Semiconductor device and manufacturing method of semiconductor device
A solder joint layer has a structure in which plural fine-grained second crystal sections ( 22 ) precipitate at crystal grain boundaries between first crystal sections ( 21 ) dispersed in a matrix. The first crystal sections ( 21 ) are Sn crystal grains containing tin and antimony in a predetermined proportion. The second crystal sections ( 22 ) are made up of a first portion containing a predetermined proportion of Ag atoms with respect to Sn atoms, or a second portion containing a predetermined proportion of Cu atoms with respect to Sn atoms, or both. The solder joint layer may have third crystal sections ( 23 ) which are crystal grains that contain a predetermined proportion of Sb atoms with respect to Sn atoms. As a result, solder joining is enabled at a low melting point, and a highly reliable solder joint layer having a substantially uniform metal structure can be formed.
1. A semiconductor device in which constituent parts in one set thereof are joined by a solder joint layer, the solder joint layer comprising:
first crystal sections containing tin and antimony at a ratio of tin atoms:antimony atoms=1:p (0<p≤0.1); and
second crystal sections having at least one among a first portion containing tin and silver at a ratio of tin atoms:silver atoms=1:q (2≤q≤5) and a second portion containing tin and copper at a ratio of tin atoms:copper atoms=1:r (0.4≤r≤4), wherein
average grain size of the second crystal sections is smaller than average grain size of the first crystal sections.
2. The semiconductor device according to claim 1 , wherein the solder joint layer has third crystal sections containing tin and antimony at a ratio of tin atoms:antimony atoms=1:s (0.8≤s≤1.6).
3. The semiconductor device according to claim 2 , wherein
the first crystal sections are tin crystal grains with antimony in solid solution, and
the third crystal sections are crystal grains resulting from a reaction between the first crystal sections and antimony that is in excess of a solid solution limit in the first crystal sections.
4. The semiconductor device according to claim 1 , wherein the first crystal sections are tin crystal grains with antimony in solid solution.
5. The semiconductor device according to claim 1 , wherein the second crystal sections precipitate at crystal grain boundaries between the first crystal sections.
6. The semiconductor device according to claim 1 , wherein average grain size of the first portion is 1 μm or less.
7. The semiconductor device according to claim 1 , wherein the solder joint layer has a melting point of 260° C. or lower.
8. A manufacturing method of a semiconductor device in which constituent parts in one set thereof are joined by a solder joint layer, the manufacturing method comprising:
a step of coating one of the constituent parts with a solder paste that contains a mixture of an alloy powder containing antimony, and an alloy powder containing no antimony; and
a step of solidifying the solder paste by a thermal treatment to form the solder joint layer, and joining the constituent parts to each other by way of the solder joint layer, wherein
the solder joint layer includes:
first crystal sections containing tin and antimony at a ratio of tin atoms:antimony atoms=1:p (0<p≤0.1); and
second crystal sections having at least one among a first portion containing tin and silver at a ratio of tin atoms:silver atoms=1:q (2≤q≤5) and a second portion containing tin and copper at a ratio of tin atoms:copper atoms=1:r (0.4≤r≤4), and
average grain size of the second crystal sections is smaller than average grain size of the first crystal sections.