EPOXY-THIOL COMPOSITIONS WITH IMPROVED STABILITY

1 . A curable one-part epoxy resin composition, comprising:

(a) an epoxy component comprising at least one epoxy compound which has two or more groups per molecule;

(b) a latent hardener component;

(c) a thixotropy-conferrring component;

(d) a polythiol component comprising a polythiol having at least one secondary or tertiary thiol group per molecule; and

(e) a stabilising component comprising a solid organic acid.

2 . The composition according to claim 1 wherein the polythiol comprises at least two secondary thiol groups.

3 . The composition according to claim 1 , wherein the polythiol comprises at least three secondary thiol groups.

4 . The composition according to claim 1 , wherein the polythiol comprises at least four secondary thiol groups.

5 . The composition according to claim 1 wherein the polythiol comprises at least two tertiary thiol groups.

6 . The composition according to claim 1 wherein the polythiol is selected from the group consisting of

7 . The composition according to claim 1 suitable for use as an adhesive to mount electronic components.

8 . The composition according to claim 1 , comprising:

(a) about 100 parts of an epoxy component comprising at least one epoxy compound;

(b) about 5 to 45 parts of a latent hardener component;

(c) about 5 to 40 parts of a thixotropy-conferring component; and

(d) about 20 to 200 parts of a secondary polythiol; and

(e) about 0.1 to 25 parts of a solid organic acid.

9 . The composition according to claim 1 comprising:

(a) about 100 parts of an epoxy component comprising at least one epoxy compound;

(b) about 10-30 parts of a latent hardener component;

(c) about 5-15 parts of a thixotropy-conferring component; and

(d) about 20 to 200 parts of a secondary polythiol; and

(e) about 0.1 to 25 parts of a solid organic acid.

10 . The composition according to claim 1 wherein the T onset is in the range of 40-120° C., more particularly in range 50-100° C.

11 . The composition according to claim 1 wherein the composition has a viscosity in the range of 0.5-100 Pa·s.

12 . The composition according to claim 1 wherein the composition has a yield point in the range 30-1000 Pa.

13 . A process for preparing a curable one-part epoxy resin composition, comprising the steps of:

combining initially (i) an epoxy component and a polythiol having at least one secondary or tertiary thiol group per molecule;

(ii) adding a solid organic acid and one or more excipients and shearing under vacuum;

(iii) allowing said mixture to cool; and

(iv) adding a latent hardener and mixing under vacuum for a time sufficient to form the curable one-part epoxy composition.

14 . A method of using a composition according to claim 1 , the method comprising the steps of: dispensing onto an appropriate location on a carrier substrate a sufficient amount of the composition, positioning over the location bearing the composition an electronic component, mating the electronic component with the carrier substrate, and exposing the mated electronic component/carrier substrate assembly to conditions favourable to effect cure of the composition.

15 . An electronic device comprising a semiconductor device and a circuit board to which said semiconductor device is electrically connected, assembled using an epoxy resin composition according to claim 1 to mount the semiconductor to the circuit board.

16 . A method of underfilling a space between an electronic component and a carrier substrate the electronic component being mounted on the carrier substrate, comprising the step of dispensing an amount of a composition according to claim 1 into the space between the electronic component and the carrier substrate, and exposing the epoxy resin composition to conditions which effect cure.