Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Entek coating

Jeremy Smith

#16565

Entek coating | 10 March, 1998

I am having a problem with Entek coated boards. The solder past seem to just ball up on the pads. I had no problems with the board when it was hot air leveled. The board is double sided surface mount. I have tried adjusting the oven profiles making sure that excessive heat is not experienced on the first pass. I have had little success in making any change in the deweting of the solder. Has any one had success with this coating ?? If so any help would be much appreciated.

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Carl mitchell

#16569

Re: Entek coating | 10 March, 1998

| I am having a problem with Entek coated boards. The solder past seem to just ball up on the pads. I had no problems with the board when it was hot air leveled. The board is double sided surface mount. I have tried adjusting the oven profiles making sure that excessive heat is not experienced on the first pass. I have had little success in making any change in the deweting of the solder. Has any one had success with this coating ?? If so any help would be much appreciated. | One of the first thing I would have to ask you is how long the boards have been exposed to the atmosphere. We have run Entek boards sucessfully for quite a while. We did however experience problems with dewetting on our first attempts quite a while back. The dewetting was due to contamination on the pad. We experienced the best results if we ran the board within 72 hours of removal from the packing. Insure you are following the paste manufactures reflow spec to achieve optimum flux activation. On your ramp through liquidous, increase your final zones about 10 to 15 degrees c.

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Steve Gregory

#16568

Re: Entek coating | 10 March, 1998

Jeremy, I'm gonna make a couple of assumptions by "reading in between the lines" of your email: 1. You're using no-clean paste. 2. This is only happening on the second side. You tell me if I'm wrong about this... First thing, if you're only experiencing the problem on the second side, it sounds to me like they've coated the boards with CU-56 entek, instead of CU-106 like they should have used with boards that will be seeing multiple thermal excursions. The CU-56 wil pretty much take a hike after the first reflow cycle...hasta la vista baby! It's gone! Although I heard a while back that IBM used CU-56 on a lot of their boards when OSP's first came out, and discovered that if you printed the second side, got the parts on, and reflowed right away, it would work...you had to do that within just a couple of hours after the first reflow occured. I HEARD that, I've not tried it myself though.... If it's happening on both sides, then there could be two possible things to look at: 1. If you are using no-clean paste, then possibly the activity in the flux just ain't got the "grunt" it needs to get through the entek...no-cleans only have about 1/4 the activity that a water soluble paste does...some pastes even less. 2. The vendor is slapping the entek on too thick. There's a lot of board vendors out there that don't have the OSP process automated and controlled the way they should. Think about it for a second, this is a new process for them. In the past, the way the solderable surfaces have been finished has either been through a HASL, or some sort of electroplating method. With OSP's all they need is basically a tank filled with the OSP that they can dip the boards into, and viola' they're doing OSP coated boards! Other than that, you sound like you know what you're doing with reflow profiles...just make sure you're not too hot though...you'll waste all the flux activity before the solder becomes molten and has a chance to wet. I hope maybe this helps! -Steve Gregory-

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Earl Moon

#16566

Re: Entek coating | 11 March, 1998

| I am having a problem with Entek coated boards. The solder past seem to just ball up on the pads. I had no problems with the board when it was hot air leveled. The board is double sided surface mount. I have tried adjusting the oven profiles making sure that excessive heat is not experienced on the first pass. I have had little success in making any change in the deweting of the solder. Has any one had success with this coating ?? If so any help would be much appreciated. | As Entek is an organic coating, with a relatively (to solder or other metal coated boards) short "shelf" life, copper oxides form preventing solder wetting thus solder balls form on the metallic surface. Surface cleaning can provide relief but often oxidation quickly returns preventing solderability again. When specifying Entek, ensure suppliers adequately qualified, determine and observe shelf life conditions, or go to another coating process to get away from HASL problems. Currently, immersion gold, silver, and palladium work well with longer shelf lives, better surface flatness, and considerably improved solderability.

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Phill Hunter

#16567

Re: Entek coating | 15 March, 1998

| | I am having a problem with Entek coated boards. The solder past seem to just ball up on the pads. I had no problems with the board when it was hot air leveled. The board is double sided surface mount. I have tried adjusting the oven profiles making sure that excessive heat is not experienced on the first pass. I have had little success in making any change in the deweting of the solder. Has any one had success with this coating ?? If so any help would be much appreciated. | | | As Entek is an organic coating, with a relatively (to solder or other metal coated boards) | short "shelf" life, copper oxides form preventing solder wetting thus solder balls form | on the metallic surface. Surface cleaning can provide relief but often oxidation quickly | returns preventing solderability again. When specifying Entek, ensure suppliers adequately | qualified, determine and observe shelf life conditions, or go to another coating process | to get away from HASL problems. Currently, immersion gold, silver, and palladium work well | with longer shelf lives, better surface flatness, and considerably improved solderability. I suggest experimentation with solder paste chemistries. Solder paste which works well on HASL boards will NOT necessarily work on Entek. Even when manufactures claim compatability it is best to perform experiments. I suggest alpha metal WS 609 water solouble or no clean formulas.

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