Search results

The purpose of this paper is to form high density interconnection (HDI) of backboard for press-fit applications with the pre-curing conditions of conductive paste. The best condition of pre-curing conductive paste should be found to obtain good electrical and physical performance of the conductive paste and avoid the simultaneous curing behavior of prepreg.

A novel structure of backboard was designed by using the connection of conductive paste-filled through holes to connect two multilayers. Pre-curing conditions of conductive paste were investigated to find their effects on resistance, bond strength and volume shrinkage. The reliability of pre-curing conductive paste was also analyzed.

Pre-curing conditions led to a great influence on the resistance, bond strength and volume shrinkage of the conductive paste. The best condition of pre-curing conductive paste was chosen as the low curing temperature of 60°C and a curing time of 30 min. Cured conductive paste exhibited square resistance of 4.205 mΩ/□ and bonding strength of 22.86 N. The as-obtained pre-curing condition could improve the reliability of conductive paste. Pre-curing process of conductive paste at extremely low temperature to interconnect two multilayer structures improved the density interconnection of backboard for press-fit applications.

The use of HDI of backboard could lead to good assembly for high-speed signal transmission of electronic products with press-fitting components. The connection of pre-curing conductive paste for multilayers could have important function for improving the application for communication backboard.

Flip chip assembly using anisotropic conductive adhesives offers an interesting alternative for making high‐density interconnections. The use of conventional organic printed circuit boards makes this technique even more attractive. However, a low‐cost adhesive flip chip bonding process will require a reduced bonding cycle time or the use of multi‐head joining equipment. Adhesive flip chip bonding is characterized by a long bonding cycle time due to the relatively long curing time of adhesives and the need for simultaneous application of pressure during the curing process. In soldered flip chip techniques, the bonding time per assembly is shorter, because all the chips on the substrate can be soldered in a reflow oven at the same time. In this study, the minimum pre‐curing time needed to make a reliable adhesive joint was determined using one commercial anisotropic conductive adhesive film used on FR‐4 substrates. The results are promising, since bonding time reduction from 40 s to 10 s does not reduce the joint reliability.

Polyurethane concrete has a high strength-to-weight ratio in the short term, and the strength-to-weight ratio stage during the maintenance period is critical. Freeze-thaw cycles have a noticeable damaging effect on the durability of polyurethane concrete. The engineering specification of polyurethane concrete with incomplete hydration reaction must be studied, as well as the development of internal structure during curing. In this paper, the polyurethane concrete tests were set up under eight distinct maintenance settings based on the climate features of the northern area and the service environment. The test results were evaluated to determine the effect of the number of early freeze-thaw cycles and the time node of early freeze-thaw cycles on the mechanical characteristics of polyurethane concrete, which revealed that the time node of freeze-thaw damage impacted the freeze-thaw resistance of polyurethane concrete susceptible to early freeze-thaw damage.

The early-age freeze-thaw damage polyurethane concrete was experimentally studied by controlling the time node of the freeze-thaw cycle and the curing environment. The test considered the time node, frequency of freeze-thaw damage of polyurethane concrete and the influence of subsequent curing environment and observed the mass change, relative dynamic elastic modulus, relative durability index, compressive strength and apparent damage of polyurethane concrete. The early mechanical properties of polyurethane concrete were studied by analyzing the change of numerical value. The microscopic mechanism of strength formation of polyurethane concrete was analyzed by XRD, FTIR and SEM image.

The closer the time of freeze-thaw damage was to the specimen hardening, the worse the mechanical properties and structure were, according to SEM photographs. For specimens with serial number of 12-groups, its compressive strength is only 82.39% of that of the standard group, even if the curing process continues after 20 times thawing, which increased early environment exacerbate strength loss in polyurethane concrete and also reduced freeze-thaw resistance. The findings of the tests reveal that curing can restore the freeze-thaw resistance of damaged polyurethane concrete. Curing in water has a better recovery impact than curing in air; the mechanical properties can be restored by sufficient re-curing time and good re-curing conditions.

By studying the freeze-thaw cycle test and test results of polyurethane concrete in different curing time nodes, the relationship between the mechanical properties of polyurethane concrete and the time node, number of freeze-thaw cycles, and subsequent maintenance environment was explored. Considering the special mechanism of strength formation of polyurethane concrete, the polyurethane concrete damaged by freeze-thaw has the ability to continue to form strength under subsequent maintenance. This experimental study can provide an analytical basis for the strength formation and reconditioning of polyurethane concrete structures subjected to freeze-thaw environments during the curing time under extreme natural conditions in fall and winter in actual projects.

The purpose of this paper is to evaluate the relationship between the Cu trace and epoxy resin and to check the validity of surface and interfacial cutting analysis system (SAICAS) by comparing its results to those of the 90° peel test.

In this study, the effects of surface morphology on the adhesion strength were studied for a Cu/epoxy resin system using a SAICAS. In order to evaluate the peel strength of the sample, the curing degree and surface morphology of the epoxy resin were varied in the Cu/epoxy resin system.

The results indicated that the peel strength is strongly affected by the curing degree and the surface morphology of the epoxy layer. As the pre-cure time increased, the interactions between the epoxy resin and permanganate during the adhesion promotion process decreased, which decreased the surface roughness (Ra) of the resin. Therefore, the surface roughness of the epoxy resin decreased with increasing pre-cure time. The curing degree was calculated with the FTIR absorption peak (910 cm−1) of the epoxy groups. The high curing degree for the epoxy resin results in a coral-like morphology that provides a better anchoring effect for the Cu trace and a higher interfacial strength.

It is necessary to study the further adhesion strength, i.e. the friction energy, the plastic deformation energy, and the interfacial fracture energy, in micro- and nanoscale areas using SAICAS owing to insufficient data regarding the effects of size and electroplating materials.

From findings, it is found that measuring the peel strength using SAICAS is particularly useful because it makes the assessment of the peel strength in the Cu/epoxy resin system of electronic packages possible.

New electrical paint curing method wins first place in Category 2 of Midlands Electricity's 1989 PEP Awards for Bromyard company.

The benefits of a “no flow” process have been well documented in the recent past. The limitations of the previously reported materials in current use have been overcome via a unique chemistry which can be tailored to the application. Room temperature storage, effective fluxing, coupled with minimal outgassing, and a choice of reworkability after reflow or, if rework is not required, a full cure, can now be achieved within a single materials technology. This paper describes the properties of the new family of materials compared to conventional post‐deposited underfills. The development sequence and the procedure for characterisation of material properties, including the evaluation of the effectiveness of the fluxing action on a range of solder alloys, is documented. A typical application is described, outlining how a minimum of two process steps can be eliminated and how improvements in materials handling, process robustness, and ultimate yield, have been realised. A simple rework regime is also proposed, and the almost “drop in replacement” aspect of the new material is discussed.

MORE than a decade ago we were assured by the then head of Imperial Chemicals Industries that the man who knows where he is going is the one who is most likely to arrive. We might venture to add as a footnote that such a man's journey will be easier, his destination more certain, if he first clears away the assorted debris that encumbers his route.

Veneering used to refer only to surfacing boards with wood veneers and the technique has been used since the days of the ancient Egyptians. (A primitive veneered casket was found in the tomb of Tutenkhamen). However, in modern usage the term now describes the surfacing of panels with a much wider range of materials including not only wood veneers but also decorative laminates and thermo‐plastics and paper foils. Paper‐based foils, in particular, are being constantly improved so that the colouring, and even the texture, of wood veneers can now be reproduced with great accuracy.