causes played different roles in either failure or the mechanisms differ. Finally, their failure mechanisms were discussed and corresponding countermeasures were put forward for prevention.

This study not only addresses a practical failure problem but also provides some clues to a better and further understanding of the effect of PCB process and management on its quality and reliability in manufacturing practice.

It sheds light on how the thickness and quality of surface finish affects its wire bonding and soldering performances.

In this paper, reproduced by permission of “Metal Finishing” (New Jersey), the author enumerates the required properties of electroplated gold coatings on printed circuit boards and wire to ensure satisfactory bonding by ultrasonic means. The gold plating procedures and process control methods which are necessary to produce coatings yielding consistently high bond strengths are described.

This paper attempts to review recent advances in wire bonding using copper wire.

Dozens of journal and conference articles published recently are reviewed.

The problems/challenges such as wire open and short tail defects, poor bondability for stitch/wedge bonds, oxidation of Cu wire, strain‐hardening effects, and stiff wire on weak support structures are briefly analysed. The solutions to the problems and recent findings/developments in wire bonding using copper wire are discussed.

Because of page limitation of the paper, only a brief review is conducted. Further reading is needed for more details.

This paper attempts to provide introduction to recent developments and the trends in wire bonding using copper wire. With the references provided, readers may explore more deeply by reading the original articles.

Plasma chemistry is employed almost exclusively for etching, cleaning and deposition processes in semiconductor device fabrication technology. As a natural expansion of this successful technique, attention has been directed at similar processes for thick film ceramic, thin film hybrid and more generally printed circuit board electronic assemblies. This paper discusses a variety of applications, some established and some experimental, where plasma is offering the benefits which semiconductor engineers have enjoyed for many years. Such applications include general organic removal, i.e., flux residues, finger print contamination and the removal/reduction of oxides and glass on thick film conductors to promote improvements in solderability and wire bondability.