PCB (Printed Circuit Board) Assembly - Wave Solder Capability

[Chris May]

Dear all,

This is my first post on this forum. (All the way from England)

I have been searching a while for a "meaningful" forum that deals with process issues.......and here you are.

Anyway,
I am looking at a way to monitor the wavesoldering or flowsoldering element of our PCB assembly.

I have been gathering data (simple tick charts) to ascertain failure modes for certain assemblies and the flowsolder machine/process is the biggest culprit.

I have now conducted soldering theory training and practical training to the two operators. This has helped.

I have been here (Horstmann Controls, OEM for heating/metering controls) for about 3 months and had a few quick wins, but I need now to monitor the processes...first wavesolder...then SMD dept (aagghhh).

There are no controls/measures at present for process.

Anyone out there in a similar environment ?
I have done a search on the site to find any useful threads...nope.

I assume that I need to perform a process capability study on the wavesolder machine (!?). (first step)
How would I achieve this? Do I need to take the fluxer, preheat and solder bath individually?

I have visited various sites and downloaded a tree load of info, but nothing that directly relates to electronic assembly/manufacturing.

Thanks in advance for your time,

Best Regards,
Chris May

 

[Sam]

Chris, The wave soldering process is ideal for "design of experimants." The best source I have (had), if I haven;t lost it , came from mcDonnel- Douglas. I' ll check this weekend and if I find it I will fax it to you.

 

[Atul Khandekar]

Chris,
Welcome to the Cove Forums.

May be a little more info would help.

What type of inspection is carried out? Is there any inspection / rejection / rework after fluxer, preheat and solder bath stage individually? How many opportunities for defects?

-Atul.

 

[Michel Saad]

Previous life !

Hi Chris,

In my previous job, we did wave and SMT soldering. We started by "calibrating" the temperature profile from entry to exit of the wave/furnace and verifying every 6 months to that profile. We monitored daily the temperature setting of the different zones of the wave/furnace. We had flowmeter with alarms for the nitrogen input. PM's did the rest. No control chart since you can't measure anyting without ripping it off the board.

The control was simply a visual inspection at the exit of the wave/furnace according to IPC-610 standards.

Regards,

 

[Dave W 2005]

Chris,

I'm also based in Bristol (maybe same company?) One of the guys I did my blackbelt training with, carried out a project to improve the capability of his wave soldering process (for CCTV camera circuits) - I'll try and get a copy of his report.

Dave

 

[Chris May]

Atul,

In the flowsolder process, the flowsolder machine is totally self contained, so the PCB goes into the load end onto a conveyor. It is then transported over a fluxer (actuated via optic sensors), over a preheat to thermally condition the board and raise it to about 100C prior to the wave and then over the wave itself.

So...after you load the board (PCB) the next time you see it is at the exit end when it is soldered. The "inspection" is then to see if there are any solder shorts/bridges. The defect opps will vary depending upon product, but this is easily counted (say 100 on a smallish board).

Some ideas I have had since my original post are as follows.

FLUXING- This is critical so I am thinking about weighin a bare laminate. Then passing the bare laminate over the fluxer and then weighing this again. On the datasheet for the flux it specifies optimum coverage in micrograms per square so I could get data that way.

PREHEAT- This could be set (and should not be changed) and measured say 20 times a day using a temp probe for a week to get "sample" temps.

SOLDER POT- This could be measured with adip type temp probe as above for preheat.

I think this could give me enough data to start with.

Any more thoughts ??........anyone?

 

[wing_a]

Chris,
We're performing a SS project on wave soldering touch-up reduction. The objective of the project is to reduce solder-related defects (missing solder, insufficient solder, solder bridging, excessive solder, etc) to a stabilized rate of 100 dppm or less. This according to the Handbook of Machine Soldering, by Ralph Woodgate (pp 206-207), is considered zero defect soldering. After conducing the process map, C&E matrix, and FMEA we drew a conclussion that the parameters of the wave solder machine such as preheat temp., conveyor velocity, flux specific- gravity, solder bath temp., etc., play a critical role to the quality of the solder joint. So in the Analysis phase of the SS project we use DOE to screen out and then optimize the significant parameter(s), Fractional Factorial Design for screening and Response Surface for optimizaion. The screening experiments are now in process. And after the DOE analysis, we will perform confirming experiments to ensure the sucess of the analysis. Finally, we will work out a control plan to monitor the wave soldering process based on the DOE analysis.

Hope this help.
Wing