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The Benefits of Soldering with Vacuum Profiles Continued from previous page
ids like water. The use of the main vacuum
extended the time above liquidus by 30 seconds to reduce the formation of voids. Because the void reduction process must be conducted for the
most part in the molten state and must not run too quickly, a longer period in the melting phase of the solder alloy must be accepted as a condition for solder void reduction.
March, 2015
sure. The second had a final pressure of 10mbar and a dwell time of 10 sec- onds. The third had a final pressure of 100mbar and the same dwell time of 10 seconds.
Surface area 100 %
Surface area 68 %
Surface area 87 %
Surface area 63 %
joy ride To Be Precise. Innovators in Wire Processing The Benchmark for Rotary and Coaxial Solutions Voids ~14%; Number ~42 Voids~11%;Number~32 Voids~8%; Number ~58 Voids~12%; Number~46
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“Schleuniger has been an integral part of our company’s growth. Because of the time savings and increased productivity, we decided to purchase another Schleuniger machine and then another. These machines became our only method of stripping coaxial cables.” Joe Di Diego, Custom Cable Assemblies
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www.schleuniger-na.com/sa_us V
Voids <1%; Number ~7 Voids <1%; Number ~10 Voids <1%; Number ~8 Voids <1%; Number ~9
Comparison of (a) stencil geometry and soldering results (b) without vacuum process, (c) with a 100 mbar vacuum, (d) with 100 mbar vac- uum and plasma-coated stencil, and (e) with a 10 mbar vacuum.
and (e) with a To examine the effect of differ-
ent pressure levels on void creation and area ratio, three different vacu- um profiles were selected for study. The first employed ambient pres-
Besides the variations in pres-
sure, the stencil apertures were var- ied to understand the influence of so- called "outgassing" channels. Figure 3a depicts the variants of apertures needed for BTCs with large thermal pads. The basic idea is to allow the gas (from solvents, activation prod- ucts, residues, etc.) to leave the sol- der joint so that the formed joint is finally without entrapped gas. Minor differences between aper-
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ture-related results can be detected, although not classified as significant. Results obtained with vacuum pres- sures of 10 and 100mbar were signif- icant, with which all solder joints were produced with a void content of less than 2 percent. Void content (less than 3 percent) and the number of voids can be significantly reduced in this case as well. Beyond this, the selection of aperture geometry and stencil type has a less significant influence on vacuum soldering results. However, one gains the sub- jective impression that in this case the plasma stencil has the tendency to leave somewhat less voiding, which could possibly be traced back to better release of the wet paste and the associated dimensional stability. Thus, stable, uniform paste release must be considered as an influencing factor. Soldering with a targeted
amount of vacuum can significantly reduce the number of solder voids. To assure no negative effects in the process, such as damage to sensitive
Continued on next page
(d) 10 mbar, 10 s
(c) Plasma Coated, 100 mbar, 10 s
(b) 100 mbar, 10 s
(a) Without Vacuum
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