Solder mask inkjet inks for manufacturing printed circuit boards
An inkjet method for producing a solder mask in the manufacture of a Printed Circuit Board uses a solder mask inkjet ink containing a polymerizable adhesion promoter and a phenolic compound including at least two phenolic groups. A high quality solder mask withstanding the high thermal stress during the soldering process while maintaining excellent physical properties is produced.
1. A radiation curable solder mask inkjet ink comprising:
a polymerizable compound;
an adhesion promoter; and
a phenolic compound including at least two phenolic groups; wherein
the adhesion promoter has a chemical structure according to Formula I, or a salt thereof:
wherein
n is 0 or 1;
R 1 is selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aryl group;
L 1 represents a divalent linking group including 20 carbon atoms or less in which L 1 is linked to carboxylic acid via an aliphatic carbon atom;
X represents O or NR 4 ;
R 4 is selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkaryl group, a substituted or unsubstituted aralkyl group, and a substituted or unsubstituted (hetero)aryl group;
R 4 and L 1 may represent atoms that form a 5 to 8 membered ring;
R 2 and R 3 are independently selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group.
2. The radiation curable solder mask inkjet ink according to claim 1 , wherein R 1 is a hydrogen atom or a methyl group.
3. The radiation curable solder mask inkjet ink according to claim 1 , wherein X is an oxygen atom or NH.
4. The radiation curable solder mask inkjet ink according to claim 1 , wherein L 1 represents a substituted or unsubstituted alkylene group.
5. The radiation curable solder mask inkjet ink according to claim 1 , wherein the phenolic compound has a structure according to Formula II:
wherein
R 5 and R 6 are independently selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a hydroxyl group, and a substituted or unsubstituted alkoxy group;
Y is selected from the group consisting of CR 7 R 8 , SO 2 , SO, S, O, and CO;
R 7 and R 8 are independently selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkaryl group, a substituted or unsubstituted aralkyl group, and a substituted or unsubstituted (hetero)aryl group; and
R 7 and R 8 may represent atoms that form a 5 to 8 membered ring.
6. The radiation curable solder mask inkjet ink according to claim 5 , wherein Y is CR 7 R 8 or SO 2 , and R 7 and R 8 represent a hydrogen atom or an alkyl group.
7. The radiation curable solder mask inkjet ink according to claim 1 , wherein the phenolic compound is a phenolic resin or a hydroxystyrene based resin.
8. The radiation curable solder mask inkjet ink according to claim 1 , wherein an amount of the adhesion promoter is between 0.5 and 20 wt % relative to a total weight of the inkjet ink.
9. The radiation curable solder mask inkjet ink according to claim 1 , wherein an amount of the phenolic compound is between 0.5 and 20 wt % relative to a total weight of the inkjet ink.
10. The radiation curable solder mask inkjet ink according to claim 1 , wherein the polymerizable compound is selected from the group consisting of neopentyl glycol hydroxypivalate diacrylate, isobornyl acrylate, dipropylene glycol diacrylate, trimethylol propane triacrylate, and 2-(vinylethoxy)ethyl acrylate.
11. The radiation curable solder mask inkjet ink according to claim 1 , further comprising a cyan pigment, a yellow pigment, or a green pigment.
12. A method of manufacturing an electronic device, the method comprising:
jetting a radiation curable solder mask inkjet ink as defined in claim 1 onto a dielectric substrate including an electrically conductive pattern; and
curing the jetted solder mask inkjet ink.
13. The method according to claim 12 , wherein the step of curing is performed using UV radiation.
14. The method according to claim 12 , further comprising:
heating the jetted solder mask inkjet ink.
15. The method according to claim 12 , wherein the electronic device is a printed circuit board.