Reliability of high aspect ratio plated through holes (PTH) for advanced printed circuit board (PCB) packages
Reliability of high aspect ratio plated through holes (PTH) for advanced printed circuit board (PCB) packages
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用于高级印刷电路板 (PCB) 封装的高深宽比电镀通孔 (PTH) 的可靠性
DOI：
10.1109/relphy.1997.584249
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
M. Lii
中科院分区：
文献类型：
--
作者：
D. Goval;H. Azimi;Kim Poh Chong;M. Lii
多层印制线路板(PWB)中的镀通孔(PTH)被定义为“通过在孔壁上电镀金属，在内部或外部导电图案之间或两者之间进行电连接的孔”。最近增加所有级别的封装密度的趋势导致了PWB布线层的显著增加，进而导致为了在电路层之间进行通信而增加的PTH密度。印刷电路板总厚度的增加，加上PTH直径的减小，使得组装过程中的PTH完整性和随后的场应力成为印制板生产和使用中的主要可靠性问题之一。PTH金属与层合材料之间的热膨胀系数(CTE)面外(z向)失配是导致PTH失效的主要原因。PTH的故障构成电气不连续，这可能是由于电镀材料在电镀桶处断裂、在接地-电桶结合处断裂或电镀从印刷电路板上剥离而引起的。本文将讨论PTH在T/C(温度循环)应力作用下的可靠性性能。在通过1000 T/C‘B’(-55到125/spl deg/C)和T/C‘C’(-65到150/spl deg/C)施加应力的初始可靠性期间，观察到电气开路。物理分析表明，开孔是由于PTH的桶破裂造成的。通过广泛的力学建模和实验验证，建议改变材料、工艺和设计，以消除大长宽比PTH中的筒体裂纹。我们将详细讨论这些分析的结果。
A plated-through hole (PTH) in multi-layer printed wiring boards (PWB) is defined as "a hole in which electrical connection is made between internal or external conductive patterns, or both, by plating of metal on the wall of the hole". The recent trend to increase the packaging density at all levels has resulted in a significant increase in PWB wiring layers and in turn for PTH density in order to communicate between the layers of circuitry. The increase in overall PCB thickness, coupled to the decrease in PTH diameter makes the PTH integrity during the assembly process and subsequent field stresses one of the primary reliability concerns in PWB production and usage. Thermo-mechanical stresses mainly due to mismatch in out-of-plane (z-direction) coefficient of thermal expansion (CTE) between the PTH metal and the laminated material can result in the failure of the PTHs. Failure of a PTH constitutes an electrical discontinuity which may be caused by fracture of the plating material at the barrel, fracture at the land-barrel junction, or delamination of the plating from the PWB. This paper will discuss the reliability performance of the PTHs when subjected to T/C (Temperature Cycle) stresses. During the initial reliability stressing through 1000 T/C 'B' (-55 to 125/spl deg/C) and T/C 'C' (-65 to 150/spl deg/C) electrical opens were observed. Physical analysis showed that the opens were due to barrel cracking of the PTHs. Extensive mechanical modeling and experimental validation were used to suggest changes in the materials, process and design to eliminate barrel cracking in high aspect ratio PTHs. Results of these analyses will be discussed in detail.