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Lead-Free SMD repair

Hi all, We produced a RoHS (lead-free) prototype order rece... - Apr 25, 2005 by siverts  

#33885

Lead-Free SMD repair | 25 April, 2005

Hi all, We produced a RoHS (lead-free) prototype order recently, and there was some components that we needed to replace on a couple of PCBA's. We found it very hard to do this even with the new solder iron. The components was just small RoHS SOIC's and small RoHS SSOP's. Problems with not only to remove the old ones but also to solder the new ones. The HFFR-4 Ni/Au PCB has 6 layer with one ground layer and one voltage/power layer, 1.7mm board thickness, 265mm x 207mm pcb. The melting temperature on lead-free solder is of course higher, so I wonder if we need to use some kind of pre-heat underneath the PCBA? We finally ended up with the use of the Sierra BGA-repair equipment and a hot air blower gun, but this is not really an option for us in a long term.

I am interested to hear about Your lead-free smd repair experience and if You also encountered any problems with leaving the solder iron temp-on with lead-free solder on the tip (wetting problem on the solder iron tip after a while)?! Best Regards,

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#33887

Lead-Free SMD repair | 25 April, 2005

It will be helpful to responders if you could list the lead free alloy used for paste and repair.

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#33896

Lead-Free SMD repair | 26 April, 2005

Sorry for my blackout, but here it comes:

Solder paste: Senju 7100-GRN360-K1MK-VS Sn 95.5 Ag 3.9 Cu 0.6

Solder wire: Kester 24-7040-8834 Sn 96.5 Ag3.5

Regards,

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steve

#33912

Lead-Free SMD repair | 27 April, 2005

I always have a difficult time with seeing people using two different manufacturers products. Here your printing with Senju and hand soldering with Kester. So if theres a problem you have to look at two different products, contact two different companies etc. etc. Not to mention are the fluxes compatable? And for rework I particularly suggest pre-heating of the board. Just my thoughts.

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#33976

Lead-Free SMD repair | 29 April, 2005

Steve, Thanks for Your replay and I agree with You. But sometimes I find it hard to always have the optimum in every aspect of our high mix/low volume electronics assembly production. We also do a lot of prototype production. In this case we had to go for the pb-free Senju paste (which worked just fine) as for customer req. and we do not have enything else than Kester pb-free solder wire at the moment. The problem in repair we are facing is reaching temp. We will soon evaluate a separate pre-heating unit for the rework station. RoHS is new for us at the production floor and we found that especially the lead-free repair process is "somewhat tricky" to deal with, so I appreciate all inputs. Regards,

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#33984

Lead-Free SMD repair | 29 April, 2005

Hi if mail me and I will talk you over some process techniques

John

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RDR

#33985

Lead-Free SMD repair | 29 April, 2005

What core size are you using with the solder wire? I would recommend that you use a "66". It is very helpful to get the area hot prior to adding the solder.

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steve

#33986

Lead-Free SMD repair | 29 April, 2005

You never mentioned the size of the board? You will find a vast array of pre-heaters with a range of prices. I could reccoment a few products based on the size of the board in question. The solder iron staying at temperature while not being used is an excellent question to ask in a Lead Free environment. I will look into that but I might suggest upgrading the station to one that has a sleep mode. Where if not used for a period of time it drops to a very low temperature. Several manufacturers offer this for not alot of money.

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Daniel

#33992

Lead-Free SMD repair | 30 April, 2005

I think he did mentioned the board size in the inital thread: "265mm x 207mm pcb", but maybe it was not clear written.

I have a question about rework and pre-heat: is it necessary to have the pre-heater to cover the whole board size, even if you only are going to do repair/rework on a certain area of the board? In our production we have products with different board size and if we need different pre-heaters for each board size (I asume we are still talking about smaller components, Not QFP:s or BGA:s), then it will be very expensive/complicated?? Please clearify.

We will very soon also produce RoHS boards and we think this is very interesting. I am looking forward to further postings about this.

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steve

#33993

Lead-Free SMD repair | 30 April, 2005

My experience with different size boards and pre-heaters. The perfect world (right?) you would saturate the complete pcb with bottom pre-heat. But it is difficult with repair and rework equipment, not to mention the expense and foot print of large pre-heaters. There are systems out there that simply pre-heat the bottom of the area you are working on and no more. This is bad, bad, bad. I have seen board warpage, experienced pop-corning or blowing the chip and also burnt boards. A decent pre-heater should be able to at least soak the board with heat, it is not necessary to have outer areas of the board the same precise temperature as the inner area you are working on. But it is nice to be close in temperature. Also a quality soldering iron with somewhat precise tip temperature helps. I cant tell you how many times I have seen a digital display of an iron at one temp and then found that the tip temperature is off by as much as 100degrees F. Same with some hot air systems. It is recommended that you thermocouple portions of the board A) the area adjacent to the component you are working on and B) possibly an outer edge of the board.

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DenM

#34032

Lead-Free SMD repair | 3 May, 2005

We sell rework stations for all kind of components and boards. The systems are designed to fit a particular size board and it's very difficult to design a one size fits all system. I personally have a lot of experience reworking high mass, high heatsinking, high temp solder. It is a bear make no mistake. I built heated work holders to get the board about 125C and measured board temp before we sucked or wicked the solder. The problem with no lead is that it does not flow and wick like tin lead. For solder wicking I would use a huge tip, much bigger than necessary as it would not cool off as much when heatsinked to the joint and could be used at a lower temp. As with all soldering you want the time at melt point to an absolute minimum. I found that Metcal soldering irons worked the best. I used a chisel point tip and would apply heat with the edge of it. For mass solder removal I would use a custom nozzle to reflow the board and this is a skilled art more than a science when done by hand. For solder sucking I used a Metcal although it needed a lot of attention to keep it clean and operating. We sell a rework station with a lot of these features and a PC that learns the thermal response of boards and adjusts accordingly. The IR underheaters are custom sized to your board so it's not a one size fits all system. Check out our website http://www.manncorp.com and call with any questions. Denis, Manncorp 215-830-1200

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billscheu

#34246

Lead-Free SMD repair | 13 May, 2005

just use 63 37 solder for repair. I do not know of any specification which prohibits this and until the people who create the rules change them this is the best. I thought mancorp was an importer of equipment and am thinking they do not have the install base or experience to help.

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Mika

#34252

Lead-Free SMD repair | 14 May, 2005

I am interested in RoHS "through-hole soldering": We have a problem with solder wetting and fillet during selective and wave soldering, with a Ni/Au PCBA!! Different fluxes has been tested, but this is really a big issue. Now; there is only a few fluxes that can be used and also the SAC can't be changed to much. Not only for us but also to everyone who are going to/already produce RoHS PCBA:s; please tell us if you encounter problems like this!! I would like to hear about your experiences about this extremly hard scenario.

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jfullerton

#34378

Lead-Free SMD repair | 20 May, 2005

billscheu wrote: "just use 63 37 solder for repair. I do not know of any specification which prohibits this and until the people who create the rules change them this is the best."

All due respect, but do you know what RoHS is? If you sell product in Europe, you'd better before 7/1/06. The specific rule states that (paraphrased) "no homogenous material may contain more than 1000 ppm lead."

Solder joint = homogenous material 1000 ppm lead = 0.1% Pb.

So, as long as the lead content of your solder joint is less than 0.1% - meaning you need a ratio of 370:1 of lead-free to leaded solder in a single joint - you meet the requirements.

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RDR

#34379

Lead-Free SMD repair | 20 May, 2005

So I guess we could repair with the 63/37 until 7/06 then. We should be able to facilitate and figure out easy/ cost effective repair by then I hope.

Senior Tech - I don't know who I am talking about when I say "we", lets ask Dave again, maybe he knows. HaHa

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#34427

Lead-Free SMD repair | 23 May, 2005

HI guys, I am new to this forum, Earlier author is asking regarding of Lead free rework. 63-37 is non lead free and this will contaminate the product itself. I do not know what are the components that you are facing to rework with. But try to set the tip temperature higher as compare to tin lead material.perhaps 350c to 380c.

rgds

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steve

#34460

Lead-Free SMD repair | 24 May, 2005

You can continue repair and rework with tin/lead solder until 7/06. However!!! Any product still on the shelves overseas after 7/06 will be returned to the USA. Thought? Maybe start repairing with SAC305 now? Also SAC is Tin, Silver and Copper. No Nickel. SN100C is Tin, Copper and Nickel but not yet available in abundance. Again, you want good wetting, good luck. Your old Metcal station ain't gonna do it. Check their web site out. what are they advertising? Their "New" lead free solder station. It's not even close to the quality the old version offers. The old version can't get you enough heat. Consider changing stations, checking the plating on tips, better tip maintenance, proper pre-heat, proper temperature at the tip. And throw out your old thru-hole desolder guns cause their gonna Clog up. Your plated thu-hole will get about 75% full with lead free. Guess what, your old thru-hole desolder guns are gonna get 75% vacuum of solder thru the chamber thus clogging. Honestly, check out http://www.hakkousa.com. They got their act together.

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Rob

#34502

Lead-Free SMD repair | 26 May, 2005

I beg to differ but the old metcals do handle lead free with no problems - Unless we have a rogue batch of ancient super MX500's.

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Philippe

#34623

Lead-Free SMD repair | 29 May, 2005

I have been following this thread with a great interest. However, the rules or legislations that control RoHS standards is maybe questionable, but I can't see why people/companys have so hard to think about the "next generation"? The fact is: RoHS is here to stay and why not try do do our best to fulfill this matter? I noticed an earlier posting that says "just use 63 37 solder for repair. I do not know of any specification which prohibits this and until the people who create the rules change them this is the best." That is not an answer to the original posting, but maybe it is a cheap way out in a short term?

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Interested in The repairable tool

#34695

Lead-Free SMD repair | 2 June, 2005

If you have some tool which can be convenient for repairing component mounted with lead free process, please email to me, I am interested in them very much.

In my opinion, to repair a SMD component is not difficult. The most important thing is how to remove or repair some component mounted on Multilayer PCB. The thermal going fast, how can we compensate the thermal loss in repairing? If a tool can meet this requirement, perhaps it will give a hand for this field.

Mail:gznewlife@yahoo.com.cn

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JH

#34696

Lead-Free SMD repair | 2 June, 2005

I concern about the Through Hole soldering as well. Currently, we have encountered some problems of Multilayer from Through Hole soldering. The root-cause is probably related to PCB Finish, machine setting, Thermal relief Pad or hole and something else.

If you would like to share some experience on RoHS, you can post mail to me, gznewlife@yahoo.com.cn

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Olof

#34902

Lead-Free SMD repair | 12 June, 2005

Hi, We have just recently ordered a pre-heater for repair. Our concerns is: What temperature shuld we working with? I reckon that it shuld/must be between 80-100 degr. Celcuis?

And also; How are we dealing with the MS-level (RoHS compliant) components; during the higher soldering tempereature?

RoHS is Not an easy task, but as Mr. Philippe said: "RoHS is here to stay and why not try do do our best to fulfill this matter? " I am looking forward to further postings, because we don't really know how to do this in a proper way Greetings,

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PCB Soldering Tools

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