Agilent 5091-9074E Beam Lead Attachment Methods - Application Note c20131025 [8] free download

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Agilent Beam Lead Attachment Methods Application Note Figure 1. General setup for attaching beam lead devices Introduction This application note gives the first time user a general description of various attach- ment methods for beam lead devices. The attached table summarizes the salient features of all the methods including the advantages, disadvantages, and the associ- ated cost of the equipment. Equipment selection as dictated by the type of substrate being used is emphasized. Attachment Methods Beam lead devices can be attached by any of the conventional means, but matching the method to the intended substrate, conductor metals and finish is imperative to a reliable, cost effective process. The various methods should be evaluated in light of this requirement. A general setup for attaching beam leads is shown in Figure 1. Characteristics of the various methods are discussed below. Thermocompression bonding Since nearly any thermocompression wire bonder can be modified for beam leads, it is a common method. A typical setup for bonding beam leads is shown in Figure 2. The wedge bonder tip contact area is 3 x 4 mils. Because of the temperatures and pressure required, the thermocompression method should be restricted to hard substrates which won't deform or allow the conductor to move. Substrate deformation or conductor movement generally results in the beam being torn or the device broken. Seldom is a reliable bond achieved since the material is deforming under the pressure and does not allow the necessary concentrated force at the bond area. Figure 2. Typical setup for thermocompression bonding of beam lead devices Reflow method 1. The deformation of the beam by the One alternative to the thermocompression bond on either soft or hard substrates bonding tool causes the gold to move into is the reflow of either tin or solder. The conductor is prepared by plating the the silicon chip. The movement of this base metal with 200 micro-inches of bright tin or solder coating. It is difficult to metal results in the chip lifting away from control the amount of solder such that it does not alter the spacing required for the substrate. This is commonly known as the beam lead, so tin is the preferred choice. In the reflow process, the wedge "bugging". A certain amount of bugging is bonder tip is replaced with one which has a tip of approximately 10