Solder Plating Research Articles

Sess. 1-1 A Sulfuration Gas Test for Chip Components With Solder Plating on Silver Termination

Sess. 1-1 A Sulfuration Gas Test for Chip Components With Solder Plating on Silver Termination

Effects of Reflow Processing and Flux Residue on Ionic Migration of Lead-Free Solder Plating Using the Quartz Crystal Microbalance Method

To investigate the ionic migration, quite a new measurement method has been developed by the authors, which enables real time monitoring of the growth process of ionic migration using a QCM (Quartz Crystal Microbalance). This research has focused on the QCM method to study the growth process of ionic migration in various types of lead-free solder plating and the effects of the reflow processing and flux residue of soldering processes. In addition, we investigated the anode dissolution characteristics of the elements in each type of solder alloy by measuring the current-potential curve in 0.1 kmol m -3 KNO 3 solution. When using Sn-3.5 mass%Ag solder plating, reflow processing segregates the stable compound Ag 3 Sn layer and Sn layer. The Sn layer selectively promotes the anode dissolution reaction, increasing the occurrence of migration. When using Sn-9 mass%Zn solder plating, the Sn effectively prevents the excessive dissolution reaction of Zn. However, since reflow processing causes each element to separate out, reflow processing lessens the effectiveness of Sn, thus promoting the occurrence of migration. The flux processing of lead-free solders suppresses anode dissolution and effectively prevents the occurrence of migration. However, with Sn-9 mass%Zn, the lowered adhesion between the flux film and the electrodes is a factor in speeding the growth of migration.

めっきの基本組成の役割 スズ，はんだおよび鉛フリー合金めっき

めっきの基本組成の役割 スズ，はんだおよび鉛フリー合金めっき

Manufacturing of Cu/electroless nickel/Sn-Pb flip chip solder bumps

A process for manufacturing Cu/electroless Ni/Sn-Pb solder bump is discussed in this paper. An attempt to replace zincation with a Cu film as an active layer for the electroless Ni (EN) deposition on Al electrode on Si wafer is presented. Cu/electroless Ni is applied as under bump metallurgy (UBM) for solder bump. The Cu film required repeated etches with nitric acid along with activation to achieve a satisfactory EN deposit. Fluxes incorporating rosin and succinic acid were investigated for wetting kinetics and reflow effectiveness of the electroplated solder bump. The solder plating current density and the reflow condition for achieving solder bumps with uniform bump height were described. The Cu/EN/Sn-Pb solder system was found to be successfully produced on Al terminal in this study that avoids using zincating process.

Polarographic methods of monitoring addition agents in the electroplating of Sn-Pb solders

The electrochemical techniques typically used to monitor organic addition agents in electroplating baths work poorly in Sn-Pb solder plating baths. These electrochemical monitoring methods are based on the principle that additives act through their effects on the kinetics of the metal-deposition reaction, and thus the reaction M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n+</sup> + ne <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−</sup> → M can be used as a probe to determine the additive concentration. The heavy metal ions in solder plating baths readily poison probe electrodes, however, and thus electrochemical methods on solid electrodes are irreproducible and unreliable in these systems. A polarographic technique, which uses a renewable Hg drop electrode, can be used for the quantitative analysis of addition agents in solder plating solutions, even though the chemical identity of these species may not be known to the user of the plating solution.

Ｐｂフリーはんだ用Ｓｎ‐Ａｇ合金めっき

We studied the effects of electrodeposition conditions on Sn-Ag alloy composition and current efficiency in Pb-free solder plating employing a new pyrophosphate-iodide bath. We also investigated the morphology, phase structure, thermal characteristics and solderability of electroplated Sn-Ag alloy films. Ag content in deposits decreased with increasing current density during both agitation and nonagitation, Sn-Ag electroplated films containing between 2.0 and 20.0 at% silver consisted of β-Sn and the e phases, β-Sn phase orientation in electrodeposited Sn-Ag alloy films became random with increasing e phase content. The melting point, i.e., the temperature at which melting first occurred, of electroplated Sn-Ag alloy films was 221°C. Wetting time of electroplated Sn-Ag alloy films became minimum at a near Sn-Ag eutectic composition and was not affected by thickness from 0.5 to 10μm.

環境規制と代替技術 Ｐｂフリーはんだめっきの現状

環境規制と代替技術 Ｐｂフリーはんだめっきの現状

５，５‐ジメチルヒダントインを用いたアルカリ系Ｓｎ‐Ａｇ合金めっき浴の検討

We studied the development of alkaline and electroplating baths of Sn-Ag binary alloy using 5, 5-dimethylhydantoin (DMHy) as a Pb-free solder plating bath under various conditions, such as metal content, complex agent concentration, pH, current density and bath temperature. From these results, e. g., adding large amount of DMHy, pH 10.5, high current density, etc., electroplating films of Sn-Ag alloy having eutectic and constant composition were obatined. Surface morphology and solder wetting time of Sn-Ag alloy electroplating films become roughened with increasing film thickness. The melting point of Sn-Ag alloy electroplating films was about 221°C, similar to that of Sn-Ag ingot, and its phase structure consisted of eutetic structure of β-Sn and the e phase (Ag3Sn).

無電解めっき 無電解はんだめっき技術の開発と実用化

無電解めっき 無電解はんだめっき技術の開発と実用化

Electroless nickel/copper plating as a new bump metallization

An electroless bumping method was developed both for flip chip and TAB applications. Electroless Ni/Cu plating is a maskless low-cost approach to bumping directly on aluminum bondpads. An immersion tin layer for coating and soldering is plated on the copper. Due to the high alkalinity (pH>12) of electroless Cu baths, a thick Ni layer of about 7 /spl mu/m is required on the aluminum for seating. A shear strength of 180 cN and a contact resistance of less than 2 m/spl Omega/ for the bumps were obtained. Because of the high hardness of nickel, conventional gang bonding techniques are not applicable. The hardness of electroless copper is about 200 mHV/sub 25/, and after annealing in the range of 130-150 mHV/sub 25/ thermocompression gang bonding of Au plated tape to the Ni/Cu/Sn metallization was carried out. The average pull strength was 50 cN. The influences of the size and electroless solder plating of the deposited copper are also investigated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

置換すずめっき処理によるはんだめっきの改質

The solder plating posttreatment we developed involved immersing the plating film in a tin fluoborate solution and substituting tin for lead as follows:Sn2+(L)+Pb(s) High temp._??_Low temp.Sn(s)+Pb2+(L)where (L) indicates “in solution” and (s) indicates “in solder film”. Increasing the concentration of Sn2+ and the temperature reversed the redox potentials, M2++2e_??_M, toward less noble Sn making the forward reaction dominant.This treatment produced a smooth surface lustrous and enriched in tin content in the outer portions of the film. This resulted in a marked inprovement in antioxidation properties, adhesion to the basis metal, solderability, and heat-humidity stability.Enriched lead in the bath due to the multitreatment was easily removed as PbSO4 precipitate by adding sulfric acid.

特集 超高密度実装のためのマイクロソルダリング技術 無電解はんだめっきによるＴＣＰの実装技術

特集 超高密度実装のためのマイクロソルダリング技術 無電解はんだめっきによるＴＣＰの実装技術

自己触媒型無電解はんだめっき

自己触媒型無電解はんだめっき

パラジウムめっきリードフレームの熱処理後の特性

When palladium-plated lead frames are used for ICs, solder bridging and silver migration do not occur.In this report, palladium plated lead frames were studied for such characteristics as solderability and wire-bondability after thermal treatment to simulate IC assembly. Their corrosion resistance was also studied.The following results were obtained.(1) Solderability of 0.05μm-thick palladium plating was virtually as good as that of 5μm-thick Sn 90wt% solder plating.(2) Palladium-plated lead frames had excellent solderability and gold wire-bondability even after heating at 300°C for about 1min.(3) The corrosion resistance of the palladium plating on copper alloy substrates was relatively good, but on ferro-alloy substrates, considerable pitting corrosion occured due to the difference in natural electrode potential between the palladium and the substrate.

Attachment reliability evaluation and failure analysis of thin small outline packages (TSOP's) with Alloy 42 leadframes

A series of studies designed to evaluate the long term surface mount reliability of Alloy 42 leaded thin small outline packages (TSOPs) using thermal cycling as an acceleration method is described. Visual inspections, pull strength, and scanning electron microscopy were used to characterize the solder joints. In addition, the solder plating, lead wetting, and aging characteristics were evaluated. Failure during thermal cycling was primarily caused by the coefficient of thermal expansion (CTE) mismatch between the package and the printed wiring board. By using acceleration factors based on solder joint strain energies induced by global and local mismatches during thermal cycling, the experimental results are extrapolated to various use conditions and life expectancies. The TSOP solder joint reliability depends on environmental conditions (cyclic temperature range, temperature maximum, and dwell time), board thickness and materials, product intended service life, and expected hazard rate limits. >

無電解はんだめっきの皮膜特性

Electroless solder plating by the displacement reaction has been investigated. The addition of free borofluoride and hydroxylamine both improved the stability and extended the life of the plating bath The plating bath reaction was initiated 10s after immersion of the copper substrate into the bath Deposition morphology after 1min of reaction was similar to the final equilibrium stage of the deposit. Wettability was decreased due to diffusion of copper at film thickness of around 0.5μm, but (film thickness of 4μm or more) wettability was excellent with no decrease observed

有機酸系無電解はんだめっき浴での添加物の影響 （第２報）； 界面活性剤および酸化防止剤についての検討

The effects of the addition to organic acid baths for displacement solder plating of surfactants used as leveling agents and oxidation inhibitors used as bath stabilizers were investigated. The most effective surfactants were found to be isolated systems of Triton X-100 and laurylpyridinium chloride for the hydrophile-lipophile balance of the surfactants and a mixture of laurylamine and Triton X-100 for a decrease in foaming. o-Aminophenol and o-phenylenediamine, which are conjugated-system compounds of 1, 2-substituted benzenes and have moderate reducing power, showed good properties as oxidation inhibitors.

有機酸系無電解はんだめっき浴での添加物の影響； 錯化剤についての検討

The effect of additives (i.e. complexing agents) to organic acid baths in obtaining solder plating films at 0.8 to 0.9 of Sn/(Sn+Pb)-molar fraction {0.6 to 0.9 of Sn/(Sn+Pb)-weight fraction} by displacement plating was investigated by physicochemical methods. An effective plating film was obtained from a basic bath composed of metal salts of Sn and Pb, an organic acid, a first complexing agent (thiourea, abbreviated as TU) and a surface active agent (laurylpyridinium chloride), and the molar fraction of Sn/(Sn+Pb) was 0.50 {the weight fraction of Sn/(Sn+Pb) was 0.36}. It was found that the effective first complexing agent in the compounds containing sulfar had a C=S group such as TU and its derivatives. The formation of Sn whiskers on the plating film was depressed by adding a second complexing agent (glycine) to the bath. The working efficiency (deposition rate and lifetime) of baths with glycine was similar or superior to those without glycine.

特集／電子部品の表面処理 半導体パッケージアウターリードへの基板実装用はんだめっき

特集／電子部品の表面処理 半導体パッケージアウターリードへの基板実装用はんだめっき

Resistance welding of fine wires to solder-plated printed circuit boards

Parallel gap resistance welding of Ag plated 0.18 mm diameter oxygen free copper wires to solder plated prined circuit boards (P/B) was investigated. Results obtained are summarized as follows.(1) Proper electrode force of weld condition is selected; the electoode force 2.5 kgf (24.5N, at the start of current on) and the maximum electrode force 2.8 kgf (27.4N).(2) Opteimum Thikness of Solder plating is 15-35μm.(3) Proper width of the Patterns is 0.8 mm (tolerance±0.1mm).(4) Electrode material of Cu-W (Cu 30%, W 70%) has seven times longer life than Mo in the number of tolerable continuous welding points. (90°peel welding strength is over 0.3 kgf (2.94N))