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Touch-up and Inspection Process

Greg

#32965

Touch-up and Inspection Process | 1 March, 2005

Hi,

I need yor help here in defining which process is better.

SMT Process --> QC --> Touch-up --> QC --> Assembly

After SMT all PWB goes to QC, QC Inspects and marks all that needs rework then PWB's goes to Touch-up to fix what QC marked for rework. After that All reworked boards goes to QC for another verification and stamping.

This is the other process:

SMT Process --> Touch-up --> QC --> Assembly

What do you think of the 2 different processes? What are their advantages and disadvantages. I'm told that the 1st is better for Quality purposes.

thanks and regards,

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Rob

#32966

Touch-up and Inspection Process | 1 March, 2005

Hi Greg,

Is anyone logging the errors at QC/touch up stage so they can feed them straight back to SMT and fix them? (i.e. skipped components, poor paste coverage etc)

Obviously the faster you spot an error the cheaper it will be for you.

Cheers,

Rob.

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pr

#32967

Touch-up and Inspection Process | 1 March, 2005

I think the 1st option would be the best. I have found that a touch up person WILL TOUCH UP SOMETHING, regardless of the electrical needs of the board. This leads to a lot of unnecessary rework of joints. I would hope QC is tracking the defects and then the process could be fixed to eliminate the need to check every board (so that you could get to a random sample for QC of say, 1 out of 5). We do a 100% inspection by QC, of the first 5 out of the wave, then go to 1 out of 5.

my 2 cents, pr

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#32968

Touch-up and Inspection Process | 1 March, 2005

A lot depends on the complexity of the board/process as well as the amount of placements. If the board has few placements and the parts are not smaller that 0805 then doing all the rework after completion is ok. The human eye can only pick out obvious defects such as tombstoning or extreme scewing. Having 3 QC's does help, 1 for each side of the board and one post rework inspector.

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#32971

Touch-up and Inspection Process | 1 March, 2005

pr is 100% correct, can't have visual inspectors touching up for the reason he states. I have always seen that- when in doubt they will always "touch up". Touching up is always a bad thing. Looks like you have some problems that need fixing to eliminate post placement and/or post solder repair. Your goal must be to get rid of these repair/touchup activities.

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Austinj

#33009

Touch-up and Inspection Process | 2 March, 2005

The tendancy always has been "when in doubt, touch it up"... this is not the way to "verify the process" and is not the best strategy for multiple reasons (unessecary rework, additional labor costs, as well as making the solder joint more brittle, [intermetallic bond] by adding more heat, etc.) The SMT process must be in control, i.e. stencil printing, pick & place and reflow. The SMT-QC-Touchup-QC-Assembly is the best way to verify that the set processes are in control. This has to be done up front. QC will need to track defects, via Statistical Process Control (SPC), Upper and Lower Control Limits will need to be set to ensure the process is in control. Then it is really a "checks and balanes" process. If the process goes "out of control" in accordance with the SPC limits set the SMT assembly should stop and the process gets fixed.

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RDR

#33015

Touch-up and Inspection Process | 3 March, 2005

Been following this thread and have a question,

Why do "touch-up" people follow different criteria than "Q.C." people. It sounds like the root of the problem is not addressed but bandaids are being put into place. We have no "Q.C." department and put the quality of the product into each operators hands. Our operators check previous operation and provide immediate feedback. We assign an operator to perform process checking throughout the day (paste height, polarities, etc..)to ensure that everything is as should be. I don't understand the inspect, then inspect the inspector process. This seems very wasteful in terms of resource. How about having the Q.C. department monitor process insted of product? As stated earlier, the key is feedback in real time. "If you don't build the defect, you won't ship the defect"

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Slow Ride

#33024

Touch-up and Inspection Process | 3 March, 2005

Generally QC is a different deptpartment than touch-up people. Most touch-up people are just general operators, so to keep their job they always see the solder joint as "not enough". Q.C. people are generally a bit better, but know they may be called to back-up any decision they made on a solder joint that questionable - so they see the joint as "just enough".

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Rob

#33026

Touch-up and Inspection Process | 3 March, 2005

Doesn't that depend on your company's culture & management style?

We (and I feel slightly dirty using this word)empowered our end of line inspection/touch up people & trained them to know what is good or bad - so issues can be immediately fed back, and joints are not unneccesarily reworked. We don't come from an area with a great work ethic or labour force but it did work for us.

However it is a lot easier with decent equipment & good process engineers as you get far less touch up/rework.

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#33055

Touch-up and Inspection Process | 5 March, 2005

This has been our practice and its worked well: SMT process-QC/Touch-Up-Assembly. We have dedicated QC/T-Up after reflow trained under IPC requirements. They do the SMT inspection and ONLY touch-up if necessary. This way we never have to inspect SMT again in the process...only the assembly parts during final QC.

Gus

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Darby

#33058

Touch-up and Inspection Process | 6 March, 2005

1st law of Surface Mount. You WILL run out of parts on the last board going through before a long weekend. 2nd law of Surface Mount. Touchies WILL touch.

I'm with Russ and Rob. Touch up is EVIL and should only be tolerated in exceptional circumstances. A touch up "culture" will do little to improve process/quality/throughput/profit. If QC can't help improve the process - move them somewhere else. Put the hard work, (and workers), into the front end.

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