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Time to use alternative finishing ???

Jose RG

#9667

Time to use alternative finishing ??? | 10 September, 1999

We have a product, with various PWBs, with over 600 parts each one (We are a low Volume/high mix company with an average component placement per PCB between 250 to 300 parts). This PWBs have 7 to 10, 20 mils pitch parts. We are having problems with our raw edge supplier because we specify 200 to 400 microinches and he can not achive it on his normal process, they are always very low below the lower limit. This PWBs are Hasl finished.

When is the time to change to an alterantive plating finishing ? 20 mils ? 15 mils ?

The supplier recommend Omikron. I already read notes about omikron suggestion. OSP ? Any suggestion ?

Thanks, Jose RG

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#9668

Re: Time to use alternative finishing ??? | 10 September, 1999

| We have a product, with various PWBs, with over 600 parts each one (We are a low Volume/high mix company with an average component placement per PCB between 250 to 300 parts). This PWBs have 7 to 10, 20 mils pitch parts. We are having problems with our raw edge supplier because we specify 200 to 400 microinches and he can not achive it on his normal process, they are always very low below the lower limit. This PWBs are Hasl finished. | | When is the time to change to an alterantive plating finishing ? 20 mils ? 15 mils ?

We use Gold over Nickel with very good results. Price is also reasonable | | The supplier recommend Omikron. I already read notes about omikron suggestion. OSP ? Any suggestion ? | | Thanks, | Jose RG |

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#9669

Re: Time to use alternative finishing ??? | 10 September, 1999

| We have a product, with various PWBs, with over 600 parts each one (We are a low Volume/high mix company with an average component placement per PCB between 250 to 300 parts). This PWBs have 7 to 10, 20 mils pitch parts. We are having problems with our raw edge supplier because we specify 200 to 400 microinches and he can not achive it on his normal process, they are always very low below the lower limit. This PWBs are Hasl finished. | | When is the time to change to an alterantive plating finishing ? 20 mils ? 15 mils ? | | The supplier recommend Omikron. I already read notes about omikron suggestion. OSP ? Any suggestion ? | | Thanks, | Jose RG | hello Jose If I read you correctly and you are getting a HASL coating of significantly less that 200 microinches NOW would be the time to change (for a number of solderability and reliability reasons). Whether you change your coating or your board supplier would be a good question. At this time I am changing to Ni/Au because of a move to 20 mil parts and because of reccurring problems with paste release on 25 mil parts because of variation in HASL plating height. I chose gold because our fabricator was most familiar with it and would provide it at little or no cost up. I eliminated OSPs simply because they didn't work well in our wave process. I've heard good things Omikron but haven't tried it. Search the forum archives for much more info. good luck John Thorup

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Earl Moon

#9670

Re: Time to use alternative finishing ??? | 10 September, 1999

| We have a product, with various PWBs, with over 600 parts each one (We are a low Volume/high mix company with an average component placement per PCB between 250 to 300 parts). This PWBs have 7 to 10, 20 mils pitch parts. We are having problems with our raw edge supplier because we specify 200 to 400 microinches and he can not achive it on his normal process, they are always very low below the lower limit. This PWBs are Hasl finished. | | When is the time to change to an alterantive plating finishing ? 20 mils ? 15 mils ? | | The supplier recommend Omikron. I already read notes about omikron suggestion. OSP ? Any suggestion ? | | Thanks, | Jose RG | It really is next to impossible to specify HASL coating thickness. The process just isn't that manageable. No such minimum or meaningful specifications in industry exist. This, among others, is a reson for seeking alternative coatings.

Alternative all have their up and down sides. Most work well within their self described scope and some specifications.

I will have another article out in October, if the SMTnetters will allow, concerning HASL and alternative coatings. For now, do what you must realizing it's all a compromise, but supplier process management, and your handling/storage/operational conditions, are key to making good decisions.

Earl Moon

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Brian

#9671

Re: Time to use alternative finishing ??? | 13 September, 1999

| We have a product, with various PWBs, with over 600 parts each one (We are a low Volume/high mix company with an average component placement per PCB between 250 to 300 parts). This PWBs have 7 to 10, 20 mils pitch parts. We are having problems with our raw edge supplier because we specify 200 to 400 microinches and he can not achive it on his normal process, they are always very low below the lower limit. This PWBs are Hasl finished. | | When is the time to change to an alterantive plating finishing ? 20 mils ? 15 mils ? | | The supplier recommend Omikron. I already read notes about omikron suggestion. OSP ? Any suggestion ? | | Thanks, | Jose RG | The other options, like HASL, all have their ad- and disad-vantages. I like OSL, but this limits the range of fluxes/pastes you can use for best results. Au/Ni can cause solderability problems, as the Au dissolves instantaneously in molten solder (forming intermetallics which may weaken the joint - see Manko or Klein Wassink) and the underlay of Ni must be oxide-free when gold plating starts and the Au must not be significantly porous to prevent re-oxidation. Oxidised nickel is hell to solder unless you use a strongish hydrochloride-activated flux (again, see M or KW).

Brian

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Earl Moon

#9672

Re: Time to use alternative finishing ??? | 13 September, 1999

| | We have a product, with various PWBs, with over 600 parts each one (We are a low Volume/high mix company with an average component placement per PCB between 250 to 300 parts). This PWBs have 7 to 10, 20 mils pitch parts. We are having problems with our raw edge supplier because we specify 200 to 400 microinches and he can not achive it on his normal process, they are always very low below the lower limit. This PWBs are Hasl finished. | | | | When is the time to change to an alterantive plating finishing ? 20 mils ? 15 mils ? | | | | The supplier recommend Omikron. I already read notes about omikron suggestion. OSP ? Any suggestion ? | | | | Thanks, | | Jose RG | | | The other options, like HASL, all have their ad- and disad-vantages. I like OSL, but this limits the range of fluxes/pastes you can use for best results. Au/Ni can cause solderability problems, as the Au dissolves instantaneously in molten solder (forming intermetallics which may weaken the joint - see Manko or Klein Wassink) and the underlay of Ni must be oxide-free when gold plating starts and the Au must not be significantly porous to prevent re-oxidation. Oxidised nickel is hell to solder unless you use a strongish hydrochloride-activated flux (again, see M or KW). | | Brian | Brian says the right things, but remember not to be too tight with your HASL specification, if you use one at all. It's just not possible to specify thickness requirements - min or max.

Also, adding to what Brian said, nickel simply is a barrier between copper and gold - nothing more. I certainly agree about nickel oxidation being a problem. It oxidizes very rapidly and can be difficult to control in the immersion deposition process.

Another hot element, though it seems few are listening but the "big" guys (Motorola, GM, H-P, etc.) is the negative impact phosphorous has in the equation. These folks have really put a damper on any type gold. Phosphorous is an essential part of the nickel deposition process and it causes solder joint failures as embrittlement,while having been found to contribute to the now notorious "dark gold" phenomonon, not always the gold - in minimal thicknesses (3-7 u"). The same possibly would be said if a supplier substituted boron, as an example, for phosphorous.

Earl Moon

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