Rosin flux provides a longer process window and is more agressive in removing oxidation than most WS or NC flux. I agree with you on preheating the PCB and utilizing some form of bottom heater during the soldering process. In addition, I would apply flux to the primary side pins identified as a heat sinks prior to installation. I am not sure about soldering without forming a heat bridge. That would require a test. Delamination and lifted pads should not occur if the operator is skilled.
________________________________
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Wed 3/1/2006 1:25 PM
To: TechNet E-Mail Forum; Jones, Evamaria
Subject: RE: [TN] Solder Joint Inspection
Why the RMA flux?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jones, Evamaria
Sent: Wednesday, March 01, 2006 11:15 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Joint Inspection
I would add using RMA flux!
Eva
________________________________
From: TechNet on behalf of Dehoyos, Ramon
Sent: Wed 3/1/2006 8:43 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Joint Inspection
Hi Chris:
It seems that a lot of good recommendations were given. In summary pretin the connectors, use a spacer if possible, do the soldering of these parts after oven preheat( 100 C for 15 min) over a hot plate (125 C), use a hot tip (117) soldering iron and lastly instruct operators not to touch the pads, but to touch the lead only with a solder wetted iron tip. This last recommendation is to avoid lifting pads and burning the butter coat. If you do the last three you will get more than 75% fill. In a previous we had to solder many metal body inductors on boards that had top and bottom exposed ground planes and many inner ground planes. The boards were silver color except for some pads that were isolated and some pads that were connected to the top and bottom planes. You may do some contract X ray to prove your process.
Best Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, February 28, 2006 3:12 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Joint Inspection
You may also wish to look at pre-tinning the connector. This sometimes aids in the wetting of the solder up to the top side of the PWB.
I have also pre-filled this type of connector hole with solder paste and used a rework machine to reflow from the topside. This really worked well.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Barmuta, Mike
Sent: Tuesday, February 28, 2006 1:22 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Joint Inspection
Hi Chris: I think if you look closely at the wording in 6.3.1, 50 % hole fill is not acceptable for class 3, only class 1 and 2.
Ken is building to class 3.
BTW You are probably looking at IPC-A-610 rev C. The new one is rev D section 7.5.5.1
Regards
Michael Barmuta
Staff Engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Schaefer, Chris
Sent: Tuesday, February 28, 2006 11:02 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Joint Inspection
Section 6.3.1 speaks about a 50% vertical hole fill on sections of the board that are considered thermal planes or conductor planes. It sounds like this applies, but it may require something from your customer to allow this or for reasons of stress it is required - not sure. We have issues such as your and we have spoken with the customer and have received the ok to allow a 50% fill versus the traditional 75%.
I agree with the previous point, but it will not allow for any process anomalies that occur on occasion. If for some reason the connector has issues related to the solderability, then you have a problem. In another scenario if the area/ connector has not been proper fluxed or achieved proper solder contact - it might look fine on the outside, but has not achieved the solderability levels you desire.
Food for thought...
Have a nice day guys!
Chris Schaefer
Suntron Corporation
Process Engineer
540 N. Rogers Road
Olathe, Kansas 66062
913.393.5878
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of John Berg
Sent: Tuesday, February 28, 2006 12:44 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Joint Inspection
If x-ray is not an option, you need to set up a soldering process that would not require inspection. On a thermally relieved pad that does not get sufficient fill, you need to preheat the pad area prior to hand soldering to compensate for the heat sinking. If you can get a dummy populated board, preheat it to a known reference level, and then remove the connector body to examine the % fill. Find the minimum reference preheat that will obtain your desired % fill. If you can't get a dummy populated board, you can use a few production boards to find the reference preheat by utilizing an ouitside x-ray service to determine the % fill.
>>> [log in to unmask] 2/28/2006 7:55 AM >>>
We are having a heck of a time inspecting some solder joints and could use your help.
Per Class 3 a solder joint is supposed to have at least a 75% fill. We have a circuit board that has large ground planes and hand soldered connectors that are impossible to inspect for top side solder.
We do not have access to an x-ray and are wondering if there are any clever ways to inspect these solder joints.
Thanks,
KennyB
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