This report shows the current status of the development of a lead-free fine pitch solder paste in EFSOT. Lead-free solder paste for fine pitch applications must fit high demands. A new solder will be developed that fits the especially high requirements for fine pitch applications in printability (very small paste deposits), stencil life and abandon time, hot and cold slump, print speed, solder balling, wettability and pin testability.
Future solder pastes have to cope with smaller components and thus solder paste deposits as small as 0.003 mm3. In lead-free soldering, mostly heavier reflow profiles with peak temperatures that are roughly 30 °C higher and might have longer duration. This reduces solderability of surfaces and possibly requires stronger activators. Activators in the paste must maintain longer reactivity at higher temperatures. But higher reactivity causes higher corrosiveness. Fine pitch applications are more sensitive to corrosiveness. The current solder pastes cannot cope with these requirements. The new solder paste will subtly balance between the contradictory demands, while other requirements like pin testability, slump etc. will be maintained or even improved (printability).
EFSOT Europe develops a robust, easy to use lead-free fine pitch solder paste. The solder paste shall meet the requirements of the automotive electronics as well as that of the consumer electronics industry thus covering a broad range of widely different re-quirements.
Figure 1- left: Printing Test, - right: EFSOT 001 (left) and EFSOT 002 (right) solder paste with long preheat and long reflow zone over 217 °C [29]
A Test-board was designed according to the requirements of the project partners. The stencil thickness was 100 and 150µm (electro-formed), on FR4 and on ceramic base materials. The printing properties of the solder paste EFSOT 001 fully match the requirements.
The test board was soldered with different reflow profiles. The soldering results were good for all joints besides the small 0201 components. With long preheated profiles and 75 s over liquidus temperature of the solder paste, the results were not satisfying.
The next development step focused on this temperature profile. The protection of the activators was improved, keeping all the other specifications and properties.
The new solder paste EFSOT 002 was soldered with different reflow temperature profiles and exhibited high resistance to long and high, non-linear thermal profiles as described above. In the next step, partners conduct reliability tests with the solder paste EFSOT 002.
AUTHOR: Anne-Marie Laügt, Avantec, France; Jacob Klerk, Paul Evers, Philips CFT, The Netherlands; Peter Wilczek, AB Mikroelektronik, Salzburg, Austria; Didier Caban, Thomson, France (12/2003)
Future solder pastes have to cope with smaller components and thus solder paste deposits as small as 0.003 mm3. In lead-free soldering, mostly heavier reflow profiles with peak temperatures that are roughly 30 °C higher and might have longer duration. This reduces solderability of surfaces and possibly requires stronger activators. Activators in the paste must maintain longer reactivity at higher temperatures. But higher reactivity causes higher corrosiveness. Fine pitch applications are more sensitive to corrosiveness. The current solder pastes cannot cope with these requirements. The new solder paste will subtly balance between the contradictory demands, while other requirements like pin testability, slump etc. will be maintained or even improved (printability).
EFSOT Europe develops a robust, easy to use lead-free fine pitch solder paste. The solder paste shall meet the requirements of the automotive electronics as well as that of the consumer electronics industry thus covering a broad range of widely different re-quirements.
Figure 1- left: Printing Test, - right: EFSOT 001 (left) and EFSOT 002 (right) solder paste with long preheat and long reflow zone over 217 °C [29]
A Test-board was designed according to the requirements of the project partners. The stencil thickness was 100 and 150µm (electro-formed), on FR4 and on ceramic base materials. The printing properties of the solder paste EFSOT 001 fully match the requirements.
The test board was soldered with different reflow profiles. The soldering results were good for all joints besides the small 0201 components. With long preheated profiles and 75 s over liquidus temperature of the solder paste, the results were not satisfying.
The next development step focused on this temperature profile. The protection of the activators was improved, keeping all the other specifications and properties.
The new solder paste EFSOT 002 was soldered with different reflow temperature profiles and exhibited high resistance to long and high, non-linear thermal profiles as described above. In the next step, partners conduct reliability tests with the solder paste EFSOT 002.
AUTHOR: Anne-Marie Laügt, Avantec, France; Jacob Klerk, Paul Evers, Philips CFT, The Netherlands; Peter Wilczek, AB Mikroelektronik, Salzburg, Austria; Didier Caban, Thomson, France (12/2003)
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