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SMT electronics assembly manufacturing forum.


King Kong

#10648

Solder on GF | 13 July, 1999

Hi All, Does any one experienced the solder on gold finger after reflow. Its about 5 to 8 mils diameter . We'd clean the entire screen printer, mounter & reflow as well, but doesn't help much.

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JohnW

#10649

Re: Solder on GF | 13 July, 1999

| Hi All, | Does any one experienced the solder on gold finger after | reflow. Its about 5 to 8 mils diameter . | We'd clean the entire screen printer, mounter & reflow as well, | but doesn't help much. | | Mr Kong.....

Solder on gold is a age old problem that everyone get's, about 70 % of the time it's down to house keeping, your screen printer is clean, but where are your boards ? are they on a table waiting tobe fed into the machine ? is the table clean, are your conveyor's clean ? and your reflow oven is it chain or belt ? boath can have different problems. Another posibility is when your loading paste onto the stencil, assuming it's done manually are your operators handling card's right after it with out cleaning or removing their gloves ??

if all of the above have been checked then it's time to worry about the process ( although I would class all of the above as part of the process). Paste, are you pasting anywhere near the gold fingers, are you leaching under the screen and contaminating the botomside due to poor printer set up ? Could the paste be getting moved by conveyor's if it's near the edge ? Reflow..how is your profile ? a slow ramp to a decent dwell then jump up to reflow and back down within your 60 second window. If your paste requirement's dont match your profile you can get spattering, if your board is full of moisture you can get it. the normal ramp, dwell and peak profile's are those that the paste manufacturer's spec but they really hark back to the day's of IR, if your using a half way decent convection oven you can ignore the dwell ( wait's for the call's of sacrilage) a slow steady ramp to reflow and down is fine since it's convection the whole board see's the same temp's so you 'in theory' don't need the soak or dwell. keep the ramp to under the 2 degree's a sec.

I think that most people though mask the gold finger's by applying kapton tape, but again you got to make sure the surface is clean and that the opertaor's hand's / gloves are clean...house keeping is really important...

hope this help's some...

JohnW

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Upinder Singh

#10650

Re: Solder on GF | 14 July, 1999

| | Hi All, | | Does any one experienced the solder on gold finger after | | reflow. Its about 5 to 8 mils diameter . | | We'd clean the entire screen printer, mounter & reflow as well, | | but doesn't help much. | | | | | Mr Kong..... | | Solder on gold is a age old problem that everyone get's, about 70 % of the time it's down to house keeping, your screen printer is clean, but where are your boards ? are they on a table waiting tobe fed into the machine ? is the table clean, are your conveyor's clean ? and your reflow oven is it chain or belt ? boath can have different problems. | Another posibility is when your loading paste onto the stencil, assuming it's done manually are your operators handling card's right after it with out cleaning or removing their gloves ?? | | if all of the above have been checked then it's time to worry about the process ( although I would class all of the above as part of the process). | Paste, are you pasting anywhere near the gold fingers, are you leaching under the screen and contaminating the botomside due to poor printer set up ? | Could the paste be getting moved by conveyor's if it's near the edge ? | Reflow..how is your profile ? a slow ramp to a decent dwell then jump up to reflow and back down within your 60 second window. If your paste requirement's dont match your profile you can get spattering, if your board is full of moisture you can get it. | the normal ramp, dwell and peak profile's are those that the paste manufacturer's spec but they really hark back to the day's of IR, if your using a half way decent convection oven you can ignore the dwell ( wait's for the call's of sacrilage) a slow steady ramp to reflow and down is fine since it's convection the whole board see's the same temp's so you 'in theory' don't need the soak or dwell. keep the ramp to under the 2 degree's a sec. | | I think that most people though mask the gold finger's by applying kapton tape, but again you got to make sure the surface is clean and that the opertaor's hand's / gloves are clean...house keeping is really important... | | hope this help's some... | | JohnW | Hi.

I totally agree with John. Though , I would like to add one thing. Did u check the boards before starting the printing process. Sometimes this is also a board house problem and has happened to me twice in last one year.

Upinder ======

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Jimmy Strain

#10651

Re: Solder on GF | 14 July, 1999

| | | Hi All, | | | Does any one experienced the solder on gold finger after | | | reflow. Its about 5 to 8 mils diameter . | | | We'd clean the entire screen printer, mounter & reflow as well, | | | but doesn't help much. | | | | | | | | Mr Kong..... | | | | Solder on gold is a age old problem that everyone get's, about 70 % of the time it's down to house keeping, your screen printer is clean, but where are your boards ? are they on a table waiting tobe fed into the machine ? is the table clean, are your conveyor's clean ? and your reflow oven is it chain or belt ? boath can have different problems. | | Another posibility is when your loading paste onto the stencil, assuming it's done manually are your operators handling card's right after it with out cleaning or removing their gloves ?? | | | | if all of the above have been checked then it's time to worry about the process ( although I would class all of the above as part of the process). | | Paste, are you pasting anywhere near the gold fingers, are you leaching under the screen and contaminating the botomside due to poor printer set up ? | | Could the paste be getting moved by conveyor's if it's near the edge ? | | Reflow..how is your profile ? a slow ramp to a decent dwell then jump up to reflow and back down within your 60 second window. If your paste requirement's dont match your profile you can get spattering, if your board is full of moisture you can get it. | | the normal ramp, dwell and peak profile's are those that the paste manufacturer's spec but they really hark back to the day's of IR, if your using a half way decent convection oven you can ignore the dwell ( wait's for the call's of sacrilage) a slow steady ramp to reflow and down is fine since it's convection the whole board see's the same temp's so you 'in theory' don't need the soak or dwell. keep the ramp to under the 2 degree's a sec. | | | | I think that most people though mask the gold finger's by applying kapton tape, but again you got to make sure the surface is clean and that the opertaor's hand's / gloves are clean...house keeping is really important... | | | | hope this help's some... | | | | JohnW | | | Hi. | | I totally agree with John. Though , I would like to add one thing. Did u check the boards before starting the printing process. Sometimes this is also a board house problem and has happened to me twice in last one year. | | Upinder | ====== | another common fault is outgassing from the via's.

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