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bottom side epoxy

John

#9133

bottom side epoxy | 6 October, 1999

I recently had the opportunity to visit the vendor who is making my boards. On my trip I noticed that the guy who was in charge of the SMD placement machine (brand new Samsung) still had to manuallly place about 20%-40% of the parts after placement because the epoxy did not have enough "stickyness" to hold the parts in place.

Personally, I thought the solder was not blown off the pads enough,creating a lump of solder on the pad, so when the the parts are placed, they are placed on this lump of solder and don't contact the epoxy enough to hold them in place.

Any thoughts on the matter? Any help would be appreciated.

Thanks,

John

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Chris May

#9134

Re: bottom side epoxy | 7 October, 1999

| I recently had the opportunity to visit the vendor who is making my boards. On my trip I noticed that the guy who was in charge of the SMD placement machine (brand new Samsung) still had to manuallly place about 20%-40% of the parts after placement because the epoxy did not have enough "stickyness" to hold the parts in place. | | Personally, I thought the solder was not blown off the pads enough,creating a lump of solder on the pad, so when the the parts are placed, they are placed on this lump of solder and don't contact the epoxy enough to hold them in place. | | Any thoughts on the matter? Any help would be appreciated. | | Thanks, | | John | John,

It sounds like the Hot Air Solder Levelling on your bare boards is not being processed correctly. Maybe you should change to a "flatter" finish (i.e. immersion gold) or have a word with the board supplier.

Regards,

Chris.

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#9135

Re: bottom side epoxy | 7 October, 1999

| | I recently had the opportunity to visit the vendor who is making my boards. On my trip I noticed that the guy who was in charge of the SMD placement machine (brand new Samsung) still had to manuallly place about 20%-40% of the parts after placement because the epoxy did not have enough "stickyness" to hold the parts in place. | | | | Personally, I thought the solder was not blown off the pads enough,creating a lump of solder on the pad, so when the the parts are placed, they are placed on this lump of solder and don't contact the epoxy enough to hold them in place. | | | | Any thoughts on the matter? Any help would be appreciated. | | | | Thanks, | | | | John | | | John, | | It sounds like the Hot Air Solder Levelling on your bare boards is not being processed correctly. Maybe you should change to a "flatter" finish (i.e. immersion gold) or have a word with the board supplier. | | Regards, | | Chris. | | What�s the standoff of those parts, something that can be influenced by design ? If both the design and the boards are not the cause there is something wrong with the process.

Regards

Wolfgang

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#9136

Re: bottom side epoxy | 7 October, 1999

| I recently had the opportunity to visit the vendor who is making my boards. On my trip I noticed that the guy who was in charge of the SMD placement machine (brand new Samsung) still had to manuallly place about 20%-40% of the parts after placement because the epoxy did not have enough "stickyness" to hold the parts in place. | | Personally, I thought the solder was not blown off the pads enough,creating a lump of solder on the pad, so when the the parts are placed, they are placed on this lump of solder and don't contact the epoxy enough to hold them in place. | | Any thoughts on the matter? Any help would be appreciated. | | Thanks, | | John | John, You're getting more questions than answers, but what the hey? My question is: How is this supplier applying the glue?

1 If dispensing, the solder stand-off height issue should be able to be over-come with prudent use of nozzles and programming. 2 If printing, then the solder height on the pads should stand the stencil off an equal amount. So, solder height should not the problem, but a lousy stencil design would do it.

So if insufficient glue is the issue, start wondering if there are other things about your suppier that's goofy.

How about this (these)?

1 How old is the glue? What condition is it in? Etc, etc. Glue is as tough to control as paste. 2 What about the board surface? Is there a residue on the board that prevents the glue from er, gluing? 3 What about components? Work with 2 above 4 What about the board finish? How well does the texture and material of the solder mask match-up with the glue your supplier has selected?

My2�

Dave F

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Charles Morris

#9137

Re: bottom side epoxy | 8 October, 1999

| I recently had the opportunity to visit the vendor who is making my boards. On my trip I noticed that the guy who was in charge of the SMD placement machine (brand new Samsung) still had to manuallly place about 20%-40% of the parts after placement because the epoxy did not have enough "stickyness" to hold the parts in place. | | Personally, I thought the solder was not blown off the pads enough,creating a lump of solder on the pad, so when the the parts are placed, they are placed on this lump of solder and don't contact the epoxy enough to hold them in place. | | Any thoughts on the matter? Any help would be appreciated. | | Thanks, | | John | One of the areas you might want to investigate would be component placement, especiallly the z axis. If the component is not being placed correctly, the small burst of air at the end of placement would simply blow the part onto the epoxy and it would not stick. The z-axis pressure is extremely important when placeing on epoxy. Just a thought. Charles

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John

#9138

Thank You Very Much | 8 October, 1999

Thanks you all, both to those who responded on the forum and to those who sent me email. I appreciate your help very much. I will contact my vendor and try to help them with your suggestions. I only hope they are open to suggestions.

Thanks Again, John

| I recently had the opportunity to visit the vendor who is making my boards. On my trip I noticed that the guy who was in charge of the SMD placement machine (brand new Samsung) still had to manuallly place about 20%-40% of the parts after placement because the epoxy did not have enough "stickyness" to hold the parts in place. | | Personally, I thought the solder was not blown off the pads enough,creating a lump of solder on the pad, so when the the parts are placed, they are placed on this lump of solder and don't contact the epoxy enough to hold them in place. | | Any thoughts on the matter? Any help would be appreciated. | | Thanks, | | John |

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John

#9139

P.S. from John | 8 October, 1999

An afterthought- if anyone knows of a good contract mfg house near SE WI/NE IL please let me know. Thanks Again, John

| I recently had the opportunity to visit the vendor who is making my boards. On my trip I noticed that the guy who was in charge of the SMD placement machine (brand new Samsung) still had to manuallly place about 20%-40% of the parts after placement because the epoxy did not have enough "stickyness" to hold the parts in place. | | Personally, I thought the solder was not blown off the pads enough,creating a lump of solder on the pad, so when the the parts are placed, they are placed on this lump of solder and don't contact the epoxy enough to hold them in place. | | Any thoughts on the matter? Any help would be appreciated. | | Thanks, | | John |

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