Dominici J T, Sobczak K P, Mitchell R J
Department of Oral Health Practice, University of Kentucky, College of Dentistry, Lexington 40536-0084, USA.
J Prosthodont. 1995 Jun;4(2):101-10. doi: 10.1111/j.1532-849x.1995.tb00324.x.
The purpose of this study was to compare the bond strengths and fracture modes of soldered joints formed by infrared and gas-oxygen torch heating of a high-fusing, gold-based solder in two metal-ceramic alloys.
Pairs of half-dumbbell-shaped specimens of either an Au-Pd or a Co-Cr alloy were positioned with a 0.25-mm gap and were joined using a high-fusing, gold-based solder by either gas-oxygen torch heating or infrared heating. The resulting specimens were subjected to a heat treatment that simulated ceramic firing. Each specimen was fractured in tension at a loading rate of 0.5 cm/min, and its bond strength was measured. The halves of the specimen were rejoined using the other heating method and were heat treated, and the specimen's bond strength was again measured. Fractured cross-sections were examined at a magnification of 40x to determine the following: the fracture mode (adhesive, cohesive, or mixed); the percentage of adhesive fracture; the presence or absence of voids, porosities, or flux inclusions; and the percentage of the cross-section that was discolored.
Three-factor analyses of variance showed that neither the heating method, the particular specimen tested, nor the order of testing significantly affected the bond strength (P < .05). For each alloy, significantly fewer infrared-heated joints than torch-heated joints contained voids, porosities, or flux inclusions visible at 40x (chi 2 test, P < .05). All fractures were either entirely cohesive in the solder or mixed cohesive and adhesive. When infrared heating was used, entirely cohesive fractures occurred more frequently in the Au-Pd alloy specimens than in the Co-Cr alloy specimens (chi 2 test, P < .05). The coefficients of variation of the bond strengths for the infrared-heated joints were smaller than those for the torch-heated joints.
Although the two heating methods produced solder joints that had strengths that were not significantly different, infrared-heated joints showed less scatter in bond strengths. It was suggested that, in the hands of most technicians, fewer infrared-heated joints would contain defects visible at a magnification of 40x. The presence of such defects may increase the probability of in vivo failure caused by cyclic stresses.
本研究旨在比较通过红外加热和燃气 - 氧气火焰加热两种方式，在两种金属 - 陶瓷合金中使用高熔点金基焊料形成的焊接接头的结合强度和断裂模式。
将成对的Au - Pd合金或Co - Cr合金半哑铃形试样以0.25毫米的间隙放置，并用高熔点金基焊料通过燃气 - 氧气火焰加热或红外加热进行连接。对所得试样进行模拟陶瓷烧制的热处理。每个试样以0.5厘米/分钟的加载速率进行拉伸断裂，并测量其结合强度。使用另一种加热方法重新连接试样的两半并进行热处理，然后再次测量试样的结合强度。在40倍放大倍数下检查断裂横截面，以确定以下内容：断裂模式（粘结、内聚或混合）；粘结断裂的百分比；是否存在空隙、气孔或助熔剂夹杂物；以及变色横截面的百分比。
方差三因素分析表明，加热方法、所测试的特定试样以及测试顺序均未对结合强度产生显著影响（P < 0.05）。对于每种合金，在40倍放大倍数下可见的空隙、气孔或助熔剂夹杂物，红外加热的接头比火焰加热的接头明显更少（卡方检验，P < 0.05）。所有断裂要么完全在内聚于焊料中，要么是内聚和粘结混合的。当使用红外加热时，Au - Pd合金试样中完全内聚断裂比Co - Cr合金试样更频繁发生（卡方检验，P < 0.05）。红外加热接头结合强度的变异系数小于火焰加热接头。
虽然两种加热方法产生的焊接接头强度没有显著差异，但红外加热接头的结合强度离散度较小。建议在大多数技术人员手中，红外加热的接头在40倍放大倍数下可见的缺陷会更少。此类缺陷的存在可能会增加由循环应力导致体内失效的概率。
