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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Hand-Solder Pre-Heat

Ryan Jennens

#11610

Hand-Solder Pre-Heat | 30 April, 1999

Mornin! We just had vendor in here pitching a "low-temperature rework system" which was intriguing, but too expensive. He did get me to thinking though, beyond heating ceramic caps before hand-soldering them, it seems like it would be advantageous to pre-heat the board according to the original profile, to below reflow temperatures, then just touch the leads of the part to be reworked with a soldering iron. The iron would only have to be around 500F to reflow the solder, because it would only have to be heated 20-30 degrees more to reach reflow temperatures. Is anybody else out there pre-heating boards before rework? Is it necessary? Wouldn't this method stress the parts and pads less, because of the slower heat-up? Is pre-heating the parts enough? If it is a good idea, is there a cheaper way to do it than buying a $700 pre-heat plate for each rework station? Hope you all are enjoying as beautiful weather as we are here in Michigan! -Ryan Jennens TelGen Corporation

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Jeff Sanchez

#11611

Re: Hand-Solder Pre-Heat | 1 May, 1999

| Mornin! | | We just had vendor in here pitching a "low-temperature rework system" which was intriguing, but too expensive. He did get me to thinking though, beyond heating ceramic caps before hand-soldering them, it seems like it would be advantageous to pre-heat the board according to the original profile, to below reflow temperatures, then just touch the leads of the part to be reworked with a soldering iron. The iron would only have to be around 500F to reflow the solder, because it would only have to be heated 20-30 degrees more to reach reflow temperatures. Is anybody else out there pre-heating boards before rework? Is it necessary? Wouldn't this method stress the parts and pads less, because of the slower heat-up? Is pre-heating the parts enough? If it is a good idea, is there a cheaper way to do it than buying a $700 pre-heat plate for each rework station? | Hope you all are enjoying as beautiful weather as we are here in Michigan! | | -Ryan Jennens | TelGen Corporation | Ryan, I like pre heating cause it makes the whole rework thing go smoother but thermal control is very key here. I preheat at 110F it dosen't sound like much but it is SAFE! I will biuld a whole board on the pad like that cause I don't have to worry about it getting dammaged. and at that low temp the board won't realy warp either. Preheating also allows you to deal with some of the more difficult tasks like boards with layered shielding and larger ground planes.As well as multilayer. They work great just make sure you know what your threshholds are.

Is it better? YES

Is it safer? That's up to you and your product.

Can it be done cheaper? Shhhhh, I have used a corning hot plate for ever and it only costed 5.oo at a yard sale. I have a fluke thermal probe to check the temp. Like you I had the same question and just never got around to spending 700.00 on Wellers gloryfied version,hehe......why bother. Just make sure you make the thing ESD safe.

I just had to tell a few thousand people that......LOL

See ya Round, Jeff Sanchez

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Bob Willis

#11612

Re: Hand-Solder Pre-Heat | 7 May, 1999

| Mornin! | | We just had vendor in here pitching a "low-temperature rework system" which was intriguing, but too expensive. He did get me to thinking though, beyond heating ceramic caps before hand-soldering them, it seems like it would be advantageous to pre-heat the board according to the original profile, to below reflow temperatures, then just touch the leads of the part to be reworked with a soldering iron. The iron would only have to be around 500F to reflow the solder, because it would only have to be heated 20-30 degrees more to reach reflow temperatures. Is anybody else out there pre-heating boards before rework? Is it necessary? Wouldn't this method stress the parts and pads less, because of the slower heat-up? Is pre-heating the parts enough? If it is a good idea, is there a cheaper way to do it than buying a $700 pre-heat plate for each rework station? | Hope you all are enjoying as beautiful weather as we are here in Michigan! | | -Ryan Jennens | TelGen Corporation | The use of pre heat for rework of chip capacitors or the original soldering of the parts should not be necessary if the parts have been properly selected during design.

The most common cause of cap cracking is board flexture not thermal shock that was the problem years ago when the quality of the parts was poor we have moved on a long way from there.

I know that the IPC training video on rework did uote the use of pre heat which I questioned when it was being produced. In the real world people do not preheat chip caps during rework and repair.

Bob Willis

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