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Soldering to Paladium vs. Tin_Lead plated comps

Gary Simbulan

#16703

Soldering to Paladium vs. Tin_Lead plated comps | 19 February, 1998

I have been involved in SMT for only a few months so I am coming from a position of extreame ignorance. I have been asked to investigate the differences in soldering to components with Paladium coated leads vs the standard Tin_lead. I would appreciate if anyone can point me to some technical info on the subject of solder joint chemistry and or machanical studies the include Paladium.

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Chrys Shea

#16715

Re: Soldering to Paladium vs. Tin_Lead plated comps | 20 February, 1998

| I have been involved in SMT for only a few months so I am coming from a position of extreame ignorance. I have been asked to investigate the differences in soldering to components with Paladium coated leads vs the standard Tin_lead. I would appreciate if anyone can point me to some technical info on the subject of solder joint chemistry and or machanical studies the include Paladium. Gary, Lots has been published on this topic. Check back issues of SMT or Circuits Assembly magazine. When soldering to Palladium, you have to get your spike temperature in your reflow oven up over 215C. It shortens your process window, but if you get up over 215, the palladium will go into the solution and you'll have a relaibale joint. It may mean reprofiling some of your boards, however. Another thing to keep in mind is inspection - palladium looks dull & kind of grainy, and inspectors with eyes trained to tin-lead may consider them cold joints. I tell them to look at all the joints and up the leads at the knees. If the plating on the knees looks dull and grainy, then it's probably a palladium plated component. Don't get sucked in to a lot of unnecessary rework! You may also get info on the palladium plating from the component supplier - they went through lots of qualification tests before switching from tin-lead. Good luck, Chrys

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Steve Gregory

#16709

Re: Soldering to Paladium vs. Tin_Lead plated comps | 20 February, 1998

The biggest difference between the two, is solder joint appearance. What I noticed mainly is that the solder does not wet and flow as readily to a palladium coated lead as it does with a tin/lead coated lead. When you look at a palladium coated lead solder joint under a microscope, it sometimes looks like the lead is sitting on a "pillow" of solder...right? The solder may appear to not have wet real good to the lead. A tin/lead plated lead will have the solder wet and flow over top of the foot making the overall joint look kind of rounded and in the shape of the lead. A little higher than normal peak temperature in your profile helps things a little, but don't cook your boards! This helps the appearance some, but it really isn't necessary. The joints are good...this plating was designed to be a drop-in replacement for tin/lead. Sure, the joints will look a little different, but that's okay. Texas Instruments was the first component manufacturer I know of that switched to palladium, and they've been doing it for at least 5-years now. I spoke with somebody from T.I. back when I first noticed it. The biggest reason they did it was that the solder plating operation was the messiest, low yielding process that they had. Once they switched to palladium they saw at least a 50% increase in yields...plus they eliminated using lead completely... -Steve Gregory-

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Igmar

#16706

Re: Soldering to Paladium vs. Tin_Lead plated comps | 23 February, 1998

| I have been involved in SMT for only a few months so I am coming from a position of extreame ignorance. I have been asked to investigate the differences in soldering to components with Paladium coated leads vs the standard Tin_lead. I would appreciate if anyone can point me to some technical info on the subject of solder joint chemistry and or machanical studies the include Paladium.

I used Palladium coated TransGuards from AVX recently, and was worried about the appearance of the dull solder joints, and small solder fillets. My supplier, Eurotech send me an information sheet from AVX that explained the properties of palladium coated TransGuards. You can contact Eurotech at sales@eurotech.co.uk. Ask for N.J. Bateman and ask them to send you the information sheet | "SMT Process Characteristics of AVX TransGuards". Else, ask your local AVX supplier to send you this information sheet.

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Gary Simbulan

#16705

Re: Don't believe the vendors about Paladium Leads | 23 February, 1998

Gary, Paladium Leads have been a win-lose proposition as far as I can tell. The vendors win because they don't have to deal with lead and get higher yields. The users lose because of extra engineering time involved with incorporating this on their line. Not only do you have to tweek your profiles, you have to retrain people in the identification of poor wetting vs. paladium lead characteristics. I'm also concerned about shelf life. Read the November issue of Circuits Assembly - good article by some good people at Compaq. Don't trust the vendors. They have their own agenda.

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Steve Gregory

#16710

Re: Paladium Pillows and Bad Dreams | 23 February, 1998

Steve - you must not work to IPC class 2 or 3 requirements. If the solder is "pillowed" around the lead, I would strongly suspect a wetting problem. Most of the Paladium leads I see soldered have a strong line of demarcation but no pillowing. Have you done any pull tests? I sure wouldn't sleep well at night if those solder characteristics were in my pacemaker.

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Doug Romm

#16704

Re: Soldering to Paladium vs. Tin_Lead plated comps | 23 February, 1998

Gary, I'm pretty much the main contact at TI for palladium lead finish questions. We have a web site at "http://www.ti.com/sc/docs/asl/palladm/index.htm" which has technical papers I have written on the subject. Also, you'll find the Pd Lead Finish User's manual that you can download with Adobe Acrobat. Contact me if you have any specific questions. Phone 903 868-7388.

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Doug Romm

#16714

Re: Paladium Pillows and Bad Dreams | 23 February, 1998

Dave, "Paladium Pillows and Bad Dreams"....that's a good one! I've been doing this for the last 9 years and I've heard quite a bit, but that's really cute! Seriously, in reference to the 'pillow effect' when the lead looks like it is "sitting" on top of the solder, I've often called this the "marshmallow effect" because it looks like your pushing your finger into a marshmallow. In my experience (9 years) I have heard of this type of performance from several customers and it's gotten to where I can guess the brand of the solder paste that the customer is using. We have found that for water soluble and no-clean solder pastes the solder paste selection has the largest impact on the contact angle...and as I said, poor contact angle performance has been limited to 1 paste supplier with tremendous improvement over the past several years. If you have any interest you're welcome to review our technical data on this subject on the TI Palladium web page.

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Steve Gregory

#16712

Re: Paladium Pillows and Bad Dreams | 25 February, 1998

Dave, I confess I was a tad too general and a bit too extreme describing the way ALL solder joints look on palladium coated leads. I should been more specific about the "pillow-effect". I've seen it regularly with palladium coated leads on small SOT devices...NOT with larger IC's. (I should have said that in the first place, huh?) The first time I encountered the problem, I didn't do a scientific pull test, but I did take a pair of tweezers and pull on the SOT with quite a bit of force. The SOT body broke apart from me pulling on it and left all 3 leads in the joints. I'm no lab technition, but that kinda told me that there was a good metallurgical bond to the bottom of the lead...and these SOT's were sitting on "pillows". I do agree with you about the strong demarcation line that you often see, 9 times out of 10 it is within class-II standards. Have you ever had a problem like I've had with some inspectors when dealing with palladium vs. tin/lead joint appearances? Some will tend to over-reject joints because of the demarcation that you spoke of. It doesn't look as smooth as a tin/lead plated lead, so they'll put a defect arrow on it. Rework operators wind-up pouring hours and hours into making the joints all look the same...and nothing more. Oh, by the way...the pacemaker deal...to be perfectly honest, I don't think I'd be catching much good sleep at all if I was wearing a pacemaker, no matter who made it!! (GRIN)

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Doug Romm

#16713

Re: Palladium Pillows and Bad Dreams | 25 February, 1998

Steve, TI does not produce any SOTs using Palladium finish leadframes. I would certainly be interested to know who is. Also, your observations are correct: In TI experience the mechanical strength of the solder joints with Pd finish ICs is always equal to or better than that for Sn/Pb finish ICs, independent of the contact angle. Customer data also supports this statement. By the way, look for my latest technical paper on Pd finish ICs (totally Pb-free solder joint) in the March issue of Surface Mount Technology magazine. Best regards, Doug Romm

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N.J Bateman

#16708

Re: Soldering to Paladium vs. Tin_Lead plated comps | 25 February, 1998

| | | I have been involved in SMT for only a few months so I am coming from a position of extreame ignorance. I have been asked to investigate the differences in soldering to components with Paladium coated leads vs the standard Tin_lead. I would appreciate if anyone can point me to some technical info on the subject of solder joint chemistry and or machanical studies the include Paladium. | | I used Palladium coated TransGuards from AVX recently, and was worried about the appearance of the dull solder joints, and small solder fillets. | My supplier, Eurotech send me an information sheet from AVX that explained the properties of palladium coated TransGuards. | You can contact Eurotech at sales@eurotech.co.uk. | Ask for N.J. Bateman and ask them to send you the information sheet | "SMT Process Characteristics of AVX TransGuards". | Else, ask your local AVX supplier to send you this information sheet. Please note;N.J bateman at Euro-Tech is NOT a supplier of data. You must contact your local AVX distributor for this information.

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N.J Bateman

#16707

Re: Soldering to Paladium vs. Tin_Lead plated comps | 25 February, 1998

| | | I have been involved in SMT for only a few months so I am coming from a position of extreame ignorance. I have been asked to investigate the differences in soldering to components with Paladium coated leads vs the standard Tin_lead. I would appreciate if anyone can point me to some technical info on the subject of solder joint chemistry and or machanical studies the include Paladium. | | I used Palladium coated TransGuards from AVX recently, and was worried about the appearance of the dull solder joints, and small solder fillets. | My supplier, Eurotech send me an information sheet from AVX that explained the properties of palladium coated TransGuards. | You can contact Eurotech at sales@eurotech.co.uk. | Ask for N.J. Bateman and ask them to send you the information sheet | "SMT Process Characteristics of AVX TransGuards". | Else, ask your local AVX supplier to send you this information sheet. Please note;N.J bateman at Euro-Tech is NOT a supplier of data. You must contact your local AVX distributor for this information.

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Eldon Sanders

#16716

Re: Soldering to Paladium vs. Tin_Lead plated comps | 25 February, 1998

I agree with Chrys, get the spike temp up and wetting is not a problem. However, when the palladium mixes in with the solder the joint will become more brittle. You need to make sure enough solder is printed on the board to minimize the concentration of the palladium. I had a problem with a board that had very small lands for AVX transguards, 0805 palladium terminated chips. The board also had many fine pitch components and I used a 5 mil stencil. The chips would break off if hit with a sharp blow . Short term solution was to overprint the lands with a new stencil to put more solder paste down and problem solved. The board has since been redesigned with proper lands, but I still enlarge the stencil aperatures for the palladium chips. These parts now hold as good as the non-palladium chip caps, and the lower concentration of palladium makes the joints look almost the same. Hope this helps. Regards,

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Doug Romm

#16717

Re: Soldering to Palladium vs. Tin_Lead plated comps | 25 February, 1998

Just a comment to clarify this discussion. Typically chip caps and other passive components that use palladium plated to the end of the component are very different from the TI nickel/palladium plated IC components (leaded devices). The main difference is the thickness of the Pd. TI plates 3 microinches on top of the nickel surface of our leaded components. Chip capacitor manufacturers normally plate 10-20X thicker palladium on their chip caps. I used to work for a capacitor manufacturer but I can't remember the exact thickness of the Pd on the chip caps. Anyway, my point is that with the TI Pd finish leaded components the Pd completely dissolves into the solder and brittle joints due to undissolved Pd have not been a problem. On our leaded components the solder actually wets to the nickel underneath the Pd.

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Doug Romm

#16711

Request for "Dave C." | 27 February, 1998

Dave, I have had several people who have read this series of conversations ask me if I know what company you work for. Are you willing to provide the name of your company and your e-mail address for anyone that wishes to correspond with you? Thanks, Doug Romm Texas Instruments drom@msg.ti.com

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