METHOD FOR PREPARING AND ASSEMBLING A SOLDERED SUBSTRATE

Abstract

A method to form solder microsockets on a first substrate (for example a chip carrier) so that when the first substrate is aligned with a second substrate having shaped solder elements (for example a semiconductor device), the shaped solder elements fit into the solder microsockets. At least one of the aligned solder elements and solder microsockets may be reflowed to effect joining of the first and second substrates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The Figures are for illustration purposes only and are not drawn to scale. Although only a few connections are shown in each of the Figures, it should be understood that a full grid array of vias and connections are often used in practice. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:

FIGS. 1A and 1B illustrate two substrates which are initially aligned and then become misregistered.

FIGS. 2A and 2B illustrate two substrates which form a nonplanar interconnect because of unequal solder volumes.

FIGS. 3A and 3B illustrate two substrates which are not completely aligned because at least one via is off center.

FIGS. 4A-4C illustrate the steps according to a first embodiment of the present invention to form microsockets to assist in the alignment and joining of two substrates.

FIGS. 5A and 5B illustrate alternative designs for the shaped element that forms the microsockets.

FIGS. 6A-6D illustrate the steps according to a second embodiment of the present invention to form microsockets to assist in the alignment and joining of two substrates.

Claims

1. A method for preparing and assembling a soldered substrate, the method comprising the steps of: forming a quantity of solder on a substrate;heating and reflowing the quantity of solder;contacting the quantity of solder with a shaped article;pressing the shaped article into the quantity of solder to form an indentation in the quantity of solder; andremoving the shaped article.

2. The method of claim 1 wherein during the step of pressing the shaped article, the quantity of solder is warmed to a temperature which is above room temperature but less than that at which the quantity of solder begins to melt.

3. The method of claim 1 in which the shaped article is warmed to a temperature which is above room temperature but less than that at which the quantity of solder begins to melt.

4. The method of claim 3 wherein the shaped article is nonwetting with respect to the quantity of solder.

5. The method of claim 1 wherein the substrate is a chip carrier.

6. The method of claim 1 wherein the substrate is a card, printed wiring board or motherboard.

7. The method of claim 1 wherein the quantity of solder is a lead-free or lead-containing solder.

8. The method of claim 1 wherein the substrate comprises a plurality of vias intersecting with a surface of the substrate and the quantity of solder comprises a quantity of solder on each of the plurality of vias.

9. A method for preparing and assembling a soldered substrate, the method comprising the steps of: forming a first quantity of solder on a first substrate;heating and reflowing the first quantity of solder;contacting the first quantity of solder with a shaped article;pressing the shaped article into the first quantity of solder to form an indentation in the first quantity of solder;removing the shaped article;contacting the first quantity of solder with a second quantity of solder on a second substrate, the second quantity of solder being shaped so as to fit with the indentation in the first quantity of solder; andheating the substrates so as to reflow at least one of the first and second quantities of solder.

10. The method of claim 9 wherein during the step of pressing the shaped article, the first quantity of solder is warmed to a temperature which is above room temperature but less than that at which the first quantity of solder begins to melt.

11. The method of claim 9 in which the shaped article is warmed to a temperature which is above room temperature but less than that at which the first quantity of solder begins to melt.

12. The method of claim 11 wherein the shaped article is nonwetting with respect to the first quantity of solder.

13. The method of claim 9 wherein the first substrate is a chip carrier and the second substrate is a semiconductor device or a capacitor.

14. The method of claim 9 wherein the first substrate is a card, printed wiring board or motherboard and the second substrate is a chip carrier.

15. The method of claim 9 wherein the first and second quantities of solder comprise a lead-free or lead-containing solder.

16. The method of claim 9 wherein the first and second quantities of solder form a single melt solder system.

17. The method of claim 9 wherein the first and second quantities of solder form a dual melt solder system.

18. The method of claim 9 wherein the first substrate comprises a plurality of vias intersecting with a surface of the first substrate and the first quantity of solder comprises a quantity of solder on each of the plurality of vias.

19. A method for preparing and assembling a soldered substrate, the method comprising the steps of: preparing a silicon wafer so as to have a plurality protrusions extending therefrom;depositing a disc of solder on each of the protrusions with at least one protrusion extending into each of the discs of solder;assembling the silicon wafer with a substrate having a plurality of vias therein so that the discs of solder contact the vias;heating and reflowing the discs of solder so as to cause joining of the discs of solder to the vias;cooling the discs of solder; andremoving the silicon wafer from the discs of solder so as to leave indentations in the discs of solder.

20. A method for preparing and assembling a soldered substrate, the method comprising the steps of: preparing a silicon wafer so as to have a plurality protrusions extending therefrom;depositing a disc of solder on each of the protrusions with at least one protrusion extending into each of the discs of solder;assembling the silicon wafer with a first substrate having a plurality of vias therein so that the discs of solder contact the vias;heating and reflowing the discs of solder so as to cause joining of the discs of solder to the vias;cooling the discs of solder;removing the silicon wafer from the discs of solder so as to leave indentations in the discs of solder;contacting the discs of solder with solder elements on a second substrate, the solder elements being shaped so as to fit with the indentations in the discs of solder; andheating the substrates so as to reflow at least one of the discs of solder and solder elements.