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Storage life of Gold Finish Boards

John W

#12920

Storage life of Gold Finish Boards | 15 January, 1999

Folk's,

I'm looking for information of how long you cna store a gold finish PCB before building it. I know there are problems with the gold disappearing into the underlying nickle over time / temperature etc but exactly how long do you have before this will cause serious problems ? If the gold has dispersed is there any way to repair it ?

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Earl Moon

#12921

Re: Storage life of Gold Finish Boards | 15 January, 1999

| Folk's, | | I'm looking for information of how long you cna store a gold finish PCB before building it. I know there are problems with the gold disappearing into the underlying nickle over time / temperature etc but exactly how long do you have before this will cause serious problems ? | If the gold has dispersed is there any way to repair it ? |

It's not so much a question of the gold dissappearing as it is other factors at work. As you and Mike G. (below) said - there is very little gold applied over the nickel barrier.

The nickel is a barrier to prevent copper from "dispersing," as you say, into the gold. As such it is a two way barrier also preventing the gold from becoming part of it or getting through it.

The probems are really two:

1) Providing plating, or deposition, processes are effectively managed, the gold will stay in place for long periods (as with any surface finish, packaging storage, handling, shipping, etc. conditions (ISO 9000) are critical factors. If all requirements are met as required, gold shelf life is indefinite.

2) As we are talking a preferred maximum of 3-10 millionths" gold over 100-120 millionths" nickel over copper, it is vital the nickel barrier be as specified. However, the biggest problem is phosphorous/nickel intermetallic formations providing the embrittlement mechanism we all wish to avoid but no one has that fix yet.

It should be noted that when the nickel barrier is not as specified, copper causes the problems in the gold, and there is no fix.

Earl Moon

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Bob Willis

#12922

Re: Storage life of Gold Finish Boards | 15 January, 1999

| | Folk's, | | | | I'm looking for information of how long you cna store a gold finish PCB before building it. I know there are problems with the gold disappearing into the underlying nickle over time / temperature etc but exactly how long do you have before this will cause serious problems ? | | If the gold has dispersed is there any way to repair it ? | | | | It's not so much a question of the gold dissappearing as it is other factors at work. As you and Mike G. (below) said - there is very little gold applied over the nickel barrier. | | The nickel is a barrier to prevent copper from "dispersing," as you say, into the gold. As such it is a two way barrier also preventing the gold from becoming part of it or getting through it. | | The probems are really two: | | 1) Providing plating, or deposition, processes are effectively managed, the gold will stay in place for long periods (as with any surface finish, packaging storage, handling, shipping, etc. conditions (ISO 9000) are critical factors. If all requirements are met as required, gold shelf life is indefinite. | | 2) As we are talking a preferred maximum of 3-10 millionths" gold over 100-120 millionths" nickel over copper, it is vital the nickel barrier be as specified. However, the biggest problem is phosphorous/nickel intermetallic formations providing the embrittlement mechanism we all wish to avoid but no one has that fix yet. | | It should be noted that when the nickel barrier is not as specified, copper causes the problems in the gold, and there is no fix. | | Earl Moon | Quite right Earl, the biggest problem with gold board is the standard of the solderability when they leave the supplier. If its done right it works if its done incorrectly find a bin. Thats why I like OSP coatings as they work fine, good price and the only finish you can have reprocessed if you have a delay in production.

Most OSP coating if processed correctly by the supplier work for in excess of six months even in air.

reply »

Earl Moon

#12923

Re: Storage life of Gold Finish Boards | 15 January, 1999

| | | Folk's, | | | | | | I'm looking for information of how long you cna store a gold finish PCB before building it. I know there are problems with the gold disappearing into the underlying nickle over time / temperature etc but exactly how long do you have before this will cause serious problems ? | | | If the gold has dispersed is there any way to repair it ? | | | | | | | It's not so much a question of the gold dissappearing as it is other factors at work. As you and Mike G. (below) said - there is very little gold applied over the nickel barrier. | | | | The nickel is a barrier to prevent copper from "dispersing," as you say, into the gold. As such it is a two way barrier also preventing the gold from becoming part of it or getting through it. | | | | The probems are really two: | | | | 1) Providing plating, or deposition, processes are effectively managed, the gold will stay in place for long periods (as with any surface finish, packaging storage, handling, shipping, etc. conditions (ISO 9000) are critical factors. If all requirements are met as required, gold shelf life is indefinite. | | | | 2) As we are talking a preferred maximum of 3-10 millionths" gold over 100-120 millionths" nickel over copper, it is vital the nickel barrier be as specified. However, the biggest problem is phosphorous/nickel intermetallic formations providing the embrittlement mechanism we all wish to avoid but no one has that fix yet. | | | | It should be noted that when the nickel barrier is not as specified, copper causes the problems in the gold, and there is no fix. | | | | Earl Moon | | | Quite right Earl, the biggest problem with gold board is the standard of the solderability when they leave the supplier. If its done right it works if its done incorrectly find a bin. Thats why I like OSP coatings as they work fine, good price and the only finish you can have reprocessed if you have a delay in production. | | Most OSP coating if processed correctly by the supplier work for in excess of six months even in air. | Bob,

I enjoyed the interchange on this one. There is hope for us all.

On the serious side: I do have a question for you. I asked earlier about possible conflicts between VOC free (water based) no clean flux and OSP's as they are organic. Does such a conflict exist and, if so, to what extent?

Respectfully,

Earl Moon

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John W

#12924

Re: Storage life of Gold Finish Boards | 18 January, 1999

| | | | Folk's, | | | | | | | | I'm looking for information of how long you cna store a gold finish PCB before building it. I know there are problems with the gold disappearing into the underlying nickle over time / temperature etc but exactly how long do you have before this will cause serious problems ? | | | | If the gold has dispersed is there any way to repair it ? | | | | | | | | | | It's not so much a question of the gold dissappearing as it is other factors at work. As you and Mike G. (below) said - there is very little gold applied over the nickel barrier. | | | | | | The nickel is a barrier to prevent copper from "dispersing," as you say, into the gold. As such it is a two way barrier also preventing the gold from becoming part of it or getting through it. | | | | | | The probems are really two: | | | | | | 1) Providing plating, or deposition, processes are effectively managed, the gold will stay in place for long periods (as with any surface finish, packaging storage, handling, shipping, etc. conditions (ISO 9000) are critical factors. If all requirements are met as required, gold shelf life is indefinite. | | | | | | 2) As we are talking a preferred maximum of 3-10 millionths" gold over 100-120 millionths" nickel over copper, it is vital the nickel barrier be as specified. However, the biggest problem is phosphorous/nickel intermetallic formations providing the embrittlement mechanism we all wish to avoid but no one has that fix yet. | | | | | | It should be noted that when the nickel barrier is not as specified, copper causes the problems in the gold, and there is no fix. | | | | | | Earl Moon | | | | | Quite right Earl, the biggest problem with gold board is the standard of the solderability when they leave the supplier. If its done right it works if its done incorrectly find a bin. Thats why I like OSP coatings as they work fine, good price and the only finish you can have reprocessed if you have a delay in production. | | | | Most OSP coating if processed correctly by the supplier work for in excess of six months even in air. | | | Bob, | | I enjoyed the interchange on this one. There is hope for us all. | | On the serious side: I do have a question for you. I asked earlier about possible conflicts between VOC free (water based) no clean flux and OSP's as they are organic. Does such a conflict exist and, if so, to what extent? | | Respectfully, | | Earl Moon

I agree that the biggest problem with the gold boards is the manufacture or the PCB. But the problem I have is that the boards have been sitting in a store room for 18 month's.... So they may have been fine when they were made but have become unsolderable over time via oxides & stuff like that, so I guess I'm back to the origonal question, what's the shelf life ?

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Dave F

#12925

Re: Storage life of Gold Finish Boards | 19 January, 1999

| | | | | Folk's, | | | | | | | | | | I'm looking for information of how long you cna store a gold finish PCB before building it. I know there are problems with the gold disappearing into the underlying nickle over time / temperature etc but exactly how long do you have before this will cause serious problems ? | | | | | If the gold has dispersed is there any way to repair it ? | | | | | | | | | | | | | It's not so much a question of the gold dissappearing as it is other factors at work. As you and Mike G. (below) said - there is very little gold applied over the nickel barrier. | | | | | | | | The nickel is a barrier to prevent copper from "dispersing," as you say, into the gold. As such it is a two way barrier also preventing the gold from becoming part of it or getting through it. | | | | | | | | The probems are really two: | | | | | | | | 1) Providing plating, or deposition, processes are effectively managed, the gold will stay in place for long periods (as with any surface finish, packaging storage, handling, shipping, etc. conditions (ISO 9000) are critical factors. If all requirements are met as required, gold shelf life is indefinite. | | | | | | | | 2) As we are talking a preferred maximum of 3-10 millionths" gold over 100-120 millionths" nickel over copper, it is vital the nickel barrier be as specified. However, the biggest problem is phosphorous/nickel intermetallic formations providing the embrittlement mechanism we all wish to avoid but no one has that fix yet. | | | | | | | | It should be noted that when the nickel barrier is not as specified, copper causes the problems in the gold, and there is no fix. | | | | | | | | Earl Moon | | | | | | | Quite right Earl, the biggest problem with gold board is the standard of the solderability when they leave the supplier. If its done right it works if its done incorrectly find a bin. Thats why I like OSP coatings as they work fine, good price and the only finish you can have reprocessed if you have a delay in production. | | | | | | Most OSP coating if processed correctly by the supplier work for in excess of six months even in air. | | | | | Bob, | | | | I enjoyed the interchange on this one. There is hope for us all. | | | | On the serious side: I do have a question for you. I asked earlier about possible conflicts between VOC free (water based) no clean flux and OSP's as they are organic. Does such a conflict exist and, if so, to what extent? | | | | Respectfully, | | | | Earl Moon | | I agree that the biggest problem with the gold boards is the manufacture or the PCB. But the problem I have is that the boards have been sitting in a store room for 18 month's.... | So they may have been fine when they were made but have become unsolderable over time via oxides & stuff like that, so I guess I'm back to the origonal question, what's the shelf life ? | | | John: Having solderable boards depends on:

VARIABLES:

1 Thickness and condition of the plating 2 Post-plating fabrication process 3 Cleanliness of the board before storage 4 Packaging while in storage 5 Storage conditions

STORAGE TIME TEST #1: How long you can store them and still produce acceptable product?.

STORAGE TIME TEST #2: If you have boards in stock for more than a year, any solderability problems that you have should be amply paid for by the person that brought-in the material early and saved so much money "volume buying."

TTYL

Dave F

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