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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Gold versus HASL

mk

#21452

Gold versus HASL | 9 September, 2002

What kind of changes could be expected by changing from a HASL finish to gold? We have a board the had been being coated with HASL but was changed to gold to make priting easier. Now, even though the soldering looks fine, we are getting fallouts at Genrad testing. Opens, impedance issues, etc.

Can changing to gold cause test errors? When the HASL boards are tested thay pass, gold version fails????

Any suggestions???

mk

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Kevin Facinelli

#21453

Gold versus HASL | 9 September, 2002

Did you switch board vendor?

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Bernard Mulcahy

#21454

Gold versus HASL | 9 September, 2002

Hi MK,

It not really as simple as changing from one to the other. VIA hole, PTH hole sizes may need to be changed. Really the designer should re-evalaute the board before changing. Also remember your soldering profiles, both reflow and wave (if applicable) will also require adjusting.

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mk

#21455

Gold versus HASL | 9 September, 2002

No change in Vendor. Here is some additional info from this morning,

There are no shorts, opens, or visible defects. The problem is that when the boards are ICT'd, the values of the resistors, caps etc are measuring out or tolerance?????

Can the gold versus HASL cause that?

mk

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Kevin Facinelli

#21456

Gold versus HASL | 9 September, 2002

I have never seen that occur when using gold plating vs. HASL. I am a big fan of the gold process and have achieved very consistent quality.

Did the board vender do an impedance measure to validate you design?

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#21462

Gold versus HASL | 9 September, 2002

Bernard

Interesting point. Please help us better understand: * Why do 'VIA hole, PTH hole sizes may need to be changed', aside from the obvious with hole-to-lead clearance? * What should the designer 're-evalaute the board before changing'? * What is it about the 'soldering profiles, both reflow and wave (if applicable) will also require adjusting'? * What are ther issues about converting from HASL to ENIG?

Tks

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blnorman

#21495

Gold versus HASL | 11 September, 2002

We had a similar problem with components being out of spec, course our problem was that they were coming in out of spec, not being damaged by our process. Do you do any incoming inspection?

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Stephen

#21496

Gold versus HASL | 11 September, 2002

Are you no clean or WS? Have you used a MultiMeter to verify the ICT failures? Maybe the components are fine but the pins are contaminated. Or the test points. Don't have any reason to suspect that due to HASL vs gold. It's just I don't trust data on blind faith.

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Bernard Mulcahy

#21522

Gold versus HASL | 13 September, 2002

Hi dave,

Only back in the forum today to see your query so here goes

(1) VIA ,PTH holes -- we found that because the amount of gold being plated is generally less that the amount of HASL that holes can be physically wider. This then (pacticularly on connectors) meant that you got in-sufficent solder fill or voiding.

(2) Designer --- Design for manufacture is what I am on about here. When designing the board the designer should be taking into account the finish that is most suitable for your manufacturing process. Similarly is you are making a change in finish best practice would be to let the designer know what you are doing and why , so he learns also.

(3) Profiles -- My own experience from doing a similar change is that when we changed a HASL baord to gold we found that on the old profile we had issues with the quality of solder joints ( typically opens on QFP) By reprofiling and slowing down the process slightly we solved this. I guess what I am saying is that it is becasue the chemisty is different the process may need fine-tuning.

(4) These are just the issues I have encountered. Personally we now recomend that all SMT boards are ENIG rather than HASL because of the better consistency of the process.

Bernard

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#21541

Gold versus HASL | 13 September, 2002

Thanks Bernard.

On your profile: Adding gold to your solder alloy will increase the liquious temperature. So slowing your reflow oven conveyor is a perfectly reasonable approach, especially for pads with low surface area. We don't even notice a difference in wave soldering.

On recommending ENIG over HASL: ENIG does have a few redeeming characteristics over HASL, especially if you are running fine pitch SMD.

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