Inherit the account invoice and use the below code for smart button,(This code for odoo 9)

        <record id="view_product_invoice_line_tree" model="ir.ui.view">
            <field name="name">product.account.invoice.line.tree</field>
            <field name="model">account.invoice.line</field>
            <field name="arch" type="xml">
                <tree string="Invoice Line">
                    <field name="invoice_id"/>
		    <field name="product_id"/>
                    <field name="account_id"/>
                    <field name="quantity"/>
                    <field name="uom_id"/>
                    <field name="price_unit"/>
                    <field name="discount"/>
                    <field name="price_subtotal"/>
                    <field name="currency_id" invisible="1"/>
                </tree>
            </field>
        </record>
        <record model="ir.actions.act_window" id="action_inv_line_product_tree">
            <field name="context">{}</field>
            <field name="domain">[('product_id','in',active_ids)]</field>
            <field name="name">Invoices</field>
            <field name="res_model">account.invoice.line</field>
            <field name="view_id" ref="view_product_invoice_line_tree"/>
        </record>
        <record id="view_product_template_invoice_buttons_from" model="ir.ui.view">
            <field name="name">product.template.invoice.button.inherit</field>
            <field name="model">product.template</field>
            <field name="inherit_id" ref="product.product_template_only_form_view"/>
            <field name="arch" type="xml">
                <div name="button_box" position="inside">
                   <button class="oe_stat_button" name="%(account.action_inv_line_product_tree)d"
                       type="action" icon="fa-shopping-cart">Invoices
                   </button>
                </div>
            </field>
        </record>