Tomohiko Shida

Characteristics of press soldered joints by using resistance heating

In order to increase the strength of soldered joints, a novel press-soldering method was investigated. In this method, materials with low melting points and low strengths (mainly Pb) were discharged from the joint interface, and an alloyed layer of high strength was left. Copper-to-copper lap joints were press-soldered using a resistance heating apparatus. In this process, heating and pressure were applied simultaneously. The copper plate was presoldered using Pb-50Sn solder and the alloyed layer was formed. The tensile strength increased at a pressure above 45 N, and fracturing occurred in the copper base metal above a 75-N pressure load. The joints fractured in the copper base metal during 150 degrees C and 250 degrees C tensile testing and showed excellent thermal resistance. Changes in joint strengths after high-temperature heating (150 degrees C, 250 degrees C for 1000 h) were also considered.<<ETX>>

Characteristics of press-soldered joints by using resistance heating

In order to increase the strengths of soldered joints, a novel press-soldering method was investigated. In this method, materials of low melting points and low strengths (mainly Pb) were discharged from the joint interface and an alloyed layer of high strength was left. Copper-to-copper lap joints were press-soldered using a resistance heating apparatus. In this process, heating and pressure were applied simultaneously. The copper plate was presoldered using Pb-50 Sn solder, and the alloyed layer was formed. The tensile strengths increased at a pressure above 45 N, and fracturing occurred in the copper base metal above a 75-N pressure load. The joints fractured in the copper base metal during the 150 degrees C and 250 degrees C tensile testing and showed excellent thermal resistance. Changes in joint strengths after high-temperature heating (150 degrees C, 250 degrees C, 1000 h) are also considered. >

Reliability of Microsoldered Thin Copper-lead by Low Melting Point Au/Sn Microsoldering. A Study on Microjoining of Leadframe for LSI Package. (No. 5).

This report considers the low melting point Au-Sn microsoldering (utilizing the Au 10 mass %-Sn eutectic ; melting point/ 490 K, bonding heat tool temperature/523 K and bonding time/5 s) which is applied to the 400-600 pin count and 0.10-0.15 mm lead pitch connection with 0.018 mmt thin copper lead. This method is performed by heat and press tool gang bonding of tin electroplated (3.5, μ mthick) copper pattern on substrate and gold electroplated (0.5, μm thick) thin copper lead with non flux in air. Au-Sn microsoldered layer has the high peel strength and has the high reliability in 218 K×30 min-423 K×30 min temperature cycle test and 423 K storage test in air that is higher than 37 mass % Pb-Sn microsoldering. As a result of this reserch, it is determined that the low melting point Au-Sn microsoldering is an excellent method for thin copper lead micro connection to the copper pattern routed substrate and the board.

Durability evaluation of press-soldered joints.

Copper to copper lap joint was made by the resistance heating apparatus by which heating and pressure was applied simultaneously. The copper plate was pre-soldered and the alloyed layer was pre-formed by using Pb-50Sn solder.Tensile test of the joints was carried out at room temperature after heat test at 150°C or 250°C for 1000h, heat cycle test from -55°C to +150°C by 1000 cycles or salt spray test at 35°C for 1000h.All of these joints were fractureed at the base metal, copper.The strengths of the joints were as those of the joints which were brazed by using BAg-6.Although the joints made by press-soldering were heated at 150°C or 250°C the thickness of the alloyed layer was constant.