Solder paste

Persistently growing High-power LED packaging is used in various flux applications especially microelectronics, aerospace, oil and gas as well. Thermo-compression die-attach layer is perceived to be the most critical element in high- power LED packages as the increase in operating temperature requires new materials with suitable thermo-chemical properties also with suitable melting points of next generation lead free die attachment material. In this situation, Hi-lead solder (RM218: Pb92.5Sn5Ag2.5) which known as high temperature material is widely being used in most semiconductor assembly for die attach, yet it deduces few reliability challenges like solder voids, the tilt performance and also solder splash which has been considered as major quality issue in assembly of high-power LED packages. As a solution, sintering epoxy paste (SPC073-3: Sn96.5/Ag3/Cu0.5) is being considered as a replacement due to the challenges faced by using Hi- lead solder paste. In this case, sintering epoxy paste demonstrating excellent electrical and thermal performance for High- power LED packages that is known to be demanded in market. Thus, this study investigates the differential pastes sintering paste and solder paste, in order to identify best die attachment material to be used in thermo-compression bonding method. Therefore, the shear strength was resulting good indication where the sintering paste was recorded 2.4 Kg/mm meanwhile the solder paste was recorded 0Kg/mm at peak temperature of 260°C. Besides of that, the pot life seems promising as the sintering paste seems to have constant viscosity of 100Pa*s throughout the 48 hours tested while, high lead solder paste records viscosity from 100Pa*s marginally increase as the time increase which effects the inconsistency of pot life. The voids performance proves sintering epoxy paste has the same pinhole voids as its individual, but the solder paste’s pinhole voids are not same as individuals which easily can fail when the particular shear force was applied. Hence, sintering epoxy paste could resolve the quality issue by using thermo-compression bonding method and produce the better reliability than the solder paste.

(Sekharan 2006), conducted a half factorial DOE by considering five factors at two levels and obtained optimal settings for a solder paste printing process. squeegee pressure, squeegee speed, snap off, separation speed and stencil wipe frequency were the five different factors that were considered for performing the DOE. The height of the solder paste deposition was considered as a response variable. The interactions of the snap off and the separation speed, the print speed and the squeegee pressure, and the separation speed and the stencil wipe frequency were identified as significant interactions that influenced the solder paste height deposition. The results of the DOE indicated that among the two levels chosen for each factor, a high squeegee pressure, high printing speed, low snapoff , low separation speed were part of optimal print parameters. The authors have also shown a 20% percent improvement in response variable by performing a validation run with the optimal print parameters.

Dust and dirt from the air that ends up on the PCBs and stencils can cause defects such as bridging and poor wet-ability in the reflow soldering process. A small piece of fibre or hair between two fine pitch solder pads can easily cause bridging. It is therefore very important that the PCBs are stored in sealed packages and if necessary, cleaned before use. Air draught in the production area can speed up evaporation of the solvents in the solder paste and thereby makes the solder paste dry out. High temperature can also make the solder paste dry out quickly. If the room temperature in the production area varies a lot, it will be very difficult to control the printing process. The viscosity of the solder paste changes with the temperature and the solder paste print will sometimes be perfected and at other times, paste will slump and result in bridging. The temperature window is between 21 – 25°C.

foral and diethylamine hydrochloride were used to help sol- dering. The specimens were heated to the soldering tempera- ture at 210C   ±  2C(solid state), 220C   ±  2C(semi-solid state) and 240  ±  2C(liquid state) by the heating table after filled the solder paste and rosin-based flux at first, and then vibrated 0 s, 5 s, 10 s and 15 s by ultrasonic, finally the sol- dering process was completed after holding 10 mins. Optical metallographic microscope (OM) and scanning electron mi- croscope (SEM) were used to analyze the microstructures of interfacial. The thickness of IMC layer was calculated by the Image-pro Plus software. The average shear strength of sev- eral joints (the shear velocity was 10 mm/min) were iden- tied by the PTR-1101 bonding strength tester.

Chapter five presents the investigation done to determine the optimum settings of the design parameters squeegee speed and pressure, print gap [snap off distance] and squeegee separation[r]

Investigation of the effect of particle size distribution on solder viscosity and on particle hydrodynamic interaction in paste flow This part of the work includes the development of a v[r]

Accurate shot size control is a precondition for dot shape control. Given good control of size, the dot shape is determined by the dispense tip shape and size, and by the height from which the dot is released. It is also influenced by paste properties. To facilitate a comparison between the three valves used in this study, solder paste masses of 8, 4, 2, 1, 0.5, 0.25, 0.125 and 0.063 milligrams were specified, and each valve was tested at the points that fell within its controllable range. ON/OFF times chosen were long enough to give repeatable dispense mass. Valve pres- sure of 70 psi (480 kPa) and reservoir pressure of 20 psi (140 kPa) were used for all dot shape tests. Prior to each test run, the valve was cycled, shots weighed, and micrometer adjusted until the required mass was obtained. Reference height was set by touching the dispense tip lightly to the slide surface, this method proved to be repeatable within +/- 0.001 in (25 µm). Non- coplanarity over the area of the test pattern contributed an additional +/- 0.001 in (25 µm) error. The 20 test dots were dispensed next to each other on the slide. For the larger dots, the first dot was dispensed from 0.080 in (2.03 mm) above the surface, the second 0.004 in (0.1 mm) lower, and so on, with the last dropped from a height of 0.004 in (0.1 mm). The smaller dots had a starting height of 0.040 in (1.02 mm) and the increment was 0.002 in (0.05 mm). After dispens- ing a dot and waiting until the required OFF time had elapsed, the tip was raised 0.25 in (6.35 mm) and moved laterally to the next site.

The solders used in this study were Sn-3.5Ag-0.5Bi-3In, Sn-3Ag-2.5Bi-2.5In, Sn-3.5Ag-0.5Bi-8In, and Sn-8Zn-3Bi, with Sn-37Pb used as the reference solder(all compositions are expressed in mass %). Each solder paste was mixed with a mildly activated rosin (RMA) flux. 20 mm 20 mm 120-pin QFPs (quad flat packages) with Sn-Bi(10 mm), Au(0.01 mm)/ Pd (0.08 mm)/Ni(0.3 mm) (from surface to inside) and Sn- Pb(10 mm) plated Cu leads were reflow-soldered in air onto Cu pads of PCBs using the solder paste composed of each solder alloy. The reflow profile consisted of pre-heating at 160 C for 90 s followed by holding at above 220 C for 20 s at

A solder alloy comprises Sn, Ag, Cu, and Mn and has a melting temperature of about 211 degrees C. A solder joint and solder process embody the solder alloy as well as solder balls and solder paste made therefrom to provide a solidified joint that includes three different intermetallic phases and a Sn metal phase. An exemplary Sn—Ag—Cu—Mn alloy consists essentially of about 3 to about 4 weight % Ag, about 0.80 to about 1.0 weight % Cu, and about 0.05 to about 0.15 weight % Mn, and balance consisting essentially of Sn.

In general, glutaric acid, adipic acid, and sebacic acid, which have high melting points, were included in soldering flux as activators to remove the surface metal oxide of solder alloy. We converted the carboxyl group of the above carboxylic acid compound into hemiacetal ester units by reaction with alkyl vinyl ether. The viscosity of glutaric acid di(2-propoxyethyl) ester was 8.3 mPas, while that of adipic acid di(2-propoxyethyl) ester was 8.6 mPas and that of sebacic acid di(2-propoxyethyl) ester was 14.9 mPas. The obtained thermal latent carboxylic acid derivatives had lower viscosity than ordinary organic solvents and exhibited better solubility and compatibility. It appears that the use of a solder paste and soldering flux produced with thermal latent processing of the carboxylic group could reduce VOC’s, because the carboxylic acid compound has poor solubility and a greater amount of organic solvent is required to dissolve it.

Contact angles were measured via a spreading method. Solder paste was placed on the Au-plated substrates using a steel mask to mount the paste. The specimens were then maintained at the testing temperature for 30 s. Next, the specimens were allowed to cool down in air (typical spec- imen is shown in Fig. 1(a)) and a cross-section (Fig. 1(b)) was obtained for the contact angle measurement.

stop the assembly at this point and check for shorts and solder bridges around the IC sockets, voltage regulators, and the lOO-pin connector... off the solder flux with alcohol or a simi[r]

racemosa, Holoptelea integrifolia, Indigofera hirsuta, Ipomoea carnea, Lepidagathis cuspidata, Litsea glutinosa, Cayratia trifolia, Commelina benghalensis, Cordia dichotoma, Crinum viviparum, Cucumis sativus, Curcuma longa, Cynodon dactylon, Dendrophthoe falcata, Phlogacanthus thyrsiformis, Plumbago zeylanica, Pogostemon benghalense, Solanum erianthum, Ruellia tuberosa, Solanum americanum, Tridex procumbens, Vallaris solanacea, Urena lobata, Wrightia arborea and Vanda tesselata. In several cases two different parts of equal species are used together for preparation of herbal drug e.g. in treatment of boils leaf and seed paste of Senna tora mixed together and used externally, like as leaf and root paste of Vitex negundo and leaf and stem paste of Withania somnifera for the same disease; the leaf and bark paste of Dalbergia sissoo together used externally as a remedy for eczema, while in some other cases parts of two different species are used together as a remedy, e.g. leaf juice of Abrus precatorius and Plumbago zeylanica for the treatment of leucoderma. The information also was checked with available prose 50-52 .

Abstract—The superior electro-thermal properties of SiC power devices permit higher temperature of operation and enable higher power density compared with silicon devices. Nevertheless, the reliability of SiC power modules has been identified as a major area of uncertainty in applications which require high reliability. Traditional power module packaging methods developed for silicon chips have been adopted for SiC and the different thermomechanical properties cause different fatigue stresses on the solder layer of the chip. In this paper a 2-D Finite Element (FE) model has been developed to evaluate the stress performance and lifetime of the solder layer for Si devices, which has been validated using accelerated power cycling tests on Si IGBTs. The proposed model was extrapolated for SiC devices of the same voltage and current rating using the same solder material and the results show that under the same cyclic power loss profile the induced stress and strain energy in the die attach layer is much higher and concentrates on the die/solder interfacial area for SiC chips. Using the validated stress-based model, the lifetime can be quantified when SiC chips are used. This ability to extrapolate the available power cycling and lifetime data of silicon chips to silicon carbide chips would be a key element for developing reliable packaging methods for SiC devices.

Thus L-cysteine is oxidized at the electrode surface, and this process occurs in the potential of 0.77 V. The oxidation process does not occur in this potential when is used glassy carbon electrode or unmodified carbon paste. The peak potential is not affected by the concentration of L-cysteine and the catalytic current is also linear with the square root of scan rate. The behavior of electrochemical oxidation of L-cysteine in the TiPhAgHCF modified electrode is very similar to the electrode modified with a film of Prussian blue, which shows an increase of the current in the two oxidation potentials (0.79 V) in the presence of L-cysteine (1.0 mol L -1 KCl, pH 7.0 vs. Ag / AgCl) [43].

Another interesting feature to note from this study is that the corrosion location will impact the required shear strength. The top-side corroded bump did not significantly affect the shear strength of the Sn-Ag solder bump under shear loading. As shown in Fig. 5, the shear strength for the bumps with corrosion at the top of the bump had similar values to that for the bumps without corrosion. The corroded part of the bump did not affect the shear loading of the bump because the cor- rosion part is far from the shearing plane. The shearing planes are indicated with red line in the Fig. 5. On the other hand, in the case of the partially corroded bump at the side of the bump, the shear strength was approximately 20 gf. Compared to the bump without corrosion, the shear strength was de- creased by approximately 25%. This correlates to the bump shearing height, which was 15 μm in this study. In the case of the partially corroded bump at the side of the bump, the cor- rosion parts are partially on the shearing plane, resulting in the deterioration of the bump shear strength during the bump shear test.

Aluminium (Al) used in integrated circuits as a most common conductor due to its better properties [20] but it soon appeared that pure Al is susceptible to EM (get rapid formation of hillocks and voids). After adding 2% - 4% of Cu to Al its shows better performance in ICs but problem is grain boundary segregation of Cu, which greatly inhibits the diffusion of Al atoms across grain boundaries. In advanced semiconductor manufacturing processes, Cu has been replaced Al as the interconnect material of choice, because it is less vulnerable as it has higher mass and a higher melting point. Although it’s greater fragility in the fabrication process, Cu is preferred for its superior conductivity. Cu is also intrinsically less susceptible to EM. However, EM continues to be an ever present challenge to device fabrication, and therefore the EM research for Cu interconnects is ongoing [12]. On the other hand, the use of Cu plate as substrates, where the electrical connection can be made very simply and they can sustain a fairly large electrical current. It is important in power ICs because we want the EM to be restricted only to the solder bumps as it is well known that the EM of the thin film metal lines in ICs is the major reliability problem since 1970s [16] [21].

Input/output (I/O) requirements for integrated circuit (IC) packages continue to increase with increasing levels of cir- cuit integration, while the package size continues to decrease. Most of interconnections of the package are based on solder- ing process-joining between Sn based solder materials and Cu(or Ni) substrate. This interconnection process, however, has several problems: toxicity and radioactivity of lead as a solder alloy element, corrosion of substrate by using flux cleaning agents and excessive growth of Sn–Cu intermetal- lic compound. 1–3) Thus, new solder materials and soldering

layer against the diffusion of Ni to solder, formation of intermetallic compound at inside of Sn–Ag solder was not occur as such even if holding time of peak temperature was extended. 4,5) While, in this Ni/Sn–Ag/Au/Ni–20Co joint, much intermetallic compounds were formed and the amount of the heat of melting decreased. The microstructure of specimen in the case of heating until 553 K was similar to that in the case of holding at 513 K for 1:8 10 3 s, moreover, the endothermic peak decreased in the case of heating at Ni-20Co/Kovar(Package side)

i so precisely laid out, the leads run very close together. Although JADE has taken the trouble , to use the most modern solder-masking techniques, it is possible to create solder bridges. So ) if you're heavy-handed with the soldering iron, beware. Too much heat, and the application A