Solder pads and method of making a solder pad

1. A method of making a solder pad comprising:

masking a substrate comprising at least a first solder pad and a second solder pad with a mask, wherein the solder pads each contain an alloy composition upon soldering having at least two of the same elements and wherein the mask exposes a greater area of the first solder pad than the second solder pad; and

depositing on at least the first solder pad at least one of the elements that becomes part of the alloy composition upon soldering,

wherein the resulting alloy composition of the first solder pad has a different ratio of the two elements by weight than the alloy composition of the second solder pad.

2. The method of claim 1 , wherein the alloy composition comprises gold-tin.

3. The method of claim 1 , wherein the alloy composition comprises gold-germanium.

4. The method of claim 1 , wherein the elements are selected from the group consisting of gold, tin, germanium, silicon and mixtures thereof.

5. The method of claim 1 , wherein the depositing the element comprises depositing a greater amount of the element on the first solder pad than on the second solder pad.

6. The method of claim 1 , wherein the masking a substrate comprises occluding the second solder pad.

7. The method of claim 1 , comprising the heating the substrate to a temperature sufficient to cause all the solder pads to melt to form solder alloys.

8. The method of claim 7 comprising the maintaining the substrate at a selected temperature sufficient to cause all of the solder pads to be melted and soldering selected components to the substrate at selected solder pads.

9. The method of claim 8 comprising the steps of reheating the substrate to another temperature sufficient to cause only some of the solder pads to melt but not solder pads to which components have been soldered so that selected components may be soldered to the substrate at selected ones of the melted solder pads.

10. The method according to claim 1 , wherein the depositing an element comprises depositing the element through the mask so that the first solder pad has a different ratio of the element deposited through the mask than that of the second solder pad.

11. A method of making a solder pad comprising:

providing a substrate comprising at least first and second solder pads, the solder pads each containing an alloy composition upon soldering having at least two of the same elements;

depositing on at least the first solder pad at least one of the elements that becomes part of the alloy composition upon soldering, wherein the amount of the element deposited on the first solder pad covers a greater fraction of the area of the first solder pad than covers the fraction of the area of the second solder pad, and

wherein the resulting alloy composition of the first solder pad has a different ratio by weight of the two elements than the alloy composition of the second solder pad to provide a different soldering temperature of the first solder pad relative to the second solder pad.

12. The method of claim 11 , wherein the alloy composition comprises gold-tin.

13. The method of claim 11 , wherein the ahoy composition comprises gold-germanium.

14. The method of claim 11 , wherein the elements are selected from the group consisting of gold, tin, germanium, silicon and mixtures thereof.

15. The method of claim 11 , wherein the depositing the element comprises depositing a greater amount of the element on the first solder pad than on the second solder pad.

16. The method of claim 11 , wherein the masking a substrate comprises occluding the second solder pad.

17. The method of claim 11 comprising the heating the substrate to a temperature sufficient to cause all the solder pads to melt to form solder alloys.

18. The method of claim 17 comprising the maintaining the substrate at a selected temperature sufficient to cause all of the solder pads to be melted and soldering selected components to the substrate at selected solder pads.

19. The method of claim 18 comprising the reheating the substrate to another temperature sufficient to cause only some of the solder pads to melt but not solder pads to which components have been soldered so that selected components may be soldered to the substrate at selected ones of the melted solder pads.

20. The method according to claim 11 , wherein the depositing an element comprises masking the substrate and depositing a first element of the at least two elements through the mask so that the first solder pad has a different ratio by weight of the first element to the second element of the at least two elements than that of the second solder pad.

21. A method of making a solder pad comprising:

masking a substrate comprising at least a first solder pad and a second solder pad, wherein the mask exposes a greater area of the first solder pad than the second solder pad; and

depositing an element that becomes part of an alloy composition upon soldering, wherein the resulting alloy composition comprises at least two elements and

wherein the alloy composition of the first pad has a different weight percentage of the element than the alloy composition of the second pad.

22. The method of claim 21 wherein the alloy composition comprises gold-tin.

23. The method of claim 21 wherein the alloy composition comprises gold-germanium.