Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


SMT production

Jim Mills

#6096

SMT production | 25 April, 2001

We build a product that requires a lithium battery. There is a Smt Battery clip soldered onto two gold pads on a FR4 PCB. The battery is forced by two little clips punched out to provided downward pressure in the battery holder, enabling the lithium battery to sit on a gold pad when installed into the battery holder.

My problem is the customer has received field failures for open lithium batteries. It seems the solder mask is higher then the gold pad where the lithium battery is suspose to sit, preventing the contact of the lithium battery body (rough dia of 0.370)with the gold pad.

The cutomer wants us to print solder on gold pad where the body of the lithium battery sits thus increasing the base to provide a contact for the battery (my current stencil used is 0.006 laser cut for printing). The battery case is however nickel, which will then be incontact with tin lead solder (we use 62,36,2 or 63/37 solder). It was always my understanding that solder will not provide a good long term reliable contact (due to tin lead oxidation) unless there is sufficient continuous pressure. Is this not how pressure connectors work which contact solder pads?

Am i correct in this assumption? How much force is required ( given the pad area is 0.280x0.280 and solder mask butts up to the edges)to ensure a reliable long term contact?

Long term we will open the solder mask area to 0.400 which will ensure battery sits only on the gold pad.Short term-I was hoping the SMTnet could help

Any help would sure be appreciated.

Signed in a bit of a pickle.

reply »

Jim Mills

#6097

SMT production | 25 April, 2001

We build a product that requires a lithium battery. There is a Smt Battery clip soldered onto two gold pads on a FR4 PCB. The battery is forced by two little clips punched out to provided downward pressure in the battery holder, enabling the lithium battery to sit on a gold pad when installed into the battery holder.

My problem is the customer has received field failures for open lithium batteries. It seems the solder mask is higher then the gold pad where the lithium battery is suspose to sit, preventing the contact of the lithium battery body (rough dia of 0.370)with the gold pad.

The cutomer wants us to print solder on gold pad where the body of the lithium battery sits thus increasing the base to provide a contact for the battery (my current stencil used is 0.006 laser cut for printing). The battery case is however nickel, which will then be incontact with tin lead solder (we use 62,36,2 or 63/37 solder). It was always my understanding that solder will not provide a good long term reliable contact (due to tin lead oxidation) unless there is sufficient continuous pressure. Is this not how pressure connectors work which contact solder pads?

Am i correct in this assumption? How much force is required ( given the pad area is 0.280x0.280 and solder mask butts up to the edges)to ensure a reliable long term contact?

Long term we will open the solder mask area to 0.400 which will ensure battery sits only on the gold pad.Short term-I was hoping the SMTnet could help

Any help would sure be appreciated.

Signed in a bit of a pickle.

reply »

Jim Mills

#6098

SMT production | 25 April, 2001

We build a product that requires a lithium battery. There is a Smt Battery clip soldered onto two gold pads on a FR4 PCB. The battery is forced by two little clips punched out to provided downward pressure in the battery holder, enabling the lithium battery to sit on a gold pad when installed into the battery holder.

My problem is the customer has received field failures for open lithium batteries. It seems the solder mask is higher then the gold pad where the lithium battery is suspose to sit, preventing the contact of the lithium battery body (rough dia of 0.370)with the gold pad.

The cutomer wants us to print solder on gold pad where the body of the lithium battery sits thus increasing the base to provide a contact for the battery (my current stencil used is 0.006 laser cut for printing). The battery case is however nickel, which will then be incontact with tin lead solder (we use 62,36,2 or 63/37 solder). It was always my understanding that solder will not provide a good long term reliable contact (due to tin lead oxidation) unless there is sufficient continuous pressure. Is this not how pressure connectors work which contact solder pads?

Am i correct in this assumption? How much force is required ( given the pad area is 0.280x0.280 and solder mask butts up to the edges)to ensure a reliable long term contact?

Long term we will open the solder mask area to 0.400 which will ensure battery sits only on the gold pad.Short term-I was hoping the SMTnet could help

Any help would sure be appreciated.

Signed in a bit of a pickle.

jmills

reply »

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