Bonding material and bonding method using same
A bonding material of a silver paste includes: fine silver particles having an average primary particle diameter of 1 to 50 nanometers, each of the fine silver particles being coated with an organic compound having a carbon number of not greater than 8, such as hexanoic acid; silver particles having an average primary particle diameter of 0.5 to 4 micrometers, each of the silver particles being coated with an organic compound, such as oleic acid; a solvent containing 3 to 7% by weight of an alcohol and 0.3 to 1% by weight of a triol; a dispersant containing 0.5 to 2% by weight of an acid dispersant and 0.01 to 0.1% by weight of phosphate ester dispersant; and 0.01 to 0.1% by weight of a sintering aid, such as diglycolic acid, wherein the content of the fine silver particles is in the range of from 5% by weight to 30% by weight, and the content of the silver particles is in the range of from 60% by weight to 90% by weight, the content of the total of the fine silver particles and the silver particles being not less than 90% by weight.
1. A bonding material of a silver paste comprising:
fine silver particles having an average primary particle diameter of 1 to 50 nanometers;
silver particles having an average primary particle diameter of 0.5 to 4 micrometers;
a solvent;
an acid dispersant; and
a phosphate ester dispersant,
wherein the content of the fine silver particles is in the range of from 5% by weight to 30% by weight, and the content of the silver particles is in the range of from 60% by weight to 90% by weight, the content of the total of the fine silver particles and the silver particles being not less than 90% by weight.
2. A bonding agent as set forth in claim 1 , wherein the amount of said phosphate ester dispersant is 0.01 to 0.1% by weight with respect to said silver paste.
3. A boding agent as set forth in claim 1 , wherein the amount of said acid dispersant is 0.5 to 2% by weight with respect to said silver paste.
4. A bonding material as set forth in claim 1 , wherein said silver paste contains a sintering aid.
5. A bonding material as set forth in claim 4 , wherein said sintering aid is diglycolic acid.
6. A bonding material as set forth in claim 4 , wherein the amount of said sintering aid is 0.01 to 0.1% by weight with respect to said silver paste.
7. A bonding material as set forth in claim 1 , wherein said solvent comprises 1-octanol or 1-decanol, and a triol.
8. A bonding material as set forth in claim 1 , wherein each of said fine silver particles is coated with an organic compound having a carbon number of not greater than 8.
9. A bonding material as set forth in claim 8 , wherein said organic compound coating said fine silver particles is hexanoic acid.
10. A bonding material as set forth in claim 1 , wherein each of said silver particles is coated with an organic compound.
11. A bonding material as set forth in claim 10 , wherein said organic compound coating said silver particles is oleic acid.
12. A bonding material as set forth in claim 1 , wherein the percentage of an area occupied by voids is less than 10% with respect to the area of a bonded surface of a silver bonding layer when the bonding material arranged between articles is heated to sinter silver therein to bond articles to each other via the silver bonding layer.
13. A bonding material as set forth in claim 1 , wherein said bonding material has a viscosity of not greater than 100 Pa's when the viscosity is measured at 25° C. and 6.4 rpm by means of a rheometer.
14. A bonding material as set forth in claim 1 , wherein said acid dispersant is a dispersant containing a carboxyl group and having an ether structure.
15. A bonding method comprising the steps of:
arranging a bonding material, as set forth in claim 1 , between articles; and
heating the bonding material to sinter silver therein to form a silver bonding layer to bond said articles to each other with the silver bonding layer.