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Electronic Assemblies
Published in Michael Pecht, Handbook of Electronic Package Design, 2018
Figure 4.8 shows an example of a cap bank. All the negative terminations are grounded to the floor of the module housing with conductive epoxy. To obtain electrical isolation between the positive terminations, small pieces of kapton tape are placed between each cap with dielectric epoxy. If the caps were ceramic with gold-plated terminations, the connections to the positive terminations could be accomplished with wire bonds or by attaching a gold ribbon with conductive epoxy. If the caps were tinned or had solder- coated terminations, a jumper wire could be hand soldered to the appropriate termination. In the example shown in Figure 4.8, a small ceramic board with a metallized pattern is placed over the caps. Tolerancing was calculated to allow for the cap leads to fit into the drilled holes of the board. The metallized pattern is only on the top surface of the board so that the ceramic material of the board, in direct contact with the caps, will act as an insulator. The leads are connected to the ring of metal around the holes with solder or conductive epoxy. Attached to these rings are the bonding pads needed for making the connections to the appropriate I/O on the associate substrate. Fuse wires can also be added to this design, as needed.
Joining processes (soldering, brazing and braze-welding)
Published in Roger Timings, Fabrication and Welding Engineering, 2008
The stages of this process are shown in Fig. 10.11. Firstly, a thin film of soldering flux is applied to the previously cleaned joint surfaces as shown in Fig. 10.11(a). The seam to be soldered should be supported on a block of wood to prevent heat loss, never on metal. The joint surfaces are ‘tinned’ with a film of soft solder. Solder flows more readily between surfaces that have been pre-tinned. Further, a pre-tinned surface does not require the use of a corrosive, active flux.The tinned joint surfaces are placed together and held down by a wooden stick or the ‘tang’ of an old file. The heated soldering iron is placed on one end of the seam, ensuring that maximum contact is made with a facet at the end of the copper bit. As the solder between the two surfaces begins to melt and flow out from under the edges of the joint, the bit is drawn slowly along the seam followed by the hold-down stick pressing down on the metal. Success of this process depends upon having a constant supply of heat so the soldering ‘bit’ must be of ample size and capable of transmitting sufficient heat through the joint.
Characterisation of the Transport Critical Current Density for Conductor Applications
Published in David A. Cardwell, David C. Larbalestier, Aleksander I. Braginski, Handbook of Superconductivity, 2022
Mark J. Raine, Simon A. Keys, Damian P. Hampshire
Consider two types of current transfer: The first of these is the initial transfer of current from the current leads into the conductor. Best results are obtained if both the leads and the sample can be separately tinned (coated in solder) and then sweated (heated while applying pressure) together so that there is good electrical contact with little excess solder. This ensures that there is a low-resistance path from the copper parts of the leads to the sample/filaments of the wire, and that any heat generated can easily be conducted into the helium bath without heating the wire excessively (avoiding quenches). Measurements of Jc are most reliable with the voltage taps as far away as possible from the current transfer regions near the current leads. This ensures that the properties of the conductor alone are measured, rather than the properties of the current lead joint resistances. The voltages produced in the current transfer region, across the matrix of the superconducting wire or tape, increase linearly with current (unless, of course, there is heating in the sample). It has been shown (Ekin, 1978) that the distance required to allow for current transfer to a monocore conductor is given by L=d0.1ρmnρ*,
Risk of overheating in low-rise naturally ventilated residential buildings of northeast India – an effect of climate change
Published in Architectural Science Review, 2022
Though from Figure 11(a&b), it appears that there is a lack of significant difference in the IOH between the RCC roofs and tinned roofs, it is pertinent to mention here that the indoor Top in the RE levels made up of tin showed a higher standard deviation than that made up of RCC slab (Table 4). This is due to the fact that the tin roofs are not good in attenuating the swing of outdoor air temperature. This is evident from the fact that they exhibit a higher maximum temperature (during day time) and lower minimum temperature (during night time) than that in levels having RCC roofs. Also, it is seen that in the case of the RE levels in 3StoreyTinnedRoof, the maximum temperature exceeded 50°C in all the three climatic scenarios of the plains (Table 4). Thus, it can be concluded that a lower IOH in tinned roof may be a result of lower night time temperature and it should not be misinterpreted for a comfortable indoor condition suffice for the replacement of a RCC roof by a tinned roof, owing to a difference in cost.
Small chamber study of lead exposures from manual soldering of microelectronics
Published in Human and Ecological Risk Assessment: An International Journal, 2021
Brent D. Kerger, Anne E. Loccisano, Russell Gerads, Matthew J. Glassman
The solder wire used in these experiments had a linear density of 38.5 mg/cm. As shown in Table 3, the vast majority of waste solder in each trial (1.2 and 1.4 grams) was observed on the cleaning sponge used to keep the soldering iron tip tinned and free of dross debris. In comparison with the solder debris observed on the cleaning sponge, a very small fraction of dross (4 and 70 mg dross mass, respectively) was observed to fall to the chamber floor. The larger chamber floor solder debris sample was analyzed for Pb content and found to contain 24.4 mg (Table 3), which corresponded with the stated lead content of the solder (24.4 mg Pb/70 mg total solder = 35% Pb). The bolded values in Table 3 identify measurements used to calculate the control-adjusted Pb mass and/or the estimated Pb surface concentration in the last column.