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The effect of the fiber laser soldering parameters, laser-soldering output power and laser-soldering scanning speed, respectively, on the Sn-Ag-Cu/Cu interfacial reaction was investigated in this paper. When the output energy was very low, the Cu6Sn5 IMC was in scallop type with smooth surface; as the energy increased, the Cu6Sn5 grains showed the morphology of scallop type grains with faceted surface; further grew the energy, the scallop-type of Cu6Sn5 would be replaced by the prism-type Cu6Sn5; the Cu6Sn5 grains which were bottom closely arranged with a convex on the top can be found if the laser soldering energy was up again; when the laser soldering energy increased again, the plate-like Cu6Sn5 can be observed at the interface between the solder and Cu substrate.

Multi-beam optics for a novel laser soldering system providing solutions for various industrial laser soldering applications have been developed and successfully applied. The key components are diffractive optical beam splitters adapted to solder point positions.

Laser tissue soldering is a method of repairing incisions. It involves the application of a biological solder to the approximated edges of the incision and heating it with a laser beam. A pilot clinical study was carried out on 10 patients who underwent laparoscopic cholecystectomy. Of the four abdominal incisions in each patient, two were sutured and two were laser soldered. Cicatrization, esthetical appearance, degree of pain, and pruritus in the incisions were examined on postoperative days 1, 7, and 30. The soldered wounds were watertight and healed well, with no discharge from these wounds or infection. The total closure time was equal in both methods, but the net soldering time was much shorter than suturing. There was no difference between the two types of wound closure with respect to the pain and pruritus on a follow-up of one month. Esthetically, the soldered incisions were estimated as good as the sutured ones. The present study confirmed that temperature-controlled laser soldering of human skin incisions is clinically feasible, and the results obtained were at least equivalent to those of standard suturing.

Solar cells have to be connected electrically to each other in a solar module. During the last years, new connection techniques with low stress have been developed, such as selective soldering. The industrially most frequently used selective soldering techniques are induction soldering, contact soldering, laser soldering and spot light soldering. The aim of this work is to evaluate the characteristics of solder joints, which are produced by the use of selective soldering techniques. Therefore adhesive strength tests, electrical characterizations and x-ray analyses have been performed. In this process one front-side metallization, a SnAg-solder and a SnPbAg-solder were used. The characterization method will be demonstrated on the spot light soldering technique. In addition the influence of the solder joint quality on the resistance of the whole solar cell will be demonstrated and discussed.

AIM To explore the feasibility and reliability of CO₂ laser soldering on the reconstruction of dura mater in the minipig model. MATERIAL AND METHODS Ten minipigs were divided into 2 groups as Group A (n=5) and Group B (n=5). Bilateral fronto-parietal craniotomy was performed and 2 cm × 1 cm dural defect created under general anesthesia. Then, the defect was repaired with autologous temporalis fascia by CO₂ laser soldering. After pressure and watertightness testing, the minipigs of group A were sacrificed immediately. Minipigs in Group B were followed for 4 weeks, with daily monitoring of behavior, food intake, skin incision and neurological condition. Animals of Group B were also subjected to the same tests as group A. Then, they were also sacrificed. The reconstructed area and underlying brain tissue were fixed in paraformaldehyde and submitted for histological analysis. RESULTS No neural impairment, hydrops or empyema, and no cerebrospinal fluid leak in the dura-fascia interface were observed in Group B. The mean burst pressures were higher than the mean intracranial crest pressure in groups A and B. This difference was significant (P=0.010, P=0.000, respectively). The physiological intracranial pressure of ten minipigs ranged between 4.53 and 6.47 mmHg. No thermal injury was observed in either group. CONCLUSION CO₂ laser soldering for dural defect reconstruction was feasible and reliable.

Fast laser soldering processes are very attractive for the production of miniaturized interconnections with high reliability as they allow solder joint quality assurance during soldering. In order to evaluate the solder joint quality temporal changes of the temperature distribution inside the solder joint due to melting of the solder and wetting of the component and the pad metallizations must be well understood. In this paper we present thermal simulations of fast laser soldering processes taking the essential changes of the solder geometry into account. Moreover, we use a new relation for the calculation of the moment of wetting in dependence of the interface temperature. With this model the influence of the wettability of the pad and the component metallization and of the position of the laser beam on the temperature distribution inside the solder joint are investigated.

Sweeping changes in federal regulations concerning solder assembly of electronic circuitry have stimulated considerable effort to find new and environmentally acceptable materials and processes. This work has led to solvents that are effective and efficient in removing flux residues from the surfaces of assembled printed wiring boards. Cleaning technologies are described that use recyclable solvents, such as supercritical CO2, and no solvents at all, such as laser ablative cleaning. Fluxless soldering with lasers is shown to be an attractive process for certain product applications. The results of a study designed to evaluate the reliability of circuits soldered with the use of “low solids “fluxes are presented along with initial results of a large effort to develop Pb-free alloys for soldering. Advanced soldering technologies, such as laser soldering, are discussed and results from continuing efforts in this area are presented.

The paper presents the results of a study of the procedure of laser soldering chip SMD components, taking into consideration various parameters of the soldering process: type and quantity of solder paste used, energy pumped into the system, etc. There are many situations in modern electronics where the heat for soldering must be controlled very accurately, for example for soldering temperature sensitive components or using different substrates that require a soldering temperature different than the usual ones (PMMA substrates need low temperature soldering). We studied the energy necessary for realizing high quality solder joints even from the first soldering, thus reducing the number of destroyed samples and decreasing the time and costs of development of the electronic module. Based on the theoretical model, we soldered components and performed electrical and mechanical tests, cross-sections, optical and X-ray inspections.

In laser soldering, one has direct control over the incident laser pulse energy and duration but only indirect control over the temperature profile of the parts to be soldered. To understand the conversion of incident laser energy into a substrate temperature profile, two processes need to be understood: first, the optical absorption as a function of temperature and, second, the temperature distribution as a function of absorbed energy. The optical absorption aspect is addressed here. A set of total reflectivity measurements for real surfaces of interest is presented along with analytical calculations of the temperature dependence of the optical absorption for both specular and rough surfaces.

The common method of closing conjunctival incisions is by suturing, which is associated with several disadvantages. It requires skill to apply and does not always provide a watertight closure, which is required in some operations (e.g., glaucoma filtration). The purpose of the present study was to evaluate laser soldering as an alternative method for closing conjunctival incisions. Conjunctival incisions of 20 ex vivo porcine eyes were laser soldered using a temperature-controlled fiberoptic laser system and an albumin mixed with indocyanine green as a solder. The control group consisted of five repaired incisions by a 10-0 nylon running suture. The leak pressure of the repaired incisions was measured. The mean leak pressure in the laser-soldered group was 132 mm Hg compared to 4 mm Hg in the sutured group. There was no statistically significant difference in both the incision's length and distance from the limbus between the groups, before and after the procedure, indicating that there was no severe thermal damage. These preliminary results clearly demonstrate that laser soldering may be a useful method for achieving an immediate watertight conjunctival wound closure. This procedure is faster and easier to apply than suturing.

This degree project has been carried out in cooperation with Enertech AB in Ljungby and is pilot study to automating all current manual soldering. The soldering process accounts for a large part of the processing cost in the production of a heat pump. The process is also a quality risk and has a major impact on the lifetime of the final product. The Main task of this project has been to evaluate automation of the soldering process, to develop automation solutions and a principle layout, to draw the design changes required for the automation and to calculate the supposed solution. This pilot study has resulted in a suggested automation solution using laser as a heat source for soldering. Calculations of the solution show that a automating a laser soldering cell is very profitable.

In this paper, soldering experiments of fine pitch quad flat package (QFP) devices were carried out when soldered with Sn–Ag–Cu and Sn–Cu–Ni lead-free solders by means of diode laser soldering system, and compared with the experimental results soldered with Sn–Pb solders and with infrared (IR) reflow soldering method. The results indicate that under the conditions of laser continuous scanning mode and the fixed laser soldering time, an optimal power is obtained when the optimal mechanical properties of QFP microjoints are achieved. Mechanical properties of QFP microjoints soldered with laser soldering system are better than that of QFP microjoints soldered with IR soldering method. Results also indicate that adding rare earth element Ce to Sn–Ag–Cu and Sn–Cu–Ni lead-free solders improves mechanical properties of QFP microjoints, and the optimal amount of Ce is about 0.03%.

Microsurgical reconstruction to correct male infertility, although usually performed for vasectomy reversal, also is performed to correct other types of iatrogenic, congenital, and postinflammatory obstruction. In an effort to improve success rates and facilitate performance of these complex microsurgical procedures, modifications are continually suggested. This article reviews some of these proposed modifications. The modifications can be divided into five general categories: (1) use of biomaterials/sealants, (2) laser soldering, (3) use of absorbable and nonabsorbable stents, (4) new intussusception vasoepididymostomy (VE) anastomotic techniques, and (5) use of robotics.

In the present paper feasibility and potential advantages of using diode laser for surgical treatment of cerebral ischemia and intracranial aneurysms will be evaluated. At this purpose non linear mathematical model was developed and experimentally validated to investigate the effects of the changes in tissue physical properties, in terms of operating time, tensile strength and tissue damage during medical laser application. The numerical simulations have been carried on by a finite-elements based software package (FEMLAB). In vitro results of human saphenous veins of inferior limbs (n=55) after 799 nm diode laser soldering, combined with an indocyanine green-enhanced, will be presented. The simulations results and their comparison with experimental measurements will be reported.

Au surface finish is common used as a protection layer on pads. In the traditional reflow process, Au will be dissolved into solder and form AuSn4 IMCs (intermetallic components). However, as for the solder joints fabricated by laser soldering, the morphology and distribution of the AuSnx IMCs are quite different from that in solder joints fabricated by traditional reflow methods. The formation, distribution and evolution of IMCs will affect the properly and reliability of solder joints directly. This paper presents a detailed analysis of AuSnx IMCs evolution in laser reflowed solder joints during isothermal aging process. To investigate the effect of Au thickness on the evolution of AuSnx IMCs, pads with 0.1, 0.5, 0.9 or 4.0 mum Au surface finish were introduced into our experiment. The solder joints were aged in the 125 degC isothermal oven. Experiment results showed that few IMCs formed at the interface of the solder and the pad with 0.1mum Au surface finish. Even in the condition of 31 days aging, the thickness of IMCs didn't increase a lot; as for the laser reflowed solder joints with 0.5 or 0.9mum Au surface finish on the pad, most of the AuSn4 IMCs stayed at the interface and formed in needle-like or dendritic morphology. With the increase of aging time, the AuSn4 IMCs became more flat and changed to a continuous layer; In the laser reflowed solder joints with 4.0mum Au surface finish on the pad, AuSn, AuSn2, AuSn4 IMCs and Au2Sn phase formed at the interface. With the increase of aging time, more Sn rich IMCs formed at the interface, and evolved to AuSn4 IMCs in the condition of long time aging. The thickness of AuSn4 IMCs can reach about 30mum

Glass plates have to be interconnected hermetically for certain applications, so that the functional elements in it are protected against oxygen and moisture. Furthermore limits are set to the joining process by temperature sensibility of the encapsulating functional elements. The low-temperature process "adhesive bonding" used so far does not offer the demanded tightness and long-term stability. The present investigations concentrate on alternative joining methods using laser beams. (Id82)

The possibility of a ban of Pb has forced the electronics industry to search for alternatives for Pb-based solders. We present a discussion of several of these alternatives and present preliminary results of experiments aimed at developing these solutions. Experimental results presented include an assessment of the strain rate sensitivity of Sn-Bi solder joints; the wetting properties of Sn-Bi solders on bare and hot-dipped Cu surfaces; and the development of a laser soldering process for fine pitched SMT using Sn-Ag solders.

Resection of a segment of the trachea is a procedure applied for the removal of cervical tumors invading the trachea, or for the treatment of severe tracheal stenosis. The current method of anastomosis is based on multiple sutures. The main drawbacks of this method are: 1) A long procedure time, 2) An air leakage, and 3) An inflammatory response to the sutures. In this study we evaluated the feasibility and effectiveness of the use of temperature controlled CO2 laser soldering of incisions in pig tracheas in vitro. A transverse incision was made in a separated pig trachea. A flexible albumin band was prepared and was laser soldered with albumin solder to the outer surface of the trachea, covering the incision. The soldered trachea ends were sealed and the burst pressure was measured. In a series of in vitro experiments, the mean burst pressure was found to be 230 mm Hg. These preliminary results demonstrated that laser soldering using a flexible albumin band may be a useful method for sealing an incision in the trachea.

Objectives: Laser tissue welding is a technology that was used for soldering of various tissues, which can be faster, less traumatic and easier to apply than conventional methods. The objective of this study was to take advantage of the laser soldering system, and to develop a simple and reliable technique for repair of dural holes after excision of brain tumors. Methods: We used a CO 2 fiber optic laser system that was developed by us for monitoring and controlling heated tissue in situ and in real time, for reducing the damage to the brain parenchyma. The system was used for soldering of dura and free fascial grafts in an animal model using pigs. Direct digital measurements of mechanical force interaction were used for tension and pressure. Results: The difference between the breaking point of the retract scan and the baseline was used to calculate the peak adhesive force (PAF) acting between the 2 tissues. We have performed 35 experiments in order to calculate the mean PAF of fascia-dura welding. Seven more experiment were performed using biological glue for comparison of the PAF. The mean PAF of fascia-dura welding was 3.94 ± 0.6 gr/cm. The PAF for fascia-dura bond using biological glue was 4.1 ± 1.2 gr/cm. No statistical difference was found between the 2 techniques. Conclusion: Implementation of laser welding in neurological oncological surgeries will allow access to anatomical areas previously considered inoperable, will shorten the length of the surgery, will allow better dural reconstruction shortly after the procedure, and therefore allow lower morbidity and mortality rates.

Objectives: Complications from tympanic membrane perforations range from no symptoms to hearing loss and vertigo. Though different grafting materials have been advocated for surgical repair, the healing time has remained constant. We propose the use of elastin (Oregon Medical Laser Center, Portland, OR) as a grafting material for the repair of traumatic tympanic membrane perforations. Furthermore, utilizing laser albumin soldering (Oregon Medical Laser Center, Portland, OR) in the repair allows exploration of possible immediate functional integrity. Methods: The protocol used 17 animals (Chinchilla laniger). Three groups were studied: (1) repair with elastin alone, (2) repair with elastin and laser albumin solder and (3) repair with paper patch. Traumatic perforations were made bilaterally in each animal. One side served as the repair group, the other as the control. Tympanograms were used to determine functional integrity immediately following the repair and at the end of 5 weeks. The tympanic membranes were then harvested for histological study. Results: Of all groups (including controls), only 1 animal showed immediate functional integrity (elastin with laser solder). The delayed tympanograms were more varied. The elastin with and without laser soldering groups had identical results (5 of 6), and compared to their respective controls (2 of 6), showed higher incidence of functional integrity. The paper patch group had similar rates (2 of 5) of integrity compared to their controls (3 of 5). Conclusion: Although the results of immediate elastin repair with and without laser albumin soldering were not superior to the matched controls, the delayed results show promise for accelerated healing.

Background and Objectives Temperature-controlled tissue laser soldering is an innovative sutureless technique awaiting only solid experimental data to become the gold-standard surgical procedure for incision closure. The goals of the current study were: (1) to define the optimal laser soldering conditions, (2) to explore the immediate skin reparative healing events after sealing the wound, and (3) to determine the long-term trajectory of skin wound healing. Study Design/Materials and Methods Skin incisions were generated over rabbit dorsa and were closed using different wound-closure interventions, in three groups: (a) closure, using a temperature-controlled infrared fiberoptic CO2 laser system, employing 47% bovine serum albumin as a solder; (b) wound closure by cyanoacrylate glues; and (c) wound closure by sutures. The reparative outcomes were evaluated macroscopically and microscopically, employing semi-quantitative grading indices. Results Laser soldering of incisions at T = 65°C emerged as the optimal method achieving immediate wound sealing. This in turn induced accelerated reparative events characterized by a reduced inflammatory reaction, followed by minimal scarring and leading to a fine quality healing. Conclusions Temperature-controlled laser soldering offers an accelerated wound reparative process with numerous advantages over the conventional methods. Further investigations may reveal additional benefits in the spectrum of advantages that this innovative surgical technology has to offer. This can introduce new scientific insight that will pave the way for clinical use. Lasers Surg. Med. 35:1–11, 2004. © 2004 Wiley-Liss, Inc.

Two temperature controlled laser soldering systems were compared, one based on a GaAs laser and the other on a CO2 laser. Both systems were used for bonding full thickness incisions. Methods: 47% bovine serum albumin (BSA) solder was used in the CO2 laser soldering experiments. BSA with 1.8 mg/ml Indocyanine Green (ICG) was used for the GaAs soldering experiments. In both cases the solder was applied onto cuts created in juvenile pig skin and an infrared fiberoptic system was used to monitor and control different temperature and time settings. Differences in tensile strength and wound reparative parameters were compared between GaAs laser, CO2 laser, and Dermabond glued incisions on the seventh day after the operation. Results: The tensile strength of CO2 laser-soldered and Dermabond glued incisions were found to be higher than that of the GaAs laser-soldered incisions. Histological study showed better and faster wound healing characteristics of the CO2 laser soldered incisions, as compared to the GaAs laser-soldered and glued incisions. Conclusions: Preliminary results of temperature controlled CO2 laser soldered incisions suggest a better wound reparative process over the temperature controlled GaAs laser soldered incisions. Laser soldering offers many advantages over gluing techniques.

In recent years the drive to adopt environmentally friendly solders and fluxes has been at the forefront of the electronics industry concerns. In parallel, the demands on soldering technology have increased rapidly, with footprint sizes reducing and boards becoming more heavily populated, in the drive towards miniaturisation. With these changes some of the existing equipment currently used in the soldering industry (reflow or wave ovens) may struggle. In an attempt to resolve some of the manufacturing issues presented to the industry, CSIRO Manufacturing and Infrastructure Technology (CMIT) conducted a project to examine the use of a 30W diode laser to manufacture some of the soldered joints currently made using the mass reflow techniques. Work was conducted on both traditional lead containing solder and the new environmentally friendly lead free containing solders.The advantages perceived by using lasers included low heat input processing, improved mechanical properties due to the reduced grain size, much thinner intermetallic layers, consistent and repeatable joints, and faster cycle time than with hand soldering. This results in a potentially superior joint, being stronger and more reliable, yet formed at competitive rates.In recent years the drive to adopt environmentally friendly solders and fluxes has been at the forefront of the electronics industry concerns. In parallel, the demands on soldering technology have increased rapidly, with footprint sizes reducing and boards becoming more heavily populated, in the drive towards miniaturisation. With these changes some of the existing equipment currently used in the soldering industry (reflow or wave ovens) may struggle. In an attempt to resolve some of the manufacturing issues presented to the industry, CSIRO Manufacturing and Infrastructure Technology (CMIT) conducted a project to examine the use of a 30W diode laser to manufacture some of the soldered joints currently made using the mass reflow techniques. Work was conducted on both traditional lead containing solder and the new environmentally friendly lead free containing solders.The advantages perceived by using lasers included low heat input processing, improved mechanical properties due to the reduced grain size, muc...

Background and objectives: Conventional methods for microvascular anastomosis are normally based on suturing, using special thin nylon sutures. These methods suffer from major drawbacks, which include: anastomosis, which is not watertight, and sutures or clips that cause an inflammatory response. In order to obtain better results, we introduced a procedure based on CO2 laser soldering. We tested the system on arteriotomy incisions in rat blood vessels, in vivo. Materials and methods: We used a fiber optic based laser soldering system, with a temperature control capability. Arteriotomy incisions of lengths 4±1mm were performed on the femoral arteries of 48 wistar rats: 24 rats in the control group (suture) and 24 rats in the test group (laser soldering). We conducted two follow-up periods: 7 days and 21 days after the surgical procedure, for each group. Flow tests and histology examination were done in order to evaluate the quality of the procedures. Results: The patency rate was 84% for both groups, soldered and sutured. The sutured group showed a significant foreign body reaction (p < 0.05), which was not observed in the soldered group. We found no evidence of thermal damage in the soldered blood vessels. Conclusions: We can conclude that laser soldering is a less traumatic procedure, compared with the conventional suturing technique. It is potentially a faster technique and easier to master.

Introduction: Laparoscopic pyeloplasty is used for the repair of uretero-pelvic junction (UPJ) obstructions. Our aim was to do it using laser tissue soldering. Materials and Methods: We developed a tissue bonding system based on a CO 2 laser, a temperature detector and infrared transmitting optical fibers, to obtain temperature controlled laser soldering of incisions. The system was then adapted for laparoscopic soldering of ureters of pigs. Results: We successfully carried out laparoscopic pyeloplasty in a porcine model, using a procedure based on CO 2 laser soldering. Conclusions: Laparoscopic laser soldering was found to be faster than suturing, it was easier to use and provided watertight bonding. This technique will be useful in other surgical procedures.

Background and Objectives To assess the potential use of diode laser soldering to improve mechanical stability of middle ear reconstruction. The diode laser with a biological solder may offer benefits over traditional methods. We evaluated the strength of soldered bonds and a means to apply such a technique in the human middle ear. Study Design/Materials and Methods The strength of soldered junctions using fascia, cartilage, bone, and hydroxyappatite was evaluated in vitro. A diode laser (810-nm wavelength) and 50% albumin with 0.1% indocyanine green dye was used. Soldered bonds were compared to those obtained with adhesive alone. A fiberoptic delivery system was evaluated. Ten hydroxyappatite prostheses were soldered to the stapes in human cadaver temporal bones, and the force required to disrupt the bonds were measured. Results Statistically significant greater strength was obtained with soldering. Ossicular prostheses can be effectively secured to the stapes in a cadaver model. Conclusions Soldering techniques show promise in middle ear reconstruction. Lasers Surg. Med. 31:242–246, 2002. © 2002 Wiley-Liss, Inc.

The acceptance of laser soldering by the microelectronics industry has recently increased dramatically due in part to the development of reliable, efficient direct diode lasers. Similarly, soldering using lead free solders has also increased, largely due to current or impending legislation across the world aimed at reducing the usage of lead. There is to date very little published data which allows a direct comparison between lead containing and lead free soldering using direct or fiber coupled diode lasers. By using solder pre-forms differing only in their composition, an experimental program was utilized to identify the subtle differences in the key laser processing variables. The resultant joints were subjected to metallurgical examination to investigate joint quality and to verify the advantages claimed for diode laser soldering. This work has led to an improved understanding of lead free diode laser soldering.The acceptance of laser soldering by the microelectronics industry has recently increased dramatically due in part to the development of reliable, efficient direct diode lasers. Similarly, soldering using lead free solders has also increased, largely due to current or impending legislation across the world aimed at reducing the usage of lead. There is to date very little published data which allows a direct comparison between lead containing and lead free soldering using direct or fiber coupled diode lasers. By using solder pre-forms differing only in their composition, an experimental program was utilized to identify the subtle differences in the key laser processing variables. The resultant joints were subjected to metallurgical examination to investigate joint quality and to verify the advantages claimed for diode laser soldering. This work has led to an improved understanding of lead free diode laser soldering.

The purpose of this study was to evaluate laser soldering using liquid albumin for welding liver lacerations and sealing raw surfaces created by segmental resection of a lobe. Major liver trauma has a high mortality due to immediate exsanguination and a delayed morbidity and mortality from septicemia, peritonitis, biliary fistulae and delayed secondary hemorrhage. Eight laceration injuries (6 cm long X 2 cm deep) and eight non-anatomical resection injuries (raw surface 6 cm X 2 cm) were repaired. An 805 nm laser was used to weld 53% liquid albumin-ICG solder to the liver surface, reinforcing it with a free autologous omental scaffold. The animals were heparinized to simulate coagulation failure and hepatic inflow occlusion was used for vascular control. For both laceration and resection injuries, eight soldering repairs each were evaluated at three hours. A single suture repair of each type was evaluated at three hours. All 16 laser mediated liver repairs were accompanied by minimal blood loss as compared to the suture controls. No dehiscence, hemorrhage or bile leakage was seen in any of the laser repairs after three hours. In conclusion laser fusion repair of the liver is a quick and reliable technique to gain hemostasis on the cut surface as well as weld lacerations.

The Clean Air Act Amendment, enacted in November 1990, empowered the Environmental Protection Agency (EPA) to completely eliminate the production and usage of chlorofluorocarbons (CFCs) by January 2000. A reduction schedule for methyl chloroform beginning in 1993 with complete elimination by January 2002 was also mandated. In order to meet the mandates, the processes, equipment, and materials used to solder and clean electronic assemblies were investigated. A vapor-containing cleaning system was developed. The system can be used with trichloroethylene or d-Limonene. The solvent can be collected for recycling if desired. Fluxless and no-clean soldering were investigated, and the variables for a laser soldering process were identified.

The aim of these investigations is to examine various solder pastes for their absorption behaviour with respect to laser beam of wavelength of 1.06 μm. It is intended to varify the importance of absorption of flux over metallic composition and reactivity of flux.

This paper describes the development of a new laser soldering technique for surface mount assemblies. The new technique, using a focused YAG laser beam, has superior performance. It can be applied to tape carrier package (TCP) assemblies for fine pitch leads and offers a no-bridge soldering process.In this paper, the performance of the new technique is evaluated experimentally. First, the new technique is compared with the conventional laser-soldering technique for TCP assemblies, and the no-bridge soldering concept is proved. Second, to obtain more flexibility in assembly, the solder flow is investigated by beam scanning. The beam-resting time on the pads of the printed circuit board (PCB), is optimized by the theoretical and experimental analysis of the volume of melted solder. The reducing atmosphere (H2-N2gas) is considered to achieve a no-clean soldering process. From these experiments, the new laser soldering technique offers the ability to assemble high lead count, fine pitch ICs such as TCPs.This paper describes the development of a new laser soldering technique for surface mount assemblies. The new technique, using a focused YAG laser beam, has superior performance. It can be applied to tape carrier package (TCP) assemblies for fine pitch leads and offers a no-bridge soldering process.In this paper, the performance of the new technique is evaluated experimentally. First, the new technique is compared with the conventional laser-soldering technique for TCP assemblies, and the no-bridge soldering concept is proved. Second, to obtain more flexibility in assembly, the solder flow is investigated by beam scanning. The beam-resting time on the pads of the printed circuit board (PCB), is optimized by the theoretical and experimental analysis of the volume of melted solder. The reducing atmosphere (H2-N2gas) is considered to achieve a no-clean soldering process. From these experiments, the new laser soldering technique offers the ability to assemble high lead count, fine pitch ICs such as TCPs.

The Planning and Staff Support of the Sandia National Laboratories publishes a monthly bulletin titled, Energy and Environment. The bulletin facilitates technology exchange with industries, universities, and with other government agencies. This bulletin is for the month of April 1992 and covers such things as new methods of soldering which reduces environmental threats by avoiding chlorofluorocarbon solvents. Some technologies developed are soldering in controlled atmospheres, acid-vapor soldering, and laser soldering. Another topic in this bulletin is the designing of catalysts of chemical reactions by computers. Biomimetic catalysts are being created by Computer-Aided Molecular Design. These biomimetic catalysts can aid in fuel conversion. In-situ remediation of soils contaminated by heavy metals was another topic in this bulletin. This in-situ process is called, electrokinetic remediation. It uses electrodes to induce a metal-attracting electric field in the ground. The last topic in this bulletin is the design of a semiconductor bridge (SCB) which is used to improve the timing and effectiveness of blasting. Timing and accuracy is important; and the blasting industry is no exception. This SCB gives a low-energy pulse which causes a doped region on a polysilicon substrate into a bright plasma. This plasma discharge causes the ignition and produces anmore » accurate explosion in microseconds. (MB)« less

We prove the first application of near-infrared-absorbing gold nanorods (GNRs) for in vivo laser closure of a rabbit carotid artery. GNRs are first functionalized with a biopolymeric shell and then embedded in hyaluronan, which gives a stabilized and handy laser-activable formulation. Four rabbits undergo closure of a 3-mm longitudinal incision performed on the carotid artery by means of a 810-nm diode laser in conjunction with the topical application of the GNRs composite. An effective surgery is obtained by using a 40-W/cm(2) laser power density. The histological and electron microscopy evaluation after a 30-day follow-up demonstrates complete healing of the treated arteries with full re-endothelization at the site of GNRs application. The absence of microgranuloma formation and/or dystrophic calcification is evidence that no host reaction to nanoparticles interspersed through the vascular tissue occurred. The observation of a reshaping and associated blue shift of the NIR absorption band of GNRs after laser treatment supports the occurrence of a self-terminating process, and thus of additional safety of the minimally invasive laser procedure. This study underlines the feasibility of using GNRs for in vivo laser soldering applications, which represents a step forward toward the introduction of nanotechnology-based therapies in minimally invasive clinical practices.

Tape Automated Bonding (TAB) is a modern technology which meets the requirements for micronnecting VLSI-circuits. Gang bonding with a thermode is the usually applied bond technique. The limitations for gang bonding of chips with high lead counts are the increased bond forces and the induced mechanical stress. Laser soldering is an alternative for inner lead bonding chips with high lead counts and reduced pitch. Because the microjoining of surfaces occurs via thermal energy from the laser beam, no mechanical pressure is necessary for laser soldering. Due to the optical properties of the laser beam and the possibility to reduce the laser spot, soldering of small pitches is possible.